8.2 Musculature of the Vertebral Column and Intrinsic Trunk

Question 1

Extrinsic vs intrinsic back muscles

Answer 1

Extrinsic: originate in back, but insert into external site

Intrinsic: originate in back, and stay within back

Question 2

What are the names of the deep and superficial layers of the intrinsic back muscles?

Answer 2

Deep: transversospinales
Superficial: erector spinae

Question 3

What are the names of each of the transversospinales muscles? How many vertebrae do they cross?

Answer 3

Rotatores: 1-2
Multifidis: 3-4
Semispinalis: 6-10

Question 4

Contraction of the transversospinal muscles causes ___lateral rotation

Answer 4

Contralateral (pyramid arrangement of muscles)

Question 5

What are the segmental names given to muscles in the head, neck, thorax, and lumbar region?

Answer 5

Head: capitis
Neck: cervicis
Thorax: thoracis
Lumbar: lumborum

Question 6

What is the anterior rectus sheath? What is it’s function?

Answer 6

• It is an aponeurosis
• Functions to synergize compressive forces of muscle
• Protects muscles, nerves, and blood vessels

Question 7

What are the functions of the internal/external obliques?

Answer 7

Both: bilateral flexion and increased intra-abdominal pressure

Unilateral contraction: ipsilateral lateral flexion and rotation (ext: contra, int: ipsi)

Question 8

In which structure do all oblique muscles insert?

Answer 8

Rectus sheath

Question 9

At what level does the posterior rectus sheath stop? What is this line called? What happens inferior to this?

Answer 9

• Stops at level of umbilicus
• Known as arcuate (bow-shaped) line
• Below this, all aponeuroses merge anteriorly

Question 10

The superficial fascia lies beneath the skin in the abdomen. What are the two components of this, and how does their structure differ?

Answer 10

Superficially, we have camper’s fascia (which is fat)

Deeper, we have Scarpa’s fascia, which is membranous connective tissue.

Question 11

What kind of fascia sits between the three muscular layers of the abdominal wall?

Answer 11

Investing fascia; smaller than the muscle, but supporting.

Question 12

Describe the three layers of the abdominal wall deep to the transversus abdominus?

Answer 12

• Transversalis fascia
• Extraperitoneal fat
• Parietal peritoneum

Question 13

Imagine the anatomical course of the psoas major muscle. From which transverse processes does it originate, where does it insert, and what is its function?

Answer 13

• Originates from transverse processes of L1-L5
• Inserts into lesser trochanter of femur
• Causes hip flexion

Question 14

Which muscles lies lateral to psoas major? Describe its anatomical course, and function.

Answer 14

• Iliacus muscle
• Originates in iliac crest
• Inserts on lesser trochanter
• Hip flexion

Question 15

Describe the anatomical course and function of quadratus lumborum

Answer 15

• Originates on iliac crest
• Inserts into L1-L3 and twelfth rib
• Laterally flexes and extends the trunk

Question 16

Which arteries supply the upper abdominal wall?

Answer 16

• Superior epigastric
• Musculophrenic artery

Question 17

Which artery supplies the mid portion of the abdominal wall (along the S-I axis)?

Answer 17

Subcostal.

Question 18

Which arteries supply the inferior abdominal wall?

Answer 18

• Inferior epigastric
• Deep circumflex iliac artery

Question 19

Which arteries supply the subcutaneous tissue of the abdominal wall?

Answer 19

• Superficial epigastric
• Superficial circumflex iliac

Question 20

Describe the blood supply to the posterior abdominal wall

Answer 20

Arteries/veins:

• Inferior phrenic
• 1st/2nd/3rd/4th lumbar vessels

Question 21

Describe the innervation of the anteriolateral abdominal wall that arises from the thoracic nerves

Answer 21

Ventral rami of 7-11th intercostal nerves. Subcostal nerves below T12.

Question 22

Which nerve supplies quadratus lumborum?

Answer 22

Subcostal (makes sense; this inserts directly below the twelfth rib)

Question 23

Which nerve innervates iliopsoas?

Answer 23

Femoral nerve

Question 24

The majority of the posterior abdominal wall is innervated by…

Answer 24

The dorsal rami of segmental spinal nerves.

Question 25

Which scalene muscles attach to which ribs?

Answer 25

Ant/medial: 1st rib
Posterior: 2nd ribv

Question 26

In what two ways do accessory abdominal expiratory muscles help in forceful expiration?

Answer 26

1. Pull down on bottom ribs
2. Push diaphragm up due to increased intra-abdominal pressure

Question 27

Describe the blood supply to the thorax.

Answer 27

Posteriorly: intercostal arteries from thoracic aorta

Anteriorly: anterior intercostal arteties from internal thoracic artery, which arise from subclavian

Superiorly: 1st and 2nd intercostal arteries arise directly from subclavian

Question 28

How does the venous drainage of the thorax differ from the arterial supply?

Answer 28

• Posterior intercostal veins drain into azygos (right), accessory azygos (left superior), and hemiazygos (left inferior)
• All drains into azygos, and into SVC
• Anterior intercostal veins drain into internal thoracic vein, which drain into the brachiocephalic veins

Question 29

Describe the motor and sensory functions of the ventral rami of thoracic spinal nerves

Answer 29

Motor: intercostal muscles, transversus thoracis, subcostal, serratus posterior

Sensory: anterolateral abdominal wall and pleura

Question 30

Describe the motor and sensory functions of the dorsal rami of thoracic spinal nerves

Answer 30

Motor: intrinsic back muscles

Sensory: posterior thoracic wall skin