Embryology Flashcards
What happens in week 1?
Fertilisation to implantation
What happens in week 2?
Bilaminar germ disc
Establish the body of axes
What’s the transcription factor for establishing left sidedness?
PTX2
What happens in week 3?
Trilaminar disc (gastrulation)
What happens in weeks 3-8?
Organogenesis
What’re the phases of embryonic development?
1) growth/ proliferation
2) morphogenesis
- development of shape, size of an organ or body part
3) differentiation
- maturation of physiological processes
During what weeks may exposure to teratogens lead to major congenital abnormalities?
4-8
What does the gut tube form from?
Endoderm lining the yolk sac during weeks 3-4
Lateral plate mesoderm gives rise to?
Parietal and visceral mesoderm
What is the gut tube closed at either end by?
Cranial=oropharyngeal membrane
Caudal=cloacal membrane
Where does the laryngo-tracheal diverticulum (lung bud) develop from?
Ventral wall
What divides the trachea and oesophagus?
Tracheo-oesophageal septum
What rotations does the stomach undergo?
1) 90 degree
2) anterio-posterior to create final adult position
What attaches the stomach to both the dorsal and ventral wall?
Mesogastrium
How is the lesser sac created?
Rotation along longitudinal axis pulls dorsal mesentry to the left and the ventral mesogastrium is pilles to the right
At which week does the liver bud appear at?
Middle of the third week
What does the liver bud form from?
Outgrowth of the endoderm in the distal end of the foregut
What does the liver bud grow into?
Septum transversum
What narrows to form the bile duct?
Connection between the foregut and liver bud
Ventral outgrowth from the bile duct forms what?
Gallbladder and cystic duct
At which week does the spleen form?
5th
The spleen is a derivative of what?
Mesochymal derivative
What is the function of spleen up to week 14?
Acts as a haemopoeitic organ forming RBCs, WBCs and bone marrow
Spleen function weeks 15-17?
Colonised by lymphocytes
What happens to the spleen at week 23?
B cell precursors arrive
What is the pancreas formed from?
Dorsal and ventral buds, which grow from the endodermal lining in week 5
What is an oesophageal atresia and tracheo-oesophageal fistula?
If the tracheo-oesophageal septum fails to deviate correctly then there is an incomplete separation
What’s an annular pancreas?
Ventral dud fails to move round the duodenum correctly.
May cause duodenal stenosis
Pancreatic tissue many form in other areas of the foregut= accessory pancreatic tissue
What will the cephalon part of the primary intestinal tube form?
Distal duodenum
Jejunum
Proximal ileum
Caudal part of primary intestinal tube will form?
Distal ileum
Caecum
Ascending Colom
Proximal 2/3rds of transverse colon
Why and when does the gut tube herniate into the extra-embryonic cavity?
Week 6. Allows growth. Will go back in about week 10
What’s omphalocele?
Herniation of abdominal viscera through an enlarged umbilical ring
What’s gastrochisis?
Herniation of contents into the amniotic cavity
Not covered by an anion or peritoneum
What’s the endoderm/ectoderm boundary in the hindgut?
Cloacal membrane
Foregut/midgut/hindgut boundaries
Foregut=pharynx>bile duct opening
Midgut=bile duct opening>2/3 of transverse colon
Hindgut=2/3 of transverse colon>rectum
What’s the allantois?
Urethra and bladder
Where does the epithelium have it’s origins?
Endoderm
Connective tissue orgins?
Mesoderm
Remenant of yolk sac?
Viteline
What was the job of the falciforme ligament?
Carry O2 blood from mother to liver
