Embryology Flashcards
4 stages in the formation of the intestines
- Growth and rotation
- Herniation and coiling
- Re-entry and placement
- Completion
The hindgut becomes the
Descending colon
The dorsal border of the stomach grows ___ than the ventral border, producing the ___ curvature of the stomach
Faster; greater
Which component of the endoderm forms a wide connection with the yolk sac
Midgut
3 primordial germ layers
-ectoderm
-mesoderm
-endoderm
The mesoderm separates into 2 layers:
-Splanchnic
-Somatic
The Coelom (2)
-space between the splanchnic and somatic mesoderm layers
-main body cavity that contains the organs
The endoderm forms
The primitive gut
3 parts to the primitive gut
-foregut (blind ending)
-midgut (connected to yolk sac)
-hindgut (blind ending)
Which 2 parts of the endoderm are blind ending
Foregut and hindgut
The foregut is supplied by the
Coeliac artery
The midgut is supplied by the
Cranial mesenteric artery
The hindgut is supplied by the
Caudal mesenteric artery
Which part of the endoderm is connected to the yolk sac
Midgut
The foregut becomes (7)
-pharynx
-oesophagus
-stomach
-liver
-pancreas
-proximal duodenum
-gall bladder
The midgut becomes (7)
-duodenum distal to bile duct
-jejunum
-yolk stalk in umbilical cord (vitelline duct)
-ileum
-caecum
-ascending colon
-part of transverse colon
The hindgut becomes (4)
-distal transverse colon
-descending colon
-rectum
-proximal anal canal
The ectoderm becomes (5)
-epithelium of oral cavity
-outer portion of anal canal
-teeth
-nerves
-skin
The mesoderm becomes (5)
-lamina propria
-submucosa
-muscle layers
-serosa/adventitia
-blood and lymph vessels
The endoderm becomes (3)
-mucosal epithelium
-mucosal glands
-glandular parts of the liver and pancreas
Formation of the digestive tract includes (3)
-thickening of the wall
-elongation of the tube (coiling and twisting)
-stomach and caecum dilations
What region of the digestive tract differentiates first during organogenesis
Cranial regions
What part of the digestive tract develops first during organogenesis
Circular layer of muscle (tunica muscularis)
The oesophagus during gestation (4)
-initially a short narrow tube
-links pharynx to stomach
-elongates with the neck and thorax
-NEVER has a typical Mesentery (serosa)
Halfway through gestation, the oesophagus goes from
Ciliated to stratified squamous epithelium
During development, the stomach (4)
-starts as a slight swelling in the foregut
-is flattened laterally
-initially in the neck
-moves caudally with elongation
Stomach development in 5 steps
- Dorsal border (greater curvature) grows faster than the ventral border (lesser curvature)
- Elongates and curves
- Rotates on long axis so the greater curvature lies on the left hand side
- Displaced by the liver, greater curvature turned caudal
- Fundic region arises as a bulge cranially
Mucosal glands on the stomach form
Halfway through gestation
The somtach’s full secretory activity (especially parietal cells) begins
After birth
The early intestine is divided into
-cranial
-caudal
The intestines grow ___ in a __ space, causing them to ___
Fast; limited; loop and coil
Early cranial intestine becomes the
Small intestine
The early caudal intestine will become the
Ileum and large intestine
During intestinal growth and rotation
intestines move ventrally and rotate clockwise
Since there is insufficient space for the intestines in the abdominal cavity,
The intestines herniated through umbilicus into the umbilical cord
Herniation of the intestine through the umbilicus and into the umbilical cord occurs
1/6 of way through gestation
The caudal loop (outpouching) of developing intestines becomes the
Caecum
The cranial loop of the developing intestine becomes the
Jejunum
Re-entry and placement of the developing intestine (5)
-growth of abdominal cavity provides extra space, intestine returns
-jejunum returns first and fills the left side of the abdomen
-descending colon is pushed to the left
-caecum and ascending colon enter last on the right hand side
-continuation of rotation of loop
During completion of the developing intestine (3)
-intestines assume adult conformation
-final growth of caecum and ascending colon (especially in the horse)
-rotation of 270 degrees around root of Mesentery
4 types of developing intestine malformations
-umbilical hernia, fistula, diverticula
-stenosis (localized narrowing of the intestine)
-atresia (closure of the intestine)
-omphalocoeal (failure of intestine to re-enter abdominal cavity)
Meckel’s Diverticulum (3)
-horses
-remnant of omphalomesenteric duct (vitelline duct/yolk sac)
-associate with the distal ileum)
3 defects associated with the vitelline duct
-meckel’s diverticulum
-cyst
-fistula
3 defects associated with the vitelline duct
-meckel’s diverticulum
-cyst
-fistula
