Embryology of the Gastrointestinal System Flashcards
A 22-year-old woman has noted no fetal movement at 17 weeks gestation. A screening fetal ultrasound shows a midline abdominal wall defect, with bowel contents contained within a membraneous sac. Additional diagnostics indicate extensive blood flow to the herniated bowel. Her serum alpha-fetoprotein is increased. What is the diagnosis?
omphalocele
When does the G.I tract start to develop?
A little behind the cardiovascular system in development
Regional specification of the gut tube into different components occurs when?
As lateral folding brings the 2 sides of the gut tube together
The mammalian primitive gut is an epithelial tube surrounded by what?
Splanchnic mesoderm
As the gut tube matures, what becomes morphologically distinct?
Foregut, midgut, and hindgut
What does mesoderm of the gut tube mature into?
Connective tissue and concentric layers of smooth muscle
The enteric nervous system is responsible for innervating what?
The smooth muscle to promote contractile movements during digestion
The gut differentiates along its ________ axis into distinct ________ organs that have specialized roles in digestion
Anterior/posterior (A/P)
Primary
The gut organ epithelia acquire distinct _______________ to help carry out their digestive functions
Luminal morphologies
In general, organs of the foregut do what?
ingest food and initiate digestion
What generally happens in the midgut?
Digestion is completed and nutrients are absorbed
What generally happens in the hindgut?
Water and ions resorbed and undigested waste is expelled
The basic function of the gut can be only accomplished through what?
The coordinate function of different tissues and organs that comprise the gut
In addition to regionalization, development of the gut tube also involves what?
continuous elongation
herniation past the body wall (into the umbilical cord)
rotation and folding for efficient packing
The gut tube becomes suspended by what?
A 2-layered fold of peritoneum-dorsal mesentery
What are mesenteries?
Reflection of parietal peritoneum onto the gut tube
Most of the gut tube has a _____ mesentery. As part of the development some of the gut will lose it.
Dorsal
In early development the 2 peritoneal cavities (right and left peritoneal diverticulum) are of _________
Equal size
In early development the gut tube is a ____________ structure
Single midline
What are the parts of the foregut?
Esophagus stomach and 1/2 duodenum Liver Gall bladder pancreas *spleen
*not part of the gut tube but can treat it as part of the gut tube
What are the parts of the midgut?
1/2 duodenum jejunum ileum cecum and appendix ascending colon 2/3 transverse colon
What are the parts of the hindgut?
1/3 transverse colon descending colon sigmoid colon rectum upper part of anal canal
What is each gut segment supplied by?
An unpaired branch of the abdominal aorta
Foregut derivatives are supplied by branches of the _____ artery
Celiac
Midgut derivatives are supplied by branches of the _______ artery
Superior mesenteric
Hindgut derivatives are supplied by branches of the _______ artery
inferior mesenteric
How does sympathetic innervation reach the foregut?
The preganglionic cell bodies are T5-T9
The exit the greater splanchnic nerve
Synapse at the celiac preaortic ganglion
Postganglionic axons follow the celiac a.
How does sympathetic innervation reach the midgut?
Preganglionic cell bodies are in T9-T12
They exit the lesser splanchnic nerve
Synapse at the superior mesenteric preaortic ganglion
Postganglionic axons follow the superior mesenteric a.
How does sympathetic innervation reach the hindgut?
Preganglionic cell bodies are in T12-L2
They exit the least splanchnic nerve
Synapse the inferior mesenteric preaortic ganglion
Postganglionic axons follow the inferior mesenteric a
How does parasympathetic innervation reach the foregut and midgut?
Preganglionic cell bodies are from the brainstem
Vagus nerve follows the blood supply to the organs
Location of ganglia: Synapse in the wall of the organs
How does parasympathetic innervation reach the hindgut?
Preganglionic cell bodies are S2-S4
Nerves: pelvic splanchnic nerves
Location of ganglia: organ walls
What is a lung bud?
An inferior outgrowth off of the esophagus that will form into a lung
What divides the lungs from the esophagus during development?
Tracheoesophageal septum
What is the separation of esophagus (gut) from respiratory system?
Laryngeotracheal diverticulum (primordium of respiratory system)
What is trachoesophageal fistula
Improper connection between trachea and esophagus
Esophageal atresia is what type of defect?
Tube of the esophagus is blocked. Loss connection from upper part to lower part of esophagus
What is the most common form (95-95%) of tracheoesophageal?
Upper segment of esophagus ending in blind pouch; lower segment originating from trachea just above bifurcation. The two segments may be connected by a solid cord
What is esophageal stenosis or atresia?
Narrowed or occluded esophagus due to incomplete recanalization, usually found in lower 1/3
What are the majority of esophageal procedures performed in infants/children done for?
Congenital esophageal atresia or acquired caustic strictures
Successful esophageal anastomoses may be performed in those few with “_______” esophageal atresia less than ___ cm between the proximal and distal esophageal remnants using various lengthening techniques
Short gap
3
**Note: in the lecture its written opposite but Dr. cole says it this way…..need to check with professor
_______ esophageal atresia will require esophageal replacement
Long gap
What are the two ways to surgically fix long gap esophageal atresia?
Colon interposition
Gastric transposition/pullup
What is colon interposition?
A section of colon is taken from its normal position in the gut and transposed, with its blood supply intact, into the chest, where it is joined to the esophagus above and the stomach below
what is gastric transposition/pullup?
The whole stomach is freed, mobilized and moved into the chest and attached to the upper end of the esophagus
When the esophagus spirals, the abnormality is called what?
Corkscrew esophagus
What is a congenital esophageal (hiatal) hernia
The upper part of the stomach pushes through the diaphragm and is in the thoracic cavity
What can hiatal hernia cause?
Barrett’s esophagus: acid backing up from the stomach changes esophagus lining
Predisposes people to esophageal cancer
What is esophagitis?
Inflammation caused by acid in stomach
Stomach is formed by the ____ of foregut
dilation