embryology Flashcards
3 primordial germ layers
endoderm, mesoderm, ectoderm
mesoderm separates into 2 layers
splanchnic layer and somatic layer
space inbetween splanchnic layer and somatic layer forms
the coelom
coelom is main
body cavity in most animals and is positioned inside the body to surround and contain the digestive tract and other organs
endoderm forms the
primitive gut
the primitive gut (formed by endoderm) later invaginates to form 3 main components;
- the foregut; blind ending
- the midgut; connected to yolk sac
- hindgut; blind ending
the foregut becomes
supplied by what artery
pharynx, esophagus, stomach, liver, pancreas, proximal duodenum, gall bladder
coeliac artery
the midgut becomes
supplied by what artery
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
hindgut becomes
supplied by what artery
Distal transverse colon, descending colon, rectum, proximal anal canal
caudal mesenteric artery
ecotderm becomes
- epithelium of oral cavity
- outer portion of anal cavity
- teeth
- nerves
- skin
mesoderm becomes
- lamina propria
- submucosa
- muscle layers
- serosa/ adventitia
- blood and lymph vessels
endoderm becomes
- mucosal epithelium
- mucosal glands
- liver and pancreas (glandular parts)
organogenesis
- formation of digestion tract
- thickening of the wall
- elongation of tube –> coiling and twisting
- dilations; stomach and caecum
in organogenesis what region develops first
what layer of muscles develops first (circular or longitudinal layer of tunica muscularis)
cranial regions differentiate first
circular layer first
esophagus links
pharynx to stomach
esophagus elongates with:
it is first:
then:
- neck and thorax
- ciliated
- stratified squamous epithelium
does the esophagus have a mesentery or serosa
no never
initial development of stomach: which part of gut
- first slight swelling in foregut, flattened laterally
- initially in neck region then moves caudally with elongation
stomach: what border grows faster; dorsal or ventral
dorsal border grows faster (greater curvature)
ventral slower (lesser curvature)
stomach development
- Dorsal border grows faster than ventral
→ Greater curvature & lesser curvature - Elongates and curves
- Rotates on long axis so greater curvature lies on left
- Displaced by liver, greater curvature turned caudal
- Fundic region arises as a bulge cranially
when do mucosal glands form in stomach, when does secretory activity occur
- mucosal glands form halfway through gestation
- full secretory activity (especially parietal cells) not until after birth
intestines have fast growth with limited space which leads to
looping and coiling
stages of development of intestines
- Growth and rotation.
- Herniation and coiling. Here the expanding knot of intestines
protrudes out into the extra‐embryonic coelom of the yolk stalk. - Re‐entry and placement.
- Completion
(stage 1 growth and rotation) early intestinal tube is divided into _____ loops by the attachment of the :
cranial and caudal loops
yolk sac
(stage 1 growth and rotation)
cranial loop of early intestine becomes
caudal loops of early intestine becomes
small intestine
ileum and large intestine
(stage 1 growth and rotation)
elongation of the early intestine allows it to move
ventral and clockwise rotation (from dorsal viewpoint)
(stage 2 herniation and coiling)
caudal loop has an out pouching just caudal to yolk sac that becomes
the caecum
(stage 2 herniation and coiling)
the cranial loop that grows faster and coils which becomes the
jejunum
(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
umbilicus into the umbilical cord (about 1/6th of the way through gestation)
temporary umbilical hernia
(stage 2 herniation and coiling)
all of the intestine herniates (umbilical hernia) except the
duodenum and terminal portion of caudal loop (eventually forms descending colon)
(stage 3 Re‐entry and placement)
what grows to provide extra space for intestines
abdominal cavity
(stage 3 Re‐entry and placement)
the intestine returns to abdominal cavity; what order and where
jejunum first; fills left side of abdomen
then descending colon to the left
then cecum and ascending colon on right
(stage 4 completion)
what occurs
Intestines assume adult configuration
Final growth of caecum & ascending colon, especially in horse
Rotation of 270 degrees around root of mesentery
omphalocoele
abdominal wall defect, intestines present outside abdomen
some malformations that can occur
umbilical hernia, a fistula, or a diverticula
local narrowing of intestine: stenosis
closure of intestine: atresia
umbilical hernia
part of intestine protrudes through wall of abdominal cavity around umbilicus
meckel’s diverticulum
remnant of the vitelline duct or yolk sac (aka omphalomesenteric duct) , associated with
the distal ileum
In early development, which primordeal germ layer seperates into two layers: the splanchnic layer and the somatic layer?
mesoderm
The endoderm forms the primitive gut. Which compartment of the endoderm forms a wide connection with the yolk sac?
Midgut
The organs supplied by the coeliac artery are derived from which of the regions?
Foregut
The hindgut becomes which of the following organs?
A.
Oesophagus
B.
Gall bladder
C.
Ascending colon
D.
Descending colon
Descending colon
Which layer of the tunica muscularis develops FIRST?
circular layer
The epithelium of the oesophagus is initially ciliated, before transitioning to statified squamous epithelium. At what point during gestation does this transition occur?
Halfway through gestation
The dorsal border of the stomach grows __________ than the ventral border, producing the __________ curvature of the stomach.
faster; greater
When does full secretory activity of the stomach occur?
after birth
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?
Re-entry and placement
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
Caecum
