Week 2 - Development Of The Peritoneum And Foregut Flashcards
How do we get a ventral body wall and a gut within a cavity?
Embryonic folding
In the 4th week when the embryo folds laterally, what does this create?
Ventral body wall, primitive gut becomes tubular
In the 4th week when the embryo folds craniocaudally, what does this create?
Cranial and caudal pockets from yolk sac endoderm
Describe the embryonic divisions of the gut?
Foregut and hindgut are blind ended diverticula
midgut has opening at first and is continuous with yolk sac
What does gut tube pinch off from yolk sac?
3rd week
Where does the gut tube run from?
Stomatodeum (future mouth) to proctodeum (future anus) with an opening at umbilicus
What is the internal ling of the primitive gut derived from?
Endoderm - future epithelial linings
What is the external lining of the primitive gut tube derived from?
Splanchnic mesoderm - future musculature and visceral peritoneum
What does the foregut mature into?
Oesophagus stomach pancreas liver and gall bladder duodenum proximal to bile duct entrance
What does the midgut develop into?
Duodenum distal to entrance of bile duct jejunum ileum cecum ascending colon proximal 2/3 transverse colon
What does the hindgut develop into?
Distal 1/3 transverse colon descending colon sigmoid colon rectum upper anal canal lining of bladder and urethra
What artery supplies the foregut?
Celiac trunk
What artery supplies the midgut?
Superior mesenteric artery
What artery supplies the hindgut?
Inferior mesenteric artery
What is the intraembryonic coelom?
Begins as one large cavity
later subdivides by future diaphragm into abdominal and thoracic cavities
What is the peritoneal cavity?
A potential space that under normal conditions should contain nothing
What are the mesenteries?
Double layer of peritoneum suspending the gut tube from the abdominal wall which allows for a blood and nervous supply
How is the mesentery formed?
Splanchnic mesoderm surround new gut, condensation of this mesoderm forms the mesentery
What are the two mesenteries and where are they?
Dorsal mesentery suspends the entire gut tube from the dorsal body wall, ventral mesentery only in the region of foregut
In the foregut how do the mesenteries divide the cavity?
Into the left and right sac
What does the left sac contribute to?
The greater sac
What does the right sac contribute to?
The lesser sac
What are omenta?
Specialised regions of peritoneum
What is the greater omentum?
Formed by dorsal mesentery
first structure seen when abdominal cavity is opened anteriorly
What is the lesser omentum?
Formed from the ventral mesentery
free edge conducts the portal triad
How are the omenta and the greater and lesser sacs formed?
Rotation of the stomach
How does the stomach rotate?
In two directions
Around the longitudinal axis and around the anteroposterior axis
What is the result of stomach rotation?
Greater and lesser curves lie first on the right and left sides
then cardia and pyloris move horizontally
pushing greater curve inferiorly
puts the vagus nerves anterior and posterior to the stomach instead of left and right
shifts cardia and pylorus from the midline
moves lesser sac behind stomach
creates greater omentum
What is peritoneal reflection?
A change in direction - from parietal peritoneum to mesentery, from mesentery to viscera, peritoneum etc.
What if there is no mesentery?
structures are not suspended within the abdominal cavity and are retroperitoneal
Whats the different between retroperitoneal and secondary retroperitoneal?
Retroperitoneal is where they were never in the peritoneal cavity and never had a mesentery
secondary retroperitoneal organs began development in the peritoneum and had a mesentery but during growth and development the mesentery was lost through fusion at posterior abdominal wall
How does the oesophagus form?
In 4th week respiratory diverticulum forms in ventral wall of foregut at junction with pharyngeal gut
Forms respiratory primordium ventrally and oesophagus dorsally
What causes the respiratory primordium to become separate from the oesophagus?
Tracheoesophageal septum develops
Name some problems that might occur from abnormal positioning of tracheoesophageal septum?
Proximal blind-ended tube
thracheoesophageal fistula
How is the greater curve of the stomach created?
Faster growth of the dorsal border
What foregut derived glands are formed in the ventral mesentery?
Liver
biliary system
part of pancreas (uncinate process and inferior head)
What foregut derived glands are formed in the dorsal mesentery?
Pancreas - superior head, neck, body and tail
What do the intestines have to develop outside the body?
The liver occupies a large proportion of the abdomen during development so there is not space
How does the duodenum develop?
Develops from caudal foregut and cranial midgut
grows rapidly
forming a C shaped loop when the stomach rotates
How does rotation of the stomach position the duodenum?
Causes duodenum to forma c shaped loop and pushes it to the right and then against the posterior abdominal wall
What are the secondary retroperitoneal structure of the foregut?
Duodenum
pancreas
