Embryology Flashcards
How is the gut tube produced
Due to lateral and craniocaudal folding in the 4th week of development
What type of mesoderm covers the gut tube
Splanchnic mesoderm
What lines the gut tube
Endoderm
What 3 areas is the gut tube divided into
Foregut, midgut and hindgut
What is derived from the foregut
Oesophagus, stomach, pancreas, liver, gall bladder, part of the duodenum
What is derived from the midgut
Duodenum, jejunum, ileum, caecum, ascending colon, transverse colon
What is derived from the hindgut
Transverse colon, descending colon, sigmoid colon, rectum, anal canal
What blood vessel supplies the foregut
coeliac trunk
What blood vessel supplies the midgut
Superior mesentry artery
What blood vessel supplies the hindgut
Inferior mesentry artery
What are retroperitoneal structures
Those which are not suspended in the abdominal cavity’s peritoneum
What are secondary retroperitoneal structures
Structures which were invested in the peritoneum but the mesentry then fused with the posterior abdominal wall, making them retroperitoneal
What causes the production of secondary retroperitoneal structures
Rotation of the stomach
What is the intraembryonic coelom
The cavity through which the gut tube is suspended in
What will the intraembryonic coelom develop into
Thoracic and abdominal cavities
What septum separates the the GI tract from the respiratory diverticulum
Tracheoesophageal septum
What is a mesentry
Double fold of peritoneum which suspends the gut tube in the intraembryonic coelom
How far along the tube does dorsal mesentry run
Along the whole length
How long does the ventral mesentry run along the gut tube
Along the foregut
why does looping of the midgut and herniation occur
as the midgut elongates massively and it runs out of room
what connects the midgut to the yolk sac in the umbilical cord
vitelline duct
how does the midgut rotate
around the superior mesenteric artery in 3 90 degree rotations
what does the descending of the caecal bud produce
the ascending colon
which limb of the midgut loop is pushed back in first after herniation
cranial limb
what is a volvulus
twisting of the GI tract, cutting off the blood supply
why does recanalisation of the GI tract occur
as there is rapid growth of the cells lining the lumen which would otherwise cause atresia or stenosis
is pyloric stenosis a recanalisation failure
no
what is pyloric stenosis
where there is hypertrophy of the circular muscle above the pyloric sphincter
would the vomit in pyloric stenosis be bilious or non bilious
non bilious as the bile duct has not drained into this prat of the GI tract
would the vomit in midgut volvulus be bilious or non bilious
bilious as the bile duct has drained into the GI tract by here
what is a vitelline cyst
where the duct forms a fibrous strands connecting the intestines to the abdominal wall
what is a vitelline fistulae
where the vitelline duct doesn’t close off, so keeps an opening between the umbilicus and intestines.
what is meckels diverticulum
where the vitelline duct doesn’t fully regress, so part remains as a remnant
what is the rule of 2s with meckels diverticulum
- affects 2% of the population
- 2:1 male to female ratio
- 2 feet from ileo-ceacal valve
what is gastroschisis
where the abdominal wall fails to close during folding so the intestines protrude out
what is omphalocoele
where there is persistence of the physiological herniation (when the midgut pushes out of the body and doesn’t go back in) it is covered by peritoneum
what is umbilical hernia
where the intestines bulge out at the belly button but are still covered by skin
what line divides the 2 regions of the anus
pectinate line
from what embryonic layer does the superior portion of the anus derive from
endoderm
from what embryonic layer does the inferior portion of the anus derive from
ectoderm
where are the innervations for the superior and inferior portions of the anus
superior = visceral innervation (can only detect stretch) inferior = somatic innervation (pain, temperature, touch sensitive)
what is an imperforate anus
where the anal membrane fails to rupture
what is a hindgut fistulae
where there is an abnormal connection of the anus to another organ e.g. the bladder
what does the development of the anal canal from 2 different tissues mean for its structure and neurovascular supply
superior = innervated by pelvic parasympathetics, has columnar epithelium, lymph drainage to internal iliac nodes
inferior = innervated by pudendal nerve, has stratified epithelium, lymph drainage to superficial inguinal nodes, vascular supply by pudendal artery
