5G.embryology - midgut and hind gut formation

Question 1

what does the midgut consist of

Answer 1

lower duodenum
jejunum
ileaum
cecum
appendix
ascending colon,
2 thirds of transverse colon

Question 2

what does the hind gut consist of

Answer 2

1/3 transverse colon
descending colon
sigmoid colon
rectum
upper anal canal

Question 3

what is the blood supply to each part of the primative gut tube

Answer 3

foregut- celiac artery
midgut- superior mesenteric artery
hindgut- inferior mesenteric artery

Question 4

how does the midgut develop

Answer 4

primary intestinal loop. the cranial limb becomes the distal duodenum, jejunum and upper ilium and the caudal limb becomes the lower ileum, cecum, ascending colon, proximal 2/3rds of transverse colon

Question 5

it initially communicates with the yolk sac via what

Answer 5

vitelline

Question 6

What is physiological herniation of the midgut?

Answer 6

during week 6
rapid growth of gut
expansion of liver
intestinal loops move through umbilical cord
lies outside developing embryo
= umbilical herniation

Question 7

how does the midgut rotate

Answer 7

90 degrees clockwise
around the superior mesenteric a.
during herniation
during week 10 the intestines retract back into the abdomen with a further 180 degree turn clockwise
totaling 270 degrees of rotation

Question 8

what are the main defects associated with midgut development?

Answer 8

Omphalocele: Failure of the intestinal loop to return to the abdomen.
Gastroschisis: Abnormal closure of the body wall.
Gut Rotation Defects: Issues with rotation can result in twisting of the intestines and constriction of the blood supply.

Question 9

what is Omphalocele

Answer 9

failure of the intestinal loop to return to the abdomen

Question 10

what is Gastroschisis:

Answer 10

abnormal closure of the body wall

Question 11

what are Gut Rotation Defects:

Answer 11

Issues with rotation can result in twisting of the intestines and constriction of the blood supply.

Question 12

How does the cloaca contribute to hindgut development?

Answer 12

The cloaca is an endoderm-lined cavity covered by ectoderm at the ventral surface. The urorectal septum, a wedge of mesoderm, separates the cloaca into the urogenital sinus and anorectal canal. The cloacal membrane ruptures at the end of the 7th week, creating openings for the hindgut and urogenital sinus.

Question 13

the cloaca is a ……..-lined cavity covered by …….. at the ventral surface

Answer 13

endoderm
ectoderm

Question 14

what are the origins of the upper and lower parts of the anal canal

Answer 14

upper 2/3 - endoderm of hindgut
lower 1/3 - proctodeum - an ectoderm invagination

Question 15

How does the urorectal septum contribute to the development of the perineal body?

Answer 15

The urorectal septum forms the perineal body between the openings for the hindgut and urogenital sinus.

Question 16

summarise the key events

Answer 16

Week 3: Liver bud formation and initial development of liver and gallbladder.
Week 4: Development of the esophagus, stomach, and spleen.
Week 5: Formation of the primary intestinal loop in the midgut.
Week 6: Physiological herniation of the midgut.
Week 7: Development of the hindgut and cloaca.
Week 8: Midgut rotation.
Week 10: Retraction of the midgut into the abdominal cavity.
Week 12: Bile formation in the liver.