3) Development of Foregut Flashcards
What does lateral folding of the embryo achieve?
Creates ventral body wall
Primitive gut becomes tubular
What does craniocaudal folding of the embryo achieve?
Creates cranial and caudal pockets from yolk sac endoderm
What are the three regions of the primitive gut tube?
Foregut
Midgut
Hindgut
Where does the primitive gut tube run from?
From future mouth to future anus with opening at umbilicus
What is the internal lining of the primitive gut tube derived from and what will this become?
Endoderm, will become epithelial lining
What is the external lining of the primitive gut tube derived from and what will this become?
Splanchnic mesoderm
Will become future musculature and visceral peritoneum
What are the adult derivatives of the foregut?
Oesophagus, stomach, pancreas, liver, gall bladder and duodenum (proximal to bile duct entrance)
What are the adult derivatives of the midgut?
Duodenum (distal to bile duct entrance), jejunum, ileum, caecum, ascending colon, proximal 2/3rds transverse colon
What are the adult derivatives of the hindgut?
Distal 1/3rd transverse colon, descending and sigmoid colon, rectum, upper anal canal and internal lining of bladder & urethra
What is each region of the gut tube’s blood supply?
Foregut - celiac trunk
Midgut - SMA
Hindgut - IMA
What is the intraembryonic coelom divided by?
Diaphragm
What do the abdominal muscles develop from?
Somatic mesoderm
What does the inguinal canal allow?
Passage of developing testis into scrotum
What is a mesentery?
Double layer of peritoneum suspending gut tube from abdominal wall
Why is a mesentery needed?
Blood and nerve supply
Mobility
What is the function of the dorsal mesentery?
Suspends entire gut tube from dorsal (back) body wall
What is the function of the ventral mesentery?
Suspends foregut from ventral body wall
What do the dorsal and ventral mesenteries do in the foregut?
Divide the cavity into left and right sacs
Which sac contributes to the greater sac?
Left sac
Where does the lesser sac come to lie?
Posterior to the stomach
What is the greater omentum?
Double sheet of peritoneum folded on itself, from dorsal mesentery. Hangs down from greater curvature of stomach over intestines and ascends back up to transverse colon and posterior abdominal wall
What is the lesser omentum?
Double layer of peritoneum from liver to lesser curvature of stomach. Free edge conducts portal triad
What does the dorsal border of the stomach become?
Greater curvature
What are retroperitoneal structures?
Those that were never in peritoneal cavity and never had a mesentery
What are secondarily retroperitoneal structures?
Began development invested in peritoneum but with successive growth and development, mesentery is lost through fusion at posterior abdominal wall
What does the respiratory diverticulum separate?
Respiratory primordium (ventrally) from oesophagus (dorsally)
What are the consequences of abnormal positioning of tracheoesophageal septum?
Tracheo-oesophageal fistulae
Oesophageal atresia
What organs are formed in the ventral mesentery?
Liver, biliary system, part of pancreas
What organs are formed in the dorsal mesentery?
Pancreas
What connects the liver to the anterior abdominal wall?
Falciform ligament
Where is the bare area of the liver?
Superior, where liver and diaphragm are connected
What happens to the lumen of duodenum in 5th and 6th weeks?
Lumen is obliterated then recanalised by end of embryonic period
Give examples of retroperitoneal organs:
Oesophagus, kidneys, rectum
Give examples of secondarily retroperitoneal organs:
Ascending and descending colon
Duodenum (except duodenal cap)
Pancreas
