L16 - Nerves and vessels of the lower limb

Question 1

What are the 3/4 generic layers of blood vessels?

Answer 1

1. Endothelium
2. Tunica intima
   - Endothelium
   - Internal elastic membrane
3. Tunica media
   - Muscle
   - External elastic membrane
4. Tunica adventitia

Question 2

Where does the descending aorta commence and end??

Answer 2

• Commences at the end of the aortic arch
• Continues down into the abdomen
• Ends by bifurcating into the left and right iliac arteries

Question 3

What are the two parts to the descending aorta called?

Answer 3

1. The thoracic aorta

2. The abdominal aorta

Question 4

Where does the thoracic aorta commence/ end?

Answer 4

• Commences at the sternal angle of Louis - the manubriosternal junction (on the thoracic plane)
• Ends at the aortic hiatus of the diaphragm

Question 5

Generally where does the thoracic aorta supply arterial blood to?

Answer 5

1. Muscles of the chest wall

2. Spinal cord

Question 6

What is the aortic hiatus of the diaphragm?

Answer 6

• A hole in the diaphragm
• The lowest and most posterior of the large apertures
• Located at approximately vertebral level T12

Question 7

What is the sternal angle an anatomical landmark for?

Answer 7

1. 2nd coastal cartilages
2. Manubriosternal joint
3. Bifurcation of trachea
4. Start of right and left bronchi
5. Left recurrent laryngeal nerve branches off the main vagus nerve
6. Divides the mediastinum into superior and inferior mediastinum - aka the thoracic plane, it separates the superior and inferior mediastinum
7. Thoracic duct (lmpahtic vessel) crosses from the right side of the body to the left side

Question 8

Where does the abdominal aorta commence/ end?

Answer 8

• Commences at the T12 vertebral level

- Ends at L3/4 intervertebral disc (there will be some individual variation therefore may differ, but better to use L4)

Question 9

Why does the abdominal aorta have two phases and what are they called?

Answer 9

1. Suprarenal segment
2. Infrarenal segment
   - Abdominal aorta can be said to be divisible into 2 parts at vertebral level L1-2 IVD, the level at which renal arteries branch off

Question 10

What are the five major arteries of the abdomen that arise by branching from the abdominal aorta?

Answer 10

1. Coeliac artery (L1)
2. Mesenteric arteries
   - Superior mesenteric artery (L1)
   - Inferior mesenteric artery (L3)
3. Renal arteries (L1/2 IVD)
4. Common iliac arteries
   - Left common iliac artery (L4/5)
   - Right common iliac artery (L4/5)
5. Arteries supplying the spinal cord (all vertebral levels L1)

Question 11

What is the supracristal plane?

Answer 11

• Top of iliac crest of pelvic bone
• At L4 vertebrae
• Transverse plane

Question 12

Describe the arterial tree of the lower limb

Answer 12

1. Common iliac artery
   - Branch internal iliac artery
2. External iliac artery
3. Common femoral artery (at groin crease)
   - Branch profunda femoris artery
4. Superficial femoral artery
5. Popliteal artery (either side of knee crease)
6. Tibio-peroneal trunk
   - Peroneal artery
7. Tibial arteries
   - Anterior and posterior
8. Dorsalis pedis and posterior tibial artery

Question 13

Where does the common iliac artery begin?

Answer 13

• L3/4 IVD disc
• Supracristal plane
• Umbilicus

Question 14

Where is the external iliac artery located?

Answer 14

L5-S1 IVD

Question 15

Where is the femoral artery located?

Answer 15

The external iliac artery passes beneath the inguinal ligament in the lower part of the abdomen and becomes the femoral artery

• Ends by entering the adductor canal
• Ends at the apex of the femoral triangle

Question 16

Where is the popliteal artery located?

Answer 16

• A continuation of the femoral artery
• Starts at the opening of the adductor canal and ends at the adductor hiatus (at the lower border of the popliteus muscle)
• Located in the knee and the back of the leg
• Runs across the popliteal fossa, posterior to the knee joint, and then travels between the gastrocnemius and popliteal muscles of the posterior compartment of the leg
• In the popliteal fossa, the popliteal artery gives off a series of geniculate arteries to supply the knee joint

Question 17

Where is the posterior tibial artery located?

Answer 17

• Runs down the leg just below the knee

Question 18

Where is the anterior tibial artery located?

Answer 18

• Passes in front of the ankle joint and continues into the dorsalis pedis artery onto the dorsum of the foot lateral to the tendon of the extensor hallucis longus and medial to the extensor digitorum longus and deep peroneal nerve

Question 19

What is the adductor canal?

Answer 19

At the apex of the femoral triangle is an opening in the adductor magnus - this is the adductor canal
AKA:
- Subsartorial canal
- Hunter’s canal

Question 20

Where can the femoral pulse be palpated?

Answer 20

At the mid-inguinal line

Question 21

What shape is the popliteal fossa?

Answer 21

Diamond shaped

Question 22

Where can the anterior tibial artery be palpated?

Answer 22

• Above the navicular bone
• Medial to the tendon of extensor hallucis longus
  (at dorsalis pedis level)

Question 23

Where can the posterior tibial artery be palpated?

Answer 23

• Halfway between the posterior border of the medial malleolus and the achilles tendon (calcaneal tendon)

Question 24

Describe the posterior tibial artery from the popliteal artery

Answer 24

• The larger of the terminal branches of the popliteal artery
• Descends deep to the soleus and then becomes superficial in the lower third of the leg
• Passes behind the medial malleolus between tendons of flexor digitorum longus and flexor hallucis longus

Question 25

What does the posterior tibial artery divide into and where does this occur?

Answer 25

Below the ankle it divides into medial and lateral plantar arteries which constitute principal blood supply to the foot

Question 26

What are accompanying veins?

Answer 26

- Typically paired veins that accompany an artery | - Found in close proximity with the artery so that the pulsations of the artery aid venous return

Question 27

What is the vasa vasorum?

Answer 27

Accompanies (larger) veins

Question 28

What is the venae commitante?

Answer 28

Accompanies (larger) arteries

Question 29

What are the spinal roots of the lumbar plexus?

Answer 29

Anterior rami of L1-4 - Forms behind within the psoas major muscle - Nerves emerge either lateral or medial to the borders of the psoas

Question 30

What are the roots of the sacral plexus?

Answer 30

Anterior rami of L4-S4

Question 31

Which nerves emerge lateral to psoas muscle?

Answer 31

1. The femoral nerve 2. The iliohypogastric muscle 3. The ilioinguinal muscle 4. The lateral cutaneous nerve of the thigh

Question 32

Which nerves emerge medial to psoas muscle?

Answer 32

1. The obturator nerve | 2. The lumbosacral trunk

Question 33

What are the terminating nerves of the lumbar plexus?

Answer 33

1. Iliohypogastric nerve 2. Ilioinguinal nerve 3. Genitofemoral nerve 4. Femoral nerve 5. Obturator nerve

Question 34

What is the sacral plexus composed of?

Answer 34

1. Lumbosacral trunk | 2. Sacral spinal segmental outflow

Question 35

Where does the sacral plexus form?

Answer 35

Sacral plexus formed within the pelvic cavity | - Plexus lies in relation to piriformis

Question 36

Where does the sacral plexus supply nerves to?

Answer 36

1. Pelvic region 2. Gluteal region 3. Perineal region 4. Lower limb (via the sciatic nerve)

Question 37

What is the sciatic nerve composed of?

Answer 37

1. Pre-axial nerve (tibial nerve) 2. Post-axial nerve (common peroneal nerve) - These nerves are covered in the same sheath in the posterior upper portion of the leg - These nerves typically divide near the popliteal fossa

Question 38

What are the neural roots of the sciatic nerve?

Answer 38

L4-S4

Question 39

Where does the sciatic nerve emerge from?

Answer 39

Emerges through the greater sciatic foramen together with the inferior gluteal artery and inferior gluteal nerve - Always emerges in relation to piriformis muscle

Question 40

Describe the piriformis-sciatic nerve variation

Answer 40

- Most cases, the common peroneal and tibial nerves travel tgt through the greater sciatic foramen - But, in approx 10% of popn, they are separated by in the GSF by all or part of the piriformis muscle (sometimes may emerge through the GSF as two separate nerves)

Question 41

What is piriformis syndrome?

Answer 41

- The piriformis muscle spasms and causes buttock pain - Can also irritate the nearby sciatic nerve and cause pain, numbness and tingling along the back of the leg and into the foot

Question 42

How could piriformis syndrome occur?

Answer 42

- Results from compression of the sciatic nerve around the piriformis muscle - If the sciatic nerve passes through piriformis and the muscle undergoes a spasm, the nerve will be compressed (variant of piriformis syndrome) - Trauma to the gluteal muscle - Spasms of the piriformis muscle - Anatomical variation - Overuse injury

Question 43

What are some possible symptoms of piriformis syndrome?

Answer 43

- Pain and numbness in the buttocks and down the leg | - Often symptoms are worsened with sitting or running

Question 44

Where does the sciatic nerve enter?

Answer 44

Enters the thigh between the ischial tuberosity and greater trochanter