 Section 24 of Anatomy of the Human Body Part 5. This LibriVox recording is in the public domain. Anatomy of the Human Body Part 5 by Henry Gray. The Liver Part 2. Development. The liver arises in the form of a diverticulum or hollow outgrowth from the ventral surface of that portion of the gut, which afterward becomes the descending part of the duodenum. This diverticulum is lined by entoderm and grows upward and forward into the septum transversum, a mass of mesoderm between the vital line duct and the pericardial cavity, and there gives off two solid buds of cells which represent the right and left lobes of the liver. The solid buds of cells grow into columns or cylinders termed the hepatic cylinders, which branch and anestomize to form a close meshwork. This network invades the vital line and umbilical veins and breaks up these vessels into a series of capillary-like vessels, term sinusoids, minot, which ramify in the meshes of the cellular network and ultimately form the venous capillaries of the liver. By the continued growth and ramification of the hepatic cylinders, the mass of the liver is gradually formed. The original diverticulum from the duodenum forms the common bile duct, and from this the cystic duct and the gallbladder arise as a solid outgrowth, which later acquires a lumen. The opening of the common duct is at first in the ventral wall of the duodenum. Later, owing to the rotation of the gut, the opening is carried to the left, and then dorsalward to the position it occupies in the adult. As the liver undergoes enlargement, both it and the ventral mesogastrium of the foregut are gradually differentiated from the septum transversum, and from the undersurface of the latter, the liver projects downward into the abdominal cavity. By the growth of the liver, the ventral mesogastrium is divided into two parts, of which the anterior forms the falsiform and coronary ligaments, and the posterior the lesser omentum. About the third month, the liver almost fills the abdominal cavity, and its left lobe is nearly as large as its right. From this period, the relative development of the liver is less active, more especially that of the left lobe, which actually undergoes some degeneration and becomes smaller than the right. But up to the end of fetal life, the liver remains relatively larger than in the adult. Vessels and Nerves The vessels connected with the liver are the hepatic artery, the portal vein, and the hepatic veins. The hepatic artery and portal vein, accompanied by numerous nerves, ascend to the porta between the layers of the lesser omentum. The bile duct and the lymphatic vessels descend from the porta between the layers of the same omentum. The relative positions of the three structures are as follows. The bile duct lies to the right, the hepatic artery to the left, and the portal vein behind and between the other two. They are enveloped in a loose areolar tissue, the fibrous capsule of glisten, which accompanies the vessels in their course through the portal canals in the interior of the organ. The hepatic veins convey the blood from the liver and are described on page 680. They have very little cellular investment, and what there is binds their parieties closely to the walls of the canals through which they run, so that, on section of the organ, they remain widely open and are solitary and may be easily distinguished from the branches of the portal vein, which are more or less collapsed and always accompanied by an artery and duct. The lymphatic vessels of the liver are described on page 711. The nerves of the liver, derived from the left vagus and sympathetic, enter at the porta and accompany the vessels and ducts to the interlobular spaces. Here, according to Coral Cove, the modulated fibers are distributed almost exclusively to the coats of the blood vessels, while the non-modulated enter the lobules and ramify between the cells and even within them. Structure of the liver The substance of the liver is composed of lobules, held together by an extremely fine areolar tissue in which ramify the portal vein, hepatic ducts, hepatic artery, hepatic veins, lymphatics, and nerves, the whole being invested by a cirrus and a fibrous coat. The cirrus coat, tunica cirrhosa, is derived from the peritoneum and invests the greater part of the surface of the organ. It is intimately adherent to the fibrous coat. The fibrous coat, capsula fibrosa, glissoni, areolar coat, lies beneath the cirrus investment and covers the entire surface of the organ. It is difficult of demonstration except where the cirrus coat is deficient. At the porta it is continuous with the fibrous capsule of glissen and on the surface of the organ with the areolar tissue separating the lobules. The lobules, lobuli hepatis, form the chief mass of the hepatic substance. They may be seen either on the surface of the organ or by making a section through the gland as small granular bodies about the size of a millet seed measuring from 1 to 2.5 mm in diameter. In the human subject their outlines are very irregular but in some of the lower animals, for example the pig, they are well defined and when divided transversely have polygonal outlines. The bases of the lobules are clustered around the smallest radicals, sub lobular of the hepatic veins to which each is connected by means of a small branch which issues from the center of the lobule, intralobular. The remaining part of the surface of each lobule is imperfectly isolated from the surrounding lobules by a thin stratum of areolar tissue in which is contained a plexus of vessels, the inter lobular plexus and ducts. In some animals as the pig the lobules are completely isolated from one another by the inter lobular areolar tissue. If one of the sub lobular veins be laid open the bases of the lobules may be seen through the thin wall of the vein on which they rest arranged in a form resembling a tessellated pavement the center of each polygonal space presenting a minute aperture the mouth of an inter lobular vein. Microscopic appearance each lobule consists of a mass of cells, hepatic cells arranged in irregular radiating columns between which are the blood channels, sinusoids. These convey the blood from the circumference to the center of the lobule and end in the intra lobular vein which runs through its center to open at its base into one of the sub lobular veins. Between the cells are also the minute biocapillaries. Therefore in the lobule there are all the essentials of a secreting gland that is to say one cells by which the secretion is formed two blood vessels in close relation with the cells containing the blood from which the secretion is derived three ducts by which the secretion when formed is carried away. One the hepatic cells are polyhedral in form they vary in size from 12 to 25 microns in diameter they contain one or sometimes two distinct nuclei the nucleus exhibits an intranuclear network and one or two refractile nucleoli. The cells usually contain granules some of which are protoplasmic while others consist of glycogen, fat, or an iron compound. In the lower vertebrates for example frog the cells are arranged in tubes with the bile duct forming the lumen and blood vessels externally. According to dillipine evidences of this arrangement can be found in the human liver. Two the blood vessels. The blood in the capillary plexus around the liver cells is brought to the liver principally by the portal vein but also to a certain extent by the hepatic artery. The hepatic artery entering the liver at the porta with the portal vein and hepatic duct ramifies with these vessels through the portal canals. It gives off vaginal branches which ramify in the fibrous capsule of glycine and appear to be destined chiefly for the nutrition of the coats of the vessels and ducts. It also gives off capsular branches which reach the surface of the organ ending in its fibrous coat in stellate plexuses. Finally it gives off interlabular branches which form a plexus outside each lobule to supply the walls of the interlabular veins and the accompanying bile ducts. From this plexus lobular branches enter the lobule and end in the network of sinusoids between the cells. The portal vein also enters at the porta and runs through the portal canals enclosed in glycine's capsule dividing in its course into branches which finally break up into a plexus, the interlabular plexus, and the interlabular spaces. These branches receive the vaginal and capsular veins corresponding to the vaginal and capsular branches of the hepatic artery. Thus it will be seen that all the blood carried to the liver by the portal vein and hepatic artery finds its way into the interlabular plexus. From this plexus the blood is carried into the lobule by fine branches which converge from the circumference to the center of the lobule and are connected by transverse branches. The walls of these small vessels are incomplete so that the blood is brought into direct relationship with the liver cells. The lining and dothelium consists of irregularly branched disconnected cells, stellate cells of cooper. Moreover, according to Herring and Simpson, minute channels penetrate the liver cells themselves, conveying the constituents of the blood into their substance. It will be seen that the blood capillaries of the liver lobule differ structurally from capillaries elsewhere. Developmentally, they are formed by the growth of the columns of liver cells into large blood spaces or sinuses, and hence they have received the name of sinusoids. Arrived at the center of the lobule, the sinusoids empty themselves into one vein of considerable size which runs down the center of the lobule from apex to base, and is called the intralobular vein. At the base of the lobule, this vein opens directly into the sub- lobular vein with which the lobule is connected. The sub- lobular veins unite to form larger and larger trunks and end at last in the hepatic veins. These converge to form three large trunks which open into the inferior vena cava while that vessel is situated in its fossa on the posterior surface of the liver. 3. The bile ducts commence by little passages in the liver cells which communicate with cannuliculi termed intercellular biliary passages, biocapillaries. These passages are merely little channels or spaces left between the contiguous surfaces of two cells or in the angle where three or more liver cells meet, and they are always separated from the blood capillaries by at least half the width of a liver cell. The channels thus form radiate to the circumference of the lobule and open into the inter- lobular bile ducts which run in glisten's capsule accompanying the portal vein and hepatic artery. These join with other ducts to form two main trunks which leave the liver at the transverse fissure and by their union form the hepatic duct. 4. Structure of the ducts Walls of the biliary ducts consist of a connective tissue coat in which our muscle cells circulally and longitudinally and an epithelial layer consisting of short columned their cells resting on a distinct basement membrane. Excretory apparatus of the liver The excretory apparatus of the liver consists of 1. the hepatic duct formed by the junction of the two main ducts which pass out of the liver at the porta 2. the gallbladder which serves as a reservoir for the bile 3. the cystic duct for the duct of the gallbladder and 4. the common bile duct formed by the junction of the hepatic and cystic ducts The hepatic duct ductus hepaticus two main trunks of nearly equal size issue from the liver at the porta one from the right, the other from the left lobe These unite to form the hepatic duct which passes downward into the right for about 4 cm between the layers of the lesser momentum where it is joined at an acute angle by the cystic duct and so forms the common bile duct The hepatic duct is accompanied by the hepatic artery and the portal vein The gallbladder vesica felea The gallbladder is a conical or pear shaped muscular membranous sac lodged in a fossa on the under surface of the right lobe of the liver and extending from near the right extremity of the porta to the anterior border of the organ to 10 cm in length 2.5 cm in breadth at its widest part and holds from 30 to 35 cm It is divided into a fundus body and neck The fundus or broad extremity is directed downward forward into the right and projects beyond the anterior border of the liver The body and neck are directed upward and backward to the left The upper surface of the gallbladder is attached to the liver by connective tissue and vessels The under surface is covered by peritoneum which is reflected onto it from the surface of the liver Occasionally the whole of the organ is invested by the cirrus membrane and is then connected to the liver by a kind of mesentery Relations The body is in relation by its upper surface with the liver by its under surface with the commencement of the transverse colon and farther back usually with the upper end of the descending portion of the duodenum or the superior portion of the duodenum or pyloric end of the stomach The fundus is completely invested by peritoneum It is in relation in front with the abdominal parietes immediately below the ninth costal cartilage behind with the transverse colon The neck is narrow and curves upon itself like the letter S At its point of connection with the cystic duct it represents a well-marked constriction Structure The gallbladder consists of three coats cirrus, fibromuscular, and mucous The external or cirrus coat tunica cirrosa vesicifelii is derived from the peritoneum It completely invests the fundus but covers the body and neck only on their under surfaces The fibromuscular coat tunica muscularis vesicifelii a thin but strong layer forming the framework of the sac consists of dense fibers tissue which interlaces in all directions and is mixed with plain muscular fibers disposed chiefly in a longitudinal direction a few running transversely The internal or mucous coat tunica mucosa vesicifelii is loosely connected with the fibrous layer It is generally of a yellowish-brown color and is elevated into minute ruggy Opposite the neck of the gallbladder the mucous membrane projects inward in the form of oblique ridges or folds forming a sort of spiral valve The mucous membrane is contained in the form of an oblique ridge forming a sort of spiral valve The mucous membrane is continuous through the hepatic duct with the mucous membrane lining the ducts of the liver and through the common bile duct with the mucous membrane of the duodenum It is covered with columnar epithelium and secretes mucin In some animals it secretes a nucleoprotein instead of mucin The cystic duct Ductis cysticus The cystic duct, about 4 centimeters long runs backward, downward, and to the left from the neck of the gallbladder and joins the hepatic duct to form the common bile duct The mucous membrane lining its interior is thrown into a series of crescentic folds from 5 to 12 in number similar to those found in the neck of the gallbladder They project into the duct in regular succession and are directed obliquely around the tube presenting much the appearance of a continuous spiral valve When the duct is distended the spaces between the folds are dilated as to give to its exterior a twisted appearance The common bile duct Ductis coladuchus The common bile duct is formed by the junction of the cystic and hepatic ducts It is about 7.5 centimeters long and of the diameter of a goosequill It descends along the right border of the lesser omentum behind the superior portion of the duodenum in front of the portal vein and to the right of the hepatic artery near the right border of the posterior surface of the head of the pancreas Here it is situated in front of the inferior vena cava and is occasionally completely embedded in the pancreatic substance At its termination it lies for a short distance along the right side of the terminal part of the pancreatic duct and passes with it obliquely between the mucous and muscular coats The two ducts unite and open by a common orifice upon the summit of the duodenal papilla on the medial side of the descending portion of the duodenum, a little below its middle and about 7 to 10 centimeters from the pylorus The short tube formed by the union of the two ducts is dilated into an ampula the ampula of Vader Structure The coats of the large biliary ducts are an external or fibrous and an internal or mucous The fibrous coat is composed of strong fibroareolar tissue with a certain amount of muscular tissue arranged for the most part in a circular manner around the duct The mucous coat is continuous with the lining membrane of the hepatic ducts and the gallbladder and also with that of the duodenum and, like the mucous membrane of these structures its epithelium is of columnar variety It is provided with numerous mucous glands which are lobulated and opened by minute orifices scattered irregularly in the larger ducts End of section 24 Section 25 of Grey's Anatomy Part 5 This is a LibriVox recording Well, LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Anatomy of the Human Body Part 5 by Henry Gray The pancreas The pancreas is a compound rassimus gland analogous in its structures to the salivary glands though softer and less compactly arranged than those organs Its secretion, the pancreatic juice carried by the pancreatic duct to the duodenum is an important digestive fluid In addition, the pancreas has an important internal secretion probably elaborated by the cells of Langerhans which is taken up by the bloodstream and is concerned with sugar metabolism It is long and irregularly prismatic in shape Its right extremity, being broad is called the head and is connected to the main portion of the organ or body by a slight constriction, the neck while its left extremity gradually tapers to form the tail It is situated transversely across the posterior wall of the abdomen at the back of the epigastric and left hypochondriac regions Its length varies from 12.5 to 15 cm and its weight from 60 to 100 g Relations The head, caput pancreatis is flattened from before backward and is lodged within the curve of the duodenum Its upper border is overlapped by the superior part of the duodenum and its lower overlaps the horizontal part Its right and left borders overlap in front and insinuate themselves behind the descending and ascending parts of the duodenum respectively The angle of junction of the lower and left lateral borders forms a prolongation termed the unsinate process In the groove between the duodenum and the right lateral and lower borders are the anastomocene superior and inferior pancreatico-duodenal arteries. The common bile duct descends behind close to the right border to its termination in the descending part of the duodenum Anterior surface The greater part of the right half of this surface is in contact with the transverse colon only areolar tissue intervening From its upper part the neck springs, its right limit being marked by a groove for the gastro-duodenal artery. The lower part of the right half below the transverse colon is covered by peritoneum continuous with the inferior layer of the transverse mesocolon and is in contact with the coils of the small intestine. The superior mesenteric artery passes down in front of the left half across the insinate process. The superior mesenteric vein runs upward on the right side of the artery and behind the neck joins with the laienal vein to form the portal vein Posterior surface Posterior surface is in relation with the inferior vena cava, the common bile duck, the renal veins, the right cruise of the diaphragm and the aorta. The neck springs from the right upper portion of the front of the head. It is about 2.5 centimeters long and is directed at first upward and forward and then upward and to the left to join the body. It is somewhat flattened from above downward and backward. Its antero superior surface supports the pylorus. Its posterior inferior surface is in relation with the commencement of the portal vein. On the right it is grooved by the gastro duodenal artery. The body, corpus pancreatis is somewhat prismatic in shape and has 3 surfaces anterior, posterior and inferior. The anterior surface, fascis anterior is somewhat concave and is directed forward and upward. It is covered by the posterior inferior surface of the stomach which rests upon it. The two organs being separated by the omental bursa. Where it joins the neck there is a well marked prominence the tuber omentale which abuts against the posterior surface of the lesser omentum. The posterior surface, fascis posterior is devoid of peritoneum and is in contact with the aorta, the laeno vein, the left kidney and its vessels, the left super renal gland, the origin of the superior mesenteric artery and the crura of the diaphragm. The inferior surface, fascis inferior is narrow on the right but broader on the left and is covered by the peritoneum. It lies upon the duodenal jejunal flexure and on some coils of the jejunum its left extremity rests on the left colic flexure. The superior border, margot superior is blunt and flat to the right narrow and sharp to the left near the tail. It commences on the right in the omental tuberosity and is in relation with the ciliac artery from which the hepatic artery courses to the right just above the gland while the laeno artery runs toward the left in a groove along this border. The anterior border, margot anterior separates the anterior from the inferior surface and along this border the two layers of the transverse mesocolon diverge from one another, one passing upward over the anterior surface, the other backward over the inferior surface. The inferior border, margot inferior separates the posterior from the inferior surface. The superior mesenteric vessels emerge under its right extremity. The tail, cota pancreates, is narrow. It extends to the left as far as the lower part of the gastric surface of the spleen, lying in the frinico-laena ligament and it is in contact with the left colic flexure. Birmingham described the body of the pancreas as projecting forward as a prominent ridge into the abdominal cavity and forming part of a shelf on which the stomach lies. The portion of the pancreas to the left of the middle line has a very considerable anterior-posterior thickness. As a result, the anterior surface is of considerable extent. It looks strongly upward and forms a large and important part of the shelf. As the pancreas extends to the left, toward the spleen, it crosses the upper part of the kidney and is so molded onto it that the top of the kidney forms an extension inward and backward of the upper surface of the pancreas and extends the bed in this direction. On the other hand, the extremity of the pancreas comes in contact with the spleen in such a way that the plane of its upper surface runs with little interruption upward and backward into the concave gastric surface of the spleen which completes the bed behind and to the left and running upward forms a partial cap for the wide end of the stomach. Footnote. Journal of Anatomy and Physiology Part 1, Volume 31, Page 102 The Pancreatic Duct. Ductus pancreaticus. Versungi. Duct of Versung. Extends transversely from left to right through the substance of the pancreas. It commences by the junction of the small ducts of the lobules situated in the tail of the pancreas and running from left to right through the body it receives the ducts of the various lobules composing the gland. Considerably augmented in size it reaches the neck and turning downward backward into the right it comes into relation with the common bile duct which lies to its right side. Leaving the head of the gland it passes very obliquely through the mucous and muscular coats of the duodenum and ends by an orifice common to it and the common bile duct upon the summit of the duodenal papilla situated at the medial side of the descending portion of the duodenum 7.5 to 10 centimeters below the pylorus. The pancreatic duct near the duodenum is about the size of an ordinary quill. Sometimes the pancreatic duct in the common bile duct opens separately into the duodenum. Frequently there is an additional duct which is given off from the pancreatic duct in the neck of the pancreas and opens into the duodenum about 2.5 centimeters above the duodenal papilla. It receives the ducts from the lower part of the head and is known as the accessory pancreatic duct duct of Santorini. Development. The pancreas is developed in two parts a dorsal and a ventral. The former arises as a diverticulum from the dorsal aspect of the duodenum a short distance above the hepatic diverticulum and growing upward and backward into the dorsal megagastrium forms a part of the head and unsinate process and the whole of the body and tail of the pancreas. The ventral part appears in the form of a diverticulum from the primitive bile duct and forms the remainder of the head and unsinate process of the pancreas. The duct of the dorsal part accessory pancreatic duct therefore opens independently into the duodenum while that of the ventral part pancreatic duct opens with the common bile duct. About the sixth week the two parts of the pancreas meet and fuse and a communication is established between their ducts. After this has occurred the terminal part of the accessory duct that is the part between the duodenum and the point of meeting of the two ducts undergoes little or no enlargement while the pancreatic duct increases in size and forms the main duct of the gland. The opening of the accessory duct into the duodenum is sometimes obliterated and even when it remains patent it is probable that the whole of the pancreatic secretion is conveyed to the pancreatic duct. At first the pancreas is directed upward and backward between the two layers of the dorsal mesogastrium which give to it a complete peritoneal investment and its surfaces look to the right and left. With the change in the position of the stomach the dorsal mesogastrium is drawn downward into the left and the right side of the pancreas is directed backward and the left forward. The right surface becomes applied to the posterior abdominal wall and the peritoneum which covered it undergoes absorption and thus in the adult the gland appears to lie behind the peritoneal cavity. Structure. In structure the pancreas resembles the salivary glands. It differs from them however in certain particulars and is looser and softer in its texture. It is not enclosed in a distinct capsule but is surrounded by areolar tissue which dips into its interior and connects together the various lobules of which it is composed. Each lobule like the lobules of the salivary glands consists of one of the ultimate ramifications of the main duct ending in a number of sequel pouches or alveoli which are tubular and somewhat convoluted. The minute ducts connected with alveoli are narrow and lined with flattened cells. The alveoli are almost completely filled with secreting cells so that scarcely any lumen is visible. In some animals spindle shaped cells occupy the center of the aviolus and are known as the centrosenar cells of Langerhans. These are prolongations of the terminal ducts. The true secreting cells which line the wall of the aviolus are very characteristic. They are columnar in shape and present two zones, an outer one clear and finely striated next to the basement membrane and an inner granular one next to the lumen. In hardened specimens the outer zone stains deeply with various dyes whereas the inner zone stains slightly. During activity the granular zone gradually diminishes in size and when exhausted is only seen as a small area next to the lumen. During the resting stages it gradually increases until it forms nearly three fourths of the cell. In some of the secreting cells of the pancreas is a spherical mass staining more easily than the rest of the cell. This is termed the paranucleus and is believed to be an extension from the nucleus. The connective tissue between the alveoli presents in certain parts collections of cells which are termed intra-alveolar cell islets, islands of Langerhans. The cells of these stain lightly with hematoxilin or carmine and are more or less polyhedral in shape forming a network in which ramify many capillaries. There are two main types of cells in the islets, distinguished A cells and B cells according to the special staining reactions of the granules they contain. The cell islets have been supposed to produce the internal secretion of the pancreas which is necessary for carbohydrate metabolism but numerous researchers have so far failed to elucidate their real function. The walls of the pancreatic duck are thin consisting of two coats an external fibrous and an internal mucus. The latter is smooth and furnished near its termination with a few scattered follicles. Vessels and nerves. The arteries of the pancreas are derived from the linole and the pancreaticoduodenal branches of the hepatic and superior mesenteric. Its veins open into the linole and superior mesenteric veins. Its synthetics are described in page 711. Its nerves are filaments from the linole plexus. End of section 25 Section 26 of Grace Anatomy part 5 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org Recording by Bianca Anatomy of the Human Body Part 5 by Henry Gray Development of urinary and generative organs Part 1 The Urogenital apparatus Aperatus urogenitalis Urogenital organs Urogenital organs The urogenital apparatus consists of A. The urinary organs for the secretion and discharge of the urine and B. The genital organs which are concerned with the process of reproduction A. Development of the urinary and generative organs The urinary and generative organs are developed from the intermediate cell mass which is situated between the primitive segments and the lateral plates of mesoderm. The permanent organs of the adult are preceded by a set of structures which are purely embryonic and which, with the exception of the duct disappear almost entirely before the end of fetal life. These embryonic structures are on either side the pronephros, the mesonephros, the metanephros and the wolfian and mullerian ducts. The pronephros disappears very early. The structural elements of the mesonephros mostly degenerate but in their place is developed the genital gland in association with which the wolfian duct remains as the duct of the male genital gland, the mullerian instead of the female. Some of the tubules of the metanephros form part of the permanent kidney. The pronephros and wolfian duct. In the outer part of the intermediate cell mass, immediately under the ectoderm, in the region from the 5th cervical to the 3rd thoracic segments, a series of short evaginations from each segment grows dorsal word and extends caudal word fusing successively from before backward to form the pronephric duct. This continues to grow caudal word until it opens into the ventral part of the cloaca. Beyond the pronephros it is termed the wolfian duct. The original evaginations form a series of transverse tubules each of which communicates by means of a funnel shaped ciliated opening with the salamic cavity and in the course of each duct a glomerulus also is developed. A secondary glomerulus is formed ventral to each of these and the complete group constitutes the pronephros. The pronephros undergoes rapid atrophy and disappears. The mesonephros, mullerian duct and genital gland. On the medial side of the wolfian duct, from the 6th cervical to the 3rd lumbar segment a series of tubules the wolfian tubules is developed. At a later stage in development they increase in number by outgrows from the original tubules. These tubules first appear as solid masses of cells which later become hollowed in the center. One end grows toward and finally opens into the wolfian duct. The other dilates and is invaginated by a tuft of capillary blood vessels to form a glomerulus. The tubules collectively constitute the mesonephros or wolfian body. By the 5th or 6th week this body forms an elongated spindle shaped structure termed the urogenital fold which projects into the salamic cavity at the side of the dorsal mesentery reaching from the septum transversum in front to the 5th lumbar segment behind. In this fold the reproductive glands are developed. The wolfian bodies persist and form the permanent kidneys in fissures and amphibians. But in reptiles, birds and mammals, they atrophy and for the most part disappear coincidentally with the development of the permanent kidneys. The atrophy begins during the 6th or 7th week and rapidly proceeds so that by the beginning of the 5th month only the ducts and a few of the tubules remain. In the male the wolfian duct persists and forms the tube of the epididymis, the duct is deference and the ejaculatory duct while the seminal vesicle arises during the 3rd month as a lateral derverticulum from its harder end. A large part of the head end of the mesonephros atrophies and disappears. Of the remainder the anterior tubules form the effluent duct of the testis. While the posterior tubules are represented by the ductular aberrantis and by the paradidymis which is sometimes found in front of the spermatic cord above the head of the epididymis. In the female the wolfian bodies and ducts atrophy. The remains of the wolfian tubules are represented by the aproothoron or organofrosinwheeler and the paraothoron two small collections of rudimentary blind tubules which are situated in the mesocellpings. The lower part of the wolfian duct disappears while the upper part persists as the longitudinal duct of the aproothoron or duct of Gertner. Food note Barry Hart has described the wolfian ducts as ending at the sight of the future hymen in bulbous enlargements which he has named the wolfian bulbs and states that the hymen is formed by these bulbs aided by a special evolution from below of the cells lining the urogenital sinus. He further believes that the lower third of the vagina is due to the coalescence of the upper portion of the urogenital sinus and the lower ends of the wolfian ducts and that the epithelial lining of the vagina is derived from the wolfian bulbs. He also regards the colliculus seminalis of the miliuritra as being formed from the lower part of the wolfian ducts and food note the mullerian ducts Shortly after the formation of the wolfian ducts a second pair of ducts is developed these are named the mullerian ducts. Each arises on the lateral aspect of the corresponding wolfian duct as a tubular invagination of the cells lining the selum. The orifice of the invagination remains patent and undergoes enlargement and modification to form the abdominal osteum of the uterine tube. The ducts pass backward lateral to the wolfian ducts but toward the posterior end of the embryo they cross to the medial side of these ducts and thus come to lie side by side between and behind the letter the four ducts forming what is termed the genital cord. The mullerian ducts end in an epithelial elevation the mullerian eminence on the ventral part of the cloaca between the orifices of the wolfian ducts. At a later date they open into the cloaca in this situation. In the male the mullerian ducts atrophy but traces of their interior ends are represented by the appendices testes high the tits of morgenyi while their terminal fused portions form the utriculus in the floor of the prosthetic portion of the urethra. In the female the mullerian ducts persist and undergo further development. The portions which lie in the genital cord fuse to form the uterus and vagina. The parts in front of this cord remain separate and each forms the corresponding uterine tube. The abdominal osteum of which is developed from the anterior extremity of the original tubular infatuation from the selum. The fusion of the mullerian ducts begins in the third month and the septum formed by their fused medial walls disappears from below upward and thus the cavities of the vagina and uterus are produced. About the fifth month an annular constriction marks the position of the neck of the uterus and after the sixth month the walls of the uterus begin to thicken. For a time the vagina is represented by a solid world of epithelial cells. A ring-like outgrowth of this epithelium occurs at the lower end of the uterus and marks the futile vaginal furnaces. About the fifth or sixth month the lumen of the vagina is produced by the breaking down of the central cells of the epithelium. The hymen represents the remains of the mullerian eminence. Genital clans The first appearance of the genital clans is essentially the same in the two sexes and consists in a thickening of the epithelial layer which lines the peritoneal cavity on the medial side of the urogenital fold. The thick plate of epithelium extends deeply pushing before it the mesoderm and forming a distinct projection. This is termed the genital ridge and from it the testis in the male and the ovary in the female are developed. At first the mesonephros and genital ridge are suspended by a common mesentery but as the embryo grows the genital ridge gradually becomes pinched off from the mesonephros with which it is at first continuous though it still remains connected to the remnant of this body by a fold of peritoneum the mesorcheum or mesovarium. About the seventh week the distinction of sex in the genital ridge begins to be perceptible. The ovary the ovary thus formed from the genital ridge is at first a mass of cells derived from the salamic epithelium. Later the mass is differentiated into a central part or medulla covered by a surface layer the germinal epithelium. Between the cells of the germinal epithelium a number of larger cells the primitive ova are formed and these are carried into the adjacent stroma by butt-like ingrowth genital cords of the germinal epithelium. The surface epithelium ultimately forms the permanent epithelial covering of this organ it soon loses its connection with the central mass and the tunica albutginia develops between them. The ova are chiefly derived from the cells of the central mass. These are separated from one another of connective tissue in an irregular manner. Each ovum assumes a covering of connective tissue follicle cells and in this way the rudiments of the ovarian follicles are formed. According to Beard the primitive ova are early set apart during the segmentation of the ovum and migrate into the germinal ridge. Waldai had thought that the primitive germ cells are derived from the germinal epithelium covering the genital ridge. Beard on the other hand maintains that in the skate they are not derived from this epithelium but are probably formed during the later stages of cell cleavage before there is any trace of an embryo and the similar view was advanced by Nusbaum as to their origin in amphibia. Beard says at the close of segmentation many of the future germ cells in the segmentation cavity just beneath the side of the future embryo and there is no doubt they subsequently wander into it. The germ cells after they enter the resting phase are sharply marked off from the cells of the embryo by entire absence of mitosis among them. They can be further recognized by their irregular form and amoebord processes and by the fact that our cytoplasm has no affinity for ordinary stains but assumes a brownish tinge when treated by osmic acid. The path along which they travel into the embryo is a very definite one namely from the yolk sac upward between the splenchnoplur and gut in the higher portion of the embryo. This pathway named by Beard the germinal path leads them directly to the position which they all finally to take up in the germinal ridge or nidus. A considerable number apparently never reach their proper destination since vagrant germ cells are found in all sorts of places but more particularly on the mesentery. Some of these may possibly find their way into the germinal ridge some probably undergo atrophy while others may persist and become the seed of dermar tumors. End of section 26 recorded by Bianca in Utrecht the Netherlands on February 2nd 2010 section 27 of Grace Anatomy part 5 This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recording by Bianca Anatomy of the human body part 5 by Henry Gray Development of urinary and generative organs Part 2 The Testis The Testis is developed in much the same way as the ovary Like the ovary in its earliest stages it consists of a central mass of epithelium covered by a surface epithelium In the central mass a series of cords appear and the periphery of the mass is converted into the tunica albutginea thus excluding the surface epithelium from any part in the formation of the tissue of the Testis The cords of the central mass run together toward the future highlands and form a network which ultimately becomes the witty Testis From the cords the seminiferous tubules are developed and between them connective tissue septa extends and the tubular tubules become connected with outgrowth from the wulfium body which, as before mentioned form the effron ducts of the Testis Descent of the Testis The Testis at an early period of fetal life are placed at the back part of the abdominal cavity behind the peritoneum and each is attached by a peritoneal fold the mesorcheum to the mesonephros the front of the mesonephros a fold of peritoneum termed the inguinal fold cross forward to meet and fuse with peritoneal fold the inguinal crest which grows backward from the entero-lateral abdominal wall The Testis does acquire an indirect connection with the anterior abdominal wall and at the same time a portion of the peritoneal cavity lateral to these fused folds is marked off as the future sacchus vaginalis In the inguinal crest a peculiar structure the gubernaculum Testis makes its appearance This is at first a slender band extending from that part of the skin of the groin which afterward forms the scrotum through the inguinal canal to the body and epididymis of the Testis As development advances the peritoneum and closing the gubernaculum two folds, one above the Testis and the other below it The one above the Testis is the pleica vascularis and contains ultimately the internal spermatic vessels The one below, the pleica gubernatrix contains the lower part of the gubernaculum which has now grown into a thick cord It ends below at the abdominal inguinal ring in a tube of peritoneum the sacchus vaginalis which protrudes itself down the inguinal canal By the fifth month the lower part of the gubernaculum has become a thick cord while the upper part has disappeared The lower part now consists of a central core of unstriped muscle fiber and outside this of a firm layer of striped elements connected behind the peritoneum with the abdominal wall As the scrotum develops the main portion of the lower end of the gubernaculum is carried with the skin to which it is attached to the bottom of this pouch Other bands are carried to the medial side of the thigh and to the perineum The tube of peritoneum constituting the sacchus vaginalis projects itself downward into the inguinal canal and emerges at the cutaneous inguinal ring pushing before it a part of the obliquus internus and the upper neurosis of the obliquus externus which form, respectively the cremastomuscle and the intercruel fessia It forms a gradually elongating pouch which eventually reaches the bottom of the scrotum and behind this pouch the testis is drawn by the growth of the body of the fetus For the gubernaculum does not grow commensurately with the growth of other parts and therefore the testis being attached by the gubernaculum to the bottom of the scrotum It is prevented from rising as the body grows and is drawn first into the inguinal canal and eventually into the scrotum It seems certain also that the gubernacular cord becomes shortened as development proceeds and this assists in causing the testis to reach the bottom of the scrotum By the end of the 8th month the testis has reached the scrotum preceded by the sacchus vaginalis which communicates by its upper extremity with the peritoneal cavity Just before birth the upper part of the sacchus vaginalis usually becomes closed and this obliteration extends gradually downward to within a short distance of the testis The process of peritoneum surrounding the testis is now entirely cut off from the general peritoneal cavity and constitutes the tunica vaginalis Descent of the ovaries In the female there is also a gubernaculum which affects a considerable change in the position of the ovary though not so extensive a change as in that of the testis The gubernaculum in the female lies in contact with the fundus of the uterus and contracts adhesions to this organ and thus the ovary is prevented from descending below this level The part of the gubernaculum between the ovary and the uterus becomes ultimately the proper ligament of the ovary while the part between the uterus and the labia mages forms the round ligament of the uterus A pouch of peritoneum analogous to the sacchus vaginalis in the male accompanies it along the inguinal canal It is called the canal of knuck In rare cases the gubernaculum may fail to contract adhesions to the uterus and then the ovary descends into the inguinal canal into the labia mages and under these circumstances its position resembles that of the testis The metanephros and the permanent kidney The rudiments of the permanent kidneys make their appearance about the end of the first or the beginning of the second month Each kidney has a two fold origin part arising from the metanephros and part as a darferticulum from the hind end of the wolfie induct close to where the letter opens into the cloaca The metanephros arises in the intermediate cell mass called all to the mesonephros which it resembles in structure The darferticulum from the wolfie induct grows dorsalward and forward along the posterior abdominal wall where its blind extremity expands and subsequently divides into several buds which form the rudiments of the pelvis and calices of the kidney By continued growth and subdivision it gives rise to the collecting tubules of the kidney The proximal portion of the darferticulum becomes the ureter The secretory tubules are developed from the metanephros which is molded over the growing end of the darferticulum from the wolfie induct The tubules of the metanephros unlike those of the pronephros and mesonephros do not open into the wolfie induct One end expands to form a glomerulus while the rest of the tubule rapidly elongates to form the convoluted and straight tubules the loops of Henley and the connecting tubules These last join and establish communications with the collecting tubules derived from the ultimate ramifications of the darferticulum from the wolfie induct The mesoderm around the tubules becomes condensed to form the connective tissue of the kidney The ureter opens at first into the hind end of the wolfie induct After the sixth week it separates from the wolfie induct and opens independently into the part of the cloaca which ultimately becomes the bladder The secretory tubules of the kidney become arranged into pyramidal masses or lobules and the lobulated condition of the kidneys exists for some time after birth while traces of it may be found even in the adult The kidney of the ox and many other animals remains lobulated throughout life The urinary bladder The bladder is formed partly from the entodermal cloaca and partly from the ends of the wolfie induct The alentuis takes no share in its formation After the separation of the rectum from the dorsal part of the cloaca the ventral part becomes subdivided into three portions One an anterior vesico urethral portion continues with the alentuis into this portion the wolfie inducts open Two an intermediate narrow channel the pelvic portion and three a posterior phallic portion closed externally by the urogenital membrane The second and third parts together constitute the urogenital sinus The vesico urethral portion absorbs the ends of the wolfie inducts and the associated ends of the renal darverticula and these give rise to the trigone of the bladder and part of the prosthetic urethra The remainder of the vesico urethral portion forms the body of the bladder and part of the prosthetic urethra Its apex is prolonged to the umbilicus as a narrow canal which later is obliterated and becomes the medial umbilical ligament urecus the prostate The prostate originally consists of two separate portions each of which arises as a series of darverticula buds from the epithelial lining of the urogenital sinus and vesico urethral part of the cloaca between the third and fourth months These buds become tubular and form the glandular substance of the two lobes which ultimately meet and fuse behind the urethra and also extend to its ventral aspect The isthmus, or middle lobe is formed as an extension of the lateral lobes between the common ejaculatory ducts and the bladder Skinny's ducts in the female urethra are regarded as the homologs of the prosthetic glands The bulbo urethral glands of cowper in the male and greater vestibular glands of bartholin in the female also arise as darverticula from the epithelial lining of the urogenital sinus The external organs of generation As already stated the cloacal membrane composed of ectoderm and entoderm originally reaches from the umbilicus to the tail The mesoderm extends to the ventral line for some distance behind the umbilicus and forms the lower part of the abdominal wall It ends below in a prominent swelling the cloacal tubercle Behind this tubercle the urogenital part of the cloacal membrane separates the ingrowing sheets of mesoderm The first rudiment of the penis, or clitoris is a structure term the phallus It is derived from the phallic portion of the cloaca which is extended on to the end and sides of the under surface of the cloacal tubercle The terminal part of the phallus representing the future glands becomes solid The remaner, which is hollow is converted into a longitudinal groove by the adsorption of the urogenital membrane In the female a deep groove forms around the phallus and separates it from the rest of the cloacal tubercle which is now termed the genital tubercle The sides of the genital tubercle grow backward as the genital swellings which ultimately form the labia majora The tubercle itself becomes the mons pubis The labia minora arise by the continued growth of the lips of the groove on the under surface of the phallus The remainder of the phallus forms the clitoris In the male the early changes are similar but the pelvic portion of the cloaca undergoes much greater development pushing before it the phallic portion The genital swellings extend around between the pelvic portion and the anus and forms a scrotal area During the changes associated with the descent of the testis this area is drawn out to form the scrotal sex The penis is developed from the phallus As in the female the urogenital membrane undergoes adsorption forming a channel on the under surface of the phallus This channel extends only as far forward as the corona glandis The corpora cavernosa of the penis or clitoris and of the urethra arise from the mesodermal tissue in the phallus They are at first dense structures but later vascular spaces appear in them and they gradually become cavernous The prepuse in both sexes is formed by the growth of a solid plate of actoderm into the superficial part of the phallus On coronal section this plate presents the shape of a horseshoe By the breaking down of its more centrally situated cells the plate is split into two lamellae and the cutaneous fold the prepuse is liberated and forms a hood over the glands Adherent prepuse is not an adhesion really but a hindered central discrimination very hard the urethra As already described in both sexes the phallic portion of the cloaca extends on to the under surface of the cloacal tubercle as far forward as the apex At the apex the walls of the phallic portion come together and fuse the lumen is obliterated and the solid plate the urethral plate is formed the phallic portion is for a time tubular and then by the absorption of the urogenital membrane it establishes a communication with the exterior this opening is the primitive urogenital osteum and it extends forward to the corona glandis in the female this condition is largely retained the portion of the groove on the clitoris broadens out while the body of the clitoris enlarges the adult urethral opening is situated behind the base of the clitoris in the male by the greater growth of the pelvic portion of the cloaca a longer urethra is formed and the primitive osteum is carried forward with the phallus but it still ends at the corona glandis later it closes from behind forward meanwhile the urethral plate of the glands breaks down centrally to form a medium groove continues with the primitive osteum this groove also closes from behind forward so that the external urethral opening is shifted forward to the end of the glands end of section 27 recorded by Bianca in Utrecht the Netherlands on March 1st 2010 section 28 of Grey's Anatomy part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org anatomy of the human body part 5 by Henry Grey the kidneys part 1 the urinary organs the urinary organs comprise the kidneys which secrete the urine the ureters or ducts which convey urine to the urinary bladder where it is for a time retained and the urethra through which it is discharged from the body the kidneys are situated in the posterior part of the abdomen one on either side of the vertebral column behind the peritoneum and surrounded by a mass of fat and loose areolar tissue their upper extremities are on a level with the upper border of the 12th thoracic vertebra their lower extremities on a level with the third lumbar the right kidney is usually slightly lower probably on account of the vicinity of the liver the long axis of each kidney is directed downward and lateral the transverse axis backward and lateral each kidney is about 11.25 cm in length 5 to 7.5 cm in breadth and rather more than 2.5 cm in thickness the left is somewhat longer and narrower than the right the weight of the kidney in the adult male varies from 125 to 170 g in the adult female from 115 to 155 g the combined weight of the two kidneys in proportion to that of the body is about 1 to 240 the kidney has a characteristic form and presents for examination two surfaces, two borders and an upper and lower extremity relations the anterior surface faces interior of each kidney is convex and looks forward and lateral word its relations to adjacent viscera differ so completely on the two sides that separate descriptions are necessary anterior surface of right kidney a narrow portion at the upper extremity is in relation with the right super renal gland a large area just below this and involving about 3 fourths of the surface lies in the renal impression on the inferior surface of the liver and a narrow but somewhat variable area near the medial border is in contact with the descending part of the duodenum the lower part of the anterior surface is in contact laterally with the right colic flexure and medially as a rule with the small intestine the areas in relation with the liver and small intestine are covered by peritoneum the super renal, duodenal and colic areas are the void of peritoneum anterior surface of the left kidney a small area along the upper part of the medial border is in relation with the left super renal gland and close to the lateral border is a long strip in contact with the renal impression on the spleen a somewhat quadrilateral field about the middle of the anterior surface marks the site of contact with the body of the pancreas on the deep surface of which are the laienal vessels above this is a small triangular portion between the super renal and spleenic areas in contact with the posterior surface of the stomach below the pancreatic area is in relation with the left colic flexure the medial with the small intestine the areas in contact with the stomach and spleen are covered by the peritoneum of the omental bursa while that in relation to the small intestine is covered by the peritoneum of the general cavity behind the latter are some branches of the left colic vessels the super renal, pancreatic and colic areas are the void of peritoneum the posterior surface facies posterior the posterior surface of each kidney is directed backward and medial it is embedded in an areolar and fatty tissue an entirely devoid of peritoneal covering it lies upon the diaphragm the medial and lateral lumbocostal arches the psoas major the quadratus lumborum and the tendon of the transversus abdominis the subcostal and one or two of the upper lumbar arteries and the last thoracic iliohypogastric the right kidney rests upon the 12th rib the left usually on the 11th and 12th the diaphragm separates the kidney from the pleura which dips down to form the phrenicocostal sinus but frequently the muscular fibers of the diaphragm are defective or absent over a triangular area immediately above the lateral lumbocostal arch and when this is the case the perinephric areolar tissue is in contact with the diaphragmatic pleura borders the lateral border margolateralis external border is convex and is directed toward the posterior lateral wall of the abdomen on the left side it is in contact at its upper part with the spleen the medial border margomedialis internal border is concave in the center and convex toward either extremity it is directed forward and a little downward its central part presents a deep longitudinal fissure bounded by prominent overhanging anterior and posterior lips this fissure is named the hylum and transmits the vessels, nerves and ureter above the hylum the medial border is in relation with the supra renal gland below the hylum with the ureter extremities the superior extremity extremitis superior is thick and rounded and is nearer the median line than the lower it is surmounted by the supra renal gland which covers also a small portion of the inferior surface the inferior extremity extremitis inferior is smaller and thinner than the superior and farther from the median line it extends to within 5 cm of the iliac crest the relative position of the main structures in the hylum is as follows the vein is in front the artery in the middle and the ureter behind and directed downward frequently however branches of both artery and vein are placed behind the ureter fixation of the kidney the kidney and its vessels are embedded in a mass of fatty tissue termed the adipose capsule which is thickest at the margins of the kidney and is prolonged through the hylum into the renal sinus the kidney and the adipose capsule are enclosed in a sheath of fibrous tissue continuous with the subperitoneal fascia and named the renal fascia at the lateral border of the kidney the renal fascia splits into an anterior and a posterior layer the anterior layer is carried medial word in front of the kidney and its vessels and is continuous over the aorta with the corresponding layer of the opposite side the posterior layer extends medial word behind the kidney and blends with the fascia on the quadratus lumborum and psoas major and through this fascia is attached to the vertebral column above the super renal gland the two layers of the renal fascia fuse and unite with the fascia of the diaphragm below they remain separate and are gradually lost in the subperitoneal fascia of the iliac fossa the renal fascia is connected to the fibrous tunic of the kidney by numerous trabicule which traverse the adipose capsule and are strongest near the lower end of the organ behind the fascia renalis is a considerable quantity of fat which constitutes the para nephric body the kidney is held in position partly through the attachment of the renal fascia and partly by the apposition of the neighboring viscera general structure of the kidney the kidney is invested by a fibrous tunic which forms a firm smooth covering to the organ the tunic can easily be stripped off but in doing so numerous fine processes of connective tissue and small blood vessels are torn through beneath this coat a thin wide mesh network of unstriped muscular fiber forms an incomplete covering to the organ when the capsule is stripped off the surface of the kidney is found to be smooth and even and of a deep red color in infants fissures extending for some depth may be seen on the surface of the organ a remnant of the lobular construction of the gland the kidney is dense in texture but is easily lacerable by mechanical force if a vertical section of the kidney be made from its convex to its concave border it will be seen that the hylum expands into a central cavity the renal sinus this contains the upper part of the renal pelvis and the calluses surrounded by some fat in which are embedded the branches of the renal vessels and nerves the renal sinus is lined by a prolongation of the fibrous tunic which is continued around the lips of the hylum the renal calluses from 7 to 13 in number are cup shaped tubes each of which embraces one or more of the renal papillae they unite to form two or three short tubes and these in turn are joined to form a funnel shaped sac the renal pelvis the renal pelvis, wide above and narrow below where it joins the ureter is partly outside the renal sinus the renal calluses and pelvis form the upper expanded end of the excretory duct of the kidney the kidney is composed of an internal medullary and an external cortical substance the medullary substance, substantial medularis consists of a series of red colored striated conical masses termed the renal pyramids the basis of which are directed toward the circumference of the kidney while their apices converge toward the renal sinus where they form prominent papillae projecting into the interior of the calluses the cortical substance substantial corticalis is reddish brown in color and soft and granular in consistence it lies immediately beneath the fibrous tunic arches over the basis of the pyramids and dips in between adjacent pyramids toward the renal sinus the parts dipping in between the pyramids are named the renal columns, pertini while the portions which connect the renal columns to each other and intervene between the basis of the pyramids and the fibrous tunic are called the cortical arches if the cortex be examined with a lens it will be seen to consist of a series of lighter colored conical areas termed the radiate part and a darker colored intervening substance which from the complexity of its structure are named the convoluted part the rays gradually taper toward the circumference of the kidney and consist of a series of outward prolongations from the base of each renal pyramid end of section 28 section 29 of gray's anatomy part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org anatomy of the human body part 5 by Henry Gray the kidneys part 2 minut anatomy the renal tubules of which the kidney is for the most part made up commence in the cortical substance and after pursuing a very circuitous course through the cortical and medullary substances finally end up at the apices of the renal pyramids by open mouths so that the fluid which they contain is emptied through the calluses into the pelvis of the kidney if the surface of one of the papillae be examined with a lens it will be seen to be studded over with minute openings the orifices of the renal tubules from 16 to 20 in number and if pressure be made on a fresh kidney urine will be seen to exude from these orifices the tubules commence in the convoluted part and renal columns as the renal corpuscles which are small rounded masses of a deep red color varying in size of an average of about 0.2 millimeters in diameter each of these little bodies is composed of two parts a central glomerulus of vessels and a membranous envelope the glomerular capsule capsule of Bowman which is the small pouch-like commencement of a renal tubule the glomerulus is a lobulated network of convoluted capillary blood vessels held together by scanty connective tissue this capillary network is derived from a small arterial twig the afferent vessel which enters the capsule generally at a point opposite to that at which the latter is connected with the tubule and the resulting vein the afferent vessel emerges from the capsule at the same point the afferent vessel is usually the larger of the two the glomerular or Bowman's capsule which surrounds the glomerulus consists of a basement membrane lined on its inner surface and epithelial cells which are reflected from the lining membrane onto the glomerulus at the point of entrance or exit of the afferent and afferent vessels the whole surface of the glomerulus is covered with a continuous layer of the same cells on a delicate supporting membrane thus between the glomerulus and the capsule a space is left forming a cavity lined by a continuous layer of squamous cells this cavity varies in size according to the state of secretion and the amount of fluid present in it in the fetus and young subject the lining epithelial cells are polyhedral or even columnar the renal tubules commencing in the renal corpuscles present during their course many changes in shape and direction and are contained partly in the medullary and partly in the cortical substance at their junction with the glomerular capsule they exhibit a somewhat constricted portion which is termed the neck beyond this the tubule becomes convoluted and pursues a considerable course in the cortical substance constituting the proximal convoluted tube after a time the convolutions disappear and the tube approaches the medullary substance in a more or less spiral manner this section of the tubule has been called the spiral tube throughout this portion of their course the renal tubules are contained entirely in the cortical substance and present a fairly uniform caliber they now enter the medullary substance suddenly become much smaller quite straight in direction and dip down for a variable depth into the pyramids constituting the descending limb of henley's loop bending on themselves they form what is termed the loop of henley and re-ascending they become suddenly enlarged forming the ascending limb of henley's loop and re-enter the cortical substance this portion of the tubule ascends for a short distance when it again becomes dilated irregular and angular this section is termed the zigzag tubule it ends in a convoluted tube which resembles the proximal convoluted tubule and is called the distal convoluted tubule this again terminates in a narrow junctional tube which enters the straight or collecting tube the straight or collecting tubes commence in the radiate part of the cortex where they receive the curved ends of the distal convoluted tubules they unite at short intervals with one another the resulting tubes presenting a considerable increase in caliber so that a series of comparatively large tubes passes from the bases of the rays into the renal pyramids in the medulla the tubes of each pyramid converge to join a central tube duct of bulini which finally opens on the summit of one of the papuli the contents of the tube are therefore discharged into one of the calluses structure of the renal tubules the renal tubules consist of a basement membrane lined with epithelium the epithelium varies considerably in different sections of the tubule in the neck the epithelium is continuous with that lining the glomerular capsule and like it consists of flattened cells each containing an oval nucleus the two convoluted tubules the spiral and zigzag tubules and the ascending limb of henley's loop are lined by a type of epithelium which is histologically the same in all the cells are somewhat columnar in shape and dovetail into one another of their lateral aspect each has a striated border near the lumen of the tube its inner part is granular and its outer portion vertically striated the nucleus is spherical and situated about the center of the cell in the descending limb of henley's loop the epithelium resembles that found in the glomerular capsule and the commencement of the tube consisting of flat clear epithelial plates each with an oval nucleus the nuclei alternate on opposite sides of the tubule so that the lumen remains fairly constant in the straight tube the epithelium is clear and cubical in its papillary portion the cells are distinctly columnar and transparent the renal blood vessels the kidney is plentifully supplied with blood by the renal artery a large branch of the abdominal aorta before it enters the kidney each artery divides into four or five branches which at the hylum lie mainly between the renal vein and ureter the vein being in front the ureter behind one branch usually lies behind the ureter each vessel gives off some small branches to the super renal glands to the ureter and to the surrounding cellular tissue and muscles frequently a second renal artery termed the inferior renal is given off from the abdominal aorta at a lower level and supplies the lower portion of the kidney while occasionally an additional artery enters the upper part of the kidney the branches of the renal artery while in the sinus give off a few twigs for the nutrition of the surrounding tissues and end in the arteriae propriae renalis which enter the kidney proper in the renal columns the arteries pass to each renal pyramid and run along its sides for its entire length giving off in their course the afferent vessels of the renal corpuscles in the renal columns having arrived at the bases of the pyramids they form arterial arches or arcades which lie in the boundary zone between the bases of the pyramids and the cortical arches and break up into two distinct sets of branches devoted to the supply of the remaining portions of the kidney the first set the inter lobular arteries are given off at right angles from the side of the arterial arcade looking toward the cortical substance and pass directly outward between the medullary rays to reach the fibrous tunic where they end in the capillary network of this part these vessels do not anastomose with each other but form what are called end arteries in their outward course they give off lateral branches these are the afferent vessels they enter the capsule and end in the glomerulus from each tuft the corresponding afferent vessel arises and having made its egress from the capsule near to the point where the afferent vessel enters breaks up into a number of branches which form a dense plexus around the adjacent urinary tubes the second set of branches from the arterial arcades supply the renal pyramids which they enter at their bases and passing straight through their substance terminate in the venous plexuses found in that situation they are called the arterii rectii the afferent vessels from the glomeruli nearest the medulla break up into leashes of straight vessels false arterii rectii which pass down into the medulla and join the plexus of vessels there the renal veins arise from three sources namely the veins beneath the fibrous tunic the plexuses around the convoluted tubules in the cortex and the plexuses situated at the apices of the renal pyramids the veins beneath the fibrous tunic veni stilati are stelae in arrangement and are derived from the capillary network into which the terminal branches of the interlabular arteries break up these join to form the interlabular veins which pass inward between the rays receive branches from the plexuses around the convoluted tubules and having arrived at the bases of the pyramids, joined with the veni rectii next to be described the veni rectii are branches from the plexuses at the apices of the medullary pyramids formed by the terminations of the arterii rectii they run outward in a straight course between the tubes of the medullary substance and joining as above stated the interlabular veins form venus arcades these in turn unite and form veins which pass along the sides of the pyramids these vessels veni propii renales accompany the arteries of the same name running along the entire length of the sides of the pyramids and quit the kidney substance to enter the sinus in this cavity they join the corresponding veins from the other pyramids to form the renal vein which emerges from the kidney at the hylum and opens into the inferior vena cava the left vein is longer than the right and crosses in front of the abdominal aorta the lymphatics of the kidney are described on page 712 nerves of the kidney the nerves of the kidney although small are about 15 in number they have small ganglia developed upon them and are derived from the renal plexus which is formed by branches from the celiac plexus the lower and outer part of the celiac ganglion and aortic plexus and from the lesser and lowest planknic nerves they communicate with the spermatic plexus a circumstance which may explain the occurrence of pain in the testes in affections of the kidney they accompany the renal artery in its branches and are distributed to the blood vessels and to the cells of the urinary tubules connective tissue intertubular stroma although the tubules and vessels are closely packed a small amount of connective tissue continuous with the fibers tunic binds them firmly together and supports the blood vessels lymphatics and nerves variations malformations of the kidney are not uncommon there may be an entire absence of one kidney but according to maris the number of these cases is excessively small or there may be congenital atrophy of one kidney when the kidney is very small but usually healthy in structure these cases are of great importance and must be duly taken into account when nephrectomy is contemplated a more common malformation is where the two kidneys are fused together they may be joined together only at their lower ends by means of a thick mass of renal tissue so as to form a horseshoe shaped body or they may be completely united forming a disc-like kidney from which two ureters descend into the bladder these fused kidneys are generally situated in the middle line of the abdomen but may be displaced as well in some mammals for example ox and bear the kidney consists of a number of distinct lobules this lobulated condition is characteristic of the kidney of the human fetus and traces of it may persist in the adult sometimes the pelvis is duplicated while a double ureter is not uncommon in some rare instances a third kidney may be present one or both kidneys may be misplaced as a congenital condition and remain fixed in this abnormal position they are then very often misshapen they may be situated higher though this is very uncommon or lower than normal or removed farther from the vertebral column than usual or they may be displaced into the iliac fossa over the sacroiliac joint onto the promontory of the sacrum or into the pelvis between the rectum and bladder or by the side of the uterus in these latter cases they may give rise to very serious trouble the kidney may also be misplaced as a congenital condition it may not be fixed it is then known as a floating kidney it is believed to be due to the fact that the kidney is completely enveloped by peritoneum which then passes backward into the vertebral column as a double layer forming a mesonephron which permits movement the kidney may also be misplaced as an acquired condition in these cases the kidney is mobile in the tissues by which it is surrounded moving with the capsule in the perinephric tissues the congenital condition is known as movable kidney and is more common in the female than in the male it occurs in badly nourished people or in those who have become emaciated from any cause it must not be confounded with the floating kidney which is a congenital condition due to the development of a mesonephron the two conditions cannot however be distinguished until the abdomen is opened or the kidney explored from the loin end of section 29 section 30 of Grey's Anatomy Part 5 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Recording by Leanne Howlett Anatomy of the Human Body Part 5 by Henry Gray The Eurichers 3B2 The Eurichers The Eurichers are the two tubes which convey the urine from the kidneys to the urinary bladder each commences within the sinus of the corresponding kidney as a number of short cup shaped tubes termed calyces which encircle the renal papillae since a single calyx may enclose more than one papilla the calyces are generally fewer number than the pyramids the former varying from 7 to 13 the latter from 8 to 18 the calyces join to form two or three short tubes and these unite to form a funnel shaped dilatation wide above and narrow below named the renal pelvis which is situated partly inside and partly outside the renal sinus it is usually placed on a level with the spinous process of the first lumbar vertebra The Eurichers measures from 25 to 30 cm in length and is a thick walled narrow cylindrical tube which is directly continuous near the lower end of the kidney with the tapering extremity of the renal pelvis it runs downward and medial word in front of the psoas major and entering the pelvic cavity finally opens into the fundus of the bladder the abdominal part parse abdominalis lies behind the peritoneum on the medial part of the psoas major and is crossed obliquely by the internal spermatic vessels it enters the pelvic cavity by crossing either the termination of the common or the commencement of the external iliac vessels at its origin the right ureter is usually covered by the descending part of the duodenum and in its course downward lies to the right of the inferior vena cava and is crossed by the right colic and iliocolic vessels while near the superior aperture of the pelvis it passes behind the lower part of the mesentary and the terminal part of the ilium the left ureter is crossed by the left colic vessels the superior aperture of the pelvis passes behind the sigmoid colon and its mesentary the pelvic part parse pulvina runs at first downward on the lateral wall of the pelvic cavity along the anterior border of the greater sciatic notch and under cover of the peritoneum it lies in front of the hypogastric artery medial to the obturator nerve and the umbilical obturator inferior vesicle and middle hemorrhoidal arteries opposite the lower part of the greater sciatic for raiment it inclines medial word and reaches the lateral angle of the bladder where it is situated in front of the upper end of the seminal vesicle and at a distance of about 5 cm from the opposite ureter here the ductus deference crosses to its medial side and the vesicle veins surround it finally the ureter is run obliquely for about 2 cm through the wall of the bladder and open by slit-like apertures into the cavity of the viscous at the lateral angles of the trigone when the bladder is distended the openings of the ureters are about 5 cm apart but when it is empty and contracted the distance between them is diminished by one half owing to their oblique course through the coats of the bladder the upper and lower walls of the terminal portions of the ureters become closely applied to each other when the viscous is descended and, acting as valves prevent regurgitation of urine from the bladder in the female the ureter forms as it lies in relation to the wall of the pelvis the posterior boundary of a shallow depression named the ovarian fossa in which the ovary is situated it then runs medial word and forward on the lateral aspect of the cervix uteri and upper part of the vagina to reach the fundus of the bladder in this part of its course it is accompanied for about 2.5 cm by the uterine artery which then crosses in front of the ureter and ascends between the two layers of the broad ligament the ureter is distant about 2 cm from the side of the cervix of the uterus the ureter is sometimes duplicated on one or both sides and the two tubes may remain distinct as far as the fundus of the bladder on rare occasions they open separately into the bladder cavity structure the ureter is composed of three coats fibrous, muscular and mucous coats the fibrous coat tunica adventitia is continuous at one end with the fibrous tunica of the kidney on the floor of the sinus while at the other it is lost in the fibrous structure of the bladder in the renal pelvis the muscular coat tunica muscularis consists of two layers longitudinal and circular the longitudinal fibers become lost upon the sides at the extremities of the calluses the circular fibers may be traced surrounding the medullary substance in the same situation in the ureter proper the muscular fibers are very distinct and are arranged in three layers an external longitudinal a middle circular and an internal less distinct than the other two but having a general longitudinal direction according to colica this internal layer is found only in the neighborhood of the bladder the mucous coat tunica mucosa is smooth and presents a few longitudinal folds which become afaced by distention it is continuous with the mucous membrane of the bladder below while it is prolonged over the papillae of the kidney above its epithelium is of a transitional character and resembles that found in the bladder it consists of several layers of cells of which the innermost that is to say the cells in contact with the urine are somewhat flattened with concavities on their deep surfaces and to which the rounded ends of the cells of the second layer fit these the intermediate cells more or less resemble columnar epithelium and are pear shaped with rounded internal extremities which fit into the concavities of the cells of the first layer and narrow external extremities which are wedged in between the cells of the third layer the external or third layer consists of conical or oval cells varying in number in different parts and presenting processes which extend down into the basement membrane beneath the epithelium and separating it from the muscular coats is a dense layer of fibrous tissue containing many elastic fibers vessels and nerves the arteries supplying the ureter are branches from the renal internal spermatic hypogastric and inferior vesicle the nerves are derived from the inferior mesenteric, spermatic, and pelvic plexuses variations the upper portion of the ureter is sometimes double more rarely it is double the greater part of its extent or even completely so in such cases there are two openings into the bladder asymmetry in these variations is common End of Section 30 Recording by Leanne Howlett Recording by Corey Samuel Anatomy of the Human Body Part 5 by Henry Gray The urinary bladder is a muscular membranous sac which acts as a reservoir for the urine and as its size, position, and relations vary according to the amount of fluid it contains it is necessary to study it as it appears a. when empty and b. when distended in both conditions the position of the bladder varies with the condition of the rectum being pushed upward and forward when the rectum is distended the empty bladder when hardened in situ the empty bladder has the form of a flattened tetrahedron with its vertex tilted forward it presents a fundus, a vertex a superior and an inferior surface the fundus is triangular in shape and is directed downward and backward toward the rectum from which it is separated by the recto-visical fascia the vesicule seminales and the terminal portions of the ductus deferentes the vertex is directed forward toward the upper part of the symphysis pubis and from it the middle umbilical ligament is continued upward on the back of the anterior abdominal wall to the umbilicus the peritoneum is carried by it from the vertex of the bladder on to the abdominal wall to form the middle umbilical fold the superior surface is triangular bounded on either side by a lateral border which separates it from the inferior surface and behind by a posterior border represented by a line joining the two ureters which intervenes between it and the fundus the lateral borders extend from the ureters to the vertex and from them the peritoneum is carried to the walls of the pelvis on either side of the bladder the peritoneum shows a depression named the paravisical fascia the superior surface is directed upward is covered by peritoneum and is in relation with the sigmoid colon and some of the coils of the small intestine when the bladder is empty and firmly contracted the surface is convex and the lateral and posterior borders are rounded whereas if the bladder be relaxed it is concave and the interior of the viscous as seen in a median sagittal section presents the appearance of a V-shaped slit with a shorter posterior and a longer anterior limb the apex of the V corresponding with the internal orifice of the urethera the inferior surface is directed downward and is uncovered by peritoneum it may be divided into a posterior or prostatic area and two infrolateral surfaces the prostatic area is somewhat triangular it rests upon and is in direct continuity with the base of the prostate and from it the urethera emerges the infrolateral portions of the inferior surface are directed downward and lateralward in front they are separated from the symphysis pubis by a mass of fatty tissue which is named the retropubic pad behind they are in contact with the fascia which covers the levatoris ani and obturatoris interni when the bladder is empty it is placed entirely within the pelvis below the level of the obliterated hypergastric arteries and below the level of those portions of the ductus deferentes which are in contact with the lateral wall of the pelvis after they cross the ureters the ductus deferentes come into contact with the fundus of the bladder as the viscous fills its fundus, being more or less fixed is only slightly depressed while its superior surface gradually rises into the abdominal cavity carrying with it its peritoneal covering and at the same time rounding off the posterior and lateral borders the distended bladder when the bladder is moderately full it contains about 0.5 litres and assumes an oval form the long diameter of the oval measures about 12 cm and is directed upward and forward in this condition it presents a posterior superior and antero inferior and two lateral surfaces a fundus and a summit the posterior superior surface is directed upward and backward and is covered by peritoneum behind it is separated from the rectum by the recto-visical excavation while its anterior part is in contact with the coils of the small intestine the antero inferior surface is devoid of peritoneum and rests below against the pubic bones above which it is in contact with the back of the anterior abdominal wall the lower parts of the lateral surfaces are destitute of peritoneum in contact with the lateral walls of the pelvis the line of peritoneal reflection from the lateral surface is raised to the level of the obliterated hypergastric artery the fundus undergoes little alteration in position being only slightly lowered it exhibits however a narrow triangular area which is separated from the rectum merely by the recto-visical fascia this area is bounded below by the prostate above by the recto-visical fold of peritoneum and laterally by the ductus deferentes the ductus deferentes frequently come into contact with each other above the prostate and under such circumstances the lower part of the triangular area is obliterated the line of reflection of the peritoneum from the rectum to the bladder appears to undergo little or no change when the later is distended it is situated about 10 cm the summit is directed upward and forward above the point of attachment of the middle umbilical ligament and hence the peritoneum which follows the ligament forms a pouch of varying depth between the summit of the bladder and the anterior abdominal wall the bladder in the child in the newborn child the internal urethral orifice is at the level of the upper border of the symphysis pubis the bladder therefore lies relatively at a much higher level in the infant than in the adult its anterior surface is in contact with about the lower two thirds of that part of the abdominal wall which lies between the symphysis pubis and the umbilicus Simington its fundus is clothed with peritoneum as far as the level of the internal orifice of the urethra although the bladder of the infant is described as an abdominal organ Simington has pointed out that only about one half of it lies above the plane of the superior aperture of the pelvis dis-maintains that the internal urethral orifice sinks rapidly during the first years and then more slowly until the ninth year after which it remains stationary until puberty when it again slowly descends and reaches its adult position the female bladder in the female the bladder is in relation behind with the uterus and the upper part of the vagina it is separated from the anterior surface of the body of the uterus by the vesicutrine excavation but below the level of this excavation it is connected to the front of the cervix uteri and the upper part of the anterior wall of the vagina by areola tissue when the bladder is empty the uterus rests upon its superior surface the female bladder is said by some to be more capacious than that of the male but probably the opposite is the case ligaments the bladder is connected to the pelvic wall by the fascia endopelvena in front this fascial attachment is strengthened by a few muscular fibres the pubovisicales which extend from the back of the pubic bones to the front of the bladder behind other muscular fibres run from the fundus of the bladder to the sides of the rectum in the sacrogenital folds and constitute the rectovisicales the vertex of the bladder is joined to the umbilicus by the remains of the urachus which forms the middle umbilical ligament a fibromuscular cord broad at its attachment to the bladder but narrowing as it ascends from the superior surface of the bladder the peritoneum is carried off in a series of folds which are sometimes termed the false ligaments of the bladder anteriorly there are three folds the middle umbilical fold on the middle umbilical ligament and two lateral umbilical folds on the obliterated hypergastric arteries the reflections of the peritoneum onto the side walls of the pelvis form the lateral false ligaments while the sacrogenital folds constitute posterior false ligaments interior of the bladder the mucous membrane lining the bladder is, over the greater part of the viscous loosely attached to the muscular coat and appears wrinkled or folded when the bladder is contracted in the distended condition of the bladder the folds are effaced over a small triangular area termed the trigonum visicii immediately above and behind the internal orifice of the urethra the mucous membrane is firmly bound to the muscular coat and is always smooth the anterior angle of the trigonum visicii is formed by the internal orifice of the urethra its postural lateral angles by the orifices of the urethras stretching behind the bladder openings is a slightly curved ridge the torus uretericus forming the base of the trigon and produced by an underlying bundle of non-striped muscular fibres the lateral parts of this ridge extend beyond the openings of the urethras and are named the pleaky uretericii they are produced by the terminal portions of the urethras as they traverse obliquely the bladder wall when the bladder is illuminated the torus uretericus appears as a pale band and forms an important guide during the operation of introducing a catheter into the ureter the orifices of the ureters are placed at the postural lateral angles of the trigonum visicii and are usually slit like in form in the contracted bladder they are about 2.5 cm apart and about the same distance from the internal urethral orifice in the distended viscous these measurements may be increased to about 5 cm the internal urethral orifice is placed at the apex of the trigonum visicii in the most dependent part of the bladder and is usually somewhat crescentic in form the mucus membrane immediately behind it presents a slight elevation the uveular visicii caused by the middle lobe of the prostate structure the bladder is composed of the four coats serous, muscular, submucous and mucus coats the serous coat tunica cirrhosa is a partial one and is derived from the peritoneum it invests the superior surface and the upper parts of the lateral surfaces and is reflected from these onto the abdominal and pelvic walls the muscular coat tunica muscularis consists of three layers of unstriped muscular fibres an external layer composed of fibres having for the most part a longitudinal arrangement a middle layer in which the fibres are arranged more or less in a circular manner and an internal layer in which the fibres have a general longitudinal arrangement the fibres of the external layer arise from the posterior surface of the body of the pubis in both sexes musculi pubivisicalis and in the male from the adjacent part of the prostate and its capsule they pass in a more or less longitudinal manner up the inferior surface of the bladder over its vertex and then descend along its fundus to become attached to the prostate in the male and to the front of the vagina in the female at the sides of the bladder the fibres are arranged obliquely and intersect one another this layer has been named the detrusa urini muscle the fibres of the middle circular layer are very thinly and irregularly scattered on the body of the organ and although to some extent placed transversely to the long axis of the bladder are for the most part arranged obliquely toward the lower part of the bladder around the internal urethral orifice they are disposed in a thick circular layer forming the sphincter visicii which is continuous with the muscular fibres of the prostate the internal longitudinal layer is thin and its visiculi have a reticular arrangement but with the tendency to assume for the most part a longitudinal direction two bands of oblique fibres originating behind the orifices of the urethas converge to the back part of the prostate and are inserted by means of a fibrous process into the middle lobe of that organ they are the muscles of the urethas described by Sir C. Bell who's supposed to that during the contraction of the bladder they serve to retain the oblique direction of the urethas and so prevent the reflux of the urine into them the submucous coat telus submucosa consists of a layer of areola tissue connecting together the muscular and mucous coats and intimately united to the latter the mucous coat tunica mucosa is thin, smooth and of a pale rose colour it is continuous above through the urethas with the lining membrane of the renal tubules and below with that of the urethra the loose texture of the submucous layer allows the mucous coat to be thrown into folds or rougi when the bladder is empty over the trigonum viscichae the mucous membrane is closely attached to the muscular coat and is not thrown into folds but is smooth and flat and the mucous coat but is smooth and flat the epithelium covering it is of the transitional variety consisting of a superficial layer of polyhedral flattened cells each with one, two or three nuclei beneath these is a stratum of large club shaped cells with their narrow extremities directed downward and wedged in between smaller spindle shaped cells containing oval nuclei the epithelium varies according as the bladder is distended or contracted in the former condition the superficial cells are flattened and those of the other layers are shortened in the latter they present the appearance described above there are no true glands in the mucous membrane of the bladder though certain mucous follicles which exist especially near the neck of the bladder have been regarded as such vessels and nerves the arteries supplying the bladder are the superior middle and inferior vesicle derived from the anterior trunk of the hypergastric the obturator and inferior gluteal arteries also supply small visceral branches to the bladder and in the female additional branches are derived from the uterine and vaginal arteries the veins form a complicated plexus on the inferior surface and fundus near the prostate and end in the hypergastric veins the lymphatics are described in part 3 of Grey's Anatomy section 49 the nerves of the bladder are 1. fine medallated fibres from the third and fourth sacral nerves and 2. non-medallated fibres from the hypergastric plexus they are connected with ganglia in the outer and sub mucous coats and are finally distributed all as non-medallated fibres to the muscular layer and epithelial lining of the viscous abnormalities a defect of development in which the bladder is implicated is known under the name of extroversion of the bladder in this condition the lower part of the abdominal wall and the anterior wall of the bladder are wanting so that the fundus of the bladder presents on the abdominal surface and is pushed forward by the pressure of the viscera within the abdomen forming a red vascular tumor on which the openings of the urethra are visible the penis, except the glands, is rudimentary and is cleft on its dorsal surface exposing the floor of the urethra a condition known as epispadius the pelvic bones are also arrested in development end of section 31