Embyology

Question 1

what is the primordial gut derived from?

Answer 1

the absorbed yolk sac

Question 2

when does the intra-embryonic coelom become the early embryonic cavity and what does it divide into?

Answer 2

during the 4th week
> pericardial cavity
> peritoneal cavity
> two pericardial-peritoneal cavities

Question 3

what does the forgut become?

Answer 3

>primordial pharynx
> oesophagus
> stomach
> duodenum, above sphincter oddi
> liver
> biliary apparatus
> pancreas

Question 4

what is polyhydramnios?

Answer 4

too much fluid in the amniotic sac

Question 5

describe the development of the stomach

Answer 5

> dilation
rotation of 90 degrees clockwise (left side becomes anterior and right side posterior)
mesenteries develop
omental bursa forms

Question 6

what nerve supplies the anterior of the stomach?

Answer 6

left vagus nerve

Question 7

what nerve supplies the posterior of the stomach?

Answer 7

right vagus nerve

Question 8

what are the symptoms of hypertrophic pyloric stenosis?

Answer 8

vomiting and refusal to eat

Question 9

describe the development of the pancreas

Answer 9

when the stomach rotates the ventral hepatic bud joins with the dorsal bud

Question 10

from what is the spleen derived?

Answer 10

the mesoderm

Question 11

what is formed from the midgut?

Answer 11

> distal duodenum
> jejunum
> ileum
> caecum
> appendix
> ascending colon
> proximal 2/3 of transverse colon

Question 12

name the 5 main stages of the midgut loop?

Answer 12

> herniation
> rotation
> retraction
> rotation
> fixation

Question 13

describe the rotation of the midgut

Answer 13

after physiological herniation the midgut rotates 90 degrees counter clockwise in the umbilical cord. after the loops retreat a further 180 degree rotation occurs counter clockwise.

Question 14

name two conditions arising from the failure of retraction of the herniated hoops

Answer 14

> omphalocele

> gastroschisis

Question 15

what is omphalocele?

Answer 15

herniation of abdominal viscera through enlarged umbilical ring, viscera is covered by layer of amonion

Question 16

what is gastroschisis?

Answer 16

herniation of abdominal contents that is not covered in peritoneum directly through body wall into amniotic cavity that is associated with cocaine use during pregnancy

Question 17

what is structures are formed from the hindgut?

Answer 17

> distal third of the colon
> descending colon
> sigmoid colon
> rectum and anal canal
(ectoderm becomes lining of the bladder and urethra)

Question 18

what problems can occur with abnormal rotation of the primary intestinal loop?

Answer 18

compression and obstruction of the large intestine

Question 19

what developmental abnormalities can occur due to incomplete separation of the hindgut from the urogenital sinus?

Answer 19

> urorectal fistula
rectal vaginal fistulation
rectal anal atresia
imperforated anus

Question 20

what is the cloaca?

Answer 20

expanded part of the hind gut that is lined with endoderm

Question 21

what is the allantois?

Answer 21

the ventral diverticular of the cloaca that is separated by the urorectal septum from the dorsal part

Question 22

what separates the cloaca and the anal pit?

Answer 22

the cloacal membrane

Question 23

when does the cloacal membrane rupture?

Answer 23

week 7

Question 24

when does the anal canal reopen?

Answer 24

week 9

Question 25

how is the caudel end of the hindgut close?

Answer 25

the ectoderm of the anal canal proliferates