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Origin: Lateral condyle of the tibia, the proximal two-thirds of the medial surface of the fibula, the adjacent anterior surface of the interosseous membrane, the anterior intermuscular septum, and the septum between it and tibialis anterior.
Insertion: Divides into four slips and inserts at the base of each of the lateral four proximal phalanges. Each tendon then divides into three slips: an intermediate slip, which attaches to the base of the middle phalanx, and two collateral slips, which attach to the base of the distal phalanx.
Actions: Extension of the four lateral toes
Innervation: Deep peroneal nerve (L5, S1)
Blood Supply: Branches from the anterior tibial artery
Primary Actions of the Extensor Digitorum Longus Muscle
1. Extension of the four lateral toes at the proximal interphalangeal joints
Agonists: Extensor Digitorum Brevis
Antagonists:
- Flexor Digitorum Longus
- Flexor Digitorum Brevis
Lumbricals, dorsal interossei, and plantar interossei assist with extension of the four lateral toes at the proximal interphalangeal joints.
2. Extension of the four lateral toes at the distal interphalangeal joints
Agonists: None
Antagonists:
- Flexor Digitorum Longus
Lumbricals, dorsal interossei, and plantar interossei assist with extension of the four lateral toes at the proximal interphalangeal joints.
3. Extension of the four lateral toes at the metatarsophalangeal joints
Agonists:
- Extensor Digitorum Brevis
Antagonists:
- Flexor Digitorum Longus
- Flexor Digitorum Brevis
- Flexor Digiti Minimi (fifth digit)
Secondary Actions of the Extensor Digitorum Longus Muscle
1. Assists with dorsiflexion of the foot at the ankle
Agonists: Tibialis anterior
Antagonists:
- Gastrocnemius
- Soleus
Peroneus tertius and extensor digitorum longus also assist with dorsiflexion of the foot at the ankle.
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