Embryology 1 - Peritoneum and Foregut Flashcards
How does the gut come to be suspended within a cavity?
Via craniocaudal folding
What is the midgut continuous with?
The yolk sac - opens out through umbilicus
Where does the primitive gut tube run between?
The stomatadeum (future mouth) and proctodeum (future anus)
How does the primitive gut tube lie within the body?
Suspended in the intraembryonic cavity by a double layer of splanchnic mesoderm
What tissue layer is the lining of the primitive gut tube derived from?
What will it later become?
Endoderm –> will become epithelia
What is the origin of the external lining of the primitive gut tube?
What will it become?
Splanchnic mesoderm –> becomes musculature and visceral peritoneum
Which parts of the GI tract are derived from the foregut?
Oesophagus
Stomach
Pancreas, liver and gallbladder
Duodenum PROXIMAL TO BILE DUCT
List the parts of the GI tract derived from the midgut
Duodenum distal to bile duct Jejunum Ileum Caecum Ascending colon Proximal 2/3rds of the transverse colon
Which parts of the GI tract are derived from the hindgut?
Distal 1/3rd of the transverse colon Descending colon Sigmoid colon Rectum and upper anal canal *Bladder and urethra*
Which branch of the abdominal aorta supplies the foregut structures?
Coeliac trunk
The superior mesenteric artery supplies the foregut, midgut or hindgut?
Midgut
Which blood vessel supplies the hindgut?
IMA
What is significant about blood supply to the duodenum and pancreas?
As they lie close to the border of the foregut and midgut, they are supplied by both the coeliac trunk and the SMA
What is a mesentery?
What are its functions?
A double layer of peritoneum suspending a part of the gut from the abdominal wall.
Allows mobility of the suspended structure, and acts as a conduit for neurovasculature
How does the mesentery form?
The gut tube lies within the body cavity surrounded by splanchnic mesoderm. This mesoderm condenses to form mesentery.
Compare and contrast the role of mesentery with regards to the foregut, midgut and hindgut
Foregut is suspended by dorsal AND ventral mesentery
Midgut and hindgut suspended by dorsal mesentery only
Why do the foregut structures appear to have less mobility than the midgut and hindgut structures?
Foregut is suspended from the dorsal body wall by dorsal mesentery AND the ventral body wall by ventral mesentery, whereas mid and hindgut have dorsal mesentery only
What structures appear to divide the foregut into right and left?
The dorsal and ventral mesenteries
What are omenta?
Specialised regions of peritoneum
From what is the greater omentum derived?
Dorsal mesentery
A region of the ventral mesentery specialises to become what?
Lesser omentum
How does the lesser sac form?
Formative question with answer from markscheme
The foregut is attached both dorsally and ventrally to the abdominal wall. Hence, when it rotates, it creates an enclosed space, which is the lesser sac.
Briefly outline how the stomach develops
Distal foregut slightly dilates around week 4
Dorsal border grows quicker - creates greater curvature
Rotates 90* clockwise around longitudinal axis, and also around anterio-posterior axis, pushing greater curvature inferiorly.
When does the liver begin to develop and from what?
Develops from hepatic bud around the 4th week
