General Digestive
What are the 3 large components of the small intestine?
duodenum, jejunum, and ileum
Which enzyme breaks down starch in the oral cavity?
beta amylase
What is the stomach pH? What substances contributes to this pH level? How does this help the organism?
-stomach pH: 1-5-2.5
-The HCl secretion regulates this level
-high HCl kills pathogens and converts pepsinogen to pepsin for breakdown of proteins (helps breakdown food)
What does the liver secrete?
secretes bile
What is a gastric bypass?
BONUS: what vitamin becomes deficient and why?
bypass the stomach storage by connecting the gastric pouch to the jejunum
BONUS:
-results in vitamin B12 deficiency so need regular vitamin B12 injections because the stomach is skipped
-results in precarious anemia if vitamin B12 isn't supplemented
What are the accessory digestive organs that secrete substances into the small intestine?
liver, pancreas, and gallbladder
Name the 5 cells in the digestive system
surface mucous cells, mucous neck cells, parietal cells, chief cells, and G-cells
What is the histology of the small intestine?
circular folds of the epithelium increases surface area for absorption
intestinal villi
How is the liver connected to the pancreas and intestines?
bile enters the hepatic duct which branches to the gallbladder for storage and concentration which is then released to the common bile duct and some bile enters the common bile duct directly
What is cirrhosis?
scarring of hepatic tissue
-caused by toxins (like alcohol), hepatitis viruses, and other liver diseases
-will cause jaundice symptoms
What is GLP-1 and what does it do?
BONUS
What do GLP-1 agonists do clinically when given as a medication?
glucagon-like peptide 1
-hormone secreted by the enteroendocrine cells of the small intestine
-increases insulin secretion
-stimulates glucose uptake (similar to insulin)
BONUS
-reduces appetite and gastric function
-GLP-1 agonists are used to treat Type II diabetes and obesity (Wegovy and Ozempic)
Name the cellular components of the small intestine.
BONUS
What are the functions?
simple columnar epithelium: absorb nutrients
Goblet cells: secrete mucous
enteroendocrine cells: secrete hormones (like CCK and secretin)
Paneth cells: secrete lysozyme (enzyme that destroys bacterial cell walls: kills bacteria)
What are the major functions of the large intestines?
-absorb water and NaCl
-commensal bacteria produce certain vitamins and digest the remaining complex carbohydrates
If your tissues have too many lipids, what happens?
the cells package lipids into HDLs and send them to the liver which keeps lipids out of the bloodstream
What is diverticulitis?
pouches called diverticula form in the colon and food gets caught in them and get inflamed (becomes painful)
What are the components and functions of pancreatic juice?
-bicarbonate: raises the pH to a more alkaline pH (~9) in the intestines which prevents infection because pathogens can't survive the switch in pH
-inactive digestive enzymes: pancreatic amylase (digests starch and other carbs), proteases (digests proteins), pancreatic lipases (digests lipids)
What does pancreatic lipase do?
Pancreatic lipase will digest triglycerides (3 FAs and a glycerol backbone) into a monoglyceride (glycerol backbone and one FA) and two free fatty acids
What are the three phases of stomach function? Explain each.
-Phase 1: cephalic phase: your brain stimulates your stomach to contract the muscles and increase secretions which is caused by the sight, smell, and taste of food
-Phase 2: gastric phase: stretch receptors and chemoreceptors detect that there is food in the stomach and stimulate the G cells to secrete gastrin which further stimulates the gastric cell secretions
-Phase 3: Intestinal phase: when chyme (partially digested food) enters the intestines, the intestines secrete CCK and secretin which are hormones that inhibit stomach function (proteins and lipids stimulate the release of the intestinal hormones, not sugar)
What are the other liver functions (apart from metabolism of macromolecules)?
-absorption and breakdown of bilirubin
-storage of excess vitamins and minerals
-detoxifying drugs, alcohol, and other toxins
-breakdown of hormones
What are gall stones?
deposits of bile salts block the bile ducts by associating together and precipitating out of solution
How does glucagon contribute to the return of blood glucose to homeostasis?
-stimulates glycogenolysis
-stimulates gluconeogenesis
-inhibits glycogenesis
The net affect is raising blood glucose levels
-adipose tissue is also stimulated by glycogen to increase lipolysis: this releases fatty acids for breakdown in the liver
How are proteins broken down into amino acids? Describe the role and activation of trypsin.
pancreatic juice includes inactive proteases
-trypsinogen (inactive trypsin) is activated by the brush border enzyme, enteropeptidase, into trypsin
-trypsin: activates other proteases
-these proteases completely break down proteins into individual amino acids
Describe absorption of monosaccarides and amino acids from the lumen to the bloodstream.
-intestinal epithelium have a high concentration of glucose amino acids and low Na+ concentration compared to the intestinal lumen
-transport proteins (symporters) import Na+ and glucose into the intestinal epithelium (use the Na+ gradient to drive transport)
-another symporter brings Na+ and amino acids into the intestinal epithelium (use the Na+ gradient to drive transport)
-passive transporters allow the amino acids and glucose to enter the bloodstream from the epithelium
Explain carb metabolism in the liver. What occurs when blood sugars are high and low?
When blood glucose levels are high,
-Glycogenesis occurs: glucose is converted into a polymer called glycogen which stores glucose (stores 24 hours worth of glucose)
When blood glucose levels are low,
-Glycogenolysis: glycogen stores are broken down into individual free glucose units (which can enter the bloodstrem)
-Gluconeogenesis: The liver also takes other monosaccarides, amino acids, and glycerol and converts them into free glucose
What is Type II diabetes?
BONUS Describe the causes and treatment.
Type II: insulin is produced but the effectors don't respond (insulin resistance: need more insulin for body cells to respond)
BONUS
-often due to chronic high blood glucose and/or excess adipose tissue
-treated with medications that improve insulin receptor function