Last's Anatomy_ Regional and Applied, 12e-1-503

The dorsal nerve of the penis (clitoris) is the other terminal branch of the pudendal. It runs forward
deep to the perineal membrane, which it pierces just below the symphysis pubis to supply the skin of
the penis (clitoris).

Muscular branches of S3 and S4 supply levator ani and coccygeus on their upper (pelvic) surfaces.

The perineal branch of S4 passes between levator ani and coccygeus to supply the puborectalis,
pubourethralis and pubovaginalis parts of levator ani from below, and the skin over the ischioanal
fossa.

The nerve to quadratus femoris (L4, 5, S1) lies on the ischium deep to the sciatic nerve and runs
down deep to obturator internus to sink into the deep surface of quadratus femoris. It also supplies the
inferior gemellus and gives a branch to the hip joint.

The nerve to obturator internus (L5, S1, 2) passes below piriformis, curls around the base of the
ischial spine and sinks into obturator internus. It also supplies the superior gemellus.

T he superior gluteal nerve (L4, 5, S1) passes back through the greater sciatic notch above
piriformis, runs in the plane between glutei medius and minimus, supplies both, and ends in the tensor
fasciae latae.

The inferior gluteal nerve (L5, S1, 2) passes back below piriformis and sinks into the deep surface
of gluteus maximus.

Sciatic nerve

The sciatic nerve is the largest branch of the sacral plexus from which it is formed at the lower
margin of piriformis by union of its tibial and common peroneal parts. It passes into the buttock lying
on the posterior surface of the ischium. Here the nerve to quadratus femoris is deep to it and the
posterior femoral cutaneous nerve lies superficial. From midway between the greater trochanter and
the ischial tuberosity, the sciatic nerve passes vertically downwards into the hamstring compartment.
It lies on obturator internus and gemelli, quadratus femoris and then on adductor magnus. It is overlaid
by the long head of biceps. The main trunk of the sciatic nerve supplies all the hamstrings and the
ischial fibres of adductor magnus and it then divides, usually at the upper angle of the popliteal fossa,
into the tibial and common peroneal nerves. The branches for the long head of biceps, the two ‘semi-’
muscles and adductor magnus are from the tibial part, but the branch to the short head of biceps comes
from the common peroneal part.

Common peroneal (fibular) nerve (L4, 5, S1, 2)

The common peroneal nerve supplies the extensor and peroneal compartments of the leg and the
dorsum of the foot. It enters the apex of the popliteal fossa and runs medial to the biceps tendon just
beneath the deep fascia. It crosses plantaris, lateral head of gastrocnemius and curves around the neck
of the fibula, through peroneus longus, where it divides into two terminal branches, the deep and
superficial peroneal (fibular) nerves. It can be palpated on the neck of the fibula, where it can be
rolled on the bone. It is the nerve most commonly injured in the lower limb.

The common peroneal nerve itself supplies no muscles. Three articular branches, the upper and lower
lateral and recurrent genicular nerves, supply the knee joint; the lateral genicular nerves accompany

the arteries, the recurrent supplies the superior tibiofibular joint as well.

There are two cutaneous branches. The sural communicating nerve joins the sural nerve below the
gastrocnemius heads. The lateral cutaneous nerve of the calf supplies skin and deep fascia over the
upper half of the peroneal compartment.

The deep peroneal nerve is formed in the substance of peroneus longus, spirals down over the fibula
deep to extensor digitorum longus and reaches the interosseous membrane. It runs down lateral to the
vessels, crosses the lower end of the tibia and the dorsum of the foot, and ends by supplying the skin
of the first interdigital cleft.

It supplies the muscles of the extensor compartment of the leg: extensor digitorum longus, tibialis
anterior, extensor hallucis longus and peroneus tertius. On the dorsum of the foot it gives a lateral
branch which supplies extensor digitorum brevis.

The superficial peroneal nerve is formed in the substance of peroneus longus and runs down in the
muscle, emerging from its anterior border about a third of the way down the leg. It supplies peroneus
longus and brevis, then perforates the fascia to supply the skin over the peronei and extensor muscles
in the lower third of the leg. Above the ankle it divides into a medial and a lateral branch which
supply skin and deep fascia on the dorsum of the foot. The medial branch breaks up to supply the
medial side of the big toe and the second interdigital cleft, while the lateral branch breaks up to
supply the third and fourth clefts.

Tibial nerve (L4, 5, S1, 2, 3)

The tibial nerve supplies the calf and the sole of the foot around to the toenails. The nerve enters the
apex of the popliteal fossa and, in the midline of the limb, passes vertically down deep to the heads of
gastrocnemius behind the knee joint and across the popliteus muscle, to run beneath the fibrous arch in
soleus.

Branches in the popliteal fossa. Three genicular nerves, upper and lower medial and a middle,
accompany the arteries and supply the knee joint. Five muscular branches supply the muscles of the
fossa: plantaris, both heads of gastrocnemius, soleus and popliteus. The last-named branch recurves
around the lower border of the muscle to enter its deep (anterior) surface. A single cutaneous branch,
the sural nerve, lies in the groove between the two heads of gastrocnemius and pierces the deep
fascia halfway down the leg. Here it is joined by the sural communicating nerve. The sural nerve runs
down alongside the small saphenous vein behind the lateral malleolus and ends on the lateral side of
the little toe.

From the fibrous arch the nerve runs down with the posterior tibial vessels deep to the soleus muscle.
The neurovascular bundle lies in the groove between the bellies of flexor hallucis longus and flexor
digitorum longus. Behind the medial malleolus, beneath the flexor retinaculum, the nerve divides into
its terminal medial and lateral plantar branches.

Branches in the calf. Four muscular branches supply soleus, tibialis posterior and the flexors
hallucis and digitorum longus. Medial calcanean branches pierce the flexor retinaculum and supply
the weight-bearing skin of the heel.

The medial and lateral plantar nerves correspond approximately to the median and ulnar nerves in
the hand as far as skin and muscle supplies are concerned. The medial plantar supplies the medial
part of the sole and plantar surface of the medial three and a half digits, and innervates flexor
digitorum brevis, abductor hallucis, flexor hallucis brevis and the first lumbrical, with the lateral
plantar supplying the rest of the sole and the other small muscles of the foot.