 Section 43 of Grey's Anatomy, Part 2. 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 Selena Arter. Anatomy of the Human Body, Part 2 by Henry Gray. The muscles connecting the upper extremity to the anterior and lateral thoracic walls. The muscles of the anterior and lateral thoracic regions are pectoralis major, pectoralis minor, subclavius, serratus anterior, superficial fascia. The superficial fascia of the anterior thoracic region is continuous with that of the neck and upper extremity above and of the abdomen below. It encloses the mammoth and gives off numerous septal which pass into the gland, supporting its various lobes. From the fascia over the front of the mammoth, fibrous processes pass forward to the integument and papilla. These were called by Sir A. Cooper, the ligamenta suspensoria. Pectoral fascia. The pectoral fascia is a thin lamina covering the surface of the pectoralis major and sending numerous prolongations between its fasciculi. It is attached in the middle line to the front of the sternum, above to the clavicle, laterally and below it is continuous with the fascia of the shoulder, axilla and thorax. It is very thin over the upper part of the pectoralis major, but thicker in the interval between it and the latissimus dorsi, where it closes in the axillary space and forms the axillary fascia. It divides at the lateral margin of the latissimus dorsi into two layers, one of which passes in front of and the other behind it. These proceed as far as the spinous processes of the thoracic vertebrae to which they are attached. As the fascia leaves the lower edge of the pectoralis major, to cross the floor of the axilla it sends a layer upward, under cover of the muscle. This lamina splits to envelop the pectoralis minor. At the upper edge of which it is continuous with the coricoclavicular fascia. The hollow of the armpit, seen when the arm is abducted, is produced mainly by the traction of this fascia on the axillary floor and hence the lamina is sometimes named the suspensory ligament of the axilla. At the lower part of the thoracic region of the deep fascia is well developed and is continuous with the fibrous sheaths of the recti abdominis. The pectoralis major is a thick, fan-shaped muscle situated at the upper and fore part of the chest. It arises from the anterior surface of the sternal half of the clavicle, from half the breadth of the anterior surface of the sternum, as low down as the attachment of the cartilage of the sixth or seventh rib. From the cartilages of all the true ribs, with the exception frequently of the first or seventh, or both, and from the aponeurosis of the obliquous externus abdominis. From this extensive origin the fibers converge toward their insertion. Those arising from the clavicle pass obliquely downward and lateralward and are usually separated from the rest by a slight interval. Those from the lower part of the sternum and the cartilages of the lower true ribs run upward and lateralward while the middle fibers pass horizontally. They all end in a flat tendon about five centimeters broad which is inserted into the crest of the greater tubercle of the humerus. This tendon consists of two laminé placed one in front of the other and usually blended together below. The anterior lamina, the thicker, receives the clavicular and the uppermost sternal fibers. They are inserted in the same order as that in which they arise. That is to say, the most lateral of the clavicular fibers are inserted at the upper part of the anterior lamina. The uppermost sternal fibers pass down to the lower part of the lamina, which extends as low as the tendon of the deltoidius and joins with it. The posterior lamina of the tendon receives the attachment of the greater part of the sternal portion and the deep fibers, i.e. those from the costal cartilages. These deep fibers and particularly those from the lower costal cartilages ascend the higher, turning backwards successively behind the superficial and upper ones so that the tendon appears to be twisted. The posterior lamina reaches higher on the humerus than the anterior one and from it an expansion is given off, which covers the enter tubercular groove and blends with the capsule of the shoulder joint. From the deepest fibers of this lamina at its insertion an expansion is given off, which lines the enter tubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia of the arm. Variations The more frequent variations are greater or less extent of attachment to the ribs and sternum, varying size of the abdominal part or its absence, greater or less extent of separation of sternocostal and clavicular parts, fusion of clavicular part with deltoid, decossation in front of the sternum. Deficiency or absence of the sternocostal part is not uncommon, absence of the clavicular part is less frequent, rarely the whole muscle is wanting. Costocorocoidius is a muscular band occasionally found arising from the ribs or aponeurosis of the external oblique between the pectoralis major and latissimus dorsi and inserted into the coracoid process. Condroepotrochliaris is a muscular slip occasionally found arising from the costal carliges or from the aponeurosis of the external oblique below the pectoralis major or from the pectoralis major itself. The insertion is variable on the inner side of the arm to fascia, intramuscular septum or internal condom. Sternalis In front of the sternal end of the pectoralis major, parallel to the margin of the sternum, it is supplied by the anterior thoracic nerves and is probably a misplaced part of the pectoralis. Coracoclavicular fascia Fascia coracoclavicularis Costocoracoid membrane Clavipectoral fascia The coracoclavicular fascia is a strong fascia situated under cover of the clavicular portion of the pectoralis major. It occupies the interval between the pectoralis minor and subclavius and protects the axillary vessels and nerves. Traced upward, it splits to enclose the subclavius and its two layers are attached to the clavicle, one in front of and the other behind the muscle. The latter layer fuses with the deep cervical fascia and with the sheath of the axillary vessels. Medially, it blends with the fascia covering the first two intercostal spaces and is attached also to the first rib medial to the origin of the subclavius. Laterally, it is very thick and dense and is attached to the coracoid process. The portion extending from the first rib to the coracoid process is often whiter and denser than the rest and is sometimes called the costocoracoid ligament. Below this, it is thin and at the upper border of the pectoralis minor it splits into two layers to invest the muscle. From the lower border of the pectoralis minor, it is continued downward to join the axillary fascia and lateralward to join the fascia over the short head of the biceps brachii. The coraco-clavicular fascia is pierced by the cephalic vein, the oracochromial artery in vein and external anterior thoracic nerve. The pectoralis minor is a thin triangular muscle situated at the upper part of the thorax beneath the pectoralis major. It arises from the upper margins and outer surfaces of the third, fourth and fifth ribs near their cartilage and from the aponeuroses covering the entercostalus. The fibers pass upward and lateralward and converge to form a flat tendon which is inserted into the medial border and upper surface of the coracoid process of the scapula. Variations Origin from second, third and fourth or fifth ribs. The tendon of insertion may extend over the coracoid process to the greater tubercle, may be split into several parts. Absence Rare Pectoralis Minimus First Rib Cartilage to Coracoid Process Rare The subclavius is a small triangular muscle placed between the clavicle and the first rib. It arises by a short, thick tendon from the first rib and its cartilage at their junction in front of the claustroclavicular ligament. The fleshy fibers proceed obliquely upward and lateralward to be inserted into the groove on the under surface of the clavicle between the claustroclavicular and conoid ligaments. Variations Insertion into coracoid process instead of clavicle or into both clavicle and coracoid process. Sternoscapular fasciculus to the upper border of scapula. Sternoclavicularis from manubrium to clavicle between pectoralis major and coracoclavicular fascia. The serratus anterior, serratus magnus is a thin muscular sheet situated between the ribs and the scapula at the upper and lateral part of the chest. It arises by fleshy digitations from the outer surfaces and superior borders of the upper eight or nine ribs and from the aponeuroses covering the intervening intercostalis. Each digitation, except the first, arises from the corresponding rib. The first springs from the first and second ribs and from the fascia covering the first intercostal space. From this extensive attachment the fibers pass backward closely applied to the chest wall and reach the vertebral border of the scapula and are inserted into its ventral surface in the following manner. The first digitation is inserted into a triangular area on the ventral surface of the medial angle. The next two digitations spread out to form a thin triangular sheet the base of which is directed backward is inserted into nearly the whole length of the ventral surface of the vertebral border. The lower five or six digitations converge to form a fan-shaped mass the apex of which is inserted by muscular and tendinous fibers into a triangular impression on the ventral surface of the inferior angle. The lower four slips interdigitate at their origins with the upper five slips of the obliquus externus abdominis. Variations Attachment to tenth rib Absence of attachments to first rib to one or more of the lower ribs Division into three parts Absence or defect of middle part Union with levator scapulae External intercostals or external oblique Nerves Pectoralis major is supplied by the medial and lateral anterior thoracic nerves. Through these nerves, the muscle receives filaments from all the spinal nerves entering into the formation of the brachial plexus. The pectoralis minor receives its fibers from the eighth cervical and first thoracic nerves through the medial anterior thoracic nerve. The subclavius is supplied by a filament from the fifth and sixth cervical nerves. The serratus anterior is supplied by the long thoracic, which is derived from the fifth, sixth, and seventh cervical nerves. Actions If the arm has been raised by the deltoidius, the pectoralis major will, conjointly with the latissimus dorsi and teres major, depress it to the side of the chest. If acting alone, it adducks and draws forward the arm, bringing it across the front of the chest and at the same time rotates it inward. The pectoralis minor depresses the point of the shoulder, drawing the scapula downward and medialward toward the thorax and throwing the inferior angle backward. The subclavius depresses the shoulder, carrying it downward and forward. When the arms are fixed, all three of these muscles act upon the ribs, drawing them upward and expanding the chest and thus becoming very important agents in forced inspiration. The serratus anterior, as a whole, carries the scapula forward and at the same time raises the vertebral border of the bone. It is therefore concerned in the action of pushing. Its lower and stronger fibers move forward the lower angle and assist the trapezius in rotating the bone at the sternoclavicular joint and thus assist this muscle in raising the acromion and supporting weights upon the shoulder. It is also an assistant to the deltoidius in raising the arm. In as much as during the action of this latter muscle, it fixes the scapula and so steadies the glenoid cavity on which the head of the humerus rotates. After the deltoidius has raised the arm to a right angle with the trunk, the serratus anterior and the trapezius, by rotating the scapula, raise the arm into an almost vertical position. It is possible that when the shoulders are fixed, the lower fibers of the serratus anterior may assist in raising and everting the ribs, but it is not the important inspiratory muscle it was formerly believed to be. The muscles and fascia of the shoulder. In this group are included deltoidius, subscapularis, supraspinatus, infraspinatus, teres minor, teres major. Deep fascia. The deep fascia covering the deltoidius invests the muscle and sends numerous septa between its vesicular. In front it is continuous with the fascia covering the pectoralis major. Behind, where it is thick and strong with that covering the infraspinatus, above it is attached to the clavicle, the acromion, and the spine of the scapula, below it is continuous with the deep fascia of the arm. The deltoidius, deltoid muscle, is a large, thick triangular muscle which covers the shoulder joint in front, behind, and laterally. It arises from the anterior border and upper surface of the lateral third of the clavicle, from the lateral margin and upper surface of the acromion, and from the lower lip of the posterior border of the spine of the scapula, as far back as the triangular surface at its medial end. From this extensive origin, the fibers converge toward their insertion, the middle passing vertically, the anterior obliquely backward and lateralward, the posterior obliquely forward and lateralward. They unite in a thick tendon, which is inserted into the deltoid prominence on the middle of the lateral side of the body of the humerus. At its insertion, the muscle gives off an expansion to the deep fascia of the arm. This muscle is remarkably coarse in texture, and the arrangement of its fibers is somewhat peculiar. The central portion of the muscle, that is to say the part arising from the acromion, consists of oblique fibers. These arise in a bipeniform manner from the sides of the tendinous intersections, generally four in number, which are attached above to the acromion and pass downward parallel to one another in the substance of the muscle. The oblique fibers thus formed are inserted into similar tendinous intersections, generally three in number, pass upward from the insertion of the muscle and alternate with the descending septa. The portions of the muscle arising from the clavicle and spine of the scapula are not arranged in this manner, but are inserted into the margins of the inferior tendon. Variations Large variations uncommon, more or less splitting common. Continuation into the trapezius, fusion with the pectoralis major, additional slips from the vertebral border of the scapula, infraspinus fascia and axillary border of scapula, not uncommon. Insertion varies in extent or rarely is prolonged to origin of brachioradialis. Nerves The deltoidius is supplied by the fifth and sixth cervical through the axillary nerve. Actions The deltoidius raises the arm from the side so as to bring it at right angles with the trunk. Its anterior fibers, assisted by the pectoralis major, draw the arm forward, and its posterior fibers, aided by the teres major and latissimus dorsi, draw it backward. Subscapular fascia Fascia subscapularis The subscapular fascia is a thin membrane attached to the entire circumference of the subscapular fossa and affording attachment by its deep surface to some of the fibers of the subscapularis. The subscapularis is a large triangular muscle which fills the subscapular fossa and arises from its medial two thirds and from the lower two thirds of the groove on the axillary border of the bone. Some fibers arise from tendon islamini which intersect the muscle and are attached to ridges on the bone. Others from an aponeurosis which separates the muscle from the teres major and the long head of the triceps brachii. The fibers pass lateralward and gradually converging and an attending which is inserted into the lesser tubercle of the humerus and the front of the capsule of the shoulder joint. The tendon of the muscle is separated from the neck of the scapula by a large bursa which communicates with the cavity of the shoulder joint through an aperture in the capsule. Nerves. The subscapularis is supplied by the fifth and sixth cervical nerves through the upper and lower subscapular nerves. Actions. The subscapularis rotates the head of the humerus inward. When the arm is raised it draws the humerus forward and downward. It is a powerful defense to the front of the shoulder joint preventing displacement of the head of the humerus. Supraspinatus fascia fascia supraspinata The supraspinatus fascia completes the osteofibrous case in which the supraspinatus muscle is contained. It affords attachment by its deep surface to some of the fibers of the muscle. It is thick medially but thinner laterally under the caracochromia ligament. The supraspinatus occupies the whole of the supraspinatus fascia arising from its medial two thirds and from the strong supraspinatus fascia. The muscular fibers converge to a tendon which crosses the upper part of the shoulder joint and is inserted into the highest of the three impressions on the greater tubercle of the humerus. The tendon is intimately adherent to the capsule of the shoulder joint. Infraspinatus fascia fascia infraspinata The infraspinatus fascia is a dense fibrous membrane covering the infraspinatus muscle and fixed to the circumference of the infraspinatus fossa. It affords attachment by its deep surface to some fibers of that muscle. It is intimately attached to the deltoid fascia along the overlapping border of the deltoidias. The infraspinatus is a thick triangular muscle which occupies the chief part of the infraspinatus fascia. It arises by fleshy fibers from its medial two thirds and by tendinous fibers from the ridges on its surface. It also arises from the infraspinatus fascia which covers it and separates it from the terides major and minor. The fibers converge to a tendon which glides over the lateral border of the spine of the scapula and passing across the posterior part of the capsule of the shoulder joint is inserted into the middle impression on the greater tubercle of the humerus. The tendon of this muscle is sometimes separated from the capsule of the shoulder joint by a bursa which may communicate with the joint cavity. The terides minor is a narrow elongated muscle which arises from the dorsal surface on the axillary border of the scapula for the upper two thirds of its extent and from two aponeurotic lamini one of which separates it from the infraspinatus the other from the teres major. Its fibers run obliquely upward and lateralward. The upper one's in a tendon which is inserted into the lowest of the three impressions on the greater tubercle of the humerus. The lowest fibers are inserted directly into the humerus immediately below this impression. The tendon of this muscle toss and is united with the posterior part of the capsule of the shoulder joint. Variations. It is sometimes inseparable from the infraspinatus The teres major is a thick but somewhat flattened muscle which arises from the oval area on the dorsal surface of the inferior angle of the scapula and from the fibers septa interposed between the muscle and the teres minor and infraspinatus. The fibers are directed upward tendon about five centimeters long, which is inserted into the crest of the lesser tubercle of the humerus. The tendon at its insertion lies behind that of the latissimus dorsi, from which it is separated by a bursa, the two tendons being, however, united along their lower borders for a short distance. Nerves The supraspinatus and infraspinatus are supplied by the fifth and sixth cervical nerves through the suprascapular nerve, the teres minor by the fifth cervical through the axillary, and the teres major by the fifth and sixth cervical through the lowest subcapular. Actions The supraspinatus assists the deltoidius in raising the arm from the side of the trunk and fixes the head of the humerus in the glenoid cavity. The infraspinatus and teres minor rotate the head of the humerus outward. They also assist in carrying the arm backward. One of the most important uses of these three muscles is to protect the shoulder joint, the supraspinatus supporting it above, and the infraspinatus and teres minor behind. The teres major assists the latissimus dorsi in drawing the previously raised humerus downward and backward, and in rotating it inward. When the arm is fixed, it may assist the pectoralis and the latissimus dorsi in drawing the trunk forward. End of section 44 of Grey's Anatomy Part 2 Section 45 of Grey's Anatomy Part 2 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 2 by Henry Grey Muscles and Phathia of the Arm The muscles of the arm are Caracobrachialis, brachialis, biceps brachii, triceps brachii, brachiorphathia, fasciobrachii, deep fascia of the arm. The brachiorphathia is continuous with it covering the deltoidus and the pectoralis major, by means of which it is attached above to the clavicle, a chromium, and spine of the scapula. It forms a thin loose membranous sheath for the muscles of the arm and sends septa between them. It is composed of fibres disposed in a circular or spiral direction and connected together by vertical and oblique fibres. It differs in thickness at different parts, being thin over the biceps brachii, but thicker where it covers the triceps brachii, and over the epicondyls of the humerus. It is strengthened by fibrus aponeurosis, derived from the pectoralis major and latimus dorsi medially, and from the deltoidus laterally. On either side it gives off a strong intermuscular septum, which is attached to the corresponding supracondylar ridge, an epicondyle of the humerus. The lateral intramuscular septum extends from the lowest part of the crest of the greater tubicle, along the lateral supracondylar ridge to the lateral epicondyle. It is blended with the tendon of the deltoidus, gives attachment to the tricep brachii behind, to the brachialis brachioradialis, an extensor carpioradialis longus in front, and is perforated by the radial nerve and profunda branch of the brachial artery. The medial intramuscular septum, thicker than the preceding, extends from the lower part of the crest of the lesser tubicle of the humerus below the teres major, along the medial supracondylar ridge to the medial epicondyle. It is blended with the tendon of the corocob brachialis, and affords attachment to the tricep brachii behind and the brachialis in front. It is perforated by the ulnar nerve, the superior ulnar collateral artery, and the posterior branch of the inferior ulnar collateral artery. At the elbow, the deep fascia is attached to the epicondyles of the humerus, and the olecranin of the ulnar, and is continuous with the deep fascia of the forearm. Just below the middle of the arm, on its medial side, is an oval opening in the deep fascia, which transmits the bacillic vein and some lymphatic vessels. The corocob brachialis, the smallest of the three muscles in this region, is situated at the upper and medial part of the arm. It arises from the apex of the coracoid process, in common with the short head of the biceps brachii, and from the intermuscular septum between the two muscles. It is inserted by means of a flat tendon into an impression at the middle of the medial surface and border of the body of the humerus, between the origins of the triceps brachii and brachialis. It is perforated by the muscular cutaneous nerve. Variations. A bony head may reach the medial epicondyle. A short head, more rarely found, may insert into the lesser tubicle. The biceps brachii, biceps flexor cubitii, is a long fusiform muscle placed on the front of the arm and arising by two heads, from which circumstance it has received its name. The short head arises by a thick, flattened tendon from the apex of the coracoid process, in common with the coracobrachialis. The long head arises from the supraglenoid tuberosity at the upper margin of the glenoid cavity and is continuous with the glenoidal labrum. This tendon enclose in a special sheath of the synoval membrane of the shoulder joint, arches over the head of the humerus. It emerges from the capsule through an opening close to the humeral attachment of the ligament and descends into the intertubercular groove. It is retained in the groove by the transverse humeral ligament and by a fibrous prolongation from the tendon of the pectoral auras major. Each tendon is succeeded by an elongated muscular belly, and the two bellies, although closely applied to each other, can readily be separated until within about 7.5 cm of the elbow joint. Here they end in a flattened tendon, which is inserted into the rough posterior portion of the tuberosity of the radius, a burst of being interposed between the tendon and the front part of the tuberosity. As the tendon of the muscle approaches the radius, it is twisted upon itself, so that its anterior surface becomes lateral and is applied to the tuberosity of the radius at its insertion. Opposite the bend of the elbow, the tendon gives off from its medial side a broad aponeurosis, the lacticis fibrosis, bicepital fascia, which passes a bleakly downward and medial wood across the brachial artery and is continuous with the deep fasso, covering the origins of the flexor muscles of the forearm. Variations. A third head, 10% to the biceps brachii, is occasionally found, arising at the upper and medial part of the brachialis, with the fibres of which it is continuous, and inserted into the lacticis fibrosis and medial side of the tendon of the muscle. In most cases, this additional slip lies behind the brachial artery and its course down the arm. In some instances, the third head consists of two slips, which pass down one in front and the other behind the artery, concealing the vessel in the lower half of the arm. More rarely a fourth-head occurs, arising from the alpha side of the uremus from the intertubercular groove or from the greater tubicle. Other heads are occasionally found. Sips sometimes pass from the inner border of the muscle over the brachial artery to the medial intermuscular septum or the medial epicondyle. More rarely to the pronated teres or brachialis. The long head may be absent or arise from the intertubercular groove. The brachialis, brachialis antichus, covers the front of the elbow joint and the lower half of the humerus. It arises from the lower half of the front of the humerus, commencing above at the insertion of the diltordius, which it embraces by two angular processes. Its origin extends below to within 2.5 centimetres of the margin of the articular surface. It also arises from the intermuscular septum, but more extensively from the medial than the lateral. It is separated from the lateral below by the brachial radialis and the extensile carpi radialis longus. Its fibres converge to a thick tendon, which is inserted into the tuberosity of the ulna and the rough depression on the anterior surface of the coronoid process. Variations. Occasionally doubles. Additional slip to the supranata pronata terrace, biceps, lecatous fibrosis or radius are more rarely found. Nerves. The coriobrachialis, biceps brachii and brachialis are supplied by the musculocotaneous nerve. The brachialis usually receives an additional filament from the radial. The caracobrachialis receives its supply primary from the seventh cervical. The biceps brachii and the brachialis from the fifth and sixth cervical nerves. Actions. The cariobrachialis draws the umus forward and medial and at the same time assists in retaining the head of the bone in contact with the glenoid cavity. The biceps brachii is a flexor of the elbow and to a lesser extent of the shoulder. It is also a powerful supranata and serves to render tense the deep fasciae of the forearm by means of the lecatous fibrosis given off from its tendon. The brachialis is a flexor of the forearm and forms an important defence to the elbow joint. When the forearm is fixed, the biceps brachii and brachialis flex the arm upon the forearm as in efforts of climbing. The triceps brachii, triceps, triceps extensor cubitii is situated on the back of the arm extending the entire length of the dorsal surface of the umus. It is of a large size and arises by three heads long, lateral and medial hence its name. The long head arises by a flattened tendon from the infragnoid tuberosity of the scalpina being blended as its upper part with the capsule of the shoulder joint. The muscular fibres pass downward between the two other heads of the muscle and join with them in the tendon of insertion. The lateral head arises from the posterior surface of the body of the humerus between the insertion of the teres minor and the upper part of the groove for the radial nerve and from the lateral border of the humerus and the lateral intermuscular septum. The fibres from this origin converge towards the tendon of insertion. The medial head arises from the posterior surface of the body of the humerus below the groove for the radial nerve. It is narrow and pointed above and extends from the insertion of the teres major to within 2.5 centimetres of the trochlea. It also arises from the medial border of the humerus and from the back of the whole length of the medial intramuscular septum. Some of the fibres are directed downward to the olocranum while others converge to the tendon of insertion. The tendon of the triceps brachii begins about the middle of the muscle. It consists of two aponeurotic laminae, one of which is subcutaneous and covers the back of the lower half of the muscle. The other is more deeply seated in the substance of the muscle. After receiving the attachment of the muscular fibres, the two lamellae join together above the elbow and are inserted for the most part into the posterior portion of the upper surf of the elecranum. A band of fibres is however continued downward on the lateral side of the anconiath to blend with the deep fasciitis of the forearm. The long head of the triceps brachii descends between the teres minor and the teres major, dividing the triangular space between these two muscles and the humerus into two smaller spaces. One triangular, the other quadrangular. The triangular space contains the scapula circumflex vessels. It is bounded by the teres minor above, the teres major below and the scapula head of the triceps laterally. The quadrangular space transmits the posterior humeral circumflex vessels and the axillary nerve. It is bounded by the teres minor and capsule of the shoulder joint above, the teres major below, the long head of the triceps brachii medially and the humerus laterally. Variations. A fourth head from the inner part of the humerus are slipped between triceps and latimus dorsi corresponding for the dorsal epitrocularis. The subanconius is the name given to a few fibres which spring from the deep surface of the lower part of the triceps brachii and are inserted into the posterior ligament and synovial membrane of the elbow joint. Nerves. The triceps brachii is supplied by the seventh and eighth cervical nerves through the radial nerve. Actions. The triceps brachii is the great extensor muscle of the forearm and is the direct antagonist of the biceps brachii and brachialis. When the arm is extended the long head of the muscle may assist the teres major and latissimus dorsi in drawing the humerus backward and in abducting it to the thorax. The long head supports the underpart of the shoulder joint. The subanconius draws up the synovial membrane of the elbow joint during extension of the forearm. End of section 45. Section 46 of Grey's Anatomy Part 2 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 Bologna Times. Anatomy of the Human Body Part 2 by Henry Gray The muscles and fascia of the forearm. The muscles and fascia of the forearm. Anti-brachial fascia fascia antibraki deep fascia of the forearm. The anti-brachial fascia continuous above with the brachial fascia is a dense membranous investment which forms a general sheath for the muscles in this region. It is attached behind to the olicranon and dorsal border of the ulna and gives off from its deep surface numerous intermuscular septa which enclose each muscle separately. Over the flexor tendons as they approach the wrist it is especially thickened and forms the volar carpal ligament. This is continuous with the transverse carpal ligament and forms a sheath for the tendon of the pulmaris longus which passes over the transverse carpal ligament to be inserted into the pulmar aponeurosis. Behind, near the wrist joint it is thickened with the addition of many transverse fibers and forms the dorsal carpal ligament. It is much thicker on the dorsal than on the volar surface and at the lower than at the upper part of the forearm and is strengthened above by tendinous fibers derived by the biceps brachae in front and from the triceps brachae behind. It gives origin to muscular fibers especially at the upper part of the medial and lateral sides of the forearm and forms the boundaries of a series of cone shaped cavities in which the muscles are contained. Besides the vertical septa separating the individual muscles transverse septa are given off both on the volar and dorsal surfaces of the forearm separating the deep from the superficial layers of muscles. Apertures exist in the fascia for the passage of vessels and nerves. One of these apertures of large size situated at the front of the elbow serves for the passage of a communicating branch between the superficial and deep veins. The antibracial or forearm muscles may be divided into a volar and dorsal group. The volar antibracial muscles these muscles are divided for convenience of description into two groups superficial and deep. The superficial group pronator teres pulmaris longus flexor carpe radialis flexor carpe ulnaris flexor digitorum sublimus. The muscles of this group take origin from the media epicondyle of the humerus by a common tendon. They receive additional fibers from the deep fascia of the forearm near the elbow and from the septa which pass from this fascia between the individual muscles. The pronator teres has two heads of origin humeral and ulnar. The humeral head the larger and more superficial arises immediately above the medial epicondyle and from the tendon common to the origin of the other muscles. Also from the intramuscular septum between it and the flexor carpe radialis and from the antibracial fascia. The ulnar head is a thin fasciilis which arises from the medial side of the coronoid process of the ulna and joins the proceeding at an acute angle. The median nerve enters the forearm between the two heads of the muscle and is separated from the ulnar artery by the ulnar head. The muscle passes obliquely across the forearm and ends in a flat tendon which is inserted into a rough impression at the middle of the lateral surface of the body of the radius. The lateral border of the muscle forms the medial boundary of a triangular hollow situated in front of the elbow joint and containing the brachial artery, median nerve and tendon of the biceps brachii. Variations absence of ulnar head additional slips from the medial intramuscular septum from the biceps and from the brachialis anticus occasionally occur. The flexor carpe radialis lies on the medial side of the proceeding muscle. It arises from the medial epicondyle by the common tendon from the fascia of the forearm and from the intramuscular septum between it and the pronator teres laterally. The palmaris longus medially and the flexor digitorum sublimus beneath. Slender and aponeurotic in structure at its commencement it increases in size and ends in a tendon which forms rather more than the lower half of its length. This tendon passes through a canal in the lateral part of the transverse carpal ligament and runs through a groove on the greater multangular bone. The groove is converted into a canal by fibrous tissue and lined by a mucus sheath. The tendon is inserted into the base of the second metacarpal bone and sends a slip to the base of the third metacarpal bone. The radial artery in the lower part of the forearm lies between the tendon and this muscle and the brachior radialis. Variations. Slips from the tendon of the biceps the lacertus fibrosis the cornoid and the radius of the bone. Its insertion often varies and may be mostly into the annular ligament the trapezium or the fourth metacarpal as well as the second or third. The muscle may be absent. The pulmaris longus is a slender fusiform muscle lying on the medial side of the proceeding. It arises from the medial epicondyle of the humerus from the intramuscular septa between it and the adjacent muscles and from the antibracial fascia. It ends in a slender flattened tendon which passes over the upper part of the transverse carpal ligament and is inserted into the central part of the transverse carpal ligament and lower part of the pulmar aponeurosis frequently sending a tendinous slip to the short muscles of the thumb. Variations One of the most variable muscles in the body. This muscle is often absent about 10% and is subject to many variations. It may be tendinous above and muscular below or it may be muscular in the center with a tendon above and below or it may be present two muscular bundles with a central tendon. Or finally it may consist solely of a tendinous band The muscle may be double. Slips of origin from the coronoid process or from the radius have been seen. Partial or complete insertion into the fascia of the forearm into the tendon of the flexor carpal and pisiform bone into the navicular and into the muscles of the little finger have been observed. Slips of the flexor carpal lies along the ulnar side of the forearm. It arises by two heads humeral and ulnar connected by a tendinous arch beneath which the ulnar nerve and posterior ulnar recurrent artery pass. The humeral head arises from the media epicondyl of the humerus by the common tendon. The ulnar head arises from the crannin and from the upper two thirds of the dorsal border of the ulna by an aponeurosis common to it and the extensor carpi ulnaris and flexor digitorum profundus and from the intramuscular septum between it and the flexor digitorum sublimus. The fibers end in a tendon which occupies the anterior part of the lower half of the muscle and is inserted into the pisiform bone. It is prolonged from this to the hamate and fifth metacarpal bones by the pisohamate and pisometacarpal ligaments. It is also attached by a few fibers to the transverse carpal ligament. The ulnar vessels and nerve lie on the lateral side of the tendon of this muscle in the lower two thirds of the forearm. Variations Slips of origin from the coronoid. The epitrocleoanoconeus a small muscle often present runs from the back of the inner condyle to the olicranon over the ulnar nerve. The flexor digitorum sublimus is placed beneath the previous muscle. It is the largest of the muscles of the superficial group and arises by three heads humeral, ulnar, and radial. The humeral head arises from the medial epicondyle of the humerus by the common tendon from the ulnar collateral ligament of the elbow joint and from the intermuscular septum between it and the preceding muscles. The ulnar head arises from the medial side of the coronoid process above the ulnar origin The radial head arises from the oblique line of the radius extending from the radial tuberosity to the insertion of the pronator terrace. The muscle speedily separates into two planes of muscular fibers superficial and deep. The superficial plane divides into two parts which end in tendons for the middle and ring fingers. The deep plane gives off a portion of the superficial plane which is associated with the tendon of the ring finger and then divides into two parts which end in tendons for the index and little fingers. As the four tendons thus formed pass beneath the transverse carpal ligament and to the palm of the hand they are arranged in pairs the superficial pair going to the middle and ring fingers the deep pair to the index and little fingers. The tendons converge from one another in the palm and form dorsal relations to the superficial follar arch and digital branches of the median and ulnar nerves. Opposite the bases of the first phalanges each tendon divides into two slips to allow of the passage of the corresponding tendon of the flexor digitorum profundus. The two slips then reunite and form a groove channel for the reception of the accompanying tendon of the flexor digitorum profundus. Finally the tendon divides and is inserted into the sides of the second phalanx about its middle. Variations absence of radial head of little finger portion accessory slips from ulnar tuberosity to the index and middle finger portions from the inner head to the flexor profundus from the ulnar to annular ligament to the little finger. The deep group flexor digitorum profundus flexor polisus longus pronator quadratus The flexor digitorum profundus is situated on the ulnar side of the forearm immediately beneath the superficial flexors. It arises from the upper three-fourths of the volar and medial surfaces of the body of the ulnar embracing the insertion of brachialis above and extending below to within a short distance of the pronator quadratus. It also arises from a depression on the medial side of the coronoid process by an aponeurosis from the upper three-fourths of the dorsal border of the ulna in common with the flexor and extensor carpi ulnaris and from the ulnar half of the interrosius membrane. The muscle ends in four tendons which run under the transverse carpal ligament dorsal to the tendons of the flexor digitorum sublimus. Opposite the first phalanges the tendons pass through the openings in the tendons of the flexor digitorum sublimus and are finally inserted into the bases of the last phalanges. The portion of the muscle of the index finger is usually distinct throughout, but the tendons for the middle ring and little fingers are connected together by areolar tissue and tendonus slips as far as the palm of the hand. Fibrous sheets of the flexor tendons. After leaving the palm the tendons of the flexorus digitorum sublimus and profundus lie in osteo-aponurotic canals formed behind the phalanges and in front by strong fibrous bands which arch across the tendons and are attached on either side to the margins of the phalanges. Opposite the middle of the proximal and second phalanges the bands, digital vaginal ligaments are very strong and the fibers are transverse but opposite the joints they are much thinner than the rest of annular and cruciate ligamentous fibers. Each canal contains a mucus sheath which is reflected on the contained tendons. Within each canal the tendons of the flexorus digitorum sublimus and profundus are connected to each other and to the phalanges by slender tendonus bands called vinculatendina. There are two sets of these A. the vincula brevia which are two in number in each finger and consist of triangular bands of fibers one connecting the tendon of the flexorus digitorum sublimus to the first interphalangeal joint and head of the first phalanges and the other the tendon of the flexorus digitorum profundus to the front of the second interphalangeal joint and head of the second phalanges. B. the vincula longa which connect the under surfaces of the tendons of the flexorus digitorum profundus to those of the subjacent flexorus sublimus after the tendons of the former have passed through the letter. Variations The index finger portion may arise partly from the upper part of the radius from the inner head of the flexorus sublimus medial epicondyle or the coronoid are found. Connection with the flexorus longus Four small muscles the lumbaricals are connected with the tendons of the flexorus profundus and the palm. They will be described with the muscles of the hand. The flexorus longus is situated on the radial side of the forearm as the proceeding. It arises from the grooved volar surface of the body of the radius extending from immediately below the tuberosity and oblique line to within a short distance of the pronator quadratus. It arises also from the adjacent part of the enterosius membrane and generally by a fleshy slip from the medial border of the coronoid process or from the medial epicondyle of the flexorus. The fibers end in a flattened tendon which passes beneath the transverse carpal ligament is then lodged between the lateral head of the flexorus brevis and the oblique part of the adductor polisus and entering an osteoaponeurotic canal similar to those for the flexor tendons of the fingers is inserted into the base of the distal phalanx of the thumb. The volar enterosius nerve and vessels pass downward on the front of the enterosius membrane between the flexor polisus longus and flexor digitorum profundus. Variations. Slips may connect with flexor sublimus or profundus or pronator terrace. An additional tendon to the index finger is sometimes bound. The pronator quadratus is a small flat quadrilateral muscle extending across the front of the lower parts of the radius and ulna. It arises from the pronator ridge on the lower part of the volar surface of the body of the ulna from the medial part of the volar surface of the lower fourth of the ulna and from a strong aponeurosis which covers the medial third of the muscle. The muscles pass lateral word and slightly downward to be inserted into the lower fourth of the lateral border and the volar surface of the body of the radius. The deeper fibers of the muscle are inserted into the triangular area above the ulna notch of the radius. An attachment comparable with the origin of the supinator from the triangular area below the radial notch of the ulna. Variations Rarely absent Split into two or three layers. Increased attachment upward or downward. Nerves All the muscles of the superficial layer are supplied by the median nerve accepting the flexor carpi ulnarus which is supplied by the ulnar. The pronator terus, the flexor carpe radialus and the pulmaris longus arrive their supply primarily from the sixth cervical nerve. The flexor digitorum sublimus from the seventh and eighth cervical and first thoracic nerves and the flexor carpi ulnarus from the eighth cervical and first thoracic. Of the deep layer the flexor digitorum profundus is applied by the eighth cervical and first thoracic through the ulnar and the volar and erasius branch of the median. The flexor pulisus longus and pronator quadratus are supplied by the eighth cervical and first thoracic through the volar and erasius branch of the median. Actions These muscles act upon the forearm, the wrist and hand. The pronator terus rotates the radius upon the ulna rendering the hand prone. When the radius is fixed it assists in flexing the forearm. The flexor carpi radialus is a flexor and abductor of the wrist. It also assists in pronating the hand and in bending the elbow. The flexor carpi ulnarus is a flexor and adductor of the wrist. It also assists in bending the elbow. The pulmaris longus is a flexor of the wrist joint. It also assists in flexing the elbow. The flexor digitorum sublimus flexes first the middle and then the proximal phalanges and then the proximal phalanges. It also assists in flexing the wrist and elbow. The flexor digitorum profundus is one of the flexors of the phalanges. After the flexor sublimus has bent the second phalanges the flexor profundus is the terminal one but it cannot do so until after the contraction of the superficial muscle. It also assists in flexing the wrist. The flexor pulisus longus is a flexor of the phalanges of the thumb. When the thumb is fixed it assists in flexing the wrist. The pronator quadratus rotates the radius upon the ulnar rendering the hand prone. End of section 46 Recording by Bologna Times, Tampa, Florida Section 47 of Gray's Anatomy Part 2 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 2 by Henry Gray Muscles and Fasci Part 2 The Dorsal Antibracial Muscles These muscles are divided for convenience of description into two groups superficial and deep The superficial group Brachioradialis Extensor Carpi Radialis Longus Extensor Carpi Radialis Brevis Extensor Digitorum Communus Extensor Digitai Quinti Proprius Extensor Digitai Quinti Proprius Extensor Digitai Quinti Proprius Extensor Carpi Ulneris Anconius The Brachioradialis Supinator Longus is the most superficial muscle on the radial side of the forearm. It arises from the upper two-thirds of the lateral supracondylar ridge of the humerus and from the lateral intermuscular septum being limited above by the groove for the radial nerve. Interposed between it and the brachialis are the radial nerve and the anastomosis between the anterior branch of the profunda artery and the radial recurrent. The fibers end above the middle of the forearm in a flat tendon which is inserted into the lateral side of the base of the styloid process of the radius. The tendon is crossed near its insertion by the tendons of the abductor pollicis longus and extensor pollicis brevis. On its honor side is the radial artery. Variations Fusion with the brachialis tendon of insertion may be divided into two or three slips insertion partial or complete into the middle of the radius. Physiculi to the tendon of the biceps, the tuberosity or oblique line of the radius slips to the extensor carbiradius longus or abductor pollicis longus. Absence rarely doubled. The extensor carbiradius longus extensor carbiradius longior is placed partly beneath the brachioradialis. It arises from the lower third of the lateral supracondylar ridge of the humerus from the lateral intramuscular septum and by a few fibers from the common tendon of origin of the extensor muscles of the forearm. The fibers end the upper third of the forearm in a flat tendon which runs along the lateral border of the radius beneath the abductor pollicis longus and extensor pollicis brevis. It then passes beneath the dorsal carpal ligament where it lies in a groove on the back of the radius common to it and the extensor carbiradius brevis immediately behind the styloid process. It is inserted into the dorsal surface of the base of the second upper bone on its radial side. The extensor carpal radialis brevis extensor carpal radialis breviore is shorter and thicker than the preceding muscle beneath which it is placed. It arises from the lateral epicondyle of the humerus by a tendon common to it and the three following muscles from the radial collateral ligament of the elbow joint from a strong aponeurosis and from the intermuscular septal between it and the adjacent muscles. The fibers end about the middle of the forearm in a flat tendon which is closely connected with that of the preceding muscle and accompanies it to the wrist. It passes beneath the abductor pollicis longus and extensor pollicis brevis then beneath the dorsal carpal ligament and is inserted into the dorsal surface of the base of the third metacarpal bone on its radial side. Under the dorsal carpal ligament the tendon lies on the back of the radius in a shallow groove to the outer side of that which lodges the tendon of the extensor carpal radialis longus and separated from it by a faint ridge. The tendons of the two preceding muscles pass through the same compartment of the dorsal carpal ligament in a single mucus sheath. Variations either muscle may split two or three tendons of insertion to the second and third or even the fourth metacarpal. The two muscles may unite into a single belly with two tendons. Cross slips between the two muscles may occur. The extensor carpal radialis intermedius rarely arises as a distinct muscle from the humerus, but is not uncommon as an accessory slip from one or both muscles to the second or third carpals. The extensor carpal radialis accessorius is occasionally found arising from the humerus with or below the extensor carpal radialis longus and inserted into the first metacarpal the abductor palusus brevis the first dorsal interosseous or elsewhere. The extensor digitorum communus arises from the lateral epicondyle of the humerus by the common tendon intermuscular septa between it and the adjacent muscles and from the anti-brachial fascia it divides below into four tendons which pass together with that of the extensor endosus proprius through a separate compartment of the dorsal carpal ligament with an amuchus sheath. The tendons then diverge on the back of the hand and are inserted into the second and third phalanges of the fingers in the same manner. Opposite the metacarpophalangeal articulation each tendon is bound by fasciculi to the collateral ligaments and serves as the dorsal ligament of this joint. After having crossed the joint it spreads out into a broad aponeurosis which covers the dorsal surface of the first phalanx and is reinforced in this situation by the tendons Opposite the first interphalangeal joint this aponeurosis divides into three slips an intermediate and two collateral. The former is inserted into the base of the second phalanx and the two collateral which are continued onward along the sides of the second phalanx unite by their contiguous margins and are inserted into the dorsal surface of the last phalanx. When the tendons cross the interphalangeal joints they furnish them with dorsal ligaments. The tendon to the index finger is accompanied by the extensor endocis proprius which lies on its on or side. On the back of the hand the tendons to the middle, ring and little fingers are connected by two obliquely placed bands one from the third tendon passing downward and lateralward to the second tendon and the other passing from the same tendon downward and medialward to the fourth. Occasionally the first tendon is connected to the second by a thin transverse band. Variations an increase or decrease in the number of tendons is common an additional slip to the thumb is sometimes present. The extensor digitia quinti proprius extensor minimi digitia is a slender muscle placed on the medial side of the extensor digitorum communis with which it is generally connected. It arises from the common extensor tendon by a thin tendonus slip from the intermuscular septa between it and the adjacent muscles. Its tendon runs through a compartment of the dorsal carpal ligament behind the distal radio-owner joint then divides into two as it crosses the hand and finally joins the expansion of the extensor digitorum communis tendon on the dorsum of the first phalanx of the little finger. Variations an additional fibrous slip from the lateral epicondyle the tendon of insertion may not divide or may send a slip to the ring finger. Absence of muscle rare fusion of the belly with the extensor digitorum communis not uncommon. The extensor carpionaris lies on the ulnar side of the forearm. It arises from the lateral epicondyle of the humerus by the common tendon by an aponeurosis from the dorsal border of the ulna in common with the flexor carpionaris and the flexor digitorum profundus and from the deep fascia of the forearm it ends in a tendon which runs in a groove between the head and the styloid process of the ulna into a separate compartment of the dorsal carpal ligament and is inserted into the prominent tubercle on the ulnar side of the base of the fifth metacarpal bone. Variations doubling reduction to tendinous band insertion partially into fourth metacarpal in many cases 52% a slip is continued from the insertion of the tendon anteriorly over the aponens digitia quinti to the fascia covering that muscle the metacarpal bone the capsule of the metacarpophilangeal articulation or the first failings of the little finger this slip may be replaced by a muscular fasciculus arising from or near the pisiform the anconias is a small triangular muscle which is placed on the back of the elbow joint and appears to be a continuation of the triceps brachii which rises by a separate tendon from the back part of the lateral epicondyle of the humerus its fibers diverge and are inserted into the side of the olecranon and upper fourth of the dorsal surface of the body of the ulna the deep group supinator abductor polisus longus extensor polisus brevis extensor polisus longus extensor endisis proprias the supinator supinator brevis is a broad muscle curved around the upper third of the radius it consists of two planes of fibers between which the deep branch of the radial nerve lies the two planes arise in common the superficial one by tendinous and the deeper by muscular fibers from the lateral epicondyle of the humerus from the radial collateral ligament of the elbow joint from the ridge on the ulna which runs obliquely downward from the dorsal end of the radial notch from the triangular depression below the notch and from a tendinous expansion which covers the surface of the muscle the superficial fibers surround the upper part of the radius and are inserted into the lateral edge of the radial tuberosity and the oblique line of the radius as low down as the insertion of the pronator teres the upper fibers of the deeper plane form a sling like fasciculus which encircles the neck of the radius above the tuberosity and is attached to the back part of its medial surface the greater part of this portion of the muscle is inserted into the dorsal and lateral surfaces of the body of the radius midway between the oblique line and the head of the bone the abductor polisus longus extensor os metacarpiopolisus lies immediately below the supinator and is sometimes united with it it arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the anconius from the enterosius membrane and from the middle third of the dorsal surface of the body of the radius passing obliquely downward and lateral word it ends in a tendon which runs through a groove on the lateral side of the lower end of the radius accompanied by the tendon of the extensor polisus brevis and is inserted into the radial side of the base of the first metacarpal bone it occasionally gives off two slips near its insertion one to the greater multangular bone and the other to blend with the origin of the abductor polisus brevis variations more or less doubling of muscle and tendon with insertion of the extra tendon into the first metacarpal the greater multangular or into the abductor polisus brevis or oponens polisus the extensor polisus brevis extensor primae internautii polisus lies on the medial side of and is closely connected with the abductor polisus longus it arises from the dorsal surface of the body of the radius and from the interosseous membrane its direction is similar to that of the abductor polisus longus it's tendon passing the same groove on the lateral side of the lower end of the radius to be inserted into the base of the first failings of the thumb variations absence fusion of tendon with that of the extensor polisus longus the extensor polisus longus the extensor secondae internautii polisus is much larger than the preceding muscle the origin of which it partly covers it arises from the lateral part of the middle third of the dorsal surface of the body of the ulna below the origin of the abductor polisus longus and from the interosseous membrane it ends in a tendon which passes through a separate compartment in the dorsal carpal ligament lying in a narrow oblique groove on the back of the lower end of the radius it then crosses obliquely the tendons of the extensoris carpai radialis longus and brevis and is separated from the extensor brevis polisus by a triangular interval in which the radial artery is found and is finally inserted into the base of the last failings of the thumb the radial artery is crossed by the tendons of the abductor polisus longus and of the extensoris polisus longus and brevis the extensor endisus perprius extensor endisus is a narrow elongated muscle placed medial to and parallel with the preceding it arises from the dorsal surface of the body of the ulna below the origin of the extensor polisus longus and from the interosseous membrane it's tendon passes under the dorsal carpal ligament in the same compartment as that which transmits the tendons of the extensor digitorum communis and opposite the head of the second metacarpal bone joins the ulna side of the tendon of the extensor digitorum communis which belongs to the index finger variations doubling the ulna part may pass beneath the dorsal carpal ligament with the extensor digitorum communis a slip from the tendon may pass to the index finger nerves the brachior radialis is supplied by the fifth and sixth the extensoris carpal radialis longus and brevis by the sixth and seventh and the anconias by the seventh and eighth cervical nerves through the radial nerve the remaining muscles are innervated through the deep radial nerve the supinator being supplied by the sixth and all the other muscles by the seventh cervical actions the muscles of the lateral and dorsal aspects of the forearm which comprise all the extensor muscles and the supinator act upon the forearm, wrist and hand they are the direct antagonists of the pronator and flexor muscles the anconias assist the triceps in extending the forearm the brachior radialis the flexor of the elbow joint but only acts as such when the movement of flexion has been initiated by the biceps brachii and brachialis the action of the supinator is suggested by its name it assist the biceps in bringing the hand into the supine position the extensor carpal radialis longus extends the wrist and abducts the hand it may also assist in bending the elbow joint at all events it serves to fix or study this articulation the extensor carpal radialis brivis extends the wrist and may also act slightly as an abductor of the hand the extensor carpal alnaris extends the wrist but when acting alone inclines the hand toward the ulnar side by its continued action it extends the elbow joint the extensor digitorum communis extends the phalanges then the wrist and finally the elbow it acts principally on the proximal phalanges the middle and terminal phalanges being extended mainly by the enterocii and lumbar callies it tends to separate the fingers as it extends them the extensor digiti quintiproprius extends the little finger and by its continued action assists in extending the wrist it is owing to this muscle that the little finger can be extended or pointed while the others are flexed the chief action of the abductor polisus longus is to carry the thumb laterally from the palm of the hand by its continued action it helps to extend and abduck the wrist the extensor polisus brivis extends the proximal phalanges and the extensor polisus longus the terminal phalanges of the thumb by their continued action they help to extend and abduck the wrist the extensor endisus proprius extends the index finger and by its continued action assists in extending the wrist end of section 47 recording by Selena Arder recording by Morgan Scorpion anatomy of the human body part 2 by Henry Gray muscles and fascii of the hand 1 F the muscles and fascii of the hand the muscles of the hand are subdivided into 3 groups 1 those of the thumb which occupy the radial side and produce the thena eminence 2 those of the little finger which occupy the ulnar side and give rise to the hypothena eminence 3 those in the middle of the palm and between the metacarpal bones volacarpal ligament ligamentum carpivolare the volacarpal ligament is the thickened band of the antibracial fascia which extends from the radius to the ulnar over the flexor tendons as they enter the wrist transverse carpal ligament ligamentum carpitransversum anterior annular ligament the transverse carpal ligament is a strong fibrous band which arches over the carpus converting the deep groove on the front of the carpal bones into a tunnel through which the flexor tendons of the digits and the median nerve pass it is attached medially to the pisiform and the hamulus of the hamate bones laterally to the tuberosity and to the medial part of the volar surface and the ridge of the greater multangular it is continuous above with the volacarpal ligament and below with the palmar aponeurosis it is crossed by the ulnar vessels and nerve and the cutaneous branches of the median and ulnar nerves at its lateral end is the tendon of the flexor carpi radialis which lies in the groove on the greater multangular attachments of the ligament to the bone on its volar surface the tendons of the palmaris longus and flexor carpi ulnaris are partially inserted below it gives origin to the short muscles of the thumb and little finger the mucus sheaths of the tendons on the front of the wrist two sheaths envelop the tendons as they pass beneath the transverse carpal ligament one for the flexoris digitorum sublimus and profundus flexor apolicis longus they extend into the forearm for about 2.5 cm above the transverse carpal ligament and occasionally communicate with each other under the ligament the sheath which surrounds the flexoris digitorum extends downward about halfway along the metacarpal bones where it ends in blind diverticular around the tendons to the index middle and ring fingers it is prolonged on the tendons to the little finger and usually communicates with the mucus sheath of these tendons the sheath of the tendon of the flexor apolicis longus is continued along the thumb as far as the insertion of the tendon the mucus sheaths enveloping the terminal parts of the tendons of the flexoris digitorum have been described on page 449 dorsal carpal ligament ligamentum carpide dorsale posterior annular ligament the dorsal carpal ligament is a strong fibrous band extending obliquely downward and medial wood across the back of the wrist and consisting of part of the deep fascia of the back of the forearm strengthened by the addition of some transverse fibres it is attached medially to the styloid process of the ulna and to the triangular and pisiform bones laterally to the lateral margin of the radius and in its passage across the wrist to the ridges on the dorsal surface of the radius the mucus sheaths of the tendons between the dorsal carpal ligament and the bones six compartments are formed for the passage of tendons each compartment having a separate mucus sheath one is found in each of the following positions one on the lateral side of the styloid process for the tendons of the abductor polychus longus and the extensor polychus brevis two behind the styloid process for the tendons of the extensoris polychus longus and brevis three about the middle of the dorsal surface of the radius for the tendon of the extensor polychus longus four to the medial side of the later for the tendons of the extensor digitorum communus and extensor indicus propius five opposite the interval between the radius and ulna for the extensor digitai quinti propius six between the head and styloid for the tendon of the extensor carpi ulnaus the sheaths lining these compartments extends from above the dorsal carpal ligament those for the tendons of abductor polychus longus extensor brevis polychus extensoris carpi radialis and extensor carpi ulnaus stop immediately proximal to the basis of the metacarpal bones while the sheaths for extensor communus digitorum extensor indicus propius and extensor digitai quinti propius are prolonged to the junction of the proximal and intermediate thirds of the metacarpus palmar aponeurosis aponeurosis palmaris palmar fascia the palmar aponeurosis invests the muscles of the palm and consists of central lateral and medial portions the central portion occupies the middle of the palm is triangular in shape and of great strength and thickness its apex is continuous with the lower margin of the transverse carpal ligament and receives the expanded tendon of the palmaris longus its base divides below into four slips one for each finger each slip gives off superficial fibers to the skin of the palm and finger those to the palm joining the skin at the foe corresponding to the metacarpal phalangeal articulations and those to the fingers passing into the skin at the transverse fold at the bases of the fingers the deeper part of each slip sub divides into two processes which are inserted into the fibrous sheaths of the flexor tendons from the sides of these processes offsets are attached to the transverse metacarpal ligament by this arrangement short channels are formed on the front of the heads of the metacarpal bones through these the flexor tendons pass the intervals between the four slips transmit the digital vessels and nerves and the tendons of the lumbricalis at the points of division into the slips mentioned numerous strong transverse vesiculi bind the separate processes together the central part of the palmar aponeurosis is intimately bound to the integument by dense fibroareola tissue forming the superficial palmar fascia and gives origin by its medial margin to the palmaris brevis it covers the superficial volar arch the tendons of the flexor muscles and the branches of the median and ulnar nerves and on either side it gives off a septum which is continuous with the interosseous aponeurosis and separates the intermediate from the collateral groups of muscles the lateral and medial portions of the palmar aponeurosis are thin fibrous lehias which cover, on the radial side the muscles of the ball of the thumb and on the ulnar side the muscles of the little finger they are continuous with the central portion and with the fascia on the dorsum of the hand the superficial transverse ligament of the fingers is a thin band of transverse vasiculi it stretches across the roots of the four fingers and is closely attached to the skin of the clefts and medially to the fifth metacarpal bone forming a sort of rudimentary web beneath it the digital vessels and nerves pass to their destinations the lateral volar muscles abductor polychus brevis flexor polychus brevis oponens polychus brevis oponens polychus brevis oponens polychus adductor polychus oblicuous adductor polychus transversus the abductor polychus brevis abductor polychus is a thin flat muscle placed immediately beneath the integument it arises from the transverse carpal ligament the tuberosity of the navicular and the ridge of the greater multangular frequently by two distinct slips running lateral wooden dangles running lateral wooden downward it is inserted by a thin flat tendon into the radial side of the base of the first palencs of the thumb and the capsule of the metacarpal palangial articulation the oponens polychus is a small triangular muscle placed beneath the preceding it arises from the ridge on the greater multangular and from the transverse carpal ligament, passes downward and lateral wood and is inserted into the whole length of the metacarpal bone in its radial side the flexor polychus brevis consists of two portions lateral and medial the lateral and more superficial portion arises from the lower border of the transverse carpal ligament and the lower part of the ridge on the greater multangular bone it passes along the radial side of the tendon of the flexor polychus longus and becoming tenderness is inserted into the radial side of the base of the first palencs there is a sesameoid bone the medial and deeper portion of the muscle is very small and arises from the ulnar side of the first metacarpal bone between the adductor polychus oblicuous and the lateral head of the first interosseous dorsalis and is inserted into the ulnar side of the base of the first palencs with the adductor polychus oblicuous the medial part of the flexor brevis polychus is sometimes described as the first interosseous rollerus the polychus oblicuous adductor oblicuous polychus arises by several slips from the capitate bone the bases of the second and third metacarpals the intercarpal ligaments and the sheath of the tendon of the flexor carpi radialis from this origin the greater number of fibres pass obliquely downward and converge to a tendon which, uniting with the tenderness of the medial portion of the flexor polychus brevis and the transverse part of the adductor is inserted into the ulnar side of the base of the first palencs of the thumb a sesameoid bone being present in the tendon a considerable fasciculus however passes more obliquely beneath the tendon of the flexor polychus lungus to join the lateral portion of the flexor brevis and the abductor polychus brevis the adductor polychus transversus adductor transversus polychus is the most deeply seated of this group of muscles it is of a triangular form arising by a broad base from the lower two thirds of the volus surface of the third metacarpal bone the fibres converge to be inserted with the medial part of the flexor polychus brevis and the adductor polychus obliquus into the ulnar side of the base of the first palencs of the thumb variations the abductor polychus brevis is often divided into an outer and an inner part accessory slips from the tendon of the abductor polychus lungus more rarely from the extents of carpi radialis lungus from the styloid process or opponent's polychus or from the skin of the thinner eminence the deep head of the flexor polychus brevis may be absent or enlarged the two adductors vary in their relative extent and in the closeness of their connection the adductor obliquus may receive a slip from the transverse metacarpal ligament nerves the abductor brevis the opponent's and lateral head of the flexor polychus brevis are supplied by the sixth and seventh cervical nerves through the median nerve the medial head of the flexor brevis and the adductor by the eighth cervical through the ulnar nerve actions the abductor polychus brevis draws the thumb forward in a plane at right angles to that of the palm of the hand the adductor polychus is the opponent of this muscle and approximates the thumb to the palm the opponent's polychus flexes the metacarpal bone i.e. draws it medial wood over the palm the flexor polychus brevis flexes and adducts the proximal phalanx two the medial volumuscles pulmaris brevis abductor digitiae quintae flexor digitiae quintae brevis opponent's digitiae quintae the pulmaris brevis is a thin quadrilateral muscle placed beneath the integument of the ulnar side of the hand it arises by tenderness fasciculi from the transverse carpal ligament and pulmar aponeurosis the fleshy fibres are inserted into the skin on the ulnar border of the palm of the hand the abductor digitiae quintae abductor minimae digitae is situated on the ulnar border of the palm of the hand it arises from the pisiform bone and from the tendon of the flexor carpae ulnaris and ends in a flat tendon which divides into two slips one is inserted into the ulnar side of the base of the first phalanx of the little finger the other into the ulnar border of the aponeurosis of the extensor digitiae quintae propleus the flexor digitiae quintae brevis flexor brevis minimae digitae lies on the same plane as the preceding muscle on its radial side it arises from the convex surface of the hamulus of the hamate bone and the volus surface of the transverse and is inserted into the ulnar side of the base of the first phalanx of the little finger it is separated from the abductor at its origin by the deep branches of the ulnar artery and nerve this muscle is sometimes wanting the abductor is then usually of large size the oponens digitiae quintae oponens minimae digitae is of a triangular form and placed immediately beneath the preceding muscles it arises from the convexity of the hamulus of the hamate bone and contiguous portion of the transverse carpal ligament it is inserted into the whole length of the metacarpal bone of the little finger along its ulnar margin variations the pulmaris brevis varies greatly in size the abductor digitiae quintae may be divided into two or three slips or united with the flexor digitiae quintae brevis accessory head from the tendon of the flexor carpi ulnaris the transverse carpal ligament the fascia of the forearm or the tendon of the pulmaris longus a portion of the muscle may insert into the metacarpal or separate slips of the pisimetacarpus pisciancinatus or the piscianularis muscle may exist nerves all the muscles of this group are supplied by the eighth cervical nerve through the ulnar nerve actions the abductor and flexor digitiae quintae brevis from the ring finger and assist in flexing the proximal phalanx the opponent's digitiae quintae draws forward the fifth metacarpal bone so as to deepen the hollow of the palm the pulmaris brevis corrugates the skin on the ulnar side of the palm three the intermediate muscles lumbricalis interosi the lumbricalis are four small fleshy fasciculi associated with the tendons of the flexor digitiae for fundus the first and second arrives from the radial sides and roller surfaces of the tendons of the index and middle fingers respectively the third from the contiguous sides of the tendons of the middle and ring fingers and the fourth from the contiguous sides of the tendons of the ring and little fingers each passes to the radial side of the corresponding finger and opposite the metacarpal phalangeal articulation is inserted into the tendonus expansion of the extensor digitorum communis covering the dorsal aspect of the finger variations the lumbricalis vary in number from two to five or six and there is considerable variation in insertions the interosi are so named from occupying the intervals between the metacarpal bones and are divided into two sets a dorsal and a roller the interosi dorsalis dorsal interosi are four in number and occupy the intervals between the metacarpal bones they are by peniform muscles each arising by two heads from the adjacent sides of the metacarpal bones but more extensively from the metacarpal bone of the finger into which the muscle is inserted they are inserted into the bases of the first phalanges and into the upper neuroses of the tendons of the extensor digitorum communis between the double origin of each of these muscles is a narrow triangular interval through the first of these the radial artery passes through each of the other three a perforating branch from the deep roller arches transmitted the first or abductive indicus is larger than the others it is flat triangular in form and arises by two heads separated by a fibrous arch for the passage of the radial artery from the dorsum to the palm of the hand the lateral head arises from the proximal half of the ulnar border of the first metacarpal bone the medial head from almost the entire length of the radial border of the second metacarpal bone the tendon is inserted into the radial side of the index finger the second and third are inserted into the middle finger the former into its radial the latter into its ulnar side the fourth is inserted into the ulnar side of the ring finger the inter-osci bolaris palmar inter-osci three in number are smaller than the inter-osci dorsalis and placed upon the roller surfaces of the metacarpal bones rather than between them each arises from the entire length of the metacarpal bone of one finger and is inserted into the side of the base of the first phalanx and aponeurotic expansion of the extensor communist tendon to the same finger the first arises from the ulnar side of the second metacarpal bone and is inserted into the same side of the first phalanx of the index finger the second arises from the radial side of the fourth metacarpal bone and is inserted into the same side of the ring finger the third arises from the radial side of the fifth metacarpal bone and is inserted into the same side of the little finger from this account it may be seen that each finger is provided with two inter-osci with the exception of the little finger in which the abductor takes the place of one of the pair as already mentioned the medial head of the flexor pollicis previs is sometimes described as the inter-osci the third is volaris primus nerves the two lateral lumbacalis are supplied by the sixth and seventh cervical nerves through the third and fourth digital branches of the median nerve the two medial lumbacalis and all the inter-osci are supplied by the eighth cervical nerve through the deep palmar branch of the ulnar nerve the third lumbacalis frequently receives a twig from the median actions the inter-osci volaris adopt the fingers to an imaginary line drawn longitudinally through the center of the middle finger and the inter-osci dorsalis abduct the fingers from that line in addition to this the inter-osci in conjunction with the lumbacalis flex the first phalanges at the metacarpophalangeal joints and extend the second and third phalanges in consequence of their insertions into the expansions of the extensor tendons the extensor digitalum communus is believed to act almost entirely on the first phalanges end of section number 48 section number 49 of Grey's Anatomy part 2 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 Morgan Scorpion Anatomy of the Human Body part 2 by Henry Grey Muscles and Pateae of the Iliac region the muscles of the lower extremity are subdivided into groups corresponding with the different regions of the limb 1. Muscles of the Iliac region 2. Muscles of the thigh 3. Muscles of the leg 4. Muscles of the foot the muscles and Pateae of the Iliac region so as major and major and major and major so as major so as minor Iliacus the fascia covering the psoas and Iliacus is thin above and becomes gradually thicker below as it approaches the ingreenal ligament the portion covering the psoas is thickened above to form the medial lumbarcostal arch which stretches from the transverse process of the first lumbar vertebra to the body of the second medially it is attached by a series of arched processes intervertebral fibro cartilages and prominent margins of the bodies of the vertebrae and to the upper part of the sacrum the intervals left opposite the constricted portions of the bodies transmit the lumbar arteries and veins and filaments of the sympathetic trunk laterally above the quest of the Ilium it is continuous with the fascia covering the front of the quadratus lumborum while below the quest of the Ilium it is continuous with the fascia covering the Iliacus the portions investing the Iliacus fascia Iliacus, Iliac fascia is connected laterally to the whole length of the inner lip of the Iliac quest and medially to the linear terminalis of the lesser pelvis where it is continuous with the periosteum at the Iliopectoneal eminence it receives the tendon of insertion of the psoas minor when that muscle exists lateral to the femoral vessels it is intimately connected to the posterior margin of the inguinal ligament and is continuous with the transversalis fascia immediately lateral to the femoral vessels the Iliac fascia is prolonged backward and medial wood from the inguinal ligament as a band the Iliopectoneal fascia which is attached to the Iliopectoneal eminence this fascia divides the space between the inguinal ligament and the hip bone into two lacunae or compartments the medial of which transmits the femoral vessels the lateral, the psoas major the femoral nerve medial to the vessels the Iliac fascia is attached to the pectoneal line behind the inguinal aponeurotic vox where it is again continuous with the transversalis fascia on the thigh the fascia of the Iliacis and psoas form a single sheet to turn the Iliopectoneal fascia where the external Iliac vessels pass into the thigh the fascia descends behind them forming the posterior wall of the femoral sheath the portion of the Iliopectoneal fascia which passes behind the femoral vessels is also attached to the pectoneal line beyond the limits of the attachment of the inguinal aponeurotic vox at this part it is continuous with the pectoneal fascia the external Iliac vessels lie in front of the Iliac fascia but all the branches of the lumbar plexus are behind it it is separated from the peritoneum by a quantity of loose ariola tissue the psoas major, psoas magnus is a long pfusiform muscle placed on the side of the lumbar region of the vertical column and brim of the lesser pelvis it arises 1. from the anterior surfaces of the bases and lower borders of the transverse processes of all the lumbar vertebrae 2. from the sides of the bodies and the corresponding intervertebral fibrocartilages of the last thoracic and all the lumbar vertebrae by five slips each of which is attached to the adjacent upper and lower margins of two vertebrae and two of the intervertebral fibrocartilage 3. from a series of tenderness arches which extend across the constricted parts of the bodies of the lumbar vertebrae between the previous slips the lumbar arteries and veins and filaments from the sympathetic trunk pass beneath these tenderness arches the muscle proceeds downward across the brim of the lesser pelvis and diminishing gradually in size passes beneath the ingrinal ligament and in front of the capsule of the hip joint and ends in a tendon the tendon receives nearly the whole of the fibres of the iliacus and is inserted into the lesser trochanter of the femur a large bursa which may communicate with the cavity of the hip joint separates the tendon from the pubis and the capsule of the joint the psoas minor psoas parvas is a long slender muscle placed in front of the psoas major it arises from the sides of the bodies of the 12th thoracic and first lumbar vertebrae and from the fibrocartilage between them ends in a long flat tendon which is inserted into the pectinial line and iliopectinial eminence and by its lateral border into the iliac fascia this muscle is often absent the iliacus is a flat triangular muscle which fills the iliac fossa it arises from the upper two thirds of this fossa and from the inner lip of the iliac crest behind from the anterior sacroiliac and the iliolumbar ligaments and base of the sacrum in front it reaches as far as the anterior superior and anterior inferior iliac spines and the notch between them the fibres converge to be inserted into the lateral side of the tendon of the psoas major some of them being prolonged on the body of the femur for about 2.5 cm below and in front of the lesser trochanter note 85 the psoas major and iliacus are sometimes regarded as a single muscle named the iliopsoas end of note 85 variations the iliacus minor or iliocapsularis a small detached part of the iliacus is frequently present it arises from the anterior inferior spine of the ilium and is inserted into the lower part of the inter trochanteric line of the femur or into the iliopemoral ligament nerves the psoas major is supplied by branches of the second and third lumbar nerve the psoas minor by a branch of the first lumbar nerve and the iliacus by branches of the second and third lumbar nerves through the femoral nerve actions the psoas major acting from above flexes the thigh upon the pelvis being assisted by the iliacus acting from below with the femur fixed it bends the lumbar portion of the vertical column forward and to its own side and then in conjunction with the iliacus tilts the pelvis forward when the muscles of both sides are acting from below they serve to maintain the erect posture by supporting the vertical column and pelvis upon the femoral or in continued action bend the trunk and pelvis forward as in raising the trunk from the recumbent posture the psoas minor is a tensor of the iliac fascia End of section number 49