Lecture 15 - SQ

Question 1

1. What are the boundaries and contents of the anterior muscle compartment of the leg? What is
   anterior tibial compartment syndrome?

Answer 1

1) The anterior compartment of the leg is enclosed by firm inextensible walls which are the deep
fascia of the leg, tibia, the interosseous membrane, fibula, and the fascia separating the
anterior compartment from the peroneal compartment. The muscles within the anterior
compartment are: tibialis anterior, extensor hallucis longus, extensor digitorum longus and
peroneus tertius. The deep peroneal nerve and the anterior tibial vessels are also found in the
anterior compartment. Compartmentalization of muscle in the leg aids peripheral venous
return by resisting muscle expansion in girth, when muscles shorten. That raised pressure in
the compartment, which (with the additional assistance of one way valves) pumps blood
against gravity. However, if unaccustomed severe and prolonged exercise is undertaken, the
muscles of the anterior compartment may swell. The swelling may be such that, in the
enclosed space, the venous return is obstructed; this can lead to further swelling, and
eventually to capillary stasis and gangrene, if not treated properly.

Question 2

2. What muscles are innervated by the femoral nerve? Are these muscles extensors or flexors?
   In the upper limb, the dorsal or posterior divisions innervated extensor muscles. Is this
   pattern the same in the lower limb?

Answer 2

2) The femoral nerve supplies the flexors of the hip and the extensors of the knee. They are as
follows: iliopsoas (psoas + iliacus), sartorius, rectus femoris, pectineus, vastus lateralis, vastus
medialis, vastus intermedius. In the lower limb at the knee, as in the upper limb at the elbow,
the extensors are, indeed, innervated by the dorsal divisions. However, the extensors of the hip
are innervated primarily by the tibial component of the sciatic nerve, which arises from ventral
divisions.

Question 3

3. What areas of skin receive innervation from the femoral nerve (L2 - L4)?

Answer 3

3) The femoral nerve provides cutaneous distributions to the anterior thigh, and to the medial leg
and medial foot (except the great toe) through the saphenous nerve.

Question 4

4. What muscles are innervated by the obturator nerve? What is the function of these muscles?

Answer 4

OBTURATOR NERVE:
-gracilis (hip adduction + knee flexion)
-pectineus (hip adduction)
-adductor longus (hip adduction)
-adductor brevis (hip adduction)
-adductor magnus (hip adduction + extension)
obturator externus (later rotator of hip)

Question 5

5. What areas of skin receive innervation from the obturator nerve (L2 - L4)?

Answer 5

5) The obturator nerve provides cutaneous innervation to the medial thigh

Question 6

6. What muscles are innervated by the common peroneal part (L4 - S3) of the sciatic nerve?
   What is the function of these muscles? Remember that the common peroneal part of the
   sciatic nerve is made up of dorsal divisions of ventral rami.

Answer 6

6) COMMON PERONEAL NERVE:
- biceps femoris (short head) (knee flexion)
- peroneus longus (foot eversion)
- peroneus brevis (foot eversion)
- tibialis anterior (dorsiflexion)
- extensor digitorum longus (dorsiflexion)
- extensor hallucis longus (dorsiflexion)
- peroneus tertius (dorsiflexion)
- extensor digitorum brevis (toe extension)

Question 7

7. What areas of skin are supplied by the common peroneal part (L4 - S3) of the sciatic nerve?

Answer 7

7) Common peroneal nerve supplies cutaneous innervation to lateral and anterior leg, and dorsum
of the foot.

Question 8

8. What muscles are innervated by the tibial part (L4 - S3) of the sciatic nerve? What is the
   function of these muscles? Remember that the tibial part of the sciatic nerve is made up of
   ventral divisions of ventral rami.

Answer 8

8) TIBIAL part of sciatic nerve, tibial nerve and its branches, medial and lateral plantar nerves:
Hip extension: 
-biceps femoris (long head)
-semitendinosus
-semimembranosus
-adductor magnus (hamstring)
Knee flexion: 
-biceps femoris (long head)
-semimembranosus
-semitendinosus
-gastrocnemius
-plantaris
-popliteus
Ankle flexion: 
-gastrocnemius
-plantaris
-soleus
-flexor hallucis longus
-flexor digitorum longus
-tibialis posterior
The tibial nerve and its branches also supply all intrinsic muscles on the plantar surface of the
foot.

Question 9

9. What areas of skin are supplied by the tibial part (L4 - S3) of the sciatic nerve?

Answer 9

The tibial nerve supplies cutaneous innervation to the following areas: lower buttock,
posterior thigh, posterior leg, sole of foot.

Question 10

10. What structures are supplied by dorsal rami of spinal nerves?

Answer 10

10) The dorsal rami of spinal nerves supply only the muscles and skin of the back proper. All of
the remainder of the trunk and the limbs are innervated by ventral rami.

Question 11

11. What dermatomes are represented on the dorsum of the foot?

Answer 11

11) The dermatomes that are represented on the dorsum of the foot are S1, L5, and some of L4.