Human Anatomy Week 7 - Outline Notes 2

Tibia: The shin bone, located medially, with:
- Condyles: Medial and lateral condyles form the knee joint.
- Intercondylar eminence: A projection between the condyles.
- Anterolateral tibial tubercle (Gerdy's tubercle): Attachment point for the IT band.
- Tibial tuberosity: Attachment point for the patellar ligament.
- Facet for fibula: Articulates with the head of the fibula.
- Shaft: The main body of the bone.
- Anterior border and medial surfaces: Provide attachment points for muscles.
- Interosseous border: Forms the interosseous membrane with the fibula.
- Soleal line: Attachment point for the soleus muscle.
- Medial malleolus: Forms the medial prominence of the ankle joint.
- Fibular notch: Articulates with the lateral malleolus of the fibula.
Fibula: The smaller bone, located laterally, with:
- Head: Connects to the tibia at the proximal tibiofibular joint.
- Neck: Below the head, susceptible to fracture.
- Lateral malleolus: Forms the lateral prominence of the ankle joint.
- Shaft: Runs parallel to the tibia.
- Interosseous Membrane: Connects the tibia and fibula, providing stability.
- Middle Tibiofibular Joint: Formed by the interosseous membrane, acts as a syndesmosis.
- Proximal and Distal Tibiofibular Joints: Planar synovial joints, important for ankle movements.

Crural Fascia: Dense connective tissue surrounding the leg, continuous with the fascia lata of the thigh.
- Intermuscular septa: Divide the leg into four compartments.
- Retinacula: Bands of fascia that prevent tendon bowstringing at the ankle.
- Superior and inferior extensor retinaculum: Supports the extensor tendons.
- Flexor retinaculum: Supports the flexor tendons.
- Fibular retinaculum: Supports the fibular tendons.
Compartment Syndrome: Increased pressure within a compartment, potentially leading to nerve damage and muscle ischemia.
- Caused by trauma or edema, requiring surgical intervention.
- Chronic overuse injuries: Can also cause inflammation and increased pressure in specific compartments.

Muscles:
- Gastrocnemius: Plantarflexes the ankle and flexes the knee.
- Soleus: Plantarflexes the ankle, independent of knee position.
- Plantaris: Weakly assists in plantarflexion, can be used for surgical repairs.
Neurovascular: Shares the posterior tibial artery and tibial nerve with the deep posterior compartment.
Clinical Considerations:
- Achilles tendonitis/rupture: Inflammation or rupture of the Achilles tendon.
- Deep vein thrombosis (DVT): Blood clots in the posterior tibial veins, more common in sedentary individuals.
- Calf pump: The triceps surae muscles can act as a pump to improve blood circulation.

Muscles:
- Popliteus: Flexes the knee and rotates the femur.
- Flexor hallucis longus: Flexes the great toe and plantarflexes the ankle.
- Flexor digitorum longus: Flexes the lateral four toes and plantarflexes the ankle.
- Tibialis posterior: Plantarflexes and inverts the foot, supports the medial longitudinal arch.
Neurovascular:
- Innervation: Tibial nerve.
- Vascular: Posterior tibial artery.
Clinical Considerations:
- Pure inversion: Tibialis anterior and posterior muscles work together to control inversion of the foot.

Muscles:
- Tibialis anterior: Dorsiflexes and inverts the ankle, draws the leg over the foot during gait.
- Extensor digitorum longus: Extends the lateral four toes and dorsiflexes the ankle.
- Extensor hallucis longus: Extends the great toe and dorsiflexes the ankle.
- Fibularis (Peroneus) tertius: Dorsiflexes and everts the foot.
- Extensor Digitorum Brevis (Dorsal Foot): Assists in extension of toes 2-4.
- Extensor Hallucis Brevis (Dorsal Foot): Assists in extension of great toe.
Neurovascular:
- Innervation: Deep fibular nerve.
- Vascular: Anterior tibial artery, becomes the dorsalis pedis artery at the ankle.
Clinical Considerations:
- Anterior shin splints: Inflammation of the anterior compartment muscles, often due to overuse.
- Foot drop: Weakness or paralysis of dorsiflexors due to injury to the deep fibular nerve.

Muscles:
- Fibularis (Peroneus) longus: Everts the foot and weakly plantarflexes.
- Fibularis (Peroneus) brevis: Everts the foot and weakly plantarflexes.
Neurovascular:
- Innervation: Superficial fibular nerve.
- Vascular: Fibular artery, a branch of the posterior tibial artery.
Clinical Considerations:
- Lateral ankle sprains: Can injure the superficial fibular nerve.

Arterial Supply:
- Popliteal artery: Branches into anterior and posterior tibial arteries.
- Anterior tibial artery: Supplies the anterior compartment.
- Posterior tibial artery: Supplies the deep posterior compartment.
Superficial Veins:
- Great saphenous vein: Medially, merges with the femoral vein.
- Small saphenous vein: Posteriorly, joins the popliteal vein.
Innervation:
- Tibial nerve: Deep posterior compartment.
- Deep fibular nerve: Anterior compartment.
- Superficial fibular nerve: Lateral compartment.
Sensory Innervation:
- The leg receives sensory innervation from the saphenous nerve, the sural nerve, and the superficial fibular nerve.

Proximal Tibiofibular Joint:
- Structure: Gliding planar joint between the head of the fibula and the tibia.
- Joint supports: Proximal anterior and posterior tibiofibular ligaments.
- Motions: Fibula glides superiorly and posteriorly with dorsiflexion.
- Neurovascular: Common peroneal nerve and lateral genicular, anterior tibial, and recurrent tibial arteries.
Middle Tibiofibular Joint:
- Structure: Syndesmosis formed by the interosseous membrane.
- Motions: Accessory movements with the ankle joint.
Distal Tibiofibular Joint:
- Structure: Fibrous/Syndesmosis, may act as a gliding planar joint.
- Joint supports: Interosseous ligament, distal anterior and posterior tibiofibular ligaments.
- Neurovascular: Deep peroneal, tibial, and saphenous nerves, perforating branches of peroneal, anterior and posterior tibial arteries.
- Motions: Fibula glides superiorly and posteriorly with dorsiflexion.

Tibial Fractures: Heal slowly due to poor blood supply.
Injuries to the Common Fibular Nerve: Occurs at the neck of the fibula, causing foot drop.
Compartment Syndrome: Compression of neurovascular structures in a compartment.
Shin Splints: Inflammation of the muscles and fascia of the shin.
- Anterior Shin Splints: Affect the tibialis anterior muscle.
- Medial Shin Splints: Can involve the tibialis posterior or soleus muscles.
Ankle Reflex: Tests the integrity of the S1 & S2 spinal segments.