Lecture 11 - Muscles Of The Lower Leg

Question 1

What type of movements are in the lower leg?

Answer 1

• ankle; Talocrural (true ankle joint): dorsiflexion/plantarflexion
• Subtalar joint: inversion/eversion
• foot: flexion/extension & abduction/adduction

Question 2

What are the 3 compartments of the lower leg?

Answer 2

• anterior
• lateral
• posterior

Question 3

How many muscles are in the anterior compartment of the lower leg? What are they?

Answer 3

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

Question 4

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

Answer 4

• O: Lateral condyle & lateral surface of tibia (upper half) & the interosseous membrane
• I: 1st cuneiform & base of the 1st metatarsal (medial & inferior surfaces)
• Inn: Deep perineal nerve
• MA: Talocrural dorsi flexion & Sub-talar inversion

Question 5

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

Answer 5

• O: Mid-portion of the medial fibula & interosseous membrane
• I: Distal phalanx of big toe
• Inn: Deep peroneal nerve
• MA: Extends the big toe & Dorsiflexion

Question 6

What is the origin/insertion/Innervation/main action of the extensor digitorum longus?

Answer 6

• O: Lateral tibial condyle, interosseous membrane, & medial fibula
• I: Distal phalanges of toes 2-5
• Inn: Deep peroneal nerve
• MA: Extension of toes 2-5 & Dorsiflexion

Question 7

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

Answer 7

• O: Lower medial fibula
• I: Base of the 5th metatarsal
• Inn: Deep peroneal nerve
• MA: Eversion & Dorsiflexion

Question 8

What is the lateral compartment of the lower leg?

Answer 8

• Small compartment on the lateral side of the fibula
• Evertors of the sub-talar joint
• Tendons run behind the lateral malleolus

Question 9

How many muscles are in the lateral compartment of the lower leg? What are they?

Answer 9

• 2
• Peroneus longus
• Peroneus brevis

Question 10

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

Answer 10

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

Question 11

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

Answer 11

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

Question 12

What is the posterior compartment of the lower leg?

Answer 12

• made up of a superficial layer & a deep layer

Question 13

What is the superficial layer of the posterior compartment of the lower leg?

Answer 13

• forms the bulk of the calf muscle
• Powerful anti-gravity muscles
• All converge as the Achilles tendon & the to the calcaneus
• There are 2 protective bursal sacs; Achilles tendon & retro-calcaneal bursa

Question 14

How many muscles are in the superficial layer of the posterior compartment of the lower leg? What are they?

Answer 14

• 3
• gastrocnemius
• soleus
• plantaris

Question 15

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

Answer 15

• O: Medial & lateral femoral condyles
• I: Posterior calcaneus
• Inn: Tibial nerve
• MA: Ankle plantar flexion or knee flexion (can’t do both at same time) & Propelling force in walking, running, & leaping

Question 16

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

Answer 16

• O: Posterior head & shaft of the fibula, across the interosseous membrane
• I: Posterior calcaneus
• Inn: Tibial nerve
• MA: Ankle plantar flexion

Question 17

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

Answer 17

• O: Just above the lateral femoral condyle
• I: Posterior calcaneus
• Inn: Tibial nerve
• MA: Knee flexion or plantar flexion

Question 18

What is the deep layer of the posterior compartment of the lower leg?

Answer 18

• Tendons run posterior to the medial malleolus
• Remember them: (“Tom, Dick, & Harry, Tom = Tibialis posterior, Dick = flexor digitorum longus, Harry = flexor Hallucis longus)

Question 19

How many muscles are in the deep layer of the posterior compartment of the lower leg? What are they?

Answer 19

• 3
• Tibialis posterior
• flexor Hallucis longus
• flexor digitorum longus

Question 20

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

Answer 20

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

Question 21

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

Answer 21

• O: Inferior posterior fibula
• I: Base of distal phalanx of big toe
• Inn: Tibial nerve
• MA: Flexion of big toe

Question 22

What is the origin/insertion/Innervation/main action of the flexor digitorum longus?

Answer 22

• O: Posteromedial tibia
• I: Bases of the distal phalanges 2-5
• Inn: Tibial nerve
• MA: Flexion of toes 2-5

Question 23

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

Answer 23

• O: Lateral femoral condyle
• I: Posterior proximal tibia
• Inn: Tibial nerve
• MA: Lateral rotation of the femur (if tibia is fixed): unlocks the screw home mechanism

Question 24

What is the popliteal fossa?

Answer 24

• Diamond shape
• Contains the popliteal artery/vein, small saphenous vein, tibial nerve, common fibular nerve, & popliteal lymph nodes
• Branching of the sciatic nerve

Question 25

What is the intrinsic muscle on the dorsal aspect of the foot?

Answer 25

• extensor digitorum brevis

Question 26

What are the 2 intrinsic muscles on the plantar side of the foot?

Answer 26

• flexor digitorum brevis
• flexor Hallucis brevis

Question 27

What do the intrinsic muscles of the foot do?

Answer 27

• act to modify actions of longer tendons as well as generate fine movements of the toes