Gi Week 2 Objective 1

Front 1

What is a Physiological Umbilical Hernia?

Back 1

The projection of the midgut loop into the proximal part of the umbilical cord. (As a consequence of rapid midgut tube elongation at the end of the 6th week)

Front 2

1. What is the midgut?
2. What is it's blood supply?
3. What is it's innervation?

Back 2

1. Gut tube which begins at the midpoint of the duodenum (below major duodenal papilla)and extends to 2/3 or 1/2 of the way along the transverse colon.
2. Superior Mesenteric Artery and Vein.
3. Sympathetic: Superior Mesenteric nn plexus (inhibition of gut, pain pathway) Parasympathetic: Vagus nn (motor to gut)

Front 3

What is the vitello-intestinal duct?

Back 3

The narrowed opening between the midgut and the yolk sac.

Front 4

Describe the two rotations of the midgut loop during midgut development?

Back 4

(Both occur along axis of Superior Mesenteric Artery)
1. CCW 90 degree during protrusion of the loop
2. CCW 180 degree during return of the loop into peritoneal cavity.

Front 5

Several parts of the midgut are pressed to the posterior abdominal wall and become retroperitoneal, these include:

Back 5

-duodenum (and pancreas except tail)
-ascending colon
(-descending colon)

Front 6

Which sections retain their dorsal mesentery?

Back 6

-jejunum
-ileum
-transverse colon (attaches to anterior 2 layers of greater omentum)
-sigmoid colon

Front 7

Describe the development of the vermiform appendix and cecum.

Back 7

The cecal diverticulum starts as a swelling of the midgut which assumes its position in the right iliac fossa during rotation and reduction of the midgut loop. The Cecum and appendix(slower) continue to grow after birth and assume their final positions.

Front 8

What is a congenital omphalocele?

Back 8

Persistence of the herniation of the abdominal contents into the proximal part of the umbilical cord. Is still covered by the amnion. (Often associated with other abnormalities eg. heart)

Front 9

What is gastrochisis?

Back 9

Direct herniation of the abdominal contents through the abdominal wall into the amniotic sac due to malformation of the anterior ab. wall.

Front 10

What are two abnormalities that can occur in rotation of the midgut loop?

Back 10

1. Nonrotation leading to Left-sided colon. Small intestine stays on right and large on the left.

2. Reversed rotation. CW rotation leads to duodenum anterior to the SMA and transverse colon posterior to SMA. The transverse colon may be obstructed because of this.

Front 11

What causes Ileal/Meckel's diverticulum? Why is it clinically significant?

Back 11

1. Vitello-intestinal duct(proximal portion of yolk sac) remains during development.
2. It's mucosa may contain patches of gastric and pancreatic tissue which can cause acid secretion, ulceration and bleeding. This may mimic appendicitis.

Front 12

What is umbilicoileal fistula?

Back 12

AKA omphaloenteric. Results from persistence of the entire intra abdominal portion of the yolk sac.

Front 13

What is duplication of the intestine?

Back 13

Failure of normal recanalization that leads to cystic or tubular duplication.

Front 14

What comprises the hindgut?

Back 14

Gut tube from the left 1/3 or 1/2 of the transverse colon through to the superior part of the anal canal. Epithelium of urinary bladder and most of the urethra.

Front 15

What is the hindgut blood supply?

Back 15

Inferior mesenteric artery. Except for the for the urinary bladder and urethra which are supplied by vesical arteries(branches of internal iliac)and internal pudendal arteries respectively.

Front 16

Describe the Cloaca and its surface contact.

Back 16

The Cloaca is the terminal dilated portion of the hindgut which contacts the surface at the cloaca membrane. This membrane is composed of cloaca endoderm and ectoderm of the proctodeum(anal pit)

Front 17

What three things does the urorectal septum end up doing?

Back 17

1. This wedge mesenchyme divides the cloaca into ventral(urogenital sinus) and dorsal (rectum) parts.
2. By fusing to the cloacal membrane it creates the anal membrane and a large urogenital membrane.
3. Divides the cloacal sphincter to form anterioraly the bulbospongiosus and ischiocavernosus muscles and posterioraly the external anal sphincter.

Front 18

What is the proctodeum?

Back 18

Invagination of ectoderm that forms the inferior 1/3 of the anal canal.

Front 19

What germ layers is the midgut and hindgut derived from?

Back 19

Mucosae -endoderm
smooth muscle, connective tissue and visceral peritoneum -lateral plate splanchnopleuric mesoderm

Front 20

What is the pectinate line?

Back 20

Demarcation line in the anal canal between the endodermally derived midgut and the ectodermally derived lower 1/3.

Front 21

What is the difference in Nerves, arteries and veins between the two parts of the anal canal?

Back 21

Upper 2/3:
Nerve-Autonomic N.S.
Artery -superior Rectal A.
Vein -Superior rectal V(portal)
Lower 1/3
Nerve -Pudendal Nerve
Artery -Inferior Rectal A.
Vein -Inferior Rectal V (IVC)

Front 22

What is Hirschsprung disease?

Back 22

Congenital megacolon. Absence of autonomic ganglion cells in the myenteric plexus causes dilation of part of the colon