Module 1: Anatomy and Physiology Flashcards
Dr. Covert
What are the organs of the GI tract?
-Mouth - chewing, hydrolysis, create a bolus
-Esophagus - muscular tube, food transport
-stomach - hydrolysis, churning, storage, making chyme (fluid form of the food)
-small intestine: duodenum, jejenum, illeum
-large intestine (colon): hydrolysis, absorption
-Rectum: storage before passing
-Anus: expulsion
Functions of the stomach
churning, breaking down the bolus
-hydrolysis: enzyme-mediated breakdown
-resulting in a chyme: mix of broken-up bolus and the enzymes
-storage of chyme until it is appropriate to the duodenum (4l storage)
Anatomy of the stomach
-stomach lining consists of pits increasing the surface area
-with a layer of parietal cells : secreting gastric juice (HCl-)
-also chief cells: secreting the pro-cursor-enzyme pepsinogen (-> pepsin performing hydrolysis)
How is pepsinogen converted into pepsin?
with HCl, secreted by parietal cells
pepsin breaks down proteins
What protects the stomach from the acidic gastric juice?
-mucous cells releasing mucin
-bicarbonate
-protection from HCl and pepsin enzyme
Functions of the liver
-metabolism of nutrients (catabolism/anabolism)
-storage of nutrients (carbs, fats)
-breakdown or usage of proteins (proteins are transported via albumin in the bloodstream)
-Detoxification CYP450: modify toxins to prevent harm to the body
-bile production: absorption of fats from the food
In which forms are nutrients stored?
-Glycogen
-Lipoproteins
-Triglycerides (one of the forms of fat we ingest in our food)
How does the liver have access to nutrients?
-portal vein: nutrients get absorbed in the intestine -> portal vein -> supplies the liver with nutrient-rich blood
-proper hepatic artery: O2-rich blood
-hepatic vein: nutrient and O2-poor blood leaving the liver -> to the heart to replenish O2 again -> passes the intestines to receive nutrients again
How does bile leave the liver?
common hepatic duct
Layers of the mucosa of the GI tract
-Epithelial layer: absorbs and secrets mucus and digestive enzymes
-Lamina propria: contains blood and lymph vessels
-muscularis mucosa: smooth muscles contracting -> breakdown of food
What are the 4 regions of the stomach?
-Cardia
-Fundus
-Body
-Pyloric Antrum
-Pyloric sphincter: closes while eating, keeping food inside the stomach to digest
epithelial cells in different parts contain different proportions of glands
Which type of cells are mostly present in the Cardia?
Foveolar cells: secrete mucus (Glycoproteins, water)
Which part of the stomach mostly contains parietal and chief cells?
-Fundus
-Body
parietal cells -> secret gastric juice (HCl-)
chief cells secrete pepsinogen
Which cells are mostly present in the Antrium?
G cells: secreting gastrin -> stimulates parietal cells to secret HCl, and stimulates the growth of glands in the epithelial layer
-gastrin is also found in the duodenum and pancreas
What are Brunner glands?
-in the duodenum
-secrete mucus -> containing bicarbonate ions to neutralize the acid in the stomach and the duodenum
Function of Prostaglandins
-stimulate mucus and bicarbonate secretion (protection)
-vasodilation of nearby blood vessels -> allowing more blood flow for epithelial cell growth, inhibits acid secretion
How does H. pylori cause gastric and duodenal ulcers?
-they colonize the mucosa and adhere to Foveolar cells
-secrete protease damaging the mucosal cells
How do NSAIDs cause ulcers?
-more in the stomach than in the duodenum
-inhibits COX enzyme involved in the prostaglandin production
-over time it decreases the protective effect of prostaglandin
Zollinger-Ellison Syndrome
-Tumor: Gastrinoma (neuroendocrine tumor)
-in the duodenal wall or pancreas
-secretes abnormal amount of gastrin -> stimulates parietal cells to secrete HCl-
-> Ulcers in the duodenum, distal duodenum, jejunum
Complications of Duodenal Ulcers
Brunner Glands Hypertrophy
-to produce more mucus to protect the damaged area
What causes an Ulcer to bleed
Erosion of the Ulcer into an underlying blood vessel
-dangerous when eroding into arteries: left gastric artery, gastroduodenal artery -> blood loss -> SHOCK
Complication of Perforation
-Ulcer erodes through the cell wall -> allowing stomach content to enter the peritoneal space (sterile)
-air starts to collect under the diaphragm -> irritating the nerve -> pain in the shoulder
Ulcers near the pyloric sphincter
-rare
-edema and scarring lead to an obstruction of the normal passage of gastric content into the intestine -> Gastric outlet obstruction
-leads to nausea and vomiting
Symptoms of Ulcers
-Epigastric pain, Bbloating, Belching, vomiting
Gastric Ulcer:
-pain when eating due to the presence of food and HCl production - associated with weight loss
Duodenal Ulcer
-less pain when eating - associated with weight gain
Study-guide questions
What is peristalsis?
wave-like muscle contraction in the esophagus, stomach, and intestines to move the food
Function of water in the stomach
-dilution of acid
-activation of enzymes: pepsin
-hydration of the stomach
Function of secretin
secreted by S cells in the duodenum
-pancreas: stimulates bicarbonate secretion into the duodenum
-pancreas: stimulates enzyme production: lipase, amylase, protease -> nutrient breakdown
-stomach: inhibits gastric acid production
-gallbladder: stimulation of the gallbladder to secrete bile -> emulsify fats (more accessible for enzyme for breakdown and absorption)
What are the parts of the colon?
-Cecum
-Ascending Colon
-Transverse Colon
-Descending Colon
-Sigmoid Colon
-Rectum
-Anus
