embryology

Question 1

3 primordial germ layers

Answer 1

endoderm, mesoderm, ectoderm

Question 2

mesoderm separates into 2 layers

Answer 2

splanchnic layer and somatic layer

Question 3

space inbetween splanchnic layer and somatic layer forms

Answer 3

the coelom

Question 4

coelom is main

Answer 4

body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs

Question 5

endoderm forms the

Answer 5

primitive gut

Question 6

the primitive gut (formed by endoderm) later invaginates to form 3 main components;

Answer 6

• the foregut; blind ending
• the midgut; connected to yolk sac
• hindgut; blind ending

Question 7

the foregut becomes

supplied by what artery

Answer 7

pharynx, esophagus, stomach, liver, pancreas, proximal duodenum, gall bladder

coeliac artery

Question 8

the midgut becomes

supplied by what artery

Answer 8

Duodenum distal to bile duct, jejunum, yolk stalk in umbilical cord (vitelline duct), ileum, caecum, ascending colon and part of transverse colon

cranial mesenteric artery

Question 9

hindgut becomes

supplied by what artery

Answer 9

Distal transverse colon, descending colon, rectum, proximal anal canal

caudal mesenteric artery

Question 10

ecotderm becomes

Answer 10

• epithelium of oral cavity
• outer portion of anal cavity
• teeth
• nerves
• skin

Question 11

mesoderm becomes

Answer 11

• lamina propria
• submucosa
• muscle layers
• serosa/ adventitia
• blood and lymph vessels

Question 12

endoderm becomes

Answer 12

• mucosal epithelium
• mucosal glands
• liver and pancreas (glandular parts)

Question 13

organogenesis

Answer 13

• formation of digestion tract
• thickening of the wall
• elongation of tube –> coiling and twisting
• dilations; stomach and caecum

Question 14

in organogenesis what region develops first

what layer of muscles develops first (circular or longitudinal layer of tunica muscularis)

Answer 14

cranial regions differentiate first

circular layer first

Question 15

esophagus links

Answer 15

pharynx to stomach

Question 16

esophagus elongates with:

it is first:

then:

Answer 16

• neck and thorax
• ciliated
• stratified squamous epithelium

Question 17

does the esophagus have a mesentery or serosa

Answer 17

no never

Question 18

initial development of stomach: which part of gut

Answer 18

• first slight swelling in foregut, flattened laterally
• initially in neck region then moves caudally with elongation

Question 19

stomach: what border grows faster; dorsal or ventral

Answer 19

dorsal border grows faster (greater curvature)

ventral slower (lesser curvature)

Question 20

stomach development

Answer 20

1. Dorsal border grows faster than ventral
   → Greater curvature & lesser curvature
2. Elongates and curves
3. Rotates on long axis so greater curvature lies on left
4. Displaced by liver, greater curvature turned caudal
5. Fundic region arises as a bulge cranially

Question 21

when do mucosal glands form in stomach, when does secretory activity occur

Answer 21

• mucosal glands form halfway through gestation
• full secretory activity (especially parietal cells) not until after birth

Question 22

intestines have fast growth with limited space which leads to

Answer 22

looping and coiling

Question 23

stages of development of intestines

Answer 23

1. Growth and rotation.
2. Herniation and coiling. Here the expanding knot of intestines
   protrudes out into the extra‐embryonic coelom of the yolk stalk.
3. Re‐entry and placement.
4. Completion

Question 24

(stage 1 growth and rotation) early intestinal tube is divided into _____ loops by the attachment of the :

Answer 24

cranial and caudal loops
yolk sac

Question 25

(stage 1 growth and rotation) cranial loop of early intestine becomes caudal loops of early intestine becomes

Answer 25

small intestine ileum and large intestine

Question 26

(stage 1 growth and rotation) elongation of the early intestine allows it to move

Answer 26

ventral and clockwise rotation (from dorsal viewpoint)

Question 27

(stage 2 herniation and coiling) caudal loop has an out pouching just caudal to yolk sac that becomes

Answer 27

the caecum

Question 28

(stage 2 herniation and coiling) the cranial loop that grows faster and coils which becomes the

Answer 28

jejunum

Question 29

(stage 2 herniation and coiling) The increasing mass of the intestine, together with the growth of the liver and the fact that the abdominal cavity lags a little in growth means that the intestines can no longer fit within the abdominal cavity. They herniate through the

Answer 29

umbilicus into the umbilical cord (about 1/6th of the way through gestation) temporary umbilical hernia

Question 30

(stage 2 herniation and coiling) all of the intestine herniates (umbilical hernia) except the

Answer 30

duodenum and terminal portion of caudal loop (eventually forms descending colon)

Question 31

(stage 3 Re‐entry and placement) what grows to provide extra space for intestines

Answer 31

abdominal cavity

Question 32

(stage 3 Re‐entry and placement) the intestine returns to abdominal cavity; what order and where

Answer 32

jejunum first; fills left side of abdomen then descending colon to the left then cecum and ascending colon on right

Question 33

(stage 4 completion) what occurs

Answer 33

Intestines assume adult configuration Final growth of caecum & ascending colon, especially in horse Rotation of 270 degrees around root of mesentery

Question 34

omphalocoele

Answer 34

abdominal wall defect, intestines present outside abdomen

Question 35

some malformations that can occur

Answer 35

umbilical hernia, a fistula, or a diverticula local narrowing of intestine: stenosis closure of intestine: atresia

Question 36

umbilical hernia

Answer 36

part of intestine protrudes through wall of abdominal cavity around umbilicus

Question 37

meckel's diverticulum

Answer 37

remnant of the vitelline duct or yolk sac (aka omphalomesenteric duct) , associated with the distal ileum

Question 38

In early development, which primordeal germ layer seperates into two layers: the splanchnic layer and the somatic layer?

Answer 38

mesoderm

Question 39

The endoderm forms the primitive gut. Which compartment of the endoderm forms a wide connection with the yolk sac?

Answer 39

Midgut

Question 40

The organs supplied by the coeliac artery are derived from which of the regions?

Answer 40

Foregut

Question 41

The hindgut becomes which of the following organs? A. Oesophagus B. Gall bladder C. Ascending colon D. Descending colon

Answer 41

Descending colon

Question 42

Which layer of the tunica muscularis develops FIRST?

Answer 42

circular layer

Question 43

The epithelium of the oesophagus is initially ciliated, before transitioning to statified squamous epithelium. At what point during gestation does this transition occur?

Answer 43

Halfway through gestation

Question 44

The dorsal border of the stomach grows __________ than the ventral border, producing the __________ curvature of the stomach.

Answer 44

faster; greater

Question 45

When does full secretory activity of the stomach occur?

Answer 45

after birth

Question 46

An omphalocoele occurs when intestines, or other abdominal organs, present in the umbilical cord result in a defect in the abdominal wall. This occurs as a result of a failure of which of the stages in the development of the intestines?

Answer 46

Re-entry and placement

Question 47

The early intestinal tube is divided into cranial and caudal loops, based on the attachment of the yolk sac. The cranial loop does NOT form the: A. Duodenum B. Jejunum C. Cranial part of the ileum D. Caecum

Answer 47

Caecum