GI Tract Flashcards
How long is the gi tract?
About 8 long.
What organs make up the GI tract?
Stomach, small and large intestines, pancreas and gallbladder
What is the function of the GI tract?
Efficient digestion and absorption of ingested nutrients
What quantity of food and water enter the small intestine and what quantity reaches the large?
~10mL enters the small intestine and only ~1.5mL reaches the large
What is digestion?
Digestion is the chemical processing of food into absorbable substance
Where does digestion begin?
In the mouth
What are the three phases of the digestive process?
Neurogenic
Gastric
Intestinal
What happens in the neurogenic phase of digestion?
Sight, smell and taste of food stimulates the brain. The brain sends impulses to the stomach via the vagus nerve and this nerve innervates the stomach inducing peristalsis and gastric secretion of HCl and gastrin
What nerve in from the brain stimulates the stomach to release HCl and gastrin?
Vagus nerve
What does the vagus nerve stimulate in the stomach?
Peristalsis and gastric secretion of HCl and gastrin
What is the second phase of the digestive process?
Gastric phase
What phase in the digestive process is initiated by the entry of food into the stomach and stomach distention?
Gastric phase
How is the gastric phase initiated?
By the entry of food into the stomach and stomach stretching.
What is the pH of HCL?
1-2
What cells release HCl? Why?
The parietal cells of the stomach. Due to cell stimulation, stretching and gastrin release
What is the major digestive hormone of the stomach?
Gastrin
What cells release gastrin?
G cells
What is the function of gastrin hormone?
Gastrin causes enzyme and gastric fluid to be released, and the start of stomach motility/churning
This hormone causes enzymes and gastric fluids to be released, and the start of stomach motility.
Gastrin
What is the major digestive enzyme of the stomach?
Pepsin
What cells release pepsin?
Gastric chief cells
This enzyme released by gastric chief cells serve in the hydrolysis of proteins.
Pepsin
Food mixed with gastric fluid is called?
Chime
What phase of the digestive process begins when chime enters the duodenum?
The intestinal phase
What is cholecystokinin (CCK)?
A hormone produced by the intestinal mucosa to stimulate the gallbladder, pancreas and intestinal motility
What is the purpose of secretin?
To neutralize pH
What happens during digestion in the small intestine?
Bile and pancreatic enzymes enter the duodenum to further degrade carbs and proteins, and solubilize fats for absorption into bloodstream.
What intestine absorbs water, sodium and potassium, and contains bacteria to form stool?
Large intestine
What cells produce CCK?
Intestinal mucosa cells
What stimulates the secretion of CCK by the intestinal mucosa cells?
The presence of aa and gastric HCl entering intestine
What are the functions of CCK?
Controls the contraction of the gallbladder
Stimulates pancreas to secrete more digestive enzymes in duodenum
Increase motility of small intestine
List the GI tract hormones.
CCK Gastrin Secretin GIP VIP
What cells produce secretin?
Intestinal S cells
Secretin hormone is produced by S cells of the intestine in response to what?
Increase acid in duodenum
What are the functions of secretin?
- Helps inhibit gastric H+ by stimulating HCO3 secretion from pancreas
- Decrease bile secretion from liver/gallbladder
- Inhibits stomach motility
Gastrin hormone is produced by the G cells in the stomach in response to what?
Distention of stomach and presence of proteins
What are the functions of gastrin?
Aid in gastric motility
Stimulate pancreatic secretions and gallbladder emptying
Stimulate secretion of gastric acid, intrinsic factor to protect Vitamin B12 in stomach
What hormone stimulates secretion of intrinsic factor to protect vitamin B12 in the stomach?
Gastrin
Where is Gastric inhibitory polypeptide secreted from?
Duodenum and Jejenum
What is the function of GIP?
Stimulate insulin release from pancreas
Reduces gastric acid secretion and motility
Where is vasoactive intestinal peptide secreted from?
From entire small and large intestines nervous system
What is the function of VIP?
Smooth muscle relaxation via CNS
Water secretion and electrolyte secretion from pancreas and gut
What is the pancreas?
A highly vascular organ connected to the small intestine that synthesizes hormones (endocrine) and enzymes (exocrine)
What is endocrine?
It is an organ secreting hormones or other products directly into the blood
What is exocrine?
It is glands that secrete their products through duct openings onto an epithelial surface.
What are the main regulators of the exocrine functions of the pancreas?
CCK and vagus nerve
CCK and vagus nerve are the main regulators of what function of the pancreas?
Exocrine function
What does the pancreatic endocrine tissue make?
Hormones
What is the endocrine tissue of the pancreas?
Islets of Langerhans which are composed of alpha, beta and delta cells.
Alpha, beta and delta cells of the pancreas are composed in what?
The islets of Langerhans
What does the pancreatic exocrine tissue make?
Enzymes
What is the exocrine tissue of the pancreas?
Acinar cells with ducts
What do alpha cells do?
They produce glucagon
Glucagon produced by alpha cells of the pancreas serves what purpose?
Stimulates the conversion of glycogen into glucose. Glycogenolysis.
Glycogenolysis is stimulated by what?.
Glucagon produced by alpha cells
What do beta cells do?
They make insulin
Insulin made by beta cells serves what purpose?
Stimulates the formation of glycogen and aids in the entry of glucose into the cells
What do delta cells produce?
Somatostatin
What is the purpose of somatostatin produced by delta cells of the pancreas?
Reduces acid production in stomach and motor activity of intestines, releases pancreatic digestive enzymes
What hormone releases pancreatic digestive enzymes?
Somatostatin produced by delta cells
What cells are responsible for the exocrine function of pancreas?
Acinar cells
What two analytes are used to diagnose pancreatitis?
Amylase
Lipase
List the enzymes made by acinar cells?
Amylase
Lipase
Trypsin
Elastase-1
What enzyme breaks down starches and glycogen?
Amylase
What is the function of the enzyme amylase?
Breaking down starches and glycogen
What enzyme hydrolysis fats especially triglycerides to produce free fatty acids?
Lipase
What does lipase do?
Hydrolyzes fats, mainly triglycerides in order to produce free fatty acids
What enzyme breaks down proteins?
Trypsin
What does elastase-1 do?
Hydrolyzes proteins elastin and collagen
What are the symptoms in someone’s with peptic ulcer disease?
Burning pain Bloating Belching Fatty food intolerance Heartburn Nausea, trouble breathing
What is peptic ulcer disease?
Defect in intestinal mucosa or stomach lining
What factors can be responsible for the development of peptic ulcers?
Bacteria H. pylori
Acid production from bicarbonate drugs or Z-E syndrome
Drugs; regular use of NSAIDS/ dry swallowing
Smoking/alcohol
Stress
Spicy foods
Genetics
List the lab analysis methods for ulcers.
Endoscopy
Blood testing
Fecal testing
Breath testing
What enzyme does the bacteria H. pylori produce that helps with the breathing test?
Urease that breaks down urea
How does the breath test work?
A person contaminated with HP will have a breath sample containing radioactive carbon in the form of CO2 after given a food or drink containing urea with radioactive carbon isotope
What is Zollinger-Ellison syndrome?
This is extreme elevation in serum gastrin levels from gastrin secreting tumor; gastrin a from stomach, pancreas or duodenum which causes greatly elevated gastric HCl from parietal cells and numerous ulcers in stomach and duodenum
What cells secrete intrinsic factor?
Parietal cells of the stomach
What does intrinsic factor do?
Protects vitamin B12 in acidic environments
AIDS in B12 absorption
What is pernicious anemia?
Autoimmune disorder characterized by anemia due to lack of B12 secondary to intrinsic factor deficiency
Why does lack of B12 cause anemia?
Vitamin B12 is important for DNA synthesis and impaired DNA synthesis causes megaloblastic anemia
What is celiac disease?
This is an autoimmune response to gluten which results in intestinal inflammation, shortening of the villi that lines the small intestine causing poor absorption of nutrients and diarrhea.
What causes lactose intolerance?
Hereditary links
Acquired through age
How is lactose intolerance tested?
Measurement of breath hydrogen
Serum/plasma measurement of glucose
How does hydrogen breath test determine lactose intolerance?
Increased hydrogen in breath identifies LI
What is inflammatory bowel disease?
Chronic inflammation of some part of the GI tract.
Name two inflammatory bowel diseases.
Crohn’s disease
Ulcerative colitis
What is Crohn’s disease?
Chronic inflammation of the small intestine usually but can be anywhere from mouth to anus in which damaged areas appear in patches that are next to areas of healthy tissues.
What is ulcerative colitis?
Chronic inflammatory of the large intestine only in which damaged areas are continuous and not patchy, usually starting at the rectum and spreading further into the colon. Inflammation present only in the innermost layer of the lining of the colon
What is the disease in which there is inflammation of the large intestine starting from rectum going into the colon with inflammation present only in the innermost lining of the colon
Ulcerative colitis
What disease is the most common lethal defect in white/European ancestry?
Cystic fibrosis
What is cystic fibrosis?
An autosomal recessive disorder with dysfunctional exocrine glands throughout the body (sweat, pancreas, lung, saliva)
What gene is mutated in cystic fibrosis?
CFTR
What causes death in cystic fibrosis patients?
Pneumonia and intestinal malabsorption
What test is made to diagnose cystic fibrosis?
Sweat tests where sweat electrolytes are tested using pilocarpine nitrate to stimulate sweating and measure chloride which is elevated in CF patients
What electrolyte is elevated in CF patients?
Chloride
What is pancreatitis?
Inflammation of the pancreas associated with alcohol abuse, DM, gallbladder disease or lipid disorders
What is the major cause of inflammation in pancreatitis?
Tissue damage caused by pancreatic enzymes leaked into pancreatic tissue
What is the end the acute and chronic phase of pancreatitis?
In acute phase, there’s severe pain and elevated pancreatic enzymes in serum while in chronic phase, there’s compromised digestion, malabsorption, hyperglycemia, and elevated enzymes although not as high as in acute phase.
What is the most specific marker of acute pancreatitis?
Lipase
List tumors of the pancreas
VIPoma
Insulinoma
Glucagonoma
Pancreatic carcinoma
What is the most common pancreatic tumor?
Pancreatic carcinoma
What is pancreatic carcinoma?
Tumor of the pancreatic duct, leading to destruction of pancreas, obstruction of bile duct.
The following tests are lab analysis of GI disorders.
Breath test for HP
Ab test from serum/plasma
Ag test from stool
Lactose intolerance test (fasting blood glucose after two hours)
Pancreatic enzymes (lipase and amylase)
CF chloride sweat test
Gastric fluid analysis, plasma gastrin analysis, fetal fat, elastase in stool
