The lower leg refers to the lower limb. It is located between the foot and the knee area. The lower leg is formed by means of two bones - small and tibial. They are surrounded by muscle fibers on three sides. The muscles of the lower leg, the anatomy of which will be discussed later, move the fingers and foot.
Tibia
This item has an extension on the top edge. Condyles are formed in this area: lateral and medial. On top of them are the surfaces of the joints. They articulate with the condyles of the thigh. On the lateral segment, there is an articular surface on the outside, through which it is connected to the head in the fibula. The body of the tibial element looks like a trihedral prism. Its base is directed backwards and has 3 surfaces, respectively: back, outer and inner. There is an edge between the last two. It's called the front. In its upper part, it passes into the tuberosity of the tibia. This area is designed to fix the tendon of the quadriceps femoral muscle. In the lower part, the tibia has an extension, and on the insidethere is a protrusion on the surface. It is oriented downward. This protrusion is called the medial malleolus. On the back side of the bone lies a rough segment of the soleus muscle. The articular surface is located on the distal epiphysis. It serves to connect with the talus.
Second element
The fibula is thin, long, located laterally. Its upper end has a thickening - the head. It connects to the tibia. The lower section of the element is also thickened and forms the lateral malleolus. It, like the head of the fibula, is oriented outward and is well palpable.
Shin muscles: their location, functions
The fibers are located on three sides. Allocate different muscles of the lower leg. The front group performs extension of the foot and fingers, supination and adduction of the foot. This segment includes three types of fibers. The tibialis anterior muscle of the lower leg was formed first. The remaining fibers form the long extensors of the fingers and a separate one for the big toe on the foot. The posterior muscle group of the lower leg forms a greater number of fibers. In particular, there are long finger flexors and separately for the large, popliteal, triceps muscle of the lower leg. There are also tibial fibers here. The outer group includes the short and long peroneal muscles of the lower leg. These fibers flex, penetrate and abduct the foot.
Tibial segment
This anterior calf muscle starts from the same-named bone, its outer surface, fascia and interosseous membrane. They are directed downward. The fibers pass under two ligaments. They are located in the area of the ankle joint and ankles. These areas - the upper and lower retainers of the extensor tendons - are represented by places of thickening of the fascia of the foot and lower leg. The site of attachment of the fibers is the sphenoid medial and the base of the metatarsal (first) bone. The muscle is quite well palpable along its entire length, especially in the area of transition to the foot. In this place, her tendon protrudes during extension. The task of this leg muscle is also the supination of the foot.
Finger extensor (long)
It runs from the anterior muscle outward in the upper region of the lower leg. Its fibers begin from the head and marginal sections of the tibia, fascia and interosseous membrane. The extensor, passing to the foot, is divided into five tendons. Four are attached to the distal phalanges of the fingers (from the second to the fifth), the last - to the base of the 5th metatarsal bone. The task of the extensor, acting as a multi-joint muscle of the lower leg, is not only to coordinate the extension of the fingers, but also the foot. Due to the fact that one tendon is fixed at its edge, the fibers also penetrate the area somewhat.
Thumb extensors
Fibers begin in the region of the lower leg from the interosseous membrane and the inner part of the fibula. The extensors have less strength than the segments described above. The site of attachment of this is the distal phalanges in the thumbs. These muscles of the lower leg not only carry out their extension, but also stop,contributing also to their supination.
Finger flexor (long)
It starts from the back of the tibia, passing under the medial malleolus to the foot. The channel for it is located under the retainer (ligament) of the flexor tendons. Next, the muscle is divided into four segments. On the foot (plantar surface), fibers cross the tendon from the flexor (long) thumb. Then the square muscle of the sole joins them. Four formed tendons are fixed to the distal phalanges (at their base) of 2-5 fingers. The task of this muscle is, among other things, to flex and supinate the foot. The fibers of the square segment are attached to the tendon. Due to this, the action of the muscle is averaged. Lying under the medial malleolus and fanning out towards the phalanges, the long flexor also provokes some adduction of the fingers to the median surface of the body. By pulling the square muscle of the tendon, this action is slightly reduced.
Triceps calf
It runs along the back surface and has 3 heads. Two form the surface area - the gastrocnemius muscle, from the third - deep - the fibers of the soleus segment depart. All heads are connected and form a common Achilles (calcaneal) tendon. It is attached to the tubercle of the corresponding bone. The gastrocnemius muscle starts from the femoral condyles: lateral and medial. The task of the two heads located in this area is twofold. They coordinate flexion at the knee joint and feet at the ankle joint. Medi althe element descends slightly lower and is better developed than the lateral element. From the back side in the upper third of the tibia, the soleus muscle departs. It is also attached to the tendon arch located between the bones. The fibers pass somewhat lower and deeper than the gastrocnemius. They lie behind the subtalar and ankle joints and cause flexion of the foot. The triceps muscle can be felt under the skin. The calcaneal tendon protrudes posteriorly from the transverse axis in the ankle joint. Due to this, the triceps muscle has a large moment of rotation relative to this line. The heads of the gastrocnemius segment are involved in the formation of the rhomboid popliteal fossa. As its boundaries are: the biceps femoral muscle (outside and top), semimembranous fibers (inside and top), plantar and two heads of the gastrocnemius segment (bottom). The bottom in the fossa is formed by the capsule of the knee joint and the femur. Vessels and nerves that feed the foot and lower leg run through this area.
Thumb flexor (long)
This calf muscle has the most strength. On the plantar side of the foot, fibers run between the heads from a short segment responsible for flexion of the big toe. The muscle starts from the back side (lower part) of the fibula and the intermuscular septum (back). The site of fixation is the plantar surface of the base of the distal phalanx in the thumb. Due to the fact that the tendon of the muscle partially passes into the element of the long flexor of the same name, it hassome influence on the movements of 2-3 fingers. The presence on the surface of the sole of the metatarsophalangeal joint of 2 large sesamoid bone elements provides an increase in the moment of rotation of the fibers. The tasks of the segment include flexion of the entire foot and thumb.
Second tibial fibers
This posterior segment is located under the triceps. The fibers start from the interosseous membrane and areas of the small and tibial bones adjacent to it. The site of attachment of the muscle is the tubercle of the navicular, the base of the metatarsal and all the wedge-shaped elements. The muscle lies under the medial malleolus and performs flexion of the foot, supination and adduction. A canal passes between the soleus and tibial fibers. It is presented in the form of a gap. Nerves and blood vessels pass through it.
Help segment
It is formed by flat short fibers. The muscle adjoins directly to the knee joint from behind. The fibers originate from the femoral condyle (lateral), below the gastrocnemius segment, and the bursa of the knee joint. They pass down and are attached above the soleus muscle to the tibia. Because the fibers are partially attached to the joint capsule, they pull it posteriorly when flexed. The task of the muscle is pronation and flexion of the lower leg.
Long fibular segment
This muscle has a feathery structure. It runs along the surface of the fibula. It starts from its head, the condyle of the tibial element, partly from the fascia. It is also attached to the region of the 2-thirds of the outersides of the fibula. When the muscle contracts, abduction, pronation, and flexion of the foot occur. The tendon of the long peroneal segment posteriorly and inferiorly bypasses the lateral malleolus. In the area of the heel bone there are ligaments - the upper and lower retainers. When moving to the plantar part of the foot, the tendon runs along the groove. It is located on the underside of the cuboid bone. The muscle reaches the inside of the foot.
Short fibular fibers
The tendon of the segment wraps around behind and below the lateral malleolus. It is attached to the tubercle on the 5th metatarsal. The segment begins from the intermuscular septa and the outer part of the fibula. The task of the fibers is abduction, pronation and flexion of the foot.
