Small & Large Animal Abdominal Wall

Question 1

What are the topographic regions on the abdomen?

Answer 1

• cranial abdominal region: xiphoid region and hypochondriac regions
• middle abdominal region: umbilical region and lateral abdominal regions
• caudal abdominal region: pubic region and inguinal region

Question 2

What nerves innervate the abdominal wall?

Name the four main lumbar nerves

Answer 2

• ventral branches of spinal nerves T13-L5
• cranial iliohypogastric (L1)
• caudal iliohypogastric (L2)
• ilioinguinal (L3)
• lateral cutaneous femoral (L4)

Question 3

Describe the Rectus sheath

Answer 3

• near pubis: all aponeuroses are superficial to rectus abdominis
• caudal to umbilicus: aponeurosis of transverse abdominis is deep to rectus abdominis
• cranial to umbilicus: aponeurosis of internal ab. oblique splits and forms a sleeve around the rectus abdominis

Question 4

Describe the Superficial Inguinal ring

Answer 4

• slit-like opening in the aponeurosis of the external abdominal oblique muscle

Question 5

What are the borders of the Deep Inguinal ring?

Answer 5

cranial: ventral border of internal abdominal oblique muscle
caudal: inguinal ligament
medial: rectus abdominis muscle

Question 6

Describe the blood supply to the four main quadrants of the abdominal wall

Answer 6

Craniodorsal: cranioabdominal artery, branches off of phrenicoabdominal artery
Cranioventral: cranial superficial epigastric artery, and cranial epigastric artery
Caudodorsal: deep circumflex iliac artery
Caudoventral: caudal superficial epigastric artery and caudal epigastric artery

Question 7

What is the fiber orientation in each of the abdominal muscles?

Answer 7

External ab. oblique: caudoventral
Internal ab. oblique: cranioventral
Transverse abdominis: transverse

Question 8

Describe the Tunica flava abdominis and its surgical relevance

Answer 8

• supports the weight of the abdominal viscera in large animals
• deep fascia of the trunk, composed largely of elastic tissue
• ventrally, fibers exchange with those of the aponeurosis of the external ab. oblique
• after surgery, must be suture properly, or it will rip open

Question 9

Explain the accessory ligament and its significance in the horse

Answer 9

• extends from the prepubic tendon, through the acetabular notch, and attaches to the femoral head, securing it in place
• prevents the horse from ride kicking

Question 10

What are the boundaries of the paralumbar fossa?

Answer 10

base: tips of the lumbar transverse processes
cranioventral: the last rib
caudoventral: ridge formed by the part of the internal ab. oblique that extends from tuber coxae to ventral end of last rib

Question 11

What is accessed via the paralumbar fossa in the horse and ox?

Answer 11

• left paralumbar fossa: rumen and reticulum in the ox

- right paralumbar fossa: cecum in the horse, descending duodenum and superficial leaf of omentum in the ox

Question 12

What are the branches of the ventral branch of cervical nerve 2, and what do they supply?

Answer 12

• greater auricular nerve: extends toward ear, supplies skin of neck, ear, and back of head
• transverse cervical nerve: branches to skin of cranioventral part of neck

Question 13

Explain the origin of the accessory nerve

Answer 13

• cranial nerve XI

- cranial root comes from brain, exits skull via foramen magnum

Question 14

Describe the composition of a spinal nerve

Answer 14

• connected to spinal cord via dorsal (afferent) and ventral (efferent) roots
• afferent cell bodies located in dorsal root ganglion
• emerge from intervertebral foramina and imediately branch into dorsal and ventral branches

Question 15

Where do the spinal nerves emerge?

Answer 15

• first pair of cervical nerves emerge from the lateral vertebral foramina of the atlas
• cervical nerves 2-7 emerge through intervertebral foramina cranial to their corresponding vertebra
• cervical nerve 8 emerges caudal to C7
• thoracic and lumbar nerves emerge caudal to their corresponding vertebra
• sacral emerge through sacral foramina