PERONEI MUSCLES 



483 



BuRSiE 



B. subtendinea m. tibialis anterioris. — A small bursa between the medial surface of the 

 first cuneiform bone and the tendon of the tibialis anterior. B. subtendinea m. extensoris 

 hallucis longi. — A small bursa beneath the tendon near the tarso-metatarsal articulation. It 

 may communicate with the synovial sheath of the tendon. B. sinus tarsi. — A large bursa in 

 the sinus tarsi and on the lateral surface of the neck of the talus (astragalus) beneath the tendons 

 of the extensor digitorum longus and the fibrous bands between the talo-calcaneal and the 

 cruciate Hgaments. It extends back to the talo-crural, forward to the talo-navicular joint, 

 and may communicate with the joint cavity of the latter. 



Synovial Tendon-sheaths 



Vagina tendinis m. tibialis anterioris. — This sheath surrounds the tendon from above 

 the transverse crural ligament to the talo-navicular joint. Vagina tendinis m. extensoris 

 hallucis longi. — The sheath begins above the proximal arm of the cruciate ligament, and 

 ends near the tarso-metatarsal joint beneath a band-like thickening of the dorsal fascia of the 

 foot. Vagina tendinum m. extensoris digitorum longi. — This sheath surrounds the tendons 

 of the long digital extensor and the peroneus tertius from above the cruciate ligament to the 

 middle of the third cuneiform bone. 



2. Lateral Musculature of the Leg 



(Figs. 416, 422) 



The lateral muscles consist of the peroneus longus and the peroneus brevis. 

 They extend and evert the foot. The thick prismatic belly of the peroneus longus 

 arises from the proximal half of the lateral surface of the fibula and from neigh- 

 bouring structures, while the smaller belly of the peroneus brevis arises from the 

 middle third of the lateral surface of this bone. The peroneus longus partly 

 covers the peroneus brevis. The tendons of the two muscles pass behind the 

 lateral malleolus, held in place by special retinacula (p. 480). There the tendon 

 of the peroneus longus lies at first lateral to and then crosses behind that of the 

 peroneus brevis and curves about the lateral side of the calcaneus and across the 

 sole of the foot closely applied to the cuboid and to the tarso-metatarsal articula- 

 tions, and terminates on the base of the first metatarsal. The tendon of the 

 peroneus brevis terminates on the lateral side of the foot at the base of the fifth 

 metatarsal. The nerve supply is from the superficial peroneal (musculo-cuta- 

 neous) nerve. 



The two muscles are probably represented in the arm by the extensor carpi ulnaris. In 

 some of the lower animals the head of the peroneus longus extends to the femur. The fibular 

 collateral ligament of the knee-joint probably represents in man the femoral head of the 

 peroneus longus. 



The peroneus longus (figs. 416, 422). — Origin. — Anterior head: tendinous from the anterior 

 tibio-fibular ligament, the neighbouring part of the lateral condyle of the tibia, and the head of 

 the fibula; fleshy from the proximal third of the anterior intermuscular septum and the crural 

 fascia near the tibia. Posterior head : fleshy from the proximal half of the lateral surface_of the 

 shaft of the fibula and from the posterior intermuscular septum. \ 



Structure. — Bipenniform. The fibre-bundles converge upon a tendon which begins'high in ' 

 the muscle. The constituent fibre-bundles of the anterior head are long and take a nearly 

 vertical course. The fibre-bundles of the posterior head take a more oblique course and their 

 attachment extends more distally on the tendon. The tendon emerges on the surface of the 

 muscle in the distal half of the leg. The fibre-bundles of the posterior head extend to within 

 a few centimetres of the lateral malleolus. The tendon passes through the retro-malleolar 

 groove, passes across the lateral face of the calcaneus, to and through the peroneal groove of 

 the cuboid, and crosses the second and third tarso-metatarsal joints. Where the tendon enters 

 the groove in the cuboid it contains a fibro-cartilaginous nodule which may become a sesamoid 

 bone. 



Insertion. — On the inferior surface of the first cuneiform and on the super o-lateral border 

 and base of the first metatarsal. From the region of the fibro-cartilaginous nodule above men- 

 tioned a fibrous slip is usually sent to the base of the fifth metatarsal. 



Nerve-supply. — Most commonly the peroneal (external pophteal) nerve before dividing 

 gives off two branches. One of these enters the deep surface of the middle third of the anterior 

 head, the other passes across the middle third of the constituent bundles of the posterior head. 

 The latter branch may arise from the superficial peroneal (musculo-cutaneous) nerve, and it<G> 

 may extend to supply the peroneus brevis. ^<^ 



The peroneus brevis (fig. 416). — Origin. — From the middle third of the lateral surface 

 of the fibula; (2) from the septa which separate it from the anterior and posterior groups ,^}<. 

 of muscles. ^ V 



Structure. — Penniform. The fibre-bundles converge upon a tendon which begins high in p 

 the muscle and becomes visible on the lateral surface of the distal half of the belly. Behind the ^ * 

 lateral malleolus the tendon becomes free, then passes forward below the maUeolus and* across »r ■< 

 the calcaneus and cuboid. V* /> 



