GIT embryology Flashcards
What do Hox genes do?
Hox genes regulate the pattern of development in embryos
Their sequence on the DNA is the same order as they are used (head to tail)
Overlapping or changes of hox genes = valve/sphincter/change in diameter/change in function
How does the gut tube form?
Develops from ventral invaginations at either end of the embryo
they elongate and fuse along the ventral midline to form a straight tube
What happens to the mesoderm, ectoderm and endoderm outside of the embryonic disc?
They becomes placenta and membranes
Describe the formation of the buccopharyngeal and cloacal membranes
2 small areas at head and tail of embryo have no mesoderm
Here the ectoderm and endoderm are in direct contact
this forms the buccopharyngeal and cloacal membranes
How are the thoracic, cardiac and abdominal cavities form?
splitting of the mesoderm to create a space
Split forms extra-embryonic coelum, somatic mesoderm and splanchnic mesoderm
Splitting continues until it reaches embryo and stalk becomes umbilical cord
GIT is pinched off yolk sac
How does the yolk sac form?
from blastocoele as embryo rolls up:
- links to midgut
- becomes the choriovitelline placenta
How does the allantoic sac form?
forms as an outgrowth of the hindgut:
- the root with gut becomes divided by the urorectal septum to create the hindgut and the bladder
- becomes the choriaallantoic placenta
Where does the abdominal cavity come from?
Extra-embryonic space (coelom)
How does the bladder and rectum form?
Growth of urorectal septum divides the cloaca into the bladder and rectum
What is a mesentery?
- A fold or membrane that conveys blood vessels, nerves and lymphatics to a visceral structure
How does the tongue develop?
as an outgrowth from the mesoderm of the lower jaw
How does the small intestine develop?
jejunum grows lengthwise - herniates from abdomen as gut initially grows faster than embryo
gradually coils on itself as it is drawn back into abdomen as fetus grows to accomodate jejunum
rotation draws duodenum and large colon anticlockwise
What is an umbilical hernia?
faulty closure of abdominal wall leaves a large opening:
- herniation of fat, then SI through umbilicus
- hereditary
- important to check for in neonates
What are clefts and give some examples
- persistance of embryonic/fetal clefts due to abnormal growth processes
How is the diaphragm formed?
Formed from the septum transversum
As the embryo rolls up the diaphragm end up in the middle of the embryo, next to the gut
What is the vitelline artery?
What organs do the coeliac artery supply?
What organs do the cranial mesenteric artery supply?
Describe the pathway of the hepatic portal vein?
how do hepatic sinusoids form?
