Abdominal wall

Question 1

What are the boundaries of the abdominal cavity?

Answer 1

• Cranial limit: diaphragm
• Caudal limit: pelvic inlet
• Abdominal wall around the outside (external, internal abdominal oblique, transversus abdominis)
• Ventrally abdominal wall (rectus sheath, rectus abdominis, linea alba)

Question 2

What are the layers of the abdominal wall going from outside to inside

Answer 2

• Skin
• Fat
• External abdominal oblique
• Internal oblique
• Transverse abdominus
• Rectus abdominus

Question 3

In what direction do the fibres of the external abdominal oblique muscle run?

Answer 3

• Caudoventrally (/)

- “hands in pocket”

Question 4

What is the function of the external abdominal oblique?

Answer 4

• Compression of abdominal cavity

- Rotation of trunk

Question 5

What are the origins and insertions of the abdominal oblique muscle?

Answer 5

• Origin: costal cartilages

- Insertion: wide aponeurosis forming inguinal ligament

Question 6

In what direction do the fibres of the internal abdominal obliue muscle run?

Answer 6

• Fibres run cranioventrally

- “Ymca” muscle (\/)

Question 7

What is the function of the internal abdominal oblique muscle?

Answer 7

• Opposes rotation caused by the external oblique

- Compresses diaphragm

Question 8

What are the origins and insertions of the internal abdominal oblique muscle?

Answer 8

• Origin: coxal tuberosity, transverse process of lumbar vertebra, iliac fascia
• Insertion: linea alba and final rib costal arch

Question 9

In what direction do the fibres of the transverse abdominal muscle run?

Answer 9

• Transversely across the abdomen (=)

- Sling type muscle

Question 10

What is the function of the transverse abdominal muscle?

Answer 10

• Compress ribs

- Provides stability

Question 11

What are the origins and insertions of the transverse abdominal muscle?

Answer 11

• Origin: transverse processes of lumbar vertebrae, ribcage

- Insertion: linea alba

Question 12

In what direction do the fibres of the rectus abdominal muscle run?

Answer 12

• Longitudinally on both sides of the linea alba (II)

Question 13

What is the function of the rectus abdominal muscle?

Answer 13

• Assists in breathing and abdominal stability

Question 14

What are teh origins and insertions of the rectus abdominal muscle?

Answer 14

• Origin: sternum, sternal rib cartilage

- Insertion: prepubic tendon and pecten of pubic bone

Question 15

What is unusual about the rectus abdominus compared to the other abdominal muscles?

Answer 15

• Lies within sheath

- Has tendinous intersections (transverse bands of fibrous tissue across muscle)

Question 16

What muscles are innervated by the ilioinguinal nerve?

Answer 16

• Internal and external oblique

- Transverse abdominal muscles

Question 17

Where does the ilioinguinal nerve originate from?

Answer 17

L2

Question 18

What muscles are innervated by the iliohypogastric nerve?

Answer 18

• Internal external abdominal obliques

- Transverse abdominal muscles

Question 19

What structures are innervated by the genitofemoral nerve?

Answer 19

• Sensory and motor to inner thigh

- Cremasteric reflex, contraction when superior medial part of thich is touched

Question 20

What areas are supplied by the cranial abdominal artery?

Answer 20

• Transversus abdominus

- Internal abdominal obliques

Question 21

What areas are supplied by the deep circumflex iliac arteries?

Answer 21

• Skin of caudal abdominal area
• Flank
• Cranial thigh

Question 22

Describe the anatomy of the inguinal canal

Answer 22

• Floor is inguinal ligament
• Formed from external oblique aponeurosis as it folds over and inserts
• More of a slit
• in males testes pass through here

Question 23

Describe the crura of the diaphragm

Answer 23

• Right arises from vertebral bodies and intervertebral fibrocartilages of the first 3 lumbar vertebrae
• Left arises from the first 2 lumbar vertebrae

Question 24

Describe the costal attachments of the diaphragm

Answer 24

Lower costal cartilages adn ribs by digitations

Question 25

What are the openings in the diaphragm?

Answer 25

- Aortic hiatus - Oesophageal hiatus - Caval foramen (fixed to diaphragm and so moves with diaphragm)

Question 26

What is the importance of the hiati in the diaphragm?

Answer 26

- Not attached to structures | - Herniation can easily occur

Question 27

What structures pass through the diaphragm to the abdomen?

Answer 27

- Oesophagus - Aorta - Vena cava - Nerves via sympathetic chain - Hemiazygous vein

Question 28

Describe the peritoneum

Answer 28

- Serous membrane which lines abdominal cavity - 3 sections - Sac between different sections called peritoneal cavity - Peritoneum can excrete and resorb fluid (function in disease and peritonitis) and resorb gas - Peritoneal fluid normally present in peritoneal cavity and acts as lubricant - Diseases include peritonitis, neoplasia and haemorrhage

Question 29

What are the 3 layers of peritoneum?

Answer 29

- Parietal (lining body wall) - Visceral (lining abdominal organs) - Connecting (forming mesentery)

Question 30

What are the layers of teh body wall?

Answer 30

- Skin, epidermis, dermis and subcutis - External fascia of trunk - Deep sheet of external fascia - External abdominal oblique - Internal abdominal oblique - Transversus abdominis - Internal fascia of trunk (transverse fascia) and peritoneum

Question 31

Describe the rectus sheath

Answer 31

- Tendinous sheath, encloses rectus abdominis | - Formed by aponeuroses of other abdominal muscles

Question 32

Describe the linea alba

Answer 32

- Fibrous tissue - Aponeurotic joining of left and right abdominal oblique and transversus muscles - Extends from xiphoid process to pubis - Includes umbilicus - Wide cranially, narrows caudally - Strongest point for abdominal incisions

Question 33

Describe the innervation of the body wall

Answer 33

- Ventral branches of thoracic and lumbar nerves (T13, L1 and L2) - Skin of abdomen supplied by dorsal and ventral rami of spinal nerves - Muscles and deep structures supplied by ventral rami - Nerves pass obliquely in caudal direction - T13, L1, L2 exit from vertebra foramina at associated transverse processes - Go in caudal direction so by the tips of transverse processes are positioned at L1, L2 adn L4

Question 34

Describe a paravertebral nerve block

Answer 34

- Used as anaesthetic for paralumbar approach in large animals - Can be blocked proximally (dorsal aspect of T13, L1 and L2) or distally (ventral to lateral tips of L1, L2, L4)

Question 35

Describe the vascular supply to the abdominal wall

Answer 35

- Cranial region: internal thoracic artery adn cranial epigastric artery (branch of brachiocephalic trunk) - Diaphragm: phrenicoabdominal artery (branch of abdominal artery) - Caudal region: caudal epigastric artery and external pudendal artery (branch of external iliac artery)

Question 36

Describe the anatomy of the inguinal canal

Answer 36

- 2 regions, superficial and deep inguinal ring - Superficial between 2 tendons of external abdominal oblique - Deep is on caudal border of internal abdominal oblique - Testes descend through here

Question 37

What structures are in the inguinal canal?

Answer 37

- Spermatic cord in males - External pudendal artery and vein - Genitofemoral nerve - Lymphatics