Embryology of the GIT Flashcards
How many days can it take from fertilisation to the implantation of a blastocyte?
5-6 days
Which gene is a transcription factor for establishing left sidedness?
->this can mean that structures which should be on the right of the body end up in the left etc :)
PTX2
When does the bilaminar disc turn into the trilaminar disc?
Week 3
What is the name of the process by which the bilaminar germ disc turns into the trilaminar germ disc?
Gastrulation
RECAP- name the three layers of the trilaminar disc
Ectoderm
Mesoderm
Endoderm
Which stage of development could organ malformation occur and why might this happen?
Any time during the organogenesis period from weeks 3-8 and can occur due to exposure to teratogenic substances like drugs or viruses
Name a common teratogenic drug which causes limb abnormalities and must be avoided during pregnancy?
Thalidomide
List the different things which arise and develop from the embryonic ectoderm.
Skin, CNS, ear, nose.
List the different things which arise and develop from the embryonic endoderm.
Epithelial lining of resp. system, GIT, bladder, pancreas, glands, liver.
List the different things which arise and develop from the embryonic mesoderm.
Muscles, bones, cartilage, dermis.
Just checking you were paying attention, and considering this is GIT embryology…what is the embryological origin for the epithelial lining of the GI and parenchymous cavities?
Endoderm
RECAP- when the lateral plate mesoderm splits, what are the two new mesoderm layers?
Parietal and visceral mesoderm
Which mesoderm layer lines the gut tube?
Visceral mesoderm
Which mesoderm layer lines body cavities?
Parietal mesoderm
What is the gut tube formed by?
Endodermal lining of the yolk sac
What is the gut tube closed by at the cranial end?
Oropharyngeal membrane
->think the pharynx is nearer the head, hence cranial end :)
What is the gut tube closed by at the caudal end?
Cloacal membrane
->think c=c, caudal=cloacal
When the gut tube is formed its connection to the yolk sac becomes smaller. The gut tube is only connected to the umbilical cord by a duct, what is the name of this duct?
Vitelline duct.
Which part of the gut tube does the oesophagus develop from?
Cranial part
Where in the foregut do lung buds develop from?
Ventral wall of foregut
What is the mesentery in terms of embryology?
Double layer of peritoneum which hangs the gut tube from the body wall
What are the two layers of mesentery?
Ventral and dorsal
What is the embryological origin of mesentery?
Mesoderm
Where does the foregut extend from and to?
Extends from the lung bud diverticulum to the bile duct opening of the duodenum.
How is the stomach formed?
The part of the foregut caudal to the oesophagus dilates and creates the greater and lesser curvatures.
Which nerve supplies the anterior part of the stomach?
Left vagus nerve
Which nerve supplies the posterior part of the stomach?
Right vagus nerve
What is the mesentery of the stomach known as?
Mesogastrium
What does the mesogastrium do?
Attaches the stomach to the dorsal and ventral wall
Where would you find the lesser omentum?
Between the liver and the lesser curvature of the stomach
Where would you find the greater omentum?
Between the greater curvature of the stomach and the transverse colon
What does the transverse mesocolon do?
Connects the transverse colon to the posterior wall of the abdomen
What is the duodenum formed from?
The caudal part of the foregut and the cranial part of the midgut
What is the blood supply for the dudenum?
As it is formed from the foregut and the midgut, it has two blood supplies, coeliac trunk and superior mesenteric artery
At what stage do liver buds devlop?
Week 3
What do the liver buds give rise to?
Gallbladder
Cystic duct
Bile duct
Where do the falciform ligament and lesser omemtum form from?
Ventral mesentery
In which week of development does the bile duct form?
Week 12
What is the origin of the spleen?
Mesodermal
What colonises the spleen during weeks 15-17?
T lymphocytes
When and why does the spleen start its lymphoid function?
Week 23 because the B lymphocytes precursor cells arrive
What is the origin of the pancreas?
Endodermal
What can incomplete separation of the lung bud result in?
Oesophageal atresia and tracheo-oesophageal fistula
What is meant by atresia?
Absence of opening
What is meant by fistula?
Abnormal connection between two parts of two structures
Where does the midgut extend from and end at?
Extends from the opening of bile duct to proximal 2/3rds of the transverse colon
Which process forms the umbilical cord?
Physiological umbilical herniation.
When the midgut loop elongates, what does it differentiate into?
Part of the duodenum, jejunum, ileum, ascending colon and 2/3 of the transverse colon
When do cecal buds develop?
Week 6
What grows from the caecum?
The appendix
What is the mesentery of the appendix called?
Mesoappendix
What is the mesentery of the small intestine called?
Mesentery proper
What is the mesentery of the transverse colon called?
Transverse metacolon
What are some of the common developmental abnormalities of the midgut?
Stenosis
Malrotation
What is meant by omphalocele?
Failure of retraction of the insestinal loop through the umbilical ring (week 10)
in 2-4% of people, remnants of the vitelline duct remain. What can they form?
Fistula/ cyst/ ligament/ Meckel’s diverticulum
What may cause stenosis of an opening?
Vascular incidents, possibly thrombosis, or twisting of the bowel
Where does the hindgut start and end?
Distal 1/3 transverse colon to the anal canal.
Which parts of the hindgut come from endoderm origin?
Distal 1/3rd transverse colon, descending colon, sigmoid colon, rectum
and upper part of the anal canal.
Which parts of the hindgut come from ectoderm origin?
Lower part of the anal canal and anal orifice
What happens to the cloacal membrane in the hindgut at 7wks?
It ruptures
What supplies the foregut?
Coeliac artery
What supplies the midgut?
Superior mesenteric artery
What supplies the hindgut?
Inferior mesenteric artery
What supplies the anal canal above the pectinate line?
Inferior mesenteric artery
What supplies the anal canal below the pectinate line?
Internal pudendal artery
Describe what happens in an urorectal fistula, a hindgut developmental anomaly
Rectum has connection with the uthera
Describe what happens in an rectovaginal fistula, a hindgut developmental anomaly
Rectum has connetion with the vagina
Describe what happens in an rectoperineal fistula, a hindgut developmental anomaly
Rectum has connection with the perineum
What happens if the cloacal membrane fails to perforate?
Foetus is born with an imperforated anus.
VIDEOS TO WATCH ON PP IF YOU WANT GAL
I know you don’t but it might help x