embryology of GI Flashcards
Which gene is a transcription factor for establishing left sidedness?
PTX2
what weeks does organogenesis happen?
3-8
what are the 3 phases of embryonic development?
growth and proliferation
morphogenesis
differentiation
what is growth and proliferation
cell division and elaboration of products
what is morphogenesis?
development of shape, size of a particular organ or part of the body
what is differentiation
maturation of physiological processes
when does exposure to teratogens occur?
week 4-8
what happens during gastrulation?
bilaminar embryonic disc is converted inti trilaminar disc
what are examples of embryonic ectoderm
Skin (epidermis, hair, nail), CNS,PNS, sensory epithelia of the eye, ear, nose & other structures (pituitary, mammary, sweat glands, enamel of teeth), liver (except the parenchyma), adrenal medulla etc.
what are examples of embryonic endoderm?
Epithelial lining of RS, GIT, glands, liver, pancreas, thyroid, parathyroid parenchyma, urinary bladder etc.
what are examples of embryonic mesoderm?
muscle, bones, cartilage, dermis, vascular system (most of the CVS connective tissues, muscles, blood cells and bone marrow, vessels associated with organs and tissues), urogenital system except bladder, spleen, suprarenal gland cortex etc.
what gives rise to the parietal and visceral mesoderm?
lateral plate mesoderm
what weeks does the gut tube form?
3rd and 4th
what is the gut tube closed by?
oropharyngeal membrane at cranial and at the caudal end by cloacal membrane
where does the esophagus develop from?
cranial part of the primitive gut tube
where does the Laryngo-tracheal diverticulum (lung bud) develop from?
ventral wall of the foregut
what does the trachea-esophageal septum divide the foregut tube into?
trachea and esophagus
at what week does the foregut dilate to form the stomach into?
4th week
what does the differential growth of the stomach wall create?
greater and lesser curvatures
why does the stomach rotate and adapt?
to fit with the other developing organs
what kind of rotation does the stomach undergo to create the final adult position?
90 degrees and anterior-posterior roation
what is the mesentery that attaches the dorsal and ventral wall of the stomach?
mesogastrium
what does the rotation along the longitudinal axis that pulls the dorsal mesentery to the left create?
omental bursa
where is the duodenum formed from?
caudal part of the foregut and the cranial part of the midgut
where is the blood supply of the duodenum?
coeliac trunk and superior mesenteric artery
what kind of shape does the duodenum create?
c-shaped
what does the duodenal cap retain?
dorsal mesentery but the rest of the duodenum is retroperitoneal
when does the liver bud appear?
middle of third week
where is the outgrowth of the endoderm?
distal end of the foregut
what does the liver bud grow into?
septum transversum
what does the connection between the liver bud and foregut narrow into?
bile duct
what does the ventral outgrowth from the bile duct form?
gall bladder and cystic duct
where does the mesenchymal condensation develop into?
dorsal mesogastrium near the body wall
when does this mesenchyme differentiates to form the spleen?
5th week
what does the mesenchyme differentiate into?
spleen
what kind of derivitive is the spleen?
mesodermal
at week 14, what does the spleen act as?
haematopoietic organ
what kind of lymphocytes colonise in weeks 15-17?
T lymphocytes
when do the B cell precursers arrive?
week 23
what does the pancreas form from?
2 buds which grow from the endodermal lining of the duodenum in week 5
what buds fuse to form the pancreas?
dorsal and ventral buds
what happens if the tracheo- esophageal,septum deviates incorrectly? and what is the result?
incomplete seperation of larynx- tracheal tube
Esophageal atresia and tracheo - esophageal fistula
what happens if the ventral bud fails to migrate around the duodenum correctly?
annular pancreas- this may cause duodenal stenosis
what is pancreatic tissue that may form in other areas of the foregut?
accessory pancreatic tissue
what/where is the midgut?
distal part of duodenum, jejunum ileum, caecum, appendix, ascending column, proximal 2/3rds of the transverse colon
what does the cephalic part of the midgut become?
distal duodenum, jejunum and peoximal 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
when does rotation of the midgut happen?
6th week
where does the initial rotation of the primary intestinal loop occur?
around the axis of the superior mesenteric artery
where does the gut tube herniate into?
extraembryonic cavity in the umbilical cord
where do the intestinal loops move after the umbilical cord?
back into the abdominal cavity
what is an omphalocele?
herniation of intestinal loop through an enlarged umbilical ring
what happens to people with small vitelline duct persists?
may form fistula or vitelline cyst/ligament
what is the hindgut?
distal 1/3rd transverse colon, descending colon, sigmoid colon, rectum and upper part of the anal canal
what does the endoderm of the hindgut also form?
lining of the bladder and urethra
what does the terminal portion of the hindgut join with?
posterior part of the cloaca
where does the allantois enter
anterior part of the cloaca
what is a cloaca?
endoderm lined cavity with surface ectoderm at its ventral boundary
what are the divisions of arteries supplying the gut tube?
celiac, superior mesenteric and inferior mesenteric arteries
what artery supplies the foregut?
coeliac artery
what artery supplies the midgut?
superior mesenteric artery
what artery supplies the hindgut?
inferior mesenteric artery
what are developmental anomalies of the hindgut?
Urorectal fistula Rectovaginal fistula
Rectoanal atresia
Imperforate anus-
