Embryology Flashcards
What is gastrulation?
formation of trilaminar germ disc from a bilaminar disc
when does ovulation start in regards to menstrual cycle?
ovulation starts roughly 14 days before your period starts
when does the bilaminar disc form?
week 2
which gene is a transcription factor for establishing left sidedness?
PTX2
What happens during week 3?
gastrulation
CNS induction
Neurulation
What is week 3-8 called?
organogenesis
where do the visceral and parietal mesoderm arise from?
lateral plate mesoderm
when does the gut tube form?
3rd and 4th week
what does the gut tube form from
the endoderm lining of the yolk sac
which membrane closes the gut tube at it’s cranial end? (closer to head)
oropharyngeal membrane
which membrane closes the gut tube at it’s caudal end?
cloacal membrane
how does the molecular regulation of craniocaudal organisation of the gut come about? which transcription factors are involved?
SHH transcription factor is secreted from the gut endoderm and induces the HOX gene in the mesoderm
where does the foregut form from?
the cranial part of the primitive gut tube
which structures/organs are included in the term foregut?
pharynx
oesophagus
stomach
upper duodenum
the laryngeal -tracheal diverticulum (lung bud) form from
ventral wall of the foregut
function of Tracheo- oesophageal septum
divided the foregut tube into trachea and oesophagus
what happens to the foregut in the 4th week?
it dilates to form the stomach
also: -
- it creates both the greater and lesser curvatures
- 2 rotations to create final adult position
how is the stomach attached to the dorsal and ventral wall?
a mesentery called mesogastrium
where does the lesser sac lie?
behind the stomach
what is the duodenum formed from
the caudal part of the foregut and cranial part of the midgut
name the blood supply of the duodenum
coeliac trunk
superior mesenteric artery
when is the liver bud created?
week 3
what does the liver bud grow into
the septum transversum
what forms the gall bladder and cystic duct?
ventral outgrowth from the bile duct
Key points of spleen formation
week 5 - spleen is a mesodermal derivative
15-17 - colonised by T- cells
23 - B cell precursors arrive and the spleen can then start its lymphoid function
Describe the formation of the pancreas
forms from 2 buds
these grow from the endodermal lining of the duodenum in week 5
dorsal and ventral buds fuse to form the pancreas
what makes up the main pancreatic duct?
ventral duct
distal part of dorsal duct
what are Esophageal atresia and trachea-esophageal fistula?
If the tracheo - esophageal septum deviates incorrectly => incomplete separation of laryngo -tracheal tube (lung bud) which results in these 2 things
annular pancreas
ventral bud fails to migrate around the duodenum
may cause duodenal stenosis
or pancreatic tissue may form in other areas of foregut - accessory pancreatic tissue
what is the midgut?
the distal part of duodenum, jejunum, ileum, caecum, appendix, asc and transverse colon
what does the cephalic part of the midgut become?
distal duodenum, jejunum and proximal ileum
what does the caudal part of the midgut become
distal ileum, caecum, appendix, ascending colon and the proximal 2/3rds of the transverse colon
what must the midgut undergo to reach adult pattern?
rotation and physiological herniation
when does rotation of the midgut begin
week 6
physiological herniation: what does the gut tube herniate through
the extraembryonic cavity in the umbilical cord
abnormalities in midgut development (4)
abnormal rotation of primary intestinal loop
reversed rotation
omphalocele - herniation of intestinal loop through enlarged umbilical ring + failure of retraction of viscera
anomaly - remnants of vitelline duct
what forms meckel’s diverticulum
remnants of vitelline duct
what does the endoderm of the hindgut form? (2)
lining of the bladder and urethra
which part of the hindgut joins with the posterior part of the cloaca?
the terminal portion
what does the allantois enter into?
the anterior part of the cloaca
define cloaca
endoderm lined cavity with surface ectoderm at its ventral boundary
blood supply to the foregut
coeliac artery
blood supply to the midgut
superior mesenteric artery
blood supply to the hindgut
inferior mesenteric artery
abnormal development of the hindgut
Urorectal fistula
Rectovaginal fistula
Rectoanal atresia
Imperforate anus
