Human Gross Anatomy Lecture 8
Human Gross Anatomy Lecture 8 BISC 2581
Popular in Human Gross Anatomy
Popular in Anatomy
This 15 page Class Notes was uploaded by Anais Ioschpe on Friday February 12, 2016. The Class Notes belongs to BISC 2581 at George Washington University taught by Jeffrey Rosenstein; Raymond Walsh; in Spring 2016. Since its upload, it has received 47 views. For similar materials see Human Gross Anatomy in Anatomy at George Washington University.
Reviews for Human Gross Anatomy Lecture 8
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 02/12/16
Introduction to the Lower Limb— The Leg and Foot Learning Objectives: 1) Describe the organization of the leg into three fascial compartments. 2) For each fascial compartment of the leg: a) Name the muscle group(s) it contains. b) Deﬁne the actions of the muscle group. c) Describe the principle neurovascular supply to the muscle group. 3) Deﬁne a retinaculum. 4) Deﬁne the signiﬁcance of the arches of the foot and the four factors that contribute to their support. 5) Describe the neurovascular supply to the foot.The leg is divided into three fascial compartments, the anterior, the lateral, and the posterior compartments. Each compartment has a muscle group(s) with distinct actions, nerve supply, and blood supply. Osteology – Tibia, Fibula, and Bones of the Foot - Tibia: is the weight bearing bone of the leg segment; the ﬁbula has little weight bearing function and serves mainly for muscle attachments and as a brace for the tibia. The tibia and ﬁbula are bound together in part by the interosseous membrane, a broad sheet of dense connective tissue that spans between the shafts of the two bones. It strengthens the bond between the two bones and serves as a partial attachment site for some muscles. - Ankle joint: formed between the talus bone, the ﬁbula, and the tibia. The ankle joint is a hinge joint meaning it moves up and down in only one direction. • Lateral malleolus: the bottom part of the ﬁbula forms the lateral malleolus • Medial malleolus: the bottom part of the tibia form the medial malleolus - Ankle Movements • Dorsaﬂexion: toes go up and you rock back on your heel Plantarﬂexion: standing up on your toes • - Joint movement • Inversion: weight on lateral side of foot • Eversion: weight on medial side of foot - Toe movement • Extension: spreading toes out • Flexion: pointing toes - Tibioﬁbular joints – the two intrasegmental joints of the leg • Superior – a synovial joint between the head of the ﬁbula and the lateral condyle of the tibia; a plane-type synovial joint that provides for a sliding or gliding type of movement. • Inferior – a ﬁbrous joint in which the deep surface of the distal ﬁbula is bound to a notch (ﬁbular notch) on the lateral side of the distal end of the tibia by dense, strong bands of ﬁbrous connective tissue. - Interosseous Membrane: The tibia and ﬁbula are bound together in part by the interosseous membrane, a broad sheet of dense connective tissue that spans between the shafts of the two bones. It strengthens the bond between the two bones and serves as a partial attachment site for some muscles. Two intermuscular septa and the interosseous membrane divide the leg into three compartments. - Foot— 19 bones in the foot (do not need to know) • The foot is a stable platform to walk and run • Three sets of bones - Phalanges - Metatarsal - Tarsal - There are 26 bones of the foot. • The 26 bones are divided into three groups, i.e. the seven tarsal bones, the ﬁve metatarsal bones, and the fourteen phalanges. Another common division of the 26 bones is into three “regions”, i.e. the hindfoot (talus and • calcaneus bones), the midfoot (navicular, cuboid, and the three cuneiforms), and the forefoot (the metatarsals and phalanges). • The joints between the different sets of bones are named by the appositions of the bones to each other, i.e. intertarsal joints (between tarsal bones), tarsometatarsal joints (between tarsal bones and metatarsal bones), intermetatarsal joints, metatarsophalangeal joints, and interphalangeal joints. - Keep in mind • Hallux: (hallucis) both refer to the “big toe”. • Digitorum: refers to the “digits”, i.e. the toes, and traditionally is limited to the four lateral toes (not the big toe). • If you have a muscle with the name “longus” in it, there is going to be another similarly named muscle with the word “brevis” in it. • A “longus” muscle would be an “ extrinsic” muscle of the foot – meaning it has an origin outside of the foot (usually in the leg segment) and an insertion in the foot. The bulk of the mass (the muscle belly) of an extrinsic muscle resides outside the foot. • A “brevis” muscle may be an extrinsic muscle of the foot but in any event it is going to be shorter in length than the similarly named “longus” muscle. • A “brevis” muscle may be an “intrinsic” muscle of the foot – meaning it has both its origin and its insertion within the foot segment. In this case the “brevis” muscle will be signiﬁcantly shorter in length than the similarly named “longus” muscle whose origin is outside the foot. • Retinacula - Regional condensations of deep fascia around the region of the ankle joint - Serve to bind down the long, cord-like te ndons of the extrinsic muscles of the foot, preventing them from “bowing out” “or “bowstringing” during contraction. - The tibia is the weight bearing bone of the leg segment; the ﬁbula has little weight bearing function and serves mainly for muscle attachments and as a brace for the tibia. Anterior Compartment of the Leg and the Dorsum of the Foot - The medial surface of the shaft of the tibia is subcutaneous throughout its length (and easily palpated) and occupies the medial half of the anterior side of the leg. Thus the anterior compartment of the leg is in fact limited to the antero-lateral region of the leg. - If you palpate the dorsum of your foot (like the dorsum of your hand) you can appreciate how “bony” it feels – it is dominated by a thin layer of superﬁcial fascia and mostly narrow, cord- like tendons. Contrast its feel with that of the sole of the foot (or palm of the hand) in which there are far more soft tissues, making palpation of the bones not as easy. - The anterior compartment of the leg and the dorsum of the foot are best studied together; most of the structures on the dorsum of the foot are narrow, cord-like tendons derived from the muscles of the anterior compartment. - Anterior Tibial Muscle Group - Members include the: • Tibialis anterior • Extensor digitorum longus • Extensor hallucis longus • Fibularis tertius - The muscles take origins from the tibia and/or the ﬁbula and the interosseous membrane between them. All of the muscles cross anterior to the ankle joint, which renders them all dorsiﬂexors of the foot. - Tibialis anterior (most important) • Used when running and exercise. Closely attached to the tibia — causes shin splints • The largest and strongest of the anterior tibial muscle group; the most powerful dorsiﬂexor of the foot. • Inserts ontothe medial side of the foot (medial cuneiform and 1st metatarsal) and its line of pull renders it a strong inverter of the foot— when the foot dorsafelxes • Injury - Micro-tears can occur, commonly called, chin splints - Extensor digitorum longus • Inserts onto the phalanges of the four lateral toes; passing over the superior surface of the toes, and as its name implies, it extends the four lateral toes. - Extensor hallucis longus • Inserts onto the distal phalanx of the big toe; passing over the superior surface of the big toe, and as its name implies, it extends the big toe. - Fibularis tertius • A small muscle that is continuous with the lower lateral side of the extensor digitorum longus (considered a partially separated portion of the extensor digitorum longus); considered to be functionally insigniﬁcant due to its size. • Insigniﬁcant and many people don’t have it - Dorsum of the Foot • Extensor digitorum brevis - a small intrinsic muscle of the foot; originates from the calcaneus of the foot and inserts into and extends the four medial toes, including the big toe. Some call the portion of the muscle that inserts into the big toe the extensor hallucis brevis muscle. - Lateral compartment • Fibularis muscle group — primary everters of the foot - The smallest compartment in the leg - Two members in the group, the ﬁbularis longus and the ﬁbers and the ﬁbularis brevis muscles - Both muscles take origin from the lateral surface of the shalft of the ﬁbula, the “longus” from the upper region of the shaft, the “brevis” from the lower region. Breves inserts on the lateral side of the foot (pinky) and longus inserts to the big t oe - Actions: primary everters of the foot • The tendons of both muscles pass posterior to the lateral malleolus and thus posterior to the axis of movement of the ankle joint – rendering them both plantarﬂexors of the foot. • The insertions are positioned such that the line of pull of the muscles causes eversion of the foot; this is considered their main action. - Posterior compartment • The posterior compartment of the leg contains seven muscles, collectively called the posterior tibial muscle group. All seven muscles pass posterior to the ankle joint and therefore are all plantarﬂexors of the ankle joint. Many course through the sole of the foot. The posterior tibial muscle group is divided into two subgroups, a superﬁcial posterior tibial muscle group and a deep posterior tibial muscle group, by a dense sheet of deep fascia. • Superﬁcial posterior tibial muscle group: - Gastrocnemius muscle • Origin from the medial and lateral condyles and adjacent popliteal surface of the femur. • Its muscle ﬁbers insert into a very large tendon called the calcaneal tendon, commonly referred to as the Achilles’ tendon. • The calcaneal tendon passes posterior to the ankle joint and inserts onto the upper posterior aspect of the calcaneus bone of the foot. • Actions - Crosses posterior to the knee joint and thus a ﬂexor of the knee joint, although not its primary function. - A powerful plantarﬂexor of the foot at the ankle joint. Its strength is such that with the foot ﬁxed on the ground, its contraction results in elevation of the body - Soleus muscle • Origin from the upper posterior surface of the ﬁbula and tibia; inserts into the calcaneal tendon with the gastrocnemius. • Action at the ankle joint is comparable to that of the gastrocnemius. - Plantaris muscle • A small, short muscle of no functional signiﬁcance. • Originates from the posterior side of the femur; has a very long, thin, cord-like tendon that inserts onto the calcaneus next to the calcaneal tendon. • While functionally insigniﬁcant, its tendon is used in reconstructive surgery and the rupture of the tendon can be quite painful. Plantaris Muscle Tendon of Plantaris Deep Posterior Tibial Muscle Group • - Consists of four muscles • Flexor hallicis longus • Flexor digitorum longus • Tibialis posterior • Popliteus muscle - The ﬁrst three above all cross posterior to the axis of movement of the ankle joint (rendering them plantarﬂexors) and insert into the foot. Their origins are from the shafts of the tibia or ﬁbula and the interosseous membrane.The popliteus muscle is conﬁned to the region posterior to the knee. - Flexor hallucis longus and ﬂexor digitorum longus muscles • insert onto the underside of the phalanges of the toes and as a result cause ﬂexion of the big toe (hallucis) and the four lateral toes (digitorum). - Tibialis posterior Passes through the sole of the foot to an insertion on the medial side of the foot, • giving it a line of pull that renders it a powerful inverter of the foot. • Note that the two major invertors of the foot, the tibialis anterior and tibialis posterior, reside on opposite sides of the leg and yet have the same inversion action. This reﬂects the fact that inversion occurs not at the ankle joint, to which the muscles are oriented differently, but rather at the intertarsal joints to which the muscles are aligned similarly in terms of their line of pull on the foot segment. - Popliteus • Attached to the lateral condyle of the femur and to the upper posterior surface of the tibia. • Crosses the knee joint posteriorly and thus is a ﬂexor of the knee joint. However, its major action is in the rotation of the tibia and femur relative to each other, a movement important in “unlocking” the knee joint prior to its ﬂexion. - Flexes the knee weakly, no action on the foot - Sole (plantar side) of the foot • The sole of the foot consists of the long, cord-like tendons of muscle in the posterior and lateral compartments of the leg as well as an extensive collection of intrinsic muscles. • “four layers: • Plantar aponeurosis - A thick layer of deep fascia that lies in the central area of the sole of the foot. It helps to protect the underlying structures and helps to support the longitudinal arch of the foot. - Functions like a “tie beam” on a bridge that, from the underside of the bridge, pulls the distant points of the bridge toward each other. Forms support for arches of the foot. - Rises from the calcaneus and ends at the toes - Injury— causes pantar fascitis • Longitudinal and transverse arches of the foot (do not need to know) - The multiple individual bones of the foot collectively form a series of arches. The arch- shapes provide for the necessary weight-bearing function of the foot as well as the ﬂexibility needs of the foot as relates to adapting to uneven surfaces and contributing mechanically to the propulsion of the body during locomotion. - Longitudinal arch: Extends between the posterior end of the calcaneus and the heads of the metatarsal bones; higher on the medial side (medial longitudinal arch) than on the lateral side (lateral longitudinal arch). - Transverse arch: Runs from side to side near the level of the tarsometatarsal joints. - Support for the arches – four factors • Strong ligaments that bind the bones together. • The interlocking shapes of the individual tarsal bones. • Muscles (do not need to know) - Long extrinsic muscle tendons function like “suspension cables” on a bridge that pull the bridge up from above when they contract. - Some intrinsic muscles function like the tie beams on a bridge. - For descriptive purposes the muscles on the sole of the foot are classiﬁed into four layers and are not divided on the basis of functional muscle groups. The layers consist of a combination of extrinsic muscle tendons and intrinsic muscles. It is not necessary to know the names of the individual muscles. The intrinsic muscles of the sole of the foot function to ﬂex, abduct, and adduct the toes. - Blood supply to the leg and foot (do not need to know) • The popliteal artery: is the continuation of the femoral artery into the popliteal fossa, which is a diamond-shaped region on the posterior side of the knee. The popliteal artery divides into the anterior tibial and posterior tibial arteries in the popliteal fossa. The two tibial arteries enter the posterior compartment of the leg and they constitute the blood supply to the leg and foot. - Anterior tibial artery – enters the anterior compartment of the leg by passing through a hole in the interosseous membrane and then descends the anterior compartment and onto the dorsum of the foot, where it is renamed the dorsalis pedis artery. • Dorsalis pedis artery: Runs between the ﬁrst and second toe; can actually take a pulse here - Posterior tibial artery - descends the posterior compartment of the leg and enters the sole of the foot by passing posterior to the medial malleolus; divides into the medial and lateral plantar arteries of the sole of the foot. - Fibular artery – largest branch of the posterior tibial artery; descends the posterior compartment, providing branches to the posterior compartment as well as the lateral compartment of the leg via perforating branches that pass through the intermuscular septum between the posterior and lateral compartments. - Nerve supply to the leg and foot • Two nerves enter the leg from the popliteal fossa, the tibial nerve and the common ﬁbular nerve (which you recall arise from the sciatic nerve in the posterior compartment of the thigh). These two nerves provide the neural innervation to the leg and foot. • Tibial nerve(L4, L5, S1, S2, and S3) - Descends into the posterior compartment of the leg where it courses with the posterior tibial artery, innervating the posterior compartment of the leg. - Passes posterior to the medial malleolus to enter the sole of the foot as the medial and lateral plantar nerves, which are the innervation to the sole of the foot. - Calcaneal /Achilles tendon reﬂex text: testing the posterior tibial nerve (S1 and S2) • Common ﬁbular nerve (L4, L5, S1, and S2) - Circumvents the neck of the ﬁbula and enters the upper aspect of the lateral compartment of the leg, where it divides into deep and superﬁcial ﬁbular nerves. • The common ﬁbular nerve lies close to the surface of the leg and immediately over (superﬁcial to) the bone of the neck of the ﬁbula – poor design in that you want to keep nerves deeper within the body where they are less susceptible to trauma on the surface of the body. • Supplies the two ﬁbularis muscles; longus and brevis • “motorcyclist nerve” — often gets crushed by rubbing against cars whist on a motorcycle - Superﬁcial ﬁbular nerve – motor to the lateral compartment of the leg. - Deep ﬁbular nerve – enters the anterior compartment of the leg, which it innervates, and descends with the anterior tibial artery to the dorsum of the foot. • Calcaneal tendon reﬂex (also called the ankle reﬂex) – a common test performed in a physical exam. The calcaneal tendon of the gastrocnemius and soleus muscles is tapped with a reﬂex hammer just proximal to the calcaneus; the normal response is plantarﬂexion of the ankle joint. Tests the S1 and S2 nerve roots, whose injury or compression results in a weak or absence ankle reﬂex. • NOTE: Putting the nerve and blood supplies of the leg together, note that in each compartment the blood and nerve supplies are not similarly named, i.e. tibial nerve and posterior tibial artery (posterior compartment), deep ﬁbular nerve and anterior tibial artery (anterior compartment), and superﬁcial ﬁbular nerve and perforating branches of the ﬁbular artery (lateral compartment). - Foot injury • Foot drop - As a lower limb in its swing phase of the gait cycle is "swung" forward the foot is dorsiﬂexed by muscles of the anterior tibial group in order to ensure that: • The toes clear the ground as the foot passes through the mid-point point of the swing and The heel of the foot strikes the ground ﬁrst at the • start of the stance phase. - Paralysis of the anterior tibial muscle group results in the condition known as footdrop, in which the person is unable to dorsiﬂex the affected foot. A characteristic gait, referred to as foot-drop gait or steppage gait, ensues. In order to avoid dragging the toes of the affected foot on the ground during the mid-swing, the individual hyper-ﬂexes the hip joint of the affected side during the swing phase, effectively raising the advancing foot high enough to prevent the downward pointing toes (due to loss of dorsiﬂexion) from touching the ground. No compensation is available for the lack of "heel down" ﬁrst. Instead the toes of the foot strike the ground ﬁrst followed quickly by the remainder of the foot, providing a somewhat characteristic “slapping" sound as the foot strikes the ground. - The anterior tibial muscle group is innervated by the deep ﬁbular nerve branch of the common ﬁbular nerve and lesions of the common ﬁbular nerve result in foot-drop. As the common ﬁbular nerve passes over the neck of the ﬁbula its close proximity to the surface of the body and its concurrent position immediately superﬁcial to bone renders it susceptible to damage at this site. Lesions may include physical trauma, such as may occur from a direct physical strike to the nerve or secondarily to a proximal fracture of the ﬁbula. The nerve can also be damaged by a compression lesion such as a too tight plaster cast applied for therapeutic reasons.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'