Exam 2 (Lecture 5) - Body Wall and Stomach

Question 1

What are the 6 natural openings into the abdomen?

Answer 1

1) Caval foramen
2) Esophageal hiatus
3) Hiatus aorticus
4 & 5) Opening of the inguinal canal (R and L)
6) Pelvic inlet

**During intrauterine life, there is an additional opening; the opening of the umbilicus (umbilical vessels and urachus pass through it).

Question 2

What are the boundaries of the abdominal cavity?

Answer 2

Cranial boundary = diaphragm

Dorsal boundary = lumbar vertebrae/hypaxial muscles

Caudal boundary = pelvic inlet

Ventral and lateral boundaries = abdominal musculature

Question 3

Where does the cranial projection of the diaphragm go?

Answer 3

The 6th rib/6th intercostal space

Question 4

How many lumbar vertebrae do the large animals typically have? What is unique about L1?

Answer 4

Typically have 6 (but can be 5 or 7; depending on breed)
- in comparison, carnivores have 7

The transverse process of L1 tends to be shorter in large animals

Question 5

What is the clinical significance of the muscles surrounding the lumbar vertebrae?

Answer 5

You should NEVER (EVER) inject anything into these muscles in a production animal (this region is where we get our loins, ribeyes, chops, T-bone steaks, filet minion from).

Question 6

Discuss the composition of abdominal muscles in the large animal and the reason for this arrangement.

Answer 6

The abdominal muscles in the large animal are under a pretty constant load; so we see more area of aponeurotic tendinous insertion and a smaller area of fleshy tissue.
- this constant load comes from supporting the abdominal viscera

Question 7

External abdominal oblique

Answer 7

• Can originate as far cranially as the 4th rib and origin will continue caudally until the last rib
• Inserts at various points (tuber coxae, inguinal ligament, prepubic tendon, and linea alba)
  - linea alba is the largest part of insertion

Question 8

Tunica flava

Answer 8

Gets incorporated into the external abdominal oblique (in the aponeurotic part); is part of the deep fascia (CT associated with body wall; high in elastic fibers)

Question 9

Internal abdominal oblique

Answer 9

Originates at the tuber coxae (and inguinal ligament in horse);

In the ruminant, there is additional points of origin from the transverse processes of the lumbar vertebrae.
- Inserts: small part on preprubic tendon, last rib, costal arch, and linea alba (largest part)

Question 10

Tranversus abdominis

Answer 10

Origin: medial aspect of last ribs (generally ribs 7/8 and caudal) and the costal arch; transverse processes of the lumbar vertebrae

Insertion: Linea alba

Question 11

Rectus abdominis

Answer 11

Origin: As far cranially as the 3rd/4th rib

Insertion: Prepubic tendon (rectus abdominis is the largest contributor to the prepubic tendon); this muscle is also fleshy throughout its course.

Question 12

Which muscles make up the external aspect of the abdominal wall?

Answer 12

1) External abdominal oblique (caudoventral fiber direction)
2) Internal abdominal oblique (cranioventral fiber direction)

Question 13

Which muscles make up the internal aspect of the abdominal wall?

Answer 13

1) Rectus abdominis
2) Transversus abdominis

**All of the internal and external muscles criss-crossing each other is what gives strength to the body wall

Question 14

Discuss the inguinal canal and inguinal rings.

Answer 14

1) Inguinal canal = present in both male and female animals

2) External inguinal ring = formed in the aponeuroses of the external abdominal oblique

3) Internal inguinal ring = formed along the caudal margin of the internal abdominal oblique and inguinal ligament

** Internal and External inguinal rings are OBLIQUELY oriented with each other; this orientation dictates the size of the inguinal canal (where the overlap).

Question 15

What is the rectus sheath?

Answer 15

The connective tissue surrounding the rectus abdominis.
- This is where you want to place your sutures on a ventral midline incision

Question 16

Discuss the contributors to the rectus sheath.

Answer 16

1) When we follow the muscles ventrally, the internal and external abdominal obliques join together before coming to the linea alba (this makes up the EXTERNAL layer of the rectus sheath).

2) The transversus abdominis does not join anything before coming to the linea alba (internal rectus sheath).
- Transversus abdominis does not extend caudal to the tuber coxae (so no internal rectus sheath here).

**This arrangement is what we see in the carnivore AT the umbilicus.

Question 17

What is the difference in the rectus sheath cranial to the umbilicus in the carnivore?

Answer 17

The aponeurosis of the internal abdominal oblique divides and joins with both the internal and external layers of the rectus sheath.

Question 18

What 2 ligaments in the horse help secure the femur in the acetabulum? What is the significance of this?

Answer 18

1) Ligament of the femoral head
2) Accessory ligament of the femoral head

This is the reason most horses kick straight back instead of to the side.

Question 19

What are the nerves of the flank region?

Answer 19

1) Costoabdominal (ventral branch of T13 or T18)

2) Iliohypogastric (ventral branch of L1); cranial and caudal in species with 7 lumbar vertebrae

3) Ilioinguinal (ventral branch of L2)

4) Genitofemoral (ventral branch of L3-L4)

**Can use local or regional anesthesia to perform a lot of surgeries in this region.

Question 20

What is a line block?

Answer 20

Local anesthetic; needle, syringe, and put in right in the line that you’re going to cut through
- simple, but now there’s anesthetic in our incision site, so healing will be delayed
- local anesthetics are also used out of a large bottle and often need reapplied, so there’s an increased
risk of introducing bacteria/foreign particleW

Question 21

What is the inverted 7 technique?

Answer 21

Local anesthetic is applied along an inverted 7 shape caudal to the 13th rib and ventral to the vertebrae
- this type of anesthetic allows us to make an incision anywhere caudal and ventral to the lines of the
inverted 7 (the area of incision makes a rectangle with the “7”).

Question 22

What is a distal paravertebral block?

Answer 22

In a distal paravertebral block, we’re going to be blocking the spinal nerve (ventral branch ventral to the transverse process) and the lateral cutaneous nerve (from the dorsal branch of the spinal nerve).
- So, we’re injecting anesthetic both dorsal and ventral to the transverse process.
- This blocks T13, L1, and L2
- The landmarks we use are the transverse process of L1

Question 23

Describe the embryologic development of the simple stomach.

Answer 23

1) Stomach is a foregut derivative

2) Differential growth of the DORSAL wall

3) 90 degree rotation around the longitudinal axis of the dorsal portion; to the left.

4) Rotation around a dorsoventral axis; caudal end of the stomach shifts to the right and cranially

Question 24

Describe the foregut mesentery.

Answer 24

The dorsal mesentery undergoes differential growth (gets larger); after rotation, it becomes the greater omentum
- ventral mesentery becomes the lesser momentum; it doesn’t undergo differential growth

Question 25

Describe the embryologic development of the ruminant stomach.

Answer 25

1) Rumen = Develops as an expansion of the funds (left)

2) Reticulum = Cranioventral pocket of the developing rumen (left)

3) Omasum = Develops as a bulge along the lesser curvature (right)

4) Abomasum = The remainder of the stomach

Question 26

Where does the entire ventral sac of the rumen sit?

Answer 26

In the omental bursa.

Question 27

Where is the intestinal mass located in the ruminant?

Answer 27

Dorsal to the deep leaf of the greater momentum in the supraomental recess.