GI embryology - development of the peritoneum and foregut Flashcards
(93 cards)
In the fourth week what two types of folding occur?
Lateral and craniocaudal folding
What are the affects of lateral folding?
- Creates ventral body wall
2. Primitive tube becomes tubular
What are the affects of craniocaudal folding?
- Creates cranial and caudal pockets from yolk sac endoderm (beginning of primitive gut development).
When does the primitive gut tube begin to develop?
Week 3 when it pinches off from the yolk sac cavity.
What is the stomatodeum?
Future mouth (stomata=primitive mouth)
What is the proctodeum?
Future anus (procta=anus)
Describe the morphology of the primitive gut tube
It runs from the rostral stomatodeum to the caudal proctodeum, with an opening at the umbilicus.
Which of the three trilaminar layers is the primitive gut tube derived from?
Endoderm - interling lining -> future epithelial linings
Splanchnic mesoderm - external lining -> future musculature of gut wall and visceral peritoneum.
Which new cavity is the primitive tube suspended in by a double layer of splanchnic mesoderm?
Intraembryonic coelom
Describe the adult derivatives of the foregut
Oesophagus -> duodenum (proximal to entrance of bile duct)
Describe the adult derivatives of the midgut
Duodenum (distal to entrance of bile duct) -> proximal 2/3 of transverse colon.
Describe the adult derivatives of the hindgut
Distal 1/3 of transverse colon -> upper anal canal (to the pectinate line).
Also includes the internal lining of bladder and urethra.
What is the pectinate line?
A line 2/3 down the anal canal which corresponds to the developmental junction between the hindgut and the proctodeum.
What reflects the embryonic derivates of the foregut, midgut and hindgut?
Blood supply
Lymphatic drainage
In the fourth week, what constitutes the ends of the foregut?
At the cranial end the lung bud and at the caudal end, the liver bud.
In the fourth week, what happens to the ventral wall of the foregut at the junction with the pharyngeal gut?
A respiratory diverticulum (blind-ended tube) forms creating the respiratory primordium (ventral) with the oesophagus (dorsal).
What is the name of the tissue that divides off the respiratory primordium from the oesophagus?
Tracheoesophageal septum.
Up to 1 in 3000 live birth can have oesophageal abnormalities. Describe what abnormalities can occur.
Consequences of abnormal positioning of the tracheoesophageal septum. The following (individually or in combination):
- Proximal blind-end oesophagus
- Tracheoesophageal fistula (abnormal connection between oesophagus and trachea)
- Distal blind-end oesophagus
In the middle of the fourth week a slight dilation in the distal foregut indicates the position of what?
The stomach primordium.
What side of the stomach primordium creates the greater curvature?
The dorsal border - which has a faster growth.
Name the foregut derived glands.
Liver
Pancreas
Biliary System
Which foregut derived glands are derived from the dorsal mesentery?
Pancreas (superior head, neck, body and tail).
Which foregut derived glands are formed in the ventral mesentery?
Part of the pancreas (uncinate process and inferior head)
Liver
Billiary system
Which is the earliest GI tract associated glands which develops?
The liver