Digestive System Development 1
Terms in this set (83)
How does the embryo fold as it grows?
It folds cephalocaudally, and laterally
What forms the primitive gut?
The part of the endoderm-lined yolk sac cavity that becomes incorporated into the embryo
What portions of the endoderm-lined cavity remain outside of the embryo?
The yolk sac and the allantois
The primitive gut extends from what to what?
From the buccopharyngeal membrane to the cloacal membrane
What do the buccopharyngeal membrane and cloacal membranes consist of?
Tightly adherent ectodermal and endodermal cells
The foregut is the...
... cranial end of the tube
The hind gut is the...
... caudal end of the tube
The midgut is...
... located between the foregut and the hind gut
What part of the gut remains attached to the yolk sac via the vitelline duct?
What are the 4 sections of the gut tube?
1. Pharyngeal gut or pharynx
What is the extent of the pharyngeal gut?
Extends from the buccopharyngeal membrane to the tracheobronchial diverticulum
What is the extent of the foregut?
Extends from the caudal end of the pharynx to the liver bud
What is the extent of the midgut?
Extends from the caudal end of the liver bud to a point between the right 2/3 of the transverse colon and the left 1/3 of the transverse colon
What is the extent of the hindgut?
Extends from the left 1/3 of the transverse colon to the cloacal membrane
What forms the epithelial lining of the digestive tract?
What forms the hepatocytes of the liver and the endocrine cells of the pancreas?
From what is the stroma of glands of the gut tube derived?
From what is the muscle, connective tissue, and peritoneal components of the gut wall derived?
Function of SOX2.
Specifies the esophagus and stomach
Function of PDX1.
Specifies the duodenum
Function of CDXC.
Specifies the remaining small intestine
Function of CDXA.
Specifies the large intestine and rectum
What does the initial patterning of the gut tube depend on?
Interactions between the endoderm and the splanchnic mesoderm adjacent to the gut tube
What initiates endoderm-mesoderm interaction?
Where is sonic hedgehog expressed?
Throughout the gut tube
What is the function of sonic hedgehog?
It up regulates factors in the mesoderm that then determine the type of structure that forms (such as the stomach, duodenum, etc.)
What dictates what type of structure will form in the gut tube?
What becomes mesothelium?
Cells of the somatic mesoderm that line the intraembryonic cavity
What does mesothelium form?
It forms the parietal layer of serous membranes that line the outside of the peritoneal, pleural, and pericardial cavities
What do cells of the splanchnic mesoderm form?
The visceral layer of the serous membranes covering the abdominal organs, lungs, and heart
The visceral and parietal layers of serous membranes are continuous as...
...dorsal mesentery that suspends the gut tube in the peritoneal cavity
What are mesenteries?
Double layers of peritoneum
What are intraperitoneal organs?
Organs suspended by mesentery
What are retroperitoneal organs?
Organs that lie against the posterior body wall and are covered by peritoneum on their anterior surfaces
What are peritoneal ligaments?
Double layers of peritoneum that pass from organ to organ or organ to body wall
The tracheoesophageal septum divides...
...the foregut into a ventral portion (respiratory primordium) and a dorsal portion (the esophagus)
From what is the muscular coat of the esophagus derived?
What innervates the upper 2/3 of the esophagus?
The vagus nerve
What innervates the lower 1/3 of the esophagus (only smooth muscle)?
The splanchnic plexus
Where does the stomach first appear?
As a fusiform dilation of the foregut
How does the stomach move during development?
It rotates 90 degrees around its longitudinal axis
The original left side of the stomach becomes...
... the anterior side
The original right side of the stomach becomes...
... the posterior side
The original posterior side of the stomach becomes the...
... greater curvature (it grows faster)
The original anterior side of the stomach becomes the...
.... lesser curvature
What forms the duodenum?
The terminal part of the foregut and the cephalic part of the midgut
Where is the junction of the two duodenal parts located?
Distal to the liver bud
As the stomach rotates, what does the duodenum form?
A C-shaped loop
What happens to the original lumen of the duodenum?
It is obliterated by proliferating cells in the second month and then recanalized shortly after
What supplies blood to the foregut?
Branches of the celiac trunk
What supplies blood to the midgut?
The superior mesenteric artery
What provides blood to the duodenum?
BOTH the celiac trunk and the superior mesenteric artery
Where does the liver first appear?
Liver primordium appears as an outgrowth of the endodermal epithelium of the distal end of the foregut
What is the outgrowth of the liver primordium called?
The Hepatic Diverticulum or Liver Bud
What does the liver bud consist of?
Rapidly proliferating cells that penetrate the septum transversum
What is the septum transversum?
A mesodermal plate that is found between the pericardial cavity and the yolk stalk
What else does the septum transversum help form?
What forms the bile duct?
The narrowing of the connection with the foregut
A ventral outgrowth of the bile duct becomes what?
The gallbladder and cystic duct
What forms the hepatic sinusoids?
Epithelial liver cords with vitelline veins and umbilical veins
What do liver cords differentiate into?
- Liver parenchyma
- The lining of the bile duct
What does the mesoderm of the septum transversum give rise to?
Hematopoietic stem cells, KUPFFER CELLS, and connective tissue
What parts of the foregut endoderm has the potential to express liver-specific genes and differentiate into liver tissue?
ALL of it, but its blocked by other factors
What is the function of FGF2?
It blocks the action of inhibitors in the prospective hepatic region
What secretes FGF2?
What produces BMPs?
What is the function of BMPs?
Participate in the induction of the liver formation
- appear to enhance the competence of prospective liver endoderm to respond to FGF2
What regulates the differentiation of cells in the liver field into hepatocytes and biliary cell lineages?
Hepatocyte nuclear transcription factor HNF3 and HNF4
What forms the pancreas?
Two buds from the endodermal lining of the duodenum:
- the Dorsal pancreatic bud
- the Ventral pancreatic bud
What happens to the ventral pancreatic duct when the duodenum rotates?
The ventral pancreatic duct moves to lie below the dorsal bud
From what does the main pancreatic duct (of Wirsung) develop?
From the distal dorsal pancreatic duct and all of the ventral duct
What happens to the proximal portion of the dorsal duct?
It is either obliterated or persists as the accessory duct (of Santorini)
What is the function of FGF2 and Activin?
They repress sonic hedgehog expression in the gut endoderm destined to from the dorsal pancreatic duct
What producers FGF2 and Activin?
The notochord and endothelium of the dorsal aorta
What induces the ventral bud?
The master gene for pancreas development!
What specifies the endocrine cell lineage of the pancreas?
PAX4 and PAX6
Cells expressing both PAX 4 and PAX 6 become what type of cells?
- Beta Cells
- Delta Cells
- Gamma Cells
What do Beta cells secrete?
What do Delta cells secrete?
What do Gamma cells secrete?
Cells expressing ONLY PAX6 become what type of cells?
What do Alpha Cells secrete?
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