lower limb

Question 1

lumbar plexus

Answer 1

L1-4

plexus is formed within the substance of psoas major anterior to the transverse processes of L2-5 from the anterior primary rami as they emerge from the intervertebral foramina.

Question 2

iliohypogastric n

Answer 2

1. L1
2. emerges lateral to psoas on the lumbar fascia at lvl L2
3. pass posterior to the lower pole of the kidney
4. over quadratus lumborum.
5. It passes above the iliac crest, between transversus and internal oblique abdominis to pierce the latter above the ASIS.
6. It supplies both muscles before becoming cutaneous: ant. abdo wall, mons pubis lateral cuteneous branch ->upper lateral buttock

Question 3

ilioinguinal

Answer 3

1. L1
2. emerges lateral to psoas on the lumbar fascia,
3. passes posterior to the lower pole of the kidney,
4. over quadratus lumborum
5. penetrates transversus and internal oblique abdominis above the ASIS.
6. It supplies the lowest fibres of these muscles and the conjoint tendon.
7. Its terminal branch enters the inguinal canal from above to pass through the superficial inguinal ring before piercing the external spermatic fascia to become subcutaneous.

Question 4

lateral femoral cutaneous

Answer 4

1. (L2,3).
2. Emerges lateral to psoas below the iliac crest,
3. passes over iliacus obliquely lying posterior to the caecum on the right and descending colon on the left.
4. It runs forward to the ASIS where it penetrates the inguinal ligament at its attachment to pass into the subcutaneous tissue of the lateral thigh.

Question 5

genitofemoral

Answer 5

1. (L1,2)
2. Emerges onto the anteromedial surface of psoas lying posterior to the ureter, gonadal and iliocolic vessels on the right and ureter, gonadal and lower left colic vessels on the left.
3. It divides into genital and femoral branches on the anterior aspect of psoas.

Genital branch.

• Crosses the external iliac artery, passes through the deep inguinal ring into the inguinal canal and through the superficial inguinalring to terminate in the spermatic cord in the male and labium majus in the female. It may also supply a small area of scrotal/labial skin.
• Supplies cremasteric muscle

Femoral branch.

• Continues down lateral to the external iliac artery, under the inguinal ligament and into the femoral sheath which it penetrates anteriorly to become subcutaneous.

Question 6

femoral nerve

Answer 6

1. Post div of ant primary rami of L2,3,4
2. It is formed within psoas major and emerges from its lateral border low down in the iliac fossa to lie in the groove between psoas and iliacus.
3. It reaches the thigh beneath the inguinal ligament lateral to the femoral artery lying on the tendon of iliacus and psoas.
4. In the femoral triangle it splits into anterior and posterior divisions which straddle the lateral circumflex femoral artery. There are usually four short superficial branches.
5. The deep branches continue down the femoral triangle, the N to vastus medialis running lateral to the femoral artery as far as the upper part of the adductor (Hunter’s) canal before entering the muscle.

• Saphenous N (post division).
• Descends in the femoral triangle to reach the adductor canal
• where it spirals over the femoral artery to lie medial to it.
• It pierces the deep fascia through the apex of the canal and emerges posterior to sartorius and anterior to gracilis to continue with the long saphenous vein.
• t passes over the subcutaneous surface of the tibia and anterior to the medial malleolus where it is palpable, closely related to the long saphenous vein.
• t terminates in branches over the medial side of the foot.

Question 7

saphenous nerve

Answer 7

1. Saphenous N (post division of femoral nerve).
2. Descends in the femoral triangle to reach the adductor canal
3. where it spirals over the femoral artery to lie medial to it.
4. It pierces the deep fascia through the apex of the canal and emerges posterior to sartorius and anterior to gracilis to continue with the long saphenous vein.
5. t passes over the subcutaneous surface of the tibia and anterior to the medial malleolus where it is palpable, closely related to the long saphenous vein.
6. t terminates in branches over the medial side of the foot.

Question 8

obturator nerve

Answer 8

1. Ant div of ant primary rami of L2,3,4
2. formed within psoas major and emerges from the medial aspect of the muscle on the ala of the sacrum
3. pass behind the common iliac vessels.
4. It runs over the pelvic brim on the lateral wall of the pelvis and over the upper fibres of obturator internus to pass through the upper anterior aspect of the obturator foramen.
5. It divides into anterior and posterior divisions which straddle adductor brevis.
6. The posterior division pierces a few fibres of obturator externus and runs deep to adductor brevis on adductor magnus. T
7. he anterior division runs on the anterior aspect of adductor brevis deep to pectineus and then deep to adductor longus to end by contributing, together with the saphenous and medial femoral cutaneous N, to the subsartorial plexus which supplies the skin over the medial thigh

Question 9

sacral plexus

Answer 9

L4-S4

Lies on piriformis on the posterior wall of the pelvis deep to the internal iliac vessels (and the sigmoid vessels on the left) and is protected by a sheet of pelvic fascia overlying it. Its roots are characteristically related to arteries which pass between them

It helps to remember that all six branches leaving sacral roots before anterior and posterior divisions begin with the letter ‘P’:

1. N to Piriformis S1,2 (remains in pelvis to supply this muscle)
2. Posterior femoral cutaneous N S1,2,3 (leaves pelvis via greater sciatic foramen)
3. Perforating cutaneous N S2,3 (leaves pelvis via greater sciatic foramen)
4. Pudendal N S2,3,4 (leaves pelvis via greater sciatic foramen)
5. Pelvic splanchnics (parasympathetic) S2,3,4 (remain in pelvis to supply pelvic organs)
6. Perineal branch of S4 (remains in pelvis to supply levator ani)

Question 10

Sciatic nerve

Answer 10

1. From: Ant primary rami of L4,S,Sl,2,3 To: Tibial & common peroneal (fibular)
2. It is formed in the upper sacral plexus and passes out of the greater sciatic foramen below piriformis. In the buttock and thigh it lies initially deep to gluteus maximus lying on gemellus superior, obturator internus tendon and gemellus inferior and then on quadratus femoris and adductor magnus.
3. It passes out of the cover of gluteus maximus and for a short distance it is covered by only deep fascia, before it passes deep to the two heads of biceps femoris.
4. It r**uns vertically down in the midline of the posterior compartment of the thigh **
5. terminates by dividing into common peroneal (fibular) and tibial Ns usually two-thirds of the way down the thigh.
6. In its course over the gemelli it is a close posterior relation of the ischium and posterior rim of the acetabulum.

• N to quadratus femoris (L4,5,S1). Arises from the anterior surface of the sciatic N in the pelvis and leaves the pelvis in this position through the greater sciatic foramen, lying between the sciatic N and the ischium. Running deep to the tendon of obturator internus and the gemelli it supplies gemellus inferior before passing into quadratus femoris from above.
  1. N to obturator internus (LS,S1,2). Arises from the anterior surface of the sciatic N in the pelvis and leaves the pelvis through the greater sciatic foramen below piriformis and medial to the sciatic N. It passes medially over the ischial spine (lateral to the pudendal neurovascular bundle) and sends a branch to gemellus superior before turning forward to pass through the lesser sciatic foramen, penetrating and supplying obturator internus as it does so.

Question 11

TIBIAL NERVE

Answer 11

1. L4-S3
2. From: Sciatic N To: Med & lat plantar
3. It arises in the lower third of the thigh above the apex of the popliteal fossa as the larger terminal branch of the sciatic N, and passes down in the midline into the fossa between semitendinosus and biceps femoris, lying deep to them.
4. It lies markedly lateral to the popliteal artery on entry to the popliteal fossa but then the artery crosses deep to the N to lie lateral to it.
5. The tibial N and the popliteal artery remain separated by the popliteal veins.
6. The n*erve leaves the fossa deep to the two heads of gastrocnemius by passing deep to the fibrous arch of soleus. *
7. then runs deep to soleus on tibialis posterior in the midline,
8. crossing over the posterior tibial artery from medial to lateral half way down the calf.
9. t slopes gently medially in the lower calf passing behind the medial malleolus of the lower tibia between the posterior tibial artery anterornedially and the tendon of flexor hallucis longus posterolaterally.
10. It runs under the flexor retinaculum where it divides into terminal branches.

• Sural N. Arises in the popliteal fossa, passing out posteriorly over the ‘V’ behind the two heads of gastrocnemius and is joined by the sural communicating N from the common peroneal (fibular) N. It pierces the deep fascia to become subcutaneous. It runs down laterally accompanied by the short saphenous vein to pass behind the lateral malleolus over the superior peroneal (fibular) retinaculum to end in terminal branches on the lateral side of the foot.

Question 12

common fibular (peroneal) nerve

Answer 12

1. (L4,5,S 1,2)
2. From: Sciatic N To: Superficial & deep peroneal (fibular)
3. It arises in the lower third of the thigh above the apex of the popliteal fossa as the smaller terminal branch of the sciatic N.
4. It passes into the popliteal fossa along the upper lateral boundary just beneath the edge of biceps femoris and runs over plantaris, the lateral head of gastrocnemius and the posterior capsule of the knee joint
5. . It runs over the fibular attachment of soleus to wind around the neck of the fibula from posterior to lateral.
6. It passes into peroneus longus where it divides.

• SUPERFICIAL PERONEAL [FIBULAR] NERVE (L5,S 1,2) From: Common peroneal (fibular) N. It arises deep to peroneus longus and passes forwards and downwards to lie over the lateral surface of the fibula between peroneus longus and brevis. It pierces the deep fascia half way down the leg to become subcutaneous. It runs downwards superficial to the superior and inferior extensor retinacula to end as terminal branches over them.
• DEEP PERONEAL [FIBULAR] NERVE (L495,S 1,2) From: Common peroneal (fibular) N. It arises deep to peroneus longus and passes forwards deep to the muscle to wind around the fibula and to pass through the anterior intermuscular septum. It continues deep to extensor digitorum longus to appear between it and tibialis anterior lying on the interosseous membrane in the upper quarter of the anterior compartment. It runs down the interosseous membrane with the anterior tibial vessels, coming to lie between extensor hallucis longus and tibialis anterior in the lower three-quarters of the compartment. It passes anterior to the tibia at the ankle joint between the anterior tibial artery medially and the tendon of extensor digitorum longus laterally, running beneath the superior and inferior extensor retinacula. It breaks up into terminal branches on the dorsum of the foot.

Question 13

internal iliac artery

Answer 13

1. The artery commences L5/ S1
2. and passes posteriorly into the pelvis for 4cm before forming anterior and posterior divisions
3. . Anterior lie the ureter and fallopian tube and ovary in the female.
4. Posterior are the internal iliac vein, lumbosacral trunk and sacro-iliac joint.
5. On the lateral side are the external iliac artery and vein, obturator nerve and psoas major.
6. The parietal peritoneum and small bowel lie medially.

• Internal pudendal artery Arises **from the anterior division of the internal iliac artery ** and descends on the lateral wall of the pelvis towards the greater sciatic foramen. It leaves the pelvis via this foramen, inferior to piriformis, before passing over the tip of the ischial spine to enter the ischio-anal fossa via the lesser sciatic foramen.
• In runs on the lateral wall of the ischio-anal fossa on obturator internus in the pudendal (Alcock’s) canal.
• It passes into the deep perinea1 pouch where it gives off its terminal branches. (Other branches of the perineal a. are transverse perineal and posterior scrotal.)

Question 14

femoral artery

Answer 14

1. External iliac art To: Popliteal art
2. This is the continuation of the external iliac a. and commences posterior to the inguinal ligament at the mid-inguinal point (half way between the ASIS and the symphysis pubis).
3. It ends as it passes through the adductor hiatus in adductor magnus to become the popliteal a.
4. It emerges from under the inguinal ligament with the femoral vein medial to it, both within the femoral sheath.
5. Lateral to it and outside the femoral sheath is the femoral nerve.
6. It lies on the tendon of psoas major and is separated from pectineus and adductor longus by the femoral vein which comes to lie progressively more posterior to the artery within the femoral triangle.
7. In the adductor canal it lies on adductor longus then adductor magnus.
8. It is covered initially only by deep fascia then by sartorius;
9. the saphenous nerve passes anteriorly from lateral to medial. Anterolateral to the artery is vastus medialis.
10. Profunda fernoris is the main branch of the femoral artery which is given off posterolaterally just below the femoral sheath 3.5cm below the inguinal ligament. It runs posteriorly between pectineus and adductor longus to pass into the deep thigh where it provides the deep structures and the posterior and medial compartments with their main arterial supply. Perforating and descending branches anastomose with the genicular branches of the popliteal artery.

Question 15

popliteal artery

Answer 15

1. Femoral art To: Ant & post tibial arts.
2. Commences as the continuation of the femoral artery as the latter passes through the hiatus in adductor magnus and ends as it passes under the fibrous arch of soleus where it immediately divides into anterior and posterior tibial arteries.
3. The popliteal artery extends from a hand’s breadth above the knee and to the same distance below it.
4. It enters the popliteal fossa medial to the femur and becomes the deepest structure, lying with only fat between it and the popliteal surface of the femur.
5. Lower down it lies on the capsule of the knee joint and then on popliteus.
6. Biceps femoris is lateral to it and semimembranosus medial.
7. Lower down it lies between the two heads of gastrocnemius.
8. It is crossed laterally to medially by the tibial nerve and the popliteal vein with the vein always between the artery and nerve.

Question 16

ANTERIOR TIBIAL ARTERY

Answer 16

1. Popliteal art To: Dorsalis pedis art
2. Commences at the bifurcation of the popliteal artery just under the fibrous arch of soleus,
3. . It supplies extensor compartment of the lower leg.
4. It passes anteriorly between the heads of tibialis posterior to pass above the upper border of the interosseous membrane, medial to the neck of the fibula accompanied by its venae commitantes.
5. It descends on the interosseous membrane and crosses the lower tibia at the ankle joint,
6. mid way between the malleoli and there becomes the dorsalis pedis artery.
7. Initially it lies between tibialis anterior (medially) and extensor digitorum longus (laterally), then between tibialis anterior and extensor hallucis longus.
8. At the ankle it is crossed anteriorly by the extensor retinacula and also from lateral to medial by the tendon of extensor hallucis longus.
9. The deep peroneal nerve is initially lateral to the artery high up in the extensor compartment but passes anterior to it half way down the leg, becoming lateral to it again under the extensor retinaculum.
10. The anterior tibial veins run in close association with the artery throughout.

Question 17

POSTERIOR TIBIAL ARTERY

Answer 17

1. From: Popliteal art To: Med & lat plantar
2. Aarises at the bifurcation of the popliteal artery just under the fibrous arch of soleus,
3. ends by bifurcating into the medial and lateral plantar arteries deep to abductor hallucis.
4. It supplies posterior compartment of the lower leg.
5. It is accompanied by venae commitantes and lies from above downwards on tibialis posterior, flexor digitorum longus, the tibia and the ankle joint. It lies deep to gastrocnemius, soleus, the flexor retinaculum and abductor hallucis.
6. Posterior to the medial malleolus it lies between the tendon of flexor digitorum longus and the tibial nerve which crosses posterior to the artery mid way down the calf from the medial side to become posterolateral.
7. (Other branch is a communicating branch to peroneal (fibular) artery.)

Question 18

FIBULAR (peroneal) ARTERY

Answer 18

1. From: Post tibial art To: Terminal brs
2. This is a branch of the posterior tibial artery arising 2.5 cm below its origin under soleus.
3. It supplies lateral compartment of the lower leg.
4. It passes inferolaterally to reach and run along the medial crest of the fibula between tibialis posterior and flexor hallucis longus to
5. divide into its terminal branches at the level of the inferior tibiofibular joint and the superior peroneal (fibular) retinaculum. Thus, although it supplies the peroneal compartment by branches that pass laterally, the main peroneal artery itself remains in the posterior compartment. Above, it is covered by soleus and deep fascia whilst in the lower leg flexor hallucis longus crosses it from lateral to medial.