What gene is a transcription factor for establishing left sideness?
PTX2
What is Gastrulation?
Gastrulation is when the single-layered blastula is reorganised into a multilayered structure known as the gastrula
What are the 3 main components for forming the trilaminar germ disk?
Gastrulation
CNS induction
Neurulation
What occurs during gastrulation?
The bilaminar disc is converted into the trilaminar disc
What are the 3 phases of embryo development
- Growth/proliferation
- Morphogenesis
- Differentiation
What are teratogens?
Agent of factor that can cause harm to the embryo e.g. drugs
What main drug may cause major congenital anomalies?
Thalidomide
What are the components of the trilaminar disc?
Embryonic ectoderm
Embryonic endoderm
Embryonic mesoderm
What does the embryonic ectoderm form?
Skin CNS,PNS Sensory epithelia of the eye Ear Nose Sweat glands enamel of teeth Liver ( except the parenchyma) Adrenal medulla ETC...
What does the embryonic endoderm form?
Epithelial lining of RS GIT Glands Liver Pancreas Urinary bladder ETC...
What does the embryonic mesoderm form?
Muscle Bones Cartilage Dermis Vascular system Urogenital system except bladder Spleen Suprarenal gland cortex ETC...
What gives rise to parietal and visceral mesoderm?
Lateral plate mesoderm
What does the gut tube form from during the 3rd and 4th week?
The endoderm lining of the yolk sac
What forms the urethra and bladder?
Allantois
What does the esophagus form from?
Develops from the cranial part of the primitive gut tube
What does the Laryngo-tracheal diverculum (lung bud) develop from?
It develops from the ventral wall of the foregut
What does the tracheo-esophageal septum (ridge) divide?
Divides the foregut tube (endoderm lined) into trachea and esophagus
What happens in the 4th week to the foregut?
The foregut dilates to form the stomach
What rotation does the stomach undergo to create a final adult position?
An arterio-posterior rotation
The stomach is attached to both the dorsal and ventral wall by a mesentary called what?
Mesogastrium
What does rotation along the longitudinal axis pulling the dorsal mesentary to the left create?
The omental bursa (lesser sac)
What is pulled to the right during the creation of omental bursa (lesser sac)?
Ventral mesogastrium
What does the duodenum form from?
Formed from the caudal part of the foregut and the cranial part of the midgut
What is the blood supply of the duodenum formed from?
Formed from the caudal part of the foregut and the cranial part of the midgut
What is the blood supply of the duodenum?
Coeliac trunk and superior mesenteric artery
What does retroperitoneal mean?
Situated or occuring behind the peritoneum
When does the liver bud appear?
Middle of the 3rd week
What does the liver bud give rise to?
The liver bud gives rise to the gallbladder and bile ducts, as well as to the parenchyma of the liver
What forms the bile duct?
Connection between the liver bud and foregut (duodenum) narrows to form bile duct
What forms the gall bladder and cystic duct?
Ventral outgrowth from the bile duct forms the gall bladder and cystic duct
What does connective tissue always form from?
Mesoderm
Foregut (spleen): What occurs at the end of the 4th week?
A mesenchymal condensation develops in the dorsal mesogastrium near the body wall
Foregut (spleen): What occurs during the 5th week?
The mesenchyme differentiates to form the spleen
What is spleen derived from?
The spleen is a mesodermal derivative
What is a falsiform ligament?
A ligament attaches the liver to the front body wall, and separates the liver into the left lobe and right lobes.
What does the pancreas form from?
It forms from the 2 buds, which grow from the endodermal lining of the duodenum in week 5.
What 2 things fuse to form the pancreas?
Dorsal and Ventral buds
What is the main pancreatic duct composed of?
Ventral duct + Distal part of dorsal duct
What occurs if the tracheo-esophageal septum deviates incorrectly?
Then there is an incomplete separation of laryngo-tracheal tube (lung bud)
What is it called if the ventral bud fails to migrate around the duodenum correctly?
Annular pancreas
- This may cause duodenal stenosis
What is the midgut?
The distal part of duodenum, jejunum, ileum, caecum, appendix, ascending colon, proximal 2/3rds of the transverse colon
What does the development of the midgut involve?
It involves rapid elongation of the gut tube and its associated mesentary
- Described as the ‘primary intestinal loop’
What part of the primary intestinal loop will become the distal duodenum, jejunum and proximal ileum?
The Cephalic part of the primary intestinal loop
What part of the primary intestinal loop becomes the distal ileum, caecum, appendix, ascending colon and the proximal 2/3rds of the transverse colon?
The Caudal part of the primary intestinal loop
What week does the rotation of the midgut begin?
6th week
know this
Where does the initial rotation of the primary intestinal loop occur?
It occurs around the axis of the superior mesenteric artery
What is physiological herniation of the midgut?
As the 90 degree rotation occurs, the gut tube herniates into the extraembryonic cavity in the umbilical cord
What is Omphalocele?
It is the herniation of abdominal viscera through an enlarged umbilical ring
- Failure of retraction of umbilical ring
What is Gastrochisis?
Herniation of abdominal contents directly through the body wall into the amniotic cavity
- Through a weak area right of umbilicus
What does the remnants of vitelline duct form?
Forms meckels’s diverticulum
- May form fistula or vitelline cyst/ligament
What is the hindgut?
Distal 1/3rd of transverse colon, descending colon, sigmoid colon, rectum and upper part of the anal canal.
- Endoderm of hindgut also forms the lining of the bladder and urethra.
What part of the hindgut joins with the posterior part of the cloaca (primitive anal canal)?
The terminal portion of the hindgut joins with the posterior part of the cloaca.
What is the Enoderm/ectoderm boundary?
It is the cloacal membrane
What artery supplies the Foregut?
Coeliac artery
What artery supplies the Midgut?
Superior mesenteric artery
What artery supplies the Hindgut?
Inferior mesenteric artery