Muscles of the anterior compartment of the leg.pptx

Summarised anatomy

1. Muscles of the anterior compartment of the leg TERMINOLOGY Inversion -foot rotates so the sole faces inward to the midline of the body Eversion – foot rotates so that the sole faces away from the midline of the body Dorsiflexion –ankle bends raising the toes upwards Plantar flexion – ankle bends in a direction that toes point downwards

2. Tibialis anterior A superficial muscle and therefore readily palpable lateral to the tibia. Origin - Lateral tibia condyle and proximal ½ to 2/3 of the lateral surface of the tibia shaft. Descends vertically and ends in a tendon on its anterior surface in the lower third of the leg. The tendon passes through the medial compartments of the superior and inferior retinacula, inclines medially, and is inserted on to the medial and inferior surfaces of the medial cuneiform and the adjoining part of the base of the first metatarsal. Vascular supply – medial and anterior branches of the anterior tibial artery Innervation - deep fibular nerve, L4 L5 Actions – dorsiflexes and inversion of the foot

3. Extensor hallucis longus lies between, and is partly overlapped by, tibialis anterior and extensor digitorum longus Origin -middle half of the medial surface of the fibula Its fibres run distally and end in a tendon that forms on the anterior border of the muscle. The tendon passes deep to the superior extensor retinaculum and through the inferior extensor retinaculum, crosses anterior to the anterior tibial vessels to lie on their medial side near the ankle Insertion - dorsal aspect of the base of the distal phalanx of the hallux. Vascular supply –anterior tibial artery via obliquely running branches, with a variable contribution from the perforating branch of the fibular artery. Innervation – deep fibular nerve, L5 Actions – extension of the great toe and dorsiflexion of the foot

4. Extensor digitorum longus Origin –inferior surface of the of the lateral condyle of tibia and the proximal three quarters of the medial surface of the fibula Insertion – tendon divides into four slips inserts in the proximal and distal phalanges of the lateral 4 digits (2-5) Vascular supply -anteriorly and laterally placed branches of the anterior tibial artery, supplemented distally from the perforating branch of the fibular artery. Innervation – deep fibular nerve, L5,S1 Actions –extends the lateral for toes and dorsiflexion of the foot

5. Fibularis tertius Also known as peroneus tertius Often appear as part of extensor digitorum longus and might be described as its fifth tendon Origin -distal third or more of the medial surface of the fibula Insertion -medial part of the dorsal surface of the base of the fifth metatarsal Vascular supply –same as extensor digitorum longus Innervation –deep fibular nerve L5,S1 Actions –eversion and dorsiflexion of the foot

6. MUSCLES OF THE LATERAL COMPARTMENT The lateral compartment contains the fibularis longus and fibularis brevis Both muscles avert the foot and are plantar flexors of the ankle and play a role in balancing the foot in standing and walking.

7. Fibularis longus Larger and More superficial of the 2 muscles Origin -head and proximal two thirds of the lateral surface of the fibula, a few fibers from the lateral condyle of the tibia. Insertion - lateral side of the base of the first metatarsal and one to the lateral aspect of the medial Cuneiform Vascular supply -anterior tibial artery, there is also a lesser contribution from the fibular artery in the distal part of the leg. Innervation –superficial fibular nerve L5,S1 Action –eversion of the foot and plantar flexion of the ankle

8. Fibularis brevis Deeper and shorter than fibularis longus Origin -distal two thirds of the lateral surface of the fibula Insertion - tuberosity on the lateral side of the base of the fifth metatarsal Vascular supply – anterior tibial artery, there is also a lesser contribution from the fibular artery in the distal part of the leg. Innervation – superficial fibular nerve Action - eversion of the foot