 Section 17 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 the Bodster. Anatomy of the Human Body Part 2 by Henry Grey Section 7b. The Knee Joint Articulatio genu. The Knee Joint was formally described as the Ginglimus or Hinge Joint, but is really of a much more complicated character. It must be regarded as consisting of three articulations in one. Two condyloid joints. One between each condyle of the femur and the corresponding meniscus and the condyle of the tibia. And a third between the patella and the femur. Part arthrodial, but not completely so, since the articular surfaces are not mutually adapted to each other, so that the movement is not a simple gliding one. This view of the construction of the Knee Joint receives confirmation from the study of the articulation in some of the lower mammals, where, corresponding to these three subdivisions, three synovial cavities are sometimes found, either entirely distinct or only connected together by small communications. This view is further rendered probable by the existence in the middle of the joint of the two cruciate ligaments, which must be regarded as the collateral ligaments of the medial and lateral joints. The existence of the patella fold of synovial membrane would further indicate a tendency to separation of the synovial cavity into two minor sacs, one corresponding to the lateral and the other to the medial joint. The bones are connected together by the following ligaments. The articular capsule, the ligamentum patellae, the oblique popliteal, the tibial collateral, the fibular collateral, the anterior cruciate, the posterior cruciate, the medial and lateral menisci, the transverse, and the coronary. The articular capsule, capsular articularis, capsular ligament. The articular capsule consists of a thin but strong fibrous membrane which is strengthened in almost its entire extent by bands inseparably connected with it, above and in front, beneath the tendon of the quadriceps femoris. It is represented only by the synovial membrane. Its chief strengthening bands are derived from the fasciolata and from the tendons surrounding the joint. In front, expansions from the vasti and from the fasciolata and its iliotibial band fill in the intervals between the anterior and collateral ligaments, constituting the medial and lateral patella retinacula. Behind the capsule consists of vertical fibres which arise from the condyles and from the sides of the intercondyloid fossa of the femur. The posterior part of the capsule is therefore situated on the sides of and in front of the cruciate ligaments which are thus excluded from the joint cavity. Behind the cruciate ligaments is the oblique popliteal ligament which is augmented by fibres derived from the tendon of the semi-membranosis. Laterally, a prolongation from the iliotibial band fills in the interval between the oblique popliteal and the fibular collateral ligaments and partly covers the latter. Immediately expansions from the sartorius and the semi-membranosis pass upward to the tibial collateral ligament and strengthen the capsule. The ligamentum patellae anterior ligament. The ligamentum patellae is the central portion of the common tendon of the quadriceps femoris which is continued from the patella to the tuberosity of the tibia. It is a strong flat ligamentus band about 8 cm in length attached above to the apex and adjoining margins of the patellae and the rough depression on its posterior surface. Below to the tuberosity of the tibia its superficial fibres are continuous over the front of the patellae with those of the tendon of the quadriceps femoris. The medial and lateral portions of the tendon of the quadriceps pass down on either side of the patellae to be inserted into the upper extremity of the tibia on either side of the tuberosity. These portions merge into the capsule as stated above forming the medial and lateral patellae retinocular. The posterior surface of the ligamentum patellae is separated from the synovial membrane of the joint by a large infra-patella pad of fat and from the tibia by a bursa. The oblique poplitea ligament ligamentum popliteum obliqueum posterior ligament. This ligament is a broad, flat, fibrous band formed of fasciculi separated from one another by apertures from the passage of vessels and nerves. It is attached above to the upper margin of the intercondyloid fossa and posterior surface of the femur close to the articular margins of the condyles and below to the posterior margin of the head of the tibia. Superficial to the main part of the ligament is a strong fasciculus derived from the tendon of the semi-membranosis and passing from the back part of the medial condyle of the tibia obliquely upward and lateralward to the back part of the lateral condyle of the femur. The oblique poplitea ligament forms part of the floor of the popliteal fossa and the popliteal artery rests upon it. The tibial collateral ligament ligamentum collateral tibial internal lateral ligament. The tibial collateral is a broad, flat, membranous band situated nearer to the back than to the front of the joint. It is attached above to the medial condyle of the femur immediately below the adductor tubicle below to the medial condyle and medial surface of the body of the tibia. The fibres of the posterior part of the ligament are short and inclined backward as they descend. They are inserted into the tibia above the groove for the semi-membranosis. The anterior part of the ligament is a flattened band about 10 centimetres long which inclines forward as it descends. It is inserted into the medial surface of the body of the tibia about 2.5 centimetres below the level of the condyle. It is crossed at its lower part by the tendons of the sartorius, gracilis and semi-tendonosis a bursa being interposed. Its deep surface covers the inferior medial genicular vessels and nerve and the anterior portion of the tendon of the semi-membranosis with which it is connected by a few fibres. It is intimately adherent to the medial meniscus. The fibular collateral ligament ligamentum collateral fibular external lateral or long external lateral ligament. The fibular collateral is a strong rounded fibrous cord attached above to the back part of the lateral condyle of the femur immediately above the groove for the tendon of the popliteus. Below to the lateral side of the head of the fibula in front of the styloid process the greater part of its lateral surface is covered by the tendon of the biceps femoris. The tendon however divides at its insertion into two parts which are separated by the ligament. Deep to the ligament are the tendon of the popliteus and the inferior lateral genicular vessels and nerve. Ligament has no attachment to the lateral meniscus and in constant bundle of fibres the short fibular collateral ligament is placed behind and parallel with the proceeding attached above to the lower and back part of the lateral condyle of the femur below to the summit of the styloid process of the fibula. Passing deep to it are the tendon of the popliteus and the inferior lateral genicular vessels and nerve. The cruciate ligaments ligamenta cruciata genu crucial ligaments. The cruciate ligaments are of considerable strength situated in the middle of the joint near to its posterior than to its anterior surface. They are called cruciate because they cross each other somewhat like the lines of the letter X and have received the names anterior and posterior from the position of their attachments to the tibia. The anterior cruciate ligament ligamentum cruciatum anteriorus external crucial ligament is attached to the depression in front of the intercondyloid eminence of the tibia being blended with the anterior extremity of the lateral meniscus. It passes upward, backward and lateral wood and is fixed into the medial and back part of the lateral condyle of the femur. The posterior cruciate ligament ligamentum cruciatum posteriorus internal crucial ligament is stronger but shorter and less oblique in its direction than the anterior. It is attached to the posterior intercondyloid fossa of the tibia and to the posterior extremity of the lateral meniscus and passes upward, forward and medial wood to be fixed into the lateral and front part of the medial condyle of the femur. The menisci semi-lunar fibrocartilages The menisci are two crescentic lamellae which serve to deepen the surfaces of the head of the tibia for articulation with the condyles of the femur. The peripheral border of each meniscus is thick, convex and attached to the inside of the capsule of the joint. The opposite border is thin, concave and free. The upper surfaces of the menisci are concave and in contact with the condyles of the femur. Their lower surfaces are flat and rest upon the head of the tibia. Both surfaces are smooth and invested by synovial membrane. Each meniscus covers approximately the peripheral two-thirds of the corresponding articular surface of the tibia. The medial meniscus, meniscus medialis internal semi-lunar fibrocartilage is nearly semicircular in form, a little elongated from before backward and broader behind than in front. Its anterior end, thin and pointed, is attached to the anterior intercondyloid fossa of the tibia in front of the anterior cruciate ligament. Its posterior end is fixed to the posterior intercondyloid fossa of the tibia between the attachments of the lateral meniscus and the posterior cruciate ligament. The lateral meniscus, meniscus lateralis, external semi-lunar fibrocartilage, is nearly circular and covers a larger portion of the articular surface than the medial one. It is grooved laterally for the tendon of the popliteus, which separates it from the fibular collateral ligament. Its anterior end is attached in front of the intercondyloid eminence of the tibia, lateral to and behind the anterior cruciate ligament with which it blends. The posterior end is attached behind the intercondyloid eminence of the tibia and in front of the posterior end of the medial meniscus. The anterior attachment of the lateral meniscus is twisted on itself so that its free margin looks backward and upward. Its anterior end resting on a sloping shelf of bone on the front of the lateral process of the intercondyloid eminence. Close to its posterior attachment, it sends off a strong fasciculus, the ligament of Risberg, which passes upward and medial wood to be inserted into the medial condyle of the femur, immediately behind the attachment of the posterior cruciate ligament. Occasionally, a small fasciculus passes forward to be inserted into the lateral part of the anterior cruciate ligament. The lateral meniscus gives off from its anterior convex margin a fasciculus which forms the transverse ligament. The transverse ligament, ligamentum transversum genu. The transverse ligament connects the anterior convex margin of the lateral meniscus to the anterior end of the medial meniscus. Its thickness varies considerably in different subjects and it is sometimes absent. The coronary ligaments are merely portions of the capsule which connect the periphery of each meniscus with the margin of the head of the tibia. End of section 17, the knee joint. From the Human Body Part 2 by Henry Gray. Section 18 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. Recording by the Bodster. Anatomy of the Human Body Part 2 by Henry Gray. Section 7b, the knee joint. Articulatio genu. Synovial membrane. The synovial membrane of the knee joint is the largest and most extensive in the body. Commencing at the upper border of the patella, it forms a large cul-de-sac beneath the quadriceps femoris on the lower part of the front of the femur and frequently communicates with a bursa interposed between the tendon and the front of the femur. The pouch of synovial membrane between the quadriceps and front of the femur is supported during the movement of the knee by a small muscle, the articularis genu, which is inserted into it. On either side of the patella, the synovial membrane extends beneath the aponeuroses of the vasty and more especially beneath that of the vastus medialis. Below the patella, it is separated from the ligamentum patella by a considerable quantity of fat. Known as the infrapatella pad. From the medial and lateral borders of the articular surface of the patella, re-duplications of the synovial membrane project into the interior of the joint. These form two fringe-like folds termed the ailer folds. Below, these folds converge and are continued as a single band, the patella fold, ligamentum mucosum, to the front of the intercondyloin fossa of the femur. On either side of the joint, the synovial membrane passes downward from the femur, lining the capsule to its point of attachment to the menisci. It may then be traced over the upper surfaces of these to their free borders and fence along their undersurfaces to the tibia. At the back part of the lateral meniscus, it forms a cul-de-sac between the groove on its surface and the tendon of the popliteus. It is reflected across the front of the cruciate ligaments, which are therefore situated outside the synovial cavity. Bursae The bursae near the knee joint are the following. In front, there are four bursae. A large one is interposed between the patella and the skin, a small one between the upper part of the tibia and the ligamentum patellae. A third between the lower part of the tuberosity of the tibia and the skin. And a fourth between the anterior surface of the lower part of the femur and the deep surface of the quadriceps femoris, usually communicating with the knee joint. Laterally, there are four bursae. One, which sometimes communicates with the joint, between the lateral head of the gastrocnemius and the capsule. One, between the fibular collateral ligament and the tendon of the biceps. One, between the fibular collateral ligament and the tendon of the popliteus. This is sometimes only an expansion from the next bursae. And one, between the tendon of the popliteus and the lateral condyle of the femur, usually an extension from the synovial membrane of the joint. Medially, there are five bursae. One, between the medial head of the gastrocnemius and the capsule. This sends a prolongation between the tendon of the medial head of the gastrocnemius and the tendon of the semi-membranosis and often communicates with the joint. One, superficial to the tibial collateral ligament between it and the tendons of the sartorius, gracilus, and semi-tendonosis. One, deep to the tibial collateral ligament between it and the tendon of the semi-membranosis. This is sometimes only an expansion from the next bursae. One, between the tendon of the semi-membranosis and the head of the tibia. And occasionally there is a bursae between the tendons of the semi-membranosis and the semi-tendonosis. Structures around the joint. In front and at the sides is the quadriceps femoris. Laterally, the tendons of the biceps femoris and the common perineal nerve. Medially, the sartorius, gracilus, semi-tendonosis, and semi-membranosis. Behind, the popliteal vessels and the tibial nerve popliteus, plantaris, and medial and lateral heads of the gastrocnemius, some lymph glands, and fat. The arteries supplying the joints are the highest genicular, anastomotica magna, a branch of the femoral, the genicular branches of the popliteal, the recurrent branches of the anterior tibial, and the descending branch from the lateral femoral circumflex of the profunda femoris. The nerves are derived from the obturata, femoral, tibial, and common perineal. Movements The movements which take place at the knee joint are flexion and extension, and, in certain positions of the joint, internal and external rotation. The movements of flexion and extension at this joint differ from those in a typical hinge joint, such as the elbow in that A. The axis around which motion takes place is not a fixed one, but shifts forward during extension and, B, the commencement of flexion and the end of extension are accompanied by rotatory movements associated with the fixation of the limb in a position of great stability. The movement from full flexion to full extension may therefore be described in three phases. One, in the fully flexed condition, the posterior parts of the femoral condyles rest on the corresponding portions of the menisco-tibial surfaces. And, in this position, a slight amount of simple rolling movement is allowed. Two, during the passage of the limb from the flexed to the extended position, a gliding movement is superposed on the rolling so that the axis, which at the commencement is represented by a line through the inner and outer condyles of the femur, gradually shifts forward. In this part of the movement, the posterior two-thirds of the tibial articular surfaces of the two femoral condyles are involved, and as these have similar curvatures and are parallel to one another, they move forward equally. And, three, the lateral condyle of the femur is brought almost to rest by the tightening of the anterior cruciate ligament. It moves, however, slightly forward and medial wood, pushing before it the anterior part of the lateral meniscus. The tibial surface on the medial condyle is prolonged farther forward than that on the lateral, and this prolongation is directed lateralward. When, therefore, the movement forward of the condyle is checked by the anterior cruciate ligament, continued muscular action causes the medial condyle dragging with it the meniscus to travel backward and medial wood, thus producing an internal rotation of the thigh on the leg. When the position of full extension is reached, the lateral part of the groove on the lateral condyle is pressed against the anterior part of the corresponding meniscus, while the medial part of the groove rests on the articular margin in front of the lateral process of the tibial intercondyloid eminence. Into the groove on the medial condyle is fitted the anterior part of the medial meniscus, while the anterior cruciate ligament and the articular margin in front of the medial process of the tibial intercondyloid eminence are received into the fore part of the intercondyloid fossa of the femur. This third phase by which all these parts are brought into accurate apposition is known as the screwing home or locking movement of the joint. The complete movement of flexion is the converse of that described above and is therefore preceded by an external rotation of the femur which unlocks the extended joint. The axes around which the movements of flexion and extension take place are not precisely at right angles to either bone. In flexion the femur and tibia are in the same plane but in extension the one bone forms an angle opening lateral wood to the other. In addition to the rotary movements associated with the completion of extension and initiation of flexion rotation inward or outward can be affected when the joint is partially flexed. These movements take place mainly between the tibia and the menisci and are freest when the leg is bent at right angles with the thigh. Movements of patella The articular surface of the patella is indistinctly divided into seven facets upper, middle and lower horizontal pairs and a medial perpendicular facet. When the knee is forcibly flexed the medial perpendicular facet is in contact with the semi-lunar surface of the lateral part of the medial condyle. This semi-lunar surface is a prolongation backward of the medial part of the patella surface. As the leg is carried from the flex to the extended position first the highest pair then the middle pair and lastly the lowest pair of horizontal facets is successively brought into contact with the patella surface of the femur. In the extended position when the quadriceps femoris is relaxed the patella lies loosely on the front of the lower end of the femur. During flexion the ligamentum patella is put upon the stretch and in extreme flexion the posterior cruciate ligament the oblique popliteal and collateral ligaments and to a slight extent the anterior cruciate ligament are relaxed. Flexion is checked during life by the contact of the leg with the thigh. When the knee joint is fully extended the oblique popliteal and collateral ligaments the anterior cruciate ligament and the posterior cruciate ligament are rendered tense. In the act of extending the knee the ligamentum patella is tightened by the quadriceps femoris but in full extension with the heel supported it is relaxed. Rotation inward is checked by the anterior cruciate ligament rotation outward tends to uncross and relax the cruciate ligaments but is checked by the tibial collateral ligament. The main function of the cruciate ligament is to act as a direct bond between the tibia and femur and to prevent the former bone from being carried too far backward or forward. They also assist the collateral ligaments in resisting any bending of the joint to either side. The menisci are intended as it seems to adapt the surfaces of the tibia to the shape of the femoral condyles to a certain extent so as to fill up the intervals which would otherwise be left of the joint and to obviate the jars which would be so frequently transmitted up the limb in jumping or by falls on the feet also to permit of the two varieties of motion flexion and extension and rotation as explained above. The patella is a great defence to the front of the knee joint and distributes upon a large and tolerably even surface during kneeling the pressure to otherwise fall upon the prominent ridges of the condyles. It also affords leverage to the quadriceps femoris. When standing erect in the attitude of tension the weight of the body falls in front of a line carried across the centres of the knee joints and therefore tends to produce overextension of the articulations. This however is prevented by the tension of the anterior cruciate, oblique, popliteal and collateral ligaments. Extension of the leg on the thigh is performed by the quadriceps femoris. Flexion by the biceps femoris semi-tendinosis and semi-membranosis assisted by the gracilis sartorius gastrocnemius popliteus and plantaris. Rotation outward is affected by the biceps femoris and rotation inward by the popliteus semi-tendinosis and to a slight extent the semi-membranosis the sartorius and the gracilis. The popliteus comes into action especially at the commencement of the movement of flexion of the knee. By its contraction the leg is rotated inward or if the tibia be fixed the thigh is rotated outward and the knee joint is unlocked. End of section 18 The Knee Joint Recorded by The Bodster from Anatomy of the Human Body Part 2 by Henry Gray Section 19 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 Recording by Ruth Golding Anatomy of the Human Body Part 2 by Henry Gray 7C Articulations between the tibia and fibula The articulations between the tibia and fibula are affected by ligaments which connect the extremities and bodies of the bones. The ligaments may consequently be subdivided into three sets 1. Those of the tibiofibular articulation 2. The interosseous membrane 3. Those of the tibiofibular cindysmosis Tibiofibular articulation Articulatio-tibiofibularis Superior tibiofibular articulation This articulation is an arthrodial joint between the lateral condyle of the tibia and the head of the fibula. The contiguous surfaces of the bones are affected by the tibia The contiguous surfaces of the bones present flat oval facets covered with cartilage and connected together by an articular capsule and by anterior and posterior ligaments. The articular capsule Capsular articularis Capsular ligament The articular capsule surrounds the articulation being attached around the margins of the articular facets on the tibia and fibula. It is much thicker in front than behind. The anterior ligament anterior superior ligament The anterior ligament of the head of the fibula consists of two or three broad and flat bands which pass obliquely upward from the front of the head of the fibula to the front of the lateral condyle of the tibia. The posterior ligament posterior superior ligament The posterior ligament of the head of the fibula is a single thick and broad band which passes obliquely upward from the back of the head of the fibula to the back of the lateral condyle of the tibia. It is covered by the tendon of the popliteus. Synovial membrane A synovial membrane lines the capsule It is continuous with that of the knee joint in occasional cases when the two joints communicate. Interosseous membrane Membrana interossea cruris Middle tibia fibula ligament An interosseous membrane extends between the interosseous crests of the tibia and fibula and separates the muscles on the front from those on the back of the leg. It consists of a thin aponeurotic lamina composed of two or three broad and flat bands of aponeurotic lamina composed of oblique fibres which for the most part run downward and lateralward Some few fibres however pass in the opposite direction It is broader above than below Its upper margin does not quite reach the tibia fibula joint but presents a free concave border above which is a large oval aperture for the passage of anterior tibial vessels to the front of the leg In its lower part is an opening for the passage of the anterior peroneal vessels It is continuous below with the interosseous ligament of the tibia fibula cindysmosis and presents numerous perforations for the passage of small vessels It is in relation in front with the tibialis anterior extensor digitorum longus extensor halusis proprius peroneus tertius and the anterior tibial vessels and deep peroneal nerve behind with the tibialis posterior and flexor halusis longus tibia fibula cindysmosis cindysmosis tibia fibularis inferior tibia fibula articulation This cindysmosis is formed by the rough convex surface of the medial side of the lower end of the fibula and a rough concave surface on the lateral side of the tibia Below, to the extent of about 4mm these surfaces are smooth and covered with cartilage which is continuous with that of the ankle joint The ligaments are anterior, posterior, inferior, posterior, inferior transverse and interosseous The anterior ligament ligamentum malleoli lateralis anterios anterior inferior ligament The anterior ligament of the lateral malleolus is a flat triangular band of fibres broader below than above which extends obliquely downward and lateral between the adjacent margins of the tibia and fibula on the front aspect of the cindysmosis It is in relation in front with the peroneus tertius the aponeurosis of the leg and the integument behind with the interosseous ligament and lies in contact with the cartilage covering the talus The posterior ligament ligamentum malleoli lateralis posterior posterior inferior ligament The posterior ligament of the lateral malleolus smaller than the preceding is disposed in a similar manner on the posterior surface of the cindysmosis The inferior transverse ligament The inferior transverse ligament lies in front of the posterior ligament and of yellowish fibres which passes transversely across the back of the joint from the lateral malleolus to the posterior border of the articular surface of the tibia almost as far as its malleola process This ligament projects below the margin of the bones and forms part of the articulating surface for the talus The interosseous ligament The interosseous ligament consists of numerous short strong fibrous bands which pass between the contiguous rough surfaces of the tibia and fibula and constitute the chief bond of union between the bones It is continuous above with the interosseous membrane Cenovial membrane The Cenovial membrane associated with the small arthrodial part of the joint is continuous with that of the ankle joint End of Section 19 Recording by Ruth Golding Section 20 of Grey's Anatomy Part 2 This is LibriVox Recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recording by Logan McCammon Anatomy of the Human Body Neural Articulation The ankle joint is a gigglemus or hinge joint The structures entering into its formation are the lower end of the tibia and its malleolus The malleolus of the fibula and the transverse ligament which together form a mortise for the reception of the upper convex surface of the talus and its medial and lateral facets The bones are connected by the following ligaments The Articular Capsule The Anterior Talofibular The Deltoid The Posterior Talofibular And the Calceniofibular The Articular Capsule Capsula Articularis Capsular Ligament The Articular Capsule surrounds the joints and is attached above to the borders of the Articular surfaces of the tibia and malleoli and below to the talus around its upper Articular surface The anterior part of the capsule anterior ligament is a broad thin membranous layer attached above to the anterior margin of the lower end of the tibia below to the talus in front of its superior Articular surface It is in relation in front with the extensor tendons of the toes The tendons of the tibialis interior and perionis, tertius and the interior tibial vessels and deep peronial nerve The posterior part of the capsule posterior ligament is very thin and consists principally of transverse fibres It is attached above to the margin of the Articular surface of the tibia, blending with the transverse ligament below to the talus behind its superior Articular facet Laterally it is somewhat thickened and is attached to the hollow on the medial surface of the lateral malleolus The deltoid ligament Ligamentum deltoidium internal lateral ligament The deltoid ligament is a strong flat triangular band attached above to the apex and interior and posterior borders of the medial malleolus It consists of two sets of fibres superficial and deep Of the superficial fibres the most interior, tibionovacular has forward to be inserted into the tuberosity of the navicular bone and immediately behind this they blend with the medial margin of the planter calcianovacular ligament The middle, calceniotibular descend almost perpendicular to be inserted into the hole of the cistentaculum talae of the calcenius the posterior fibres, posterior telotibial, has backward and lateral word to be attached to the inner side of the talus and to the prominent tubercle its posterior surface medial to the groove for the tendon of the flexor halusus longus the deep fibres, anterior telotibial are attached above to the tip of the medial malleolus and below to the medial surface of the talus the deltoid ligament is covered by the tendons of the tibialis posterior and flexor digatorum longus the anterior and posterior talaeofibular calceniotibular ligaments were formally described as the three fessiculi of the external lateral ligament of the ankle joint the anterior talofibular ligament ligamentum talofibular enterius the anterior talofibular ligament, the shortest of the three passes from the anterior margin of the fibular malleolus forward and mediali to the talus in front of its lateral articular facet the posterior talofibular ligament ligamentum talofibular posterius the posterior talofibular ligament, the strongest and most deeply seated runs almost horizontally from the depression medial and back part of the fibular malleolus to a prominent tubercle on the posterior surface of the talus immediately lateral to the groove from the tendon of the flexor halusus longus the calceniotibular ligament ligamentum calceniotibular the calceniotibular ligament the longest of the three is a narrow rounded cord running from the apex of the fibular malleolus downward and slightly backward to a tubercle on the lateral surface of the calceniotis it is covered by the tendons of the peronei longus and bravis synovial membrane the synovial membrane invests the deep surfaces of the ligaments and sends a small process upward between the lower ends of the tibia and fibula relations the tendons vessels and nerves in connection with the joint R in front from the medial side the tibialis interior flexor halusius proprius anterior tibial vessels deep peroneal nerve extensor digitorum longus and peroneus tertius behind from the medial side the tibialis posterior flexor digitorum longus posterior tibial vessels tibial nerve flexor halusius longus and in the groove behind the fibular malleolus the tendons of the peronei longus and bravis the arteries supplying the joint are derived from the malleolar branches of the anterior tibial and the peroneal the nerves are derived from the deep peroneal and tibial movements when the body is in the erect position the foot is at a right angle to the leg the movements of the joint are those of dorsiflexion and extension dorsiflexion consists in the approximation of the dorsum of the foot to the front of the leg while in extension the heel is drawn up and the toes pointed downward the range of movement varies in different individuals from about 50 degrees to 90 degrees the transverse axis about which movement takes place is slightly oblique the malleoli tightly embrace the talus in all positions of the joint so that any slight degree of side to side movement which may exist in simply due to stretching of the ligaments of the talofibular syndesmosis the bending of the body of the fibula the superior articular surface of the talus is broader in front than behind dorsiflexion, therefore greater space is required between the two malleoli this is obtained by a slight outward rotatory movement of the lower end of the fibula in a stretching of the ligaments of the syndesmosis this lateral movement is facilitated by a slight gliding of the tibiofibular articulation and possibly also by the bending of the body of the fibula of the ligaments the deltoid is a very great power so much so that it usually resists a force which fractures the process of the bone to which it is attached its middle portion together with the calcinofibular ligament finds the bone of the leg firmly to the foot and resists displacement in every direction its anterior and posterior fibers limit extension and flexion in the foot respectively and the anterior fibers also limit abduction the posterior talofibular ligament assists the calcinofibular in resisting the displacement of the foot backward and deepens the cavity for the reception of the talus the anterior talofibular is a security against the displacement of the foot forward and limits extension of the joint the talus is a version and a version of the foot together with the minute changes informed by which it is applied to the ground or takes hold of an object in climbing etc are mainly affected in the tarsal joints the joint which enjoys the greatest amount of motion being that between the talus and consaneus behind and the navicular and cuboid in front that is often called the transverse tarsal joint and it can with the subordinate joints of the tarsus replace the ankle joint in a great measure when the ladder has become ankylosed extension of the foot upon the tibia and fibula is produced by the gastrocnemius soleus, plantaris, tibialis posterior, heronylangus and brevis flexor digatorum langus and flexor halusius langus dorsiflexion or the tibialis anterior, heronis tertius extensor digatorum langus and extensor halusius propius note 74 the student must bear in mind that the extensor digatorum langus and extensor halusius propius are extensors of the toes but flexors of the ankle and that flexor digatorum langus and flexor halusius langus are flexors of the toes but extensors of the ankle end of section 20 recording by Logan McCammon section 21 section 21 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 the Bodster anatomy of the human body part 2 by Henry Grey section 7e intertarsal articulations articulations intertarsiae articulations of the tarsus talo-calcaneal articulation articulatio-talo-calcanea articulation of the calcaneus and astragalus calcaneo-astragalloid articulation the articulations between the calcaneus and the talus are two in number anterior and posterior of these the anterior forms part of the talo-calcaneo navicular joint and will be described with that articulation the posterior or talo-calcaneal articulation is formed between the posterior-calcaneal facet on the inferior surface of the talus and the posterior facet on the superior surface of the calcaneus it is an arthrodial joint and the two bones are connected by an articular capsule and by anterior, posterior lateral, medial and interosseous talo-calcaneal ligaments the articular capsule capsular articularis the articular capsule envelopes the joint and consists for the most part of the short fibres which are split up into distinct slips between these there is only a weak fibrous investment the anterior talo-calcaneal ligament ligamentum talo-calcaneum anterior anterior calcaneo astragalloid ligament the anterior talo-calcaneal ligament extends from the front and lateral surface of the neck of the talus to the superior surface of the calcaneus it forms the posterior boundary of the talo-calcaneo navicular joint and is sometimes described as the anterior interosseous ligament the posterior talo-calcaneal ligament ligamentum talo-calcaneum posterior posterior calcaneo astragalloid ligament the posterior talo-calcaneal ligament connects the lateral tubicle of the talus with the upper and medial part of the calcaneus it is a short band and its fibres radiate from their narrow attachment to the talus the lateral talo-calcaneal ligament mantum talo-calcaneum lateral external calcaneo astragalloid ligament the lateral talo-calcaneal ligament is a short strong fasciculus passing from the lateral surface of the talus immediately beneath its fibular facet to the lateral surface of the calcaneus it is placed in front of but on a deeper plane then the calcaneo fibular ligament with the fibres of which it is parallel the medial talo-calcaneal ligament ligamentum talo-calcaneum medial internal calcaneo astragalloid ligament the medial talo-calcaneal ligament connects the medial tubicle of the back of the talus with the back of the cistendaculum tali its fibres blend with those of the plantar calcaneo navicular ligament the interosseous talo-calcaneal ligament ligamentum talo-calcaneum interosseum the interosseous talo-calcaneal ligament forms the chief bond of union between the bones it is in fact a portion of the united capsules of the talo-calcaneo navicular and the talo-calcaneal joints and consists of two partially united layers of fibres one belonging to the former and the other to the latter joint it is attached above to the groove between the articular facets of the undersurface of the talus below to a corresponding depression on the upper surface of the calcaneus it is very thick and strong being at least two and a half centimetres in breadth from side to side and serves to bind the calcaneus and the talus firmly together synovial membrane the synovial membrane lines the capsule of the joint and is distinct from the other synovial membranes of the tarsus movements the movements permitted between the talus and calcaneus are limited to gliding of the one bone on the other backward and forward and from side to side talo-calcaneo navicular articulation articulatio talo-calcaneo navicularis this articulation is an arthrodial joint the rounded head of the talus being received into the concavity formed by the posterior surface of the navicular the anterior articular surface of the calcaneus and the upper surface of the plant are calcaneo-navicular ligament there are two ligaments in this joint the articular capsule and the dorsal talo-navicular the articular capsule capsular articularis the articular capsule is imperfectly developed except posteriorly where it is considerably thickened it forms with a part of the capsule of the talo-calcaneo joint the strong interosseous ligament which fills in the canal formed by the opposing grooves on the calcaneus and talus as above mentioned the dorsal talo-navicular ligament ligamentum talo-navicular dorsal superior astragalo-navicular ligament this ligament is a broad thin band which connects the neck of the talus to the dorsal surface of the navicular bone it is covered by the extensor tendons the plantar calcaneo-navicular supplies the place of a plantar ligament for this joint sonovial membrane the sonovial membrane lines all parts of the capsule of the joint movements this articulation permits of a considerable range of gliding movements and some rotation its feeble construction allows occasionally of dislocation of the other bones of the tarsus from the talus calcaneo-cuboid articulation articulatio-calcaneo-cuboidia articulation of the calcaneus with the cuboid the ligaments connecting the calcaneus with the cuboid are five in number vis, the articular capsule the dorsal calcaneo-cuboid part of the bifurcated the long plantar and the plantar calcaneo-cuboid the articular capsule capsular articularis the articular capsule is an imperfectly developed investment containing certain strength in the bands which form the other ligaments of the joint the dorsal calcaneo-cuboid ligament ligamentum calcaneo-cuboidium dorsal superior calcaneo-cuboid ligament the dorsal calcaneo-cuboid ligament is a thin but broad fasciculus which passes between the contiguous surfaces of the calcaneus and cuboid on the dorsal surface of the joint the bifurcated ligament ligamentum bifurcatum internal calcaneo-cuboid interosseous ligament the bifurcated ligament is a strong band attached behind to the deep hollow of the upper surface of the calcaneus and dividing in front in a Y shaped manner into the calcaneo-cuboid and a calcaneo-navicular part the calcaneo-cuboid part is fixed to the medial side of the cuboid and forms one of the principal bonds between the first and second rows of the tarsal bones the calcaneo-navicular part is attached to the lateral side of the navicular the long plantar ligament ligamentum plantari longum long calcaneo-cuboid ligament superficial long plantar ligament the long plantar ligament is the longest of all the ligaments of the tarsus it is attached behind to the plantar surface of the calcaneus in front of the tuberosity and in front to the tuberosity on the plantar surface of the cuboid bone the more superficial fibres being continued forward to the bases of the second third and fourth metatarsal bones this ligament converts the groove on the plantar surface of the cuboid into a canal for the tendon of the peronius longus the plantar calcaneo-cuboid ligament ligamentum calcaneo-cuboidium plantari short calcaneo-cuboid ligament short plantar ligament plantar ligament the plantar calcaneo-cuboid ligament lies nearer to the bones than the proceeding from which it is separated by a little areola tissue it is a short but wide band of great strength and extends from the tubicle and the depression in front of it on the four part of the plantar surface of the calcaneus to the plantar surface of the cuboid behind the peroneal groove synovial membrane the synovial membrane lines the inner surface of the capsule and is distinct from that of the other tarsal articulations movements the movements permitted between the calcaneus and cuboid are limited to slight gliding movements of the bones upon each other the transverse tarsal joint is formed by the articulation of the calcaneus with the cuboid and the articulation of the talus with the navicular the movement which takes place in this joint is more extensive than that in the other tarsal joints and consists of a sort of rotation by means of which the foot may be slightly flexed or extended the sole being at the same time carried immediately inverted or laterally inverted the ligaments connecting the calcaneus and navicular though the calcaneus and navicular do not directly articulate they are connected by two ligaments the calcaneus and navicular part of the bifurcated and the plantar calcaneus and navicular the calcaneus and navicular part of the bifurcated ligament is described on page 354 the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament the plantar calcaneus and navicular ligament The plantar calcaneo-nevicular ligament is a broad and thick band of fibres which connects the anterior margin of the sustenaculum tallae of the calcaneus to the plantar surface of the navicular. This ligament not only serves to connect the calcaneus and navicular but supports the head of the talus forming part of the articular cavity in which it is received. The dorsal surface of the ligament presents a fibrocartiliginous facet lined by the synovial membrane and upon this a portion of the head of the talus rests. Its plantar surface is supported by the tendon of the tibialis posterior. Its medial border is blended with the forepart of the deltoid ligament of the ankle joint. The plantar calcaneo-nevicular ligament by supporting the head of the talus is principally concerned in maintaining the arch of the foot. When it yields the head of the talus is pressed downward medial wood and forward by the weight of the body and the foot becomes flattened expanded and turned lateral wood and exhibits the condition known as flat foot. This ligament contains a considerable amount of elastic fibres so as to give elasticity to the arch and spring to the foot. Hence it is sometimes called the spring ligament. It is supported on its plantar surface by the tendon of the tibialis posterior which spreads out at its insertion into a number of fasciculi to be attached to most of the tarsal and metatarsal bones. This prevents undue stretching of the ligament and is a protection against the occurrence of flat foot. Hence muscular weakness is in most cases the primary cause of the deformity. Cuneo-nevicular articulation, articulatio cuneo-nevicularis articulation of the nevicular with the cuneiform bones. The nevicular is connected to the three cuneiform bones by dorsal and plantar ligaments. The dorsal ligaments, ligamenta, neviculari, cuneiformia, dorsalia. The dorsal ligaments are three small bundles, one attached to each of the cuneiform bones. The bundle connecting the nevicular with the first cuneiform is continuous around the medial side of the articulation with the plantar ligament which unites these two bones. The plantar ligaments, ligamenta, neviculari, cuneiformia, plantaria. The plantar ligaments have a similar arrangement to the dorsal and are strengthened by slips from the tendon of the tibialis posterior. Sinovial membrane, the sinovial membrane of these joints is part of the great tarsal sinovial membrane. Movements, mere gliding movements are permitted between the nevicular and the cuneiform bones. Cuboidio-nevicular articulation. The nevicular bone is connected with the cuboid by dorsal, plantar and interosseous ligaments. The dorsal ligament, ligamentum, cuboidio-neviculari, dorsali. The dorsal ligament extends obliquely forward and lateral wood from the nevicular to the cuboid bone. The plantar ligament, ligamentum, cuboidio-neviculari, plantari. The plantar ligament passes nearly transversely between these two bones. The interosseous ligament. The interosseous ligament consists of strong transverse fibres and connects the rough non-articular portions of the adjacent surfaces of the two bones. Sinovial membrane, the sinovial membrane of this joint is part of the great tarsal sinovial membrane. Movements, the movements permitted between the nevicular and cuboid bones are limited to a slight gliding upon each other. Intercuneiform and cuneo cuboid articulations. The three cuneiform bones and the cuboid are connected together by dorsal, plantar and interosseous ligaments. The dorsal ligaments, ligamenta, intercuneiformia, dorsalia. The dorsal ligaments consist of three transverse bands. One connects the first with the second cuneiform, another the second with the third cuneiform, and another the third cuneiform with the cuboid. The plantar ligaments, ligamenta, intercuneiformia, plantaria. The plantar ligaments have a similar arrangement to the dorsal and are strengthened by slips from the tendon of the tibialis posterior. The interosseous ligaments, ligamenta, intercuneiformia, interossea. The interosseous ligaments consist of strong transverse fibres, which pass between the rough non-articular portions of the adjacent surfaces of the bones. Sinovial membrane, the sinovial membrane of these joints is part of the great tarsal sinovial membrane. Movements, the movements permitted between these bones are limited to a slight gliding upon each other. End of section 21, recording by the Bodster. Section 22 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. Recording by Leanne Howlett. Anatomy of the Human Body. Part 2 by Henry Gray. Tarsometatarsal articulations. One F. Tarsometatarsal articulations. Articulations Tarsometatarsie. These are arthrodial joints. The bones entering into their formation are the first, second, and third cuneiforms and the cuboid, which articulate with the bases of the metatarsal bones. The first metatarsal bone articulates with the first cuneiform. The second is deeply wedged in between the first and third cuneiforms, articulating by its base with the second cuneiform. The third articulates with the third cuneiform. The fourth with the cuboid and third cuneiform. And the fifth with the cuboid. The bones are connected by dorsal, planter, and enterosius ligaments. The dorsal ligaments. Ligamenta. Tarsometatarsie. Dorsalia. The dorsal ligaments are strong, flat bands. The first metatarsal is joined to the first cuneiform by a broad, thin band. The second has three, one from each cuneiform bone. The third has one from the third cuneiform. The fourth has one from the third cuneiform and one from the cuboid. And the fifth one from the cuboid. The planter ligaments. Ligamenta. Tarsometatarsie. Plantaria. The planter ligaments consist of longitudinal and oblique bands, disposed with less regularity than the dorsal ligaments. Those for the first and second metatarsals are the strongest. The second and third metatarsals are joined by oblique bands to the first cuneiform. The fourth and fifth metatarsals are connected by a few fibers to the cuboid. The enterosius ligaments. Ligamenta. Cuneometatarsie. Enterosia. The enterosius ligaments are three in number. The first is the strongest and passes from the lateral surface of the first cuneiform to the adjacent angle of the second metatarsal. The second connects the third cuneiform with the adjacent angle of the second metatarsal. The third connects the lateral angle of the third cuneiform with the adjacent side of the base of the third metatarsal. Sinovial membrane. The synovial membrane between the first cuneiform and the first metatarsal forms a distinct sac. The synovial membrane between the second and third cuneiforms behind and the second and third metatarsal bones in front is part of the great tarsal synovial membrane. Two prolongations are sent forward from it. One between the adjacent sides of the second and third and another between those of the third and fourth metatarsal bones. The synovial membrane between the cuboid and the fourth and fifth metatarsal bones forms the distinct sac. From it a prolongation is sent forward between the fourth and fifth metatarsal bones. Movements. The movements permitted between the tarsal and metatarsal bones are limited to slight gliding of the bones upon each other. Nerve supply. The intertarsal and tarso-metatarsal joints are supplied by the deep peroneal nerve. 7g. Inter-metatarsal articulations. Articulations intometatarsae. The base of the first metatarsal is not connected with that of the second by any ligaments. In this respect the great toe resembles the thumb. The bases of the other four metatarsals are connected by the dorsal, planter, and interosseous ligaments. The dorsal ligaments. Ligamenta basium. Os-metatars dorsalia. Pass transversely between the dorsal surfaces of the bases of the adjacent metatarsal bones. The plantar ligaments. Ligamenta basium. Os-metatars plantaria. The plantar ligaments have a similar arrangement to the dorsal. The interosseous ligaments. Ligamenta basium. Os-metatars interossea. The interosseous ligaments consist of strong transverse fibers which connect the rough nonarticular portions of the adjacent surfaces. Sinovial membranes. The sinovial membranes between the second and third and the third and fourth metatarsal bones are part of the great tarsal-sinovial membrane that between the fourth and fifth is a prolongation of the sinovial membrane of the cuboidio-metatarsal joint. Movements. The movement permitted between the tarsal ends of the metatarsal bones is limited to a slight gliding of the articular surfaces upon one another. The heads of all the metatarsal bones are connected together by the transverse metatarsal ligament. The transverse metatarsal ligament. The transverse metatarsal ligament is a narrow band which runs across and connects together the heads of all the metatarsal bones. It is blended anteriorly with the planter glenoid ligaments of the metatarsophalangial articulations. Its planter surface is concave where the flexor tendons run below it. Above it the tendons of the enterocii pass to their insertions. It differs from the transverse metacarpal ligament in that it connects the metatarsal to the others. The sinovial membranes in the tarsal and tarsometatarsal joints. The sinovial membranes found in the articulations of the tarsus and metatarsus are six in number. One for the talo-calcaneal articulation. A second for the talo-calcaneo-avicular articulation. A third for the calcaneo-cuboid articulation. And a fourth for the cuneo-avicular intercuneiform and cuneo-cuboid articulations. The articulations of the second and third cuneiforms with the bases of the second and third metatarsal bones and the adjacent surfaces of the bases of the second, third, and fourth metatarsal bones. A fifth for the first cuneiform with the metatarsal bone of the great toe. And a sixth for the articulation of the cuboid with the fourth and fifth metatarsal bones. A small synovial cavity is sometimes found between the contiguous surfaces of the navicular and cuboid bones. End of section 22, recording by Leanne Howlett. Section 23 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. Recording by Leanne Howlett. Anatomy of the Human Body, Part 2 by Henry Gray. Metatarsal Phalangeal Articulations 7H, Metatarsal Phalangeal Articulations, Articulations Metatarsal Phalangee. The Metatarsal Phalangeal Articulations are of the condyloid kind formed by the reception of the rounded heads of the metatarsal bones and shallow cavities on the ends of the first phalanges. The ligaments are the planter and two collateral. The planter ligaments, ligamenta, exasoria, plantaria, glenoid ligaments of cruvea. The planter ligaments are thick, dense, fibrous structures. They are placed on the planter surfaces of the joints and the intervals between the collateral ligaments to which they are connected. They are loosely united to the metatarsal bones but very firmly to the bases of the first phalanges. Their planter surfaces are intimately blended with the transverse metatarsal ligament and grooved for the passage of the flexor tendons, the sheaths surrounding which are connected to the sides of the grooves. Their deep surfaces form part of the articular facets for the heads of the metatarsal bones and are lined by synovial membrane. The collateral ligaments, ligamenta, collateralia, lateral ligaments. The collateral ligaments are strong, rounded cords, placed one on either side of each joint and attached by one end to the posterior tubicle on the side of the head of the metatarsal bone and by the other to the contiguous extremity of the phalanx. The place of dorsal ligaments is supplied by the extensor tendons on the dorsal surfaces of the joints. Movements. The movements permitted in the metatarsal phalangeal articulations are flexion, extension, abduction, and adduction. Seven eye. Articulations of the digits. Articulations, digitorum, pedis. Articulations of the phalanges. The interphalangeal articulations are ginglomoid joints and each has a planter and two collateral ligaments. The arrangement of these ligaments is similar to that in the metatarsal phalangeal articulations. The extensor tendons supply the places of dorsal ligaments. Movements. The only movements permitted in the joints of the digits are flexion and extension. These movements are more extensive between the first and second phalanges than between the second and third. The amount of flexion is very considerable, but extension is limited by the planter and collateral ligaments. Seven J. Arches of the Foot. In order to allow it to support the weight of the body and the erect posture with the least expenditure of material, the foot is constructed of a series of arches formed by the tarsal and metatarsal bones and strengthened by the ligaments and tendons of the foot. The main arches are the antero-posterior arches, which may for descriptive purposes be regarded as divisible into two types, a medial and a lateral. The medial arch is made up by the calcaneus, the talus, the navicular, the three cuneiforms, and the first, second, and third metatarsals. Its summit is at the superior articular surface of the talus, and its two extremities or piers on which it rests in standing are the tuberosity on the planter surface of the calcaneus posteriorly and the heads of the first, second, and third metatarsal bones anteriorly. The chief characteristic of this arch is its elasticity due to its height and to the number of small joints between its component parts. Its weakest part, that is, the part most liable to yield from overpressure, is the joint between the talus and navicular, but this portion is braced by the planter calcaneo-navicular ligament, which is elastic and is thus able to quickly restore the arch to its pristine condition when the disturbing force is removed. The ligament is strengthened medially by blending with the deltoid ligament of the ankle joint and is supported inferiorly by the tendon of the tibialis posterior, which is spread out in a fan-shaped insertion and prevents undue tension of the ligament or such an amount of stretching as would permanently elongate it. The arch is further supported by the planter aponeurosis by the small muscles in the sole of the foot by the tendons of the tibialis anterior and posterior and peronius longus and by the ligaments of all the articulations involved. The lateral arch is composed of the calcaneus, the cuboid, and the fourth and fifth metatarsals. Its summit is at the talo-calcaneal articulation and its chief joint is the calcaneo-cuboid, which possesses a special mechanism for locking and allows only a limited movement. The most marked features of this arch are its solidity and its slight elevation. Two strong ligaments, the long planter and the planter calcaneo-cuboid, together with the extensor tendons and the short muscles of the little toe, preserve its integrity. While these medial and lateral arches may be readily demonstrated as the component antero-posterior arches of the foot, yet the fundamental longitudinal arch is contributed to by both and consists of the calcaneus, cuboid, third uniform, and third metatarsal. All the other bones of the foot may be removed without destroying this arch. In addition to the longitudinal arches, the foot presents a series of transverse arches. At the posterior part of the metatarsus and the anterior part of the tarsus, the arches are complete, but in the middle of the tarsus they present more the characters of half domes, the concavities of which are directed downward and medial word, so that when the medial borders of the feet are placed in opposition, a complete tarsal dome is formed. The transverse arches are strengthened by the enterosius, planter, and dorsal ligaments by the short muscles of the first and fifth toes, especially the transverse head of the adductor helusus, and by the peronius longus whose tendons stretches across between the piers of the arches. End of section 23, recording by Leanne Howlett. The muscles are connected with the bones, cartilages, ligaments, and skin, either directly or through the intervention of fibrous structures called tendons or aponeuroses. Footnote, the muscles and fascia are described conjointly in order that the student may consider the arrangement of the latter in his dissection of the former. It is rare for the student of anatomy in this country to have the opportunity of dissecting the fascia separately, and it is for this reason as well as from the close connection that exists between the muscles and their investing sheaths that they are considered together. Some general observations are first made on the anatomy of the muscles and fascia, the special descriptions being given in connection with the different regions. End footnote, where a muscle is attached to bone or cartilage, the fibers end in blunt extremities upon the periosteum or pericondrium and do not come into direct relation with the osseous or cartilaginous tissue. Where muscles are connected with its skin, they lie as a flattened layer beneath it and are connected with its areolar tissue by larger or smaller bundles of fibers as in the muscles of the face. The muscles vary extremely in their form. In the limbs they are of considerable length, especially the more superficial ones. They surround the bones and constitute an important protection to the various joints. In the trunk they are broad, flattened, and expanded and assist in forming the walls of the trunk cavities. Hence the reason of the terms long, broad, short, etc. used in the description of a muscle. There is considerable variation in the arrangement of the fibers of certain muscles with reference to the tendons to which they are attached. In some muscles the fibers are parallel and run directly from their origin to their insertion. These are quadrilateral muscles such as the thario hyoidius. A modification of these is found in the fusiform muscles in which the fibers are not quite parallel but slightly curved so that the muscle tapers at either end. In their actions however they resemble the quadrilateral muscles. Secondly in other muscles the fibers are convergent arising by a broad origin they converge to a narrow or pointed insertion. This arrangement of fibers is found in the triangular muscles for example the temporalis. In some muscles which otherwise would belong to the quadrilateral or triangular type the origin and insertion are not in the same plane but the plane of the line of origin intersects that of the line of insertion such is the case in the pectoneus. Thirdly in some muscles for example the perineae the fibers are oblique and converge like the plumes of a quill pin to one side of a tendon which runs the entire length of the muscle. Such muscles are termed unipenate. A modification of this condition is found where oblique fibers converge to both sides of a central tendon. These are called bipenate and an example is afforded in the rectus femoris. Finally there are muscles in which the fibers are arranged in curved bundles in one or more planes as in the sphincters. The arrangement of the fibers is of considerable importance in respect to the relative strength and range of movement of the muscle. Those muscles where the fibers are long and few in number have great range but diminished strength where on the other hand the fibers are short and more numerous there is great power but lessened range. The names applied to the various muscles have been derived one from their situation as the tibialis radialis ulnarus perineus two from their direction as the rectus abdominis oblique capitis transversus abdominis three from their uses as flexors extensors abductors etc four from their shape as the deltoidius rhomboidius five from the number of their divisions as the biceps and triceps six from their points of attachment as the sternocleidomastoidius sternohioidius sternotheroidius in the description of a muscle the term origin is meant to imply its more fixed or central attachment and the term insertion the movable point on which the force of the muscle is applied but the origin is absolutely fixed in only a small number of muscles such as those of the face which are attached by one extremity to immovable bones and by the other to the movable integument in the greater number the muscle can be made to act from either extremity in the dissection of the muscles attention should be directed to the exact origin insertion and actions of each and to its more important relations with surrounding parts while accurate knowledge of the points of attachment of the muscles is of great importance in the determination of their actions it is not to be regarded as conclusive the action of the muscle deduced from its attachments or even by pulling on it in the dead subject is not necessarily its action in the living by pulling for example on the brachioradialis in the cadaver the hand may be slightly supinated when in the prone position and slightly pronated when in the supine position but there is no evidence that these actions are performed by the muscle during life it is impossible for an individual to throw into action any one muscle in other words movements not muscles are represented in the central nervous system to carry out a movement a definite combination of muscles is called into play and the individual has no power either to leave out a muscle from this combination or to add one to it one or more muscle of the combination is the chief moving force when this muscle passes over more than one joint other muscles synergic muscles come into play to inhibit the movement not required a third set of muscles fixation muscles fix the limb for example in the case of the limb movements and also prevent disturbances of the equilibrium of the body generally as an example the movement of the closing of the fist may be considered one the prime movers are the flexories digitorum flexor policies longest and the small muscles of the thumb two the synergic muscles are the extensores carpi which prevent flexion of the wrist while three the fixation muscles are the biceps and triceps brachii which steady the elbow and shoulder a further point which must be born in mind in considering the actions of muscles is that in certain positions a movement can be affected by gravity and in such a case the muscles acting are the antagonists of those which might be supposed to be in action thus inflexing the trunk when no resistance is interposed the sacro spinales contract to regulate the action of gravity and the recti abdominis are relaxed footnote consult in this connection the cronian lectures 1903 on muscular movements and their representation in the central nervous system by charles e beaver md in footnote by a consideration of the action of the muscles the surgeon is able to explain the causes of displacement in various forms of fracture and the causes which produce distortion in various deformities and consequently to adopt appropriate treatment in each case the relations also of some of the muscles especially those in immediate opposition with the larger blood vessels and the surface markings they produce should be remembered as they form useful guides in the application of ligatures to those vessels end of section 24 section 25 of graze anatomy part 2 this is a lubricant recording all lubricant recordings are in the public domain for more information or to volunteer please visit libervox.org recorded by larry ann walden anatomy of the human body by henry gray part 2 mechanics of muscle in studying the mechanical action of muscles the individual muscle cannot always be treated as a single unit since different parts of the same muscle may have entirely different actions as with the pectoralis major the deltoid and the trapezius where the nerve impulses control and stimulate different portions of the muscle in succession or at different times most muscles are however in a mechanical sense units but in either case the muscle fibers constitute the elementary motor elements the direction of the muscle pull and those muscles where the fibers always run in a straight line from origin to insertion and all positions of the joint a straight line joining the middle of the surface of origin with the middle of the insertion surface will give the direction of the pull if however the muscle or its tendon is bent out of a straight line by a bony process or ligament so that it runs over a pulley like arrangement the direction of the muscle pull is naturally bent out of line the direction of the pull in such cases is from the middle point of insertion to the middle point of the pulley where the muscle or tendon is bent muscles or tendons of muscles which pass over more than one joint and pass through more than one pulley may be resolved so far as the direction of the pull is concerned into two or more units or single joint muscles the tendons of the flexor profundus digitorum for example pass through several pulleys formed by fibrous sheaths the direction of the pull is different for each joint and varies for each joint according to the position of the bones the direction is determined in each case however by a straight line between the centers of the pulleys on either side of the joint the direction of the pull in any of the segments would not be altered by any change in the position or origin of the muscle belly above the proximal pulley the action of the muscle pull on the tendon where the muscle fibers are parallel or nearly parallel to the direction of the tendon the entire strength of the muscle contraction acts in the direction of the tendon in pin eight muscles however only a portion of the strength of contraction is efficient in the direction of the tendon since a portion of the pull would tend to draw the tendon to one side this is mostly annulled by pressure of surrounding parts in bi pin eight muscles this lateral pull is counterbalanced if for example the muscle fibers are inserted into the tendon at an angle of 60 degrees it is easy to determine by the parallelogram of forces that the strength of the pull along the direction of the tendon is equal to one half the muscle pull capital t equals tendon m equals strength and direction of muscle pull small t equals component acting in the direction of the tendon phi equals angle of insertion of muscle fibers into tendon cosine phi equals small t divided by m cosine angle 60 degrees equals point five point five equals small t over m t equals one half m if phi equals 72 degrees 30 minutes cosine equals one over three if phi equals 41 degrees 20 minutes cosine equals three over four if phi equals 90 degrees cosine equals zero if phi equals zero degrees cosine equals one the more acute the angle phi that is the smaller the angle the greater the component acting in the direction of the tendon pull at 41 degrees 20 minutes three-fourths of the pull would be exerted in the direction of the tendon and at zero degrees the entire strength on the other hand the greater the angle the smaller the tendon component at 72 degrees 30 minutes one third the muscle strength would act in the direction of the tendon and at 90 degrees the tendon component would be nil the strength of muscles the strength of a muscle depends upon the number of fibers in what is known as the physiological cross section that is a section which passes through practically all of the fibers in a muscle with parallel or nearly parallel fibers which have the same direction as the tendon this corresponds to the anatomical cross section but in unipen eight and bipen eight muscles the physiological cross section may be nearly at right angles to the anatomical cross section since huber has shown that muscle fibers in a single fasciculus of a given muscle vary greatly in length in some fasciculi from 9 millimeters to 30.4 millimeters it is unlikely that the physiological cross section will pass through all the fibers estimates have been made of the strength of muscles and it is probable that coarse fibrid muscles are somewhat stronger per square centimeter of physiological cross section than are the fine fibrid muscles thick estimates the average strength is about 10 kilograms per square centimeter this is known as the absolute muscle strength the total strength of a muscle would be equal to the number of square centimeters in its physiological cross section times 10 kilograms the work accomplished by muscles for practical uses this should be expressed in kilogram meters in order to reckon the amount of work which a muscle can perform under the most favorable conditions it is necessary to know one it's physiological cross section two the maximum shortening and three the position of the joint when the ladder is obtained work equals lifted weight times height through which the weight is lifted or work equals tension times distance tension equals physiological cross section times absolute muscle strength if a muscle has a physiological cross section of five square centimeters its tension strength equals five times 10 or 50 kilograms if it shortens five centimeters the work equals 50 times 0.05 equals 2.5 kilogram meters if one determines then the physiological cross section and multiplies the absolute muscle strength 10 kilograms by this the amount of tension is easily obtained then one must determine only the amount of shortening of the muscle for any particular position of the joint in order to determine the amount of work the muscle can do since work equals tension times distance the tension of a muscle is however not constant during the course of contraction but is continually decreasing during contraction it is at a maximum at the beginning and gradually decreases this can be illustrated by the work diagram amd ordinate equals tension avx abscissa equals shortening ad equals tension of muscle in extended or antagonistic position av equals amount of actual shortening am equals tension in mid position equals absolute muscle strength dv shows how the tension sinks from maximum in the extended position of the muscle where it is about double that in the mid position m to nothing on complete contraction delta adv equals work diagram in reality the hypotenuse is not straight but has a concave curve the delta has the same area as the rectangle amm prime v am equals the average tension work equals am times av kilogram meters if the size of the ordinate is expressed in kilograms and the abscissa in meters although the muscle works with a changing tension yet the accomplishment is the same as if it were contracting with the tension of the mid position in reality the amount of work is somewhat greater since even in extreme contraction the muscle still retains a certain amount of tension so that the maximum amount of work is more nearly like adx we know that a muscle may have an extreme actual shortening of about 80 percent of its length when the tendon of insertion is cut the trapezoid adsv represents more nearly the amount of work but since there are only approximate values and adsv is not much larger than amm prime v we may use the latter only the tension and amount of shortening are needed to determine the amount of work of the muscle neither the lever arm nor the fiber angle in pennate muscles need be considered the diagram shows that the lever arm is of no importance for determining the amount of work the muscle performs jb and jb one equals two bones jointed at j c d and e f equal the direction of the pull of two muscles of equal cross section each having a muscle tension of 1000 grams the centers of the attachments are such that perpendicular j small c and j small e to c d and e f are equal to 40 and 23 millimeters respectively j small c equals 40 millimeters and j small e equals 23 millimeters the static moments are equal to 1000 times 40 and 1000 times 23 therefore the first muscle can hold a much larger load l on the bone jb one at h one 100 millimeters from j then the second muscle whose load can be designated as l one equilibrium exists for the first muscle if l times 100 equals 1000 times 40 or l equals 1000 times 40 over 100 equals 400 grams for the second muscle l one times 100 equals 1000 times 23 l one equals 1000 times 23 over 100 equals 230 grams if we suppose jb to be fixed and jb one to move in the plane of the paper about j and the muscle c d to shorten five millimeters c small d equals c d minus five millimeters and with the tension of 1000 grams jb one will take the position jb two and the load l will be lifted from h one to h two if the second muscle likewise shortens five millimeters then e small f equals e f minus five millimeters and with the tension of 1000 grams the bone jb one will take the position jb three and the weight or load l one will be lifted from h one to h three the question now is to prove that the work done is the same in both cases namely five times 1000 gram millimeters if so 400 times h one h two equals 230 times h one h three equals 5000 gram millimeters since the two radii c small d and c small d prime are very long as compared with the arc small d d prime we may consider this short arc as a line to c d at small d prime likewise the arc small f small f prime may be considered as a straight line to e f f in the same manner we can consider the short arcs f small f d small d h one h two and h one h three to the line jb one the sides d small d prime and f small f prime of the delta d small d small d prime and f small f small f prime are each five millimeters the lever arm d j equals 60 millimeters and j f equals 30 millimeters the delta d small d small d prime is similar to the delta d small c j hence d small d to five is to 60 to 40 d small d equals 300 divided by 40 also h one h two to d small d as to 100 to 60 h one h two to 300 over 40 as to 100 to 60 h one h two equals 300 divided by 24 hence f small f to five is to 30 to 23 f small f equals 150 divided by 23 also h one h three is to f small f as to 100 to 30 h one h three is to 150 over 23 as 100 to 30 h one h three equals 1500 over 69 400 times 300 divided by 24 equals 230 times 1500 divided by 69 equals 5000 thus we see that the work of the two muscles depends on the size of the contraction and on the tension and not on the lever arm in very small contractions or in the summation of such contractions and therefore for large contractions in the first muscle a large load is moved through a short distance and in the second muscle a lighter load is moved through a greater distance the amount of work accomplished by pin eight muscles is not dependent upon the angle of insertion of the muscle fibers into the tendon as will be seen by the following diagram t prime t equals direction of the tendon pull w a equals direction of muscle fiber before contraction m prime equals direction of muscle fiber after contraction v equals amount of contraction m equals tension of the muscle phi equals angle of insertion of muscle fiber t equals tendon component equals m times cosine phi equals the weight carried by the tendon to balance the muscle tension d equals distance tendon is drawn up one m times v equals work done by the muscle fiber two t times d equals work done by the movement of the tendon if we consider the distance v is being very short then the line bc can be dealt with as though it were perpendicular to ac then v equals d times cosine phi or d equals v over cosine phi since t equals m times cosine phi or m equals t over cosine phi m times v equals t over cosine phi times d times cosine phi equals t times d if this is true for very minute contractions it is likewise true for a series of such contraction and hence for larger contractions if we assume that phi equals 60 degrees m equals 10 kilograms and v equals five millimeters the work done by the contracting muscle fiber equals m v or 10 times five kilogram millimeters cosine angle 60 degrees equals one half hence t equals one half m and d equals v over one half equals two v one half m equals five kilograms and two v equals 10 millimeters hence t d equals 50 kilogram millimeters or the work done by the movement of the tendon in lifting the load of five kilograms a distance of 10 millimeters and is exactly the same as that done by the muscle fiber the load on the tendon is but one half the tension of the muscle but the distance through which the load is lifted is twice that of the amount of shortening of the muscle if phi equals 41 degrees 20 minutes then cosine phi equals three over four hence t equals three fourths m and d equals four thirds v and t d equals m v in pin eight muscles then we have the rather unexpected condition in which the same amount of movement of the tendon can be accomplished with less contraction of the muscle than in muscles where the fibers have the same direction as the tendon the action of muscles on joints if we consider now the action of a single muscle extending over a single joint in which one bone is fixed in the other movable we will find that muscle pull can be resolved into two components a turning component and a friction or pressure component as shown in figure 369 d f equals the fixed bone from which the muscle takes its origin d k equals the movable bone oh i equals a line from the middle of origin to the middle of insertion i m equals size and direction of the muscle pull if the parallelogram is constructed with it and m b perpendicular to d k then it equals the turning component and i b equals the component which acts against the joint the size of the two components depends upon the insertion angle phi the smaller this angle the smaller the turning component and the nearer this angle phi is to 90 degrees the larger the turning component i t equals i m times sine phi i b equals i m times cosine phi if phi equals 90 degrees cosine phi equals 0 sine phi equals 1 hence i b equals 0 and i t equals i m if phi equals 0 degrees cosine phi equals 1 sine phi equals 0 hence i b equals 1 and i t equals 0 with movements of the bone d k the angle of insertion is continually changing and hence the two components are changing in value if for example the distance from origin o to the joint d is greater than from d to i as in the brachialis or biceps muscles the turning component increases until the insertion angle phi equals 90 degrees which is the optimum angle for muscle action while the pressure component gradually decreases if the movement continues beyond this point the turning component gradually decreases and the pressure component changes into a component which tends to draw the two bones apart and which gradually increases when the bone d k is in such a position that the insertion angle phi equals 41 degrees 20 minutes the pressure component equals three quarters i m and the turning component one quarter i m at 60 degrees the two components are equal at 90 degrees the pressure component equals zero and the turning component equals i m and at 131 degrees 21 minutes the pressure component has been converted into a pulling component equals one fourth i m and the turning component equals three fourths i m if for example the distance from the origin o to the joint d is less than the distance from the insertion i to the joint d as in the brachio radialis muscle the insertion angle increases with deflection but never reaches 90 degrees the turning component gradually increases to a certain point and then slowly decreases as shown in figure 371 while the pressure component gradually decreases and then slowly increases it always remains large and its action is always in the direction of the joint levers the majority of the muscles of the body act on bones as the power on levers levers of the three class are the most common as the action of the biceps and the brachialis muscles on the forearm bones levers of the one class are found in movements of the head where the occipito-atlantle joint acts as the fulcrum and the muscles on the back of the neck as the power another common example is the foot when one raises the body by contracting the gastrocnemius and soleus here the ankle joint acts as the fulcrum and the pressure of the toes on the ground as the weight this is frequently though wrongly considered a lever of the two class if one were to stand on one's head with the legs up and with a weight on the plantar surface of the toes it is easy to see that we would have a lever of the one class if the weight were raised by contraction of the gastrocnemius muscle the confusion has arisen by not considering the fact that the fulcrum and the power in all three classes of levers must have a common basis of action as shown in figure 372 if the fulcrum rests on the earth the power must either directly or indirectly push from the earth or be attached to the earth either by gravity or otherwise if it pulls toward the earth if the power were attached to the weight no lever action could be obtained there are no levers of the two class represented in the body end of section 25