Lecture 25 - Muscles Of The Leg

Question 1

What are the 3 compartments of the muscles of the leg?

Answer 1

• anterior
• lateral
• posterior

Question 2

How many muscles are in the anterior compartment? What are they?

Answer 2

• 4
• Tibialis anterior
• extensor Hallucis longus
• extensor Digitorum longus
• Peroneus tertius

Question 3

What is the origin/insertion/innervation/main action of the Tibialis anterior?

Answer 3

• O: Lateral condyle & lateral surface of tibia (upper half) & the interosseous membrane
• I: 1st cuneiform & base of the 1st metatarsal (dorsum surface)
• Inn: Deep Peroneal nerve
• MA: Talocrural dorsiflexion & Sub-talar inversion

Question 4

What is the origin/insertion/innervation/main action of the extensor Hallucis longus?

Answer 4

• O: Mid-portion of the medial fibula & interosseous membrane
• I: Distal phalanax of big toe (dorsum surface)
• Inn: Deep Peroneal Nerve
• MA: Extends the big toe & dorsiflexion

Question 5

What is the origin/insertion/innervation/main action of the extensor Digitorum longus?

Answer 5

• O: Lateral tibial condyle, interosseous membrane, medial fibula
• I: Distal phalanges of toes 2-5 (dorsum surface)
• Inn: Deep Peroneal Nerve
• MA: Extension of toes 2-5 & dorsi flexion

Question 6

What is the origin/insertion/innervation/main action of the Peroneus tertius?

Answer 6

• O: Lower medial fibula
• I: Base of the 5th metatarsal
• Inn: Deep Peroneal Nerve
• MA: Eversion & dorsiflexion

Question 7

What is the lateral compartment of the muscles of the leg?

Answer 7

• Small compartment on the lateral side of the fibula
• Evertors of the sub-Talar joint
• Tendons run behind the lateral malleolus
• share a common innervation of the superficial Peroneal nerve & main action of sub-talar eversion

Question 8

How many muscles in the lateral compartment? What are they?

Answer 8

• 2
• Peroneus longus/brevis

Question 9

What is the origin/insertion/innervation/main action of the Peroneus longus?

Answer 9

• O: Head & upper 2/3 lateral fibula
• I: 1st cuneiform & the base of the 1st metatarsal (on plantar aspect of foot)
• Inn: Superficial Peroneal nerve
• MA: Subtalar eversion

Question 10

What is the origin/insertion/innervation/main action of the Peroneus brevis?

Answer 10

• O: Lower 2/3 lateral fibula
• I: Base of 5th metatarsal
• Inn: Superficial Peroneal nerve
• MA: Subtalar eversion

Question 11

What is the posterior compartment of the muscles of the leg?

Answer 11

• made up of 2 layers: superficial & deep

Question 12

What is the superficial layer of the posterior compartment? How many muscles? What are they?

Answer 12

• Forms the bulk of the calf muscle, All converge as the Achilles tendon & then to the calcaneus
• made up by 3 muscles: gastrocnemius, soleus, plantaris
• all share a common insertion of calcaneus, innervation of the tibial nerve, & main action of plantar flexion

Question 13

What is the origin/insertion/innervation/main action of the gastrocnemius?

Answer 13

• O: Medial & lateral femoral condyles
• I: Posterior calcaneus vis the Achilles tendon
• Inn: Tibial Nerve
• MA: Ankle plantar flexion or knee flexion (cannot do both at same time)

Question 14

What is the origin/insertion/innervation/main action of the soleus?

Answer 14

• O: Posterior head & shaft of the fibula, across the interosseous membrane & obliquely up the tibia
• I: Posterior calcaneus via the Achilles tendon
• Inn: Tibial Nerve
• MA: Ankle plantar flexion

Question 15

What is the origin/insertion/innervation/main action of the plantaris?

Answer 15

• O: Just above the lateral femoral condyle
• I: Posterior calcaneus via the Achilles tendon
• Inn: Tibial Nerve
• MA: Knee flexion or plantar flexion

Question 16

What is the deep layer of the posterior compartment? How many muscles? What are they?

Answer 16

• 3 muscles: Tibialis posterior, flexor Digitorum longus, flexor Hallucis longus
• Tendons run posterior to the medial malleolus (through ‘tarsal tunnel’)
• Can remember by “TOM DICK & HARRY”
• share a common innervation of the tibial nerve

Question 17

What is the origin/insertion/innervation/main action of the Tibialis posterior?

Answer 17

• O: Interosseous membrane & adjacent surfaces of the posterior tibia & fibula
• I: Navicular & 1st Cuneiform
• Inn: Tibial nerve
• MA: sub-talar inversion

Question 18

What is the origin/insertion/innervation/main action of the flexor Digitorum longus?

Answer 18

• O: Posteromedial tibia
• I: Bases of the distal phalanges 2-5 (plantar surface)
• Inn: Tibial nerve
• MA: Flexion of toes 2-5, Some ankle plantar flexion

Question 19

What is the origin/insertion/innervation/main action of the flexor Hallucis longus?

Answer 19

• O: Inferior posterior fibula
• I: Base of distal phalanx of big toe (plantar surface)
• Inn: Tibial nerve
• MA: Flexion of big toe, some ankle plantar flexion

Question 20

What is the origin/insertion/innervation/main action of the popliteus?

Answer 20

• O: Lateral femoral condyle
• I: Posterior proximal tibia (between LCL & synovial capsule of knee)
• Inn: Tibial nerve
• MA: Lateral rotation of the femur (if tibia is fixed), Stabilizes knee joint

Question 21

What are intrinsic muscles of the foot?

Answer 21

• Only 1 on the dorsal aspect of the foot
  - Extensor Digitorum Brevis
• The others are all on the plantar side of the foot
  - Flexor Digitorum Brevis
  - Flexor Hallucis Brevis
• Act to modify actions of longer tendons as well as generate fine movements of the toes