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Alcohol-induced liver disease
Alpha 1-antitrypsin deficiency
Benign liver tumors
Cholestatic liver disease
Non-alcoholic fatty liver disease
Primary biliary cirrhosis
Primary sclerosing cholangitis
Pancreatic neuroendocrine neoplasms
Familial adenomatous polyposis
Juvenile polyposis syndrome
Small bowel ischemia and infarction
Protein losing enteropathy
Short bowel syndrome (NORD)
Small bowel bacterial overgrowth syndrome
Diverticulosis and diverticulitis
Irritable bowel syndrome
Cleft lip and palate
Congenital diaphragmatic hernia
Diffuse esophageal spasm
Eosinophilic esophagitis (NORD)
Gastroesophageal reflux disease (GERD)
Cyclic vomiting syndrome
Gastric dumping syndrome
Dental caries disease
Gingivitis and periodontitis
Temporomandibular joint dysfunction
Appendicitis: Pathology review
Cirrhosis: Pathology review
Colorectal polyps and cancer: Pathology review
Congenital gastrointestinal disorders: Pathology review
Diverticular disease: Pathology review
Esophageal disorders: Pathology review
Gallbladder disorders: Pathology review
Gastrointestinal bleeding: Pathology review
GERD, peptic ulcers, gastritis, and stomach cancer: Pathology review
Inflammatory bowel disease: Pathology review
Jaundice: Pathology review
Malabsorption syndromes: Pathology review
Neuroendocrine tumors of the gastrointestinal system: Pathology review
Pancreatitis: Pathology review
Viral hepatitis: Pathology review
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Congenital GI Disorders
Hirschsprung disease p. 391
Hirschsprung disease and p. 391
Down syndome p. 61
in Hirschsprung disease p. 391
Hirschsprung disease is also known as congenital aganglionic megacolon, so Hirschsprung’s is a disease that’s present since birth, in which a ganglion, or cluster of nerves is missing, which ultimately leads to a blocked colon, causing it to enlarge.
Alright, so the intestines move waste through the bowels via peristalsis, which is this series of coordinated wave-like muscle contractions that helps move feces in one direction, and this is essentially automatic, happening without you even having to think about it.
The type of muscle that causes these contractions is smooth muscle, as opposed to skeletal muscle or cardiac muscle.
In the gut, there’s a layer of smooth muscle just under the submucosa, which sits under the mucosa, which is the innermost layer of the gut nearest to the lumen.
On the other side of the smooth muscle layer is the serosa.
Now if we look closer at the smooth muscle layer, it’s actually composed of the circular muscle layer, arranged in circular rings which contract and constrict the gut behind the feces, which keeps it from moving backward, while the longitudinal muscle layer, arranged along the length of the gut, relaxes which lengthens and therefore pulls things forward.
Also though, within these layers are two plexuses, or networks of nerves, which are made up of ganglia—which are clusters of individual nerves, which help coordinate muscle contraction and relaxation.
First there’s the myenteric plexus, also known as Auerbach’s plexus, which when activated, primarily causes smooth muscle relaxation.
The myenteric plexus connects with the second plexus—the submucous plexus, or also known as Meissner’s plexus, which is buried in the submucosa and is responsible for helping to control blood flow and epithelial cell absorption and secretion.
These groups of nerves are clearly super important for normal bowel function.
For people with Hirschsprung’s disease, both these plexuses are gone—they’re completely absent in some parts of the gut. Why is that?
Well during fetal development, there are cells called neural crest cells, which are basically a group of fetal cells that migrate away and differentiate into a variety of different cell types.
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