Abdomen and Pelvis

Question 1

What are the species differences in how we enter the abdomen in surgery?

Answer 1

Bitch = midline spay
Cat = left flank spay
Cow rumenotomy = left flank spay
Horse = midline spay

Question 2

What are the layers of muscle that make up the abdominal flank?

Answer 2

External abdominal oblique
Internal abdominal oblique
Transverse abdominis

Also rectus abdominis, which forms the ventral aspect of the body wall either side of the midline.

Question 3

What are the functions of the abdominal wall?

Answer 3

When they contract:

• Involved in locomotion and cause flexion in the spine
• Give greater force to abdominal organs for urination, defecation and parturition
• Diseased lungs are less compliant and have less elastic recoil so abdominal muscles aid respiration by contracting against the diaphragm to help push air out

Question 4

How and where do abdominal muscles insert?

Answer 4

Flank muscles travel around and insert on the linea alba via the aponeurotic tendon - a flat tendon that travels around the body wall and inserts on the linea alba on the midline.

Question 5

Where does the external abdominal oblique arise from, which direction are its muscle fibres and what does it form?

Answer 5

• Arises from last ribs and thoracolumbar fascia
• Muscles fibres run caudoventrally
• Forms wide aponeurosis that splits into 2 to form the superficial inguinal ring
• Inserts on the linea alba and prepubic tendon

Question 6

Where does the internal abdominal oblique arise, which direction are its muscle fibres and what does it form?

Answer 6

• Arises from last ribs, thoracolumbar fascia, iliac crest and lumbar transverse processes
• Muscle fibres run cranioventrally and fan out caudally
• Inserts on caudal ribs via aponeurotic tendon to linea alba, which fuses with the fibres of the EAO aponeurotic tendon (the 2 tendons fuse)
• Caudal edge is free and forms part of the inguinal canal

Question 7

Where does the transverse abdominis arise, which direction are its muscle fibres and where does it lie?

Answer 7

• Arises from the inner surface of the last ribs and the lumbar transverse processes
• Muscle fibres run dorsoventrally
• Runs deep to the rectus abdominis (where EAO and IAO lie superficial to)
• Can have white lines where the spinal segmental nerves run

Question 8

What is the linea alba?

Answer 8

A big fibrous cord that runs from the xiphoid cartilage of the sternum to the cranial end of the pubic symphysis. It has a lump in the middle, a remnant of the umbilicus, a useful landmark for surgery.

Question 9

Where does the rectus abdominis lie and what is its structure?

Answer 9

Lies either side of midline with linea alba between them. Runs from ventral rib cartilage and sternum to pubic brim of pubic tendon. Inserts via prepubic tendon.

Is a one big muscle that appears to be divided by small teninous interssections, called irregular transverse septa (these are polysegmental in development but fuse in maturation to one big muscle).

Question 10

Describe the blood supply to the abdominal body wall.

Answer 10

• Head vessels coming off aorta after passing through the aortic hiatus. Phrenicoabdominal artery supplies the cranial dorsal quadrant
• Deep circumflex iliac supplies caudal quadrant
• Cranial ventral quadrant supplied by cranial epigastric (supplied by internal thoracic artery)
• Caudal ventral quadrant supplied by caudal epigastric (supplied by internal thoracic artery)

Question 11

What is inguinal canal?

Answer 11

Perforates the abdominal wall bilaterally in the groin/inguinal region.
Acts as a conduit/passageway for blood vessels, nerves and descent of testes. Potential space between internal and external rings.

Question 12

What is the inguinal ligament?

Answer 12

Caudal part of the prepubic tendon that attaches IAO to the pelvis is a condensation of fibres that goes to form the inguinal ligament, which is important in the formation of the inguinal canal.

Question 13

What does the outpouching of peritoneum through the inguinal cord form?

Answer 13

In males, this envelops the testes, forming the vaginal tunic.

In females, develops only in the bitch where it extends towards the vulva.

Question 14

What does VETMEDG stand for when referring to structures passing through the inguinal canal?

Answer 14

Vaginal process/tunic 
External cremaster muscle 
Testicular artery, vein and nerve
Mesoductus and mesorchium 
External pudendal vessels 
Ductus deferens 
Genitofemoral nerve

Question 15

What are the species differences in inguinal canals and how does this affect castration?

Answer 15

Can be open or closed:

• Open canal can be seen in pigs, guinea pigs and rabbits
• Closed canals can be seen in dogs, cats, cows and horse (but has breed variations)

Closed canal species do not need the vaginal tunic closing back up but open canal species do, otherwise the abdominal organs can herniate through the castration wound.

Question 16

What is the femoral canal?

Answer 16

Is a conduit for structures to pass from the abdomen to the outside environment.

It is an opening between the caudal edges of the abdominal wall and the (pelvic) ileum.

Lateral dorsal to the inguinal canal
and bounded by inguinal ligament, ileum, rectus abdominis and prepubic tendon.

Question 17

Which structures pass through the femoral canal?

Answer 17

Femoral artery and vein (pulse point)
Femoral nerve
Iliopsoas muscle
The deep inguinal lymph nodes lie within the femoral canal

Question 18

What is the sacrotuberous ligament?

Answer 18

Present in dogs, but not cats.

A fibrous like cord that runs from the sacrum to is the ischial tubers.

Question 19

What is the sacrosciatic ligament?

Answer 19

In large animals. A broad sheet between the ileum pubis, ischium and ischial tubers to the sacrum and 1st coccygeal vertebrae. Has 2 foramen:

• Greater sciatic foramen – sciatic nerve and cranial gluteal vein, artery and nerve pass through.
• Lesser sciatic foramen – the caudal gluteal artery and vein passes through.

Less easily palpated in horses and pigs than cows, as this is often covered in muscle.

Question 20

What are the boundaries of the ischiorectal fossa?

Answer 20

Sarcotuberous/sacrosciatic ligament (laterally)

The pelvic diaphragm (medially)

The floor of the pelvis (ventrally)

Question 21

Which structures pass through the ischiorectal fossa?

Answer 21

Caudal gluteal artery and vein
Internal pudendal artery and vein
Pudendal nerve

Question 22

What is the pelvic outlet and what is it made up of?

Answer 22

Where the gastrointestinal, genital and urinary tracts exit the abdominal cavity. It is made up of of the pelvic girdle, pelvic diaphragm and urogenital diaphragm.

Question 23

What is the pelvic girdle?

Answer 23

Paired pelvic bones, consisting of the ileum, ischium, pubis, sacrum and first few coccygeal vertebrae to create a ring.

Question 24

What is the pelvic diaphragm?

Answer 24

2 paired muscles that attach laterally to the pelvic wall and run caudomedially close to the annual, the coccygeus and the levator ani muscles. These act to oppose forces created in abdominal pressures, such as in defecation, so that organs to do herniate out. Levator ani does this by moving tail up and down to alter pressure.

Question 25

What is the urogenital diaphragm?

Answer 25

Muscles fix the reproductive tract into place to prevent cranial drag of the uterus in pregnancy and caudal drag in parturition.

Question 26

What are the anal glands?

Answer 26

Smooth glandular structures that sit between the internal and external sphincters.
They produce oily secretions that drain into the anal junction.
Used for territory marking.
Can sometimes develop abscesses and become infected.

Question 27

When can impaction of the anal glands occur and how is this treated?

Answer 27

Obesity
Soft faeces
Narrow ducts
Breed and many more

Treatment:
• Express manually
• Diet
• If recurrent, can remove