Exam 2 (Lecture 5) - Body Wall and Stomach Flashcards
What are the 6 natural openings into the abdomen?
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).
What are the boundaries of the abdominal cavity?
Cranial boundary = diaphragm
Dorsal boundary = lumbar vertebrae/hypaxial muscles
Caudal boundary = pelvic inlet
Ventral and lateral boundaries = abdominal musculature
Where does the cranial projection of the diaphragm go?
The 6th rib/6th intercostal space
How many lumbar vertebrae do the large animals typically have? What is unique about L1?
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
What is the clinical significance of the muscles surrounding the lumbar vertebrae?
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).
Discuss the composition of abdominal muscles in the large animal and the reason for this arrangement.
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
External abdominal oblique
- 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
Tunica flava
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)
Internal abdominal oblique
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)
Tranversus abdominis
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
Rectus abdominis
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.
Which muscles make up the external aspect of the abdominal wall?
1) External abdominal oblique (caudoventral fiber direction)
2) Internal abdominal oblique (cranioventral fiber direction)
Which muscles make up the internal aspect of the abdominal wall?
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
Discuss the inguinal canal and inguinal rings.
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).
What is the rectus sheath?
The connective tissue surrounding the rectus abdominis.
- This is where you want to place your sutures on a ventral midline incision
Discuss the contributors to the rectus sheath.
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.
What is the difference in the rectus sheath cranial to the umbilicus in the carnivore?
The aponeurosis of the internal abdominal oblique divides and joins with both the internal and external layers of the rectus sheath.
What 2 ligaments in the horse help secure the femur in the acetabulum? What is the significance of this?
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.
What are the nerves of the flank region?
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.
What is a line block?
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
What is the inverted 7 technique?
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”).
What is a distal paravertebral block?
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
Describe the embryologic development of the simple stomach.
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
Describe the foregut mesentery.
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
Describe the embryologic development of the ruminant stomach.
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
Where does the entire ventral sac of the rumen sit?
In the omental bursa.
Where is the intestinal mass located in the ruminant?
Dorsal to the deep leaf of the greater momentum in the supraomental recess.
