What 2 organs are primarily responsible for water absorption?
1. Small intestines
2. Large intestines
What are the main functions of the stomach
1. Store ingested food
2. Disruption of chemical bonds in food through the action of acid and enzymes
3. Mechanical breakdown of food
4. Production of intrinsic factor needed for absorption of vitamin B12
What are the 3 types of cells found in the stomach and what substances do they secrete?
1. G cells: Gastrin (reduces pH of gastric juice and stimulates motility)
2. Chief cells: pepsinogen (converts to pepsin in acidic environment of stomach to break apart peptide bonds in proteins)
3. Parietal cells: intrinsic factor and HCl (H2CO3 dissociates, HCO3- is transported out/Cl- transported in, Cl- diffuses across cell membrane and H+ is transported out, results in HCl inside the stomach)
Where is the hormone cholecystokinin (CCK) found and what does it do?
1. Produced by enteroendocrine cells in the duodenum
2. Secreted when chyme arrives in the duodenum (especially lipids and partially digested proteins)
3. Increases the secretion of pancreatic enzymes
4. Relaxes hepatopancreatic sphincter, contracts gallbladder to eject bile and pancreatic juice into the duodenum
Where is the hormone gastrin found and what does it do?
1. Secreted by G cells in the stomach and duodenum when exposed to incompletely digested proteins
2. Increases stomach motility
3. Stimulates production of gastric acids and enzymes
Where is the hormone secretin found and what does it do?
1. Released in the duodenum when chyme is present
2. Increases the secretion of bile and buffers that act to increase the pH of the chyme
3. Reduces gastric motility and secretory rates
Where is the hormone gastric inhibitory peptide (GIP) and what does it do?
1. Secreted in the duodenum when fats and carbs (glucose) enter the small intestines
2. Inhibits gastric activity and stimulates the release of insulin
3. Stimulates duodenal gland activity, synthesis of adipose tissue and increases glucose use by skeletal muscles
Where is the hormone vasoactive intestinal peptide (VIP) and what does it do?
1. Secreted in the duodenum
2. Stimulates the secretion of intestinal glands, dilates regional capillaries, and inhibits acid production in the stomach
3. Dilation provides an efficient mechanism for removing absorbed nutrients in the intestinal tract
Where is the hormone enterocrinin found and what does it do?
1. Secreted in the duodenum when chyme enters
2. Stimulates mucin production by the submucosal glands
What are the 3 phases of gastric secretion?
1. Cephalic phase
2. Gastric phase
3. Intestinal phase
What happens during the cephalic phase of gastric secretion?
1. Prepares stomach for the arrival of food
2. Begins when you see, smell, taste or think of food
3. Generally lasts only a couple minutes
What happens during the gastric phase of gastric secretion?
1. Stomach secretes juice and mixes food into chyme
2. Initiated by distension of the stomach, increased pH of gastric contents and presence of undigested material
3. Generally lasts 3 to 4 hours
What happens during the intestinal phase of gastric secretion?
1. Stomach empties and decreases secretions
2. Controls the rate of gastric emptying to ensure that secretory, digestive and absorptive function of the small intestine can proceed efficiently
What are the 2 central gastric reflexes?
1. Gastroenteric reflex: stimulates motility and secretion along the entire small intestine
2. Gastroileal reflex: triggers the opening of the ileocecal valve, allowing materials to pass from the small intestine to the large intestine
What is rugae and what is its function in the stomach?
1. Prominent folds in the mucosa
2. Allows the gastric lumen to expand when you eat
3. Stomach can stretch up to 50x its empty size
4. As stomach fills, rugae flatten out until they almost disappear at maximum distension
What is the function of the pyloric sphincter and where is it located?
1. Located at the distal end of the pylorus separating the stomach from the duodenum
2. Regulates gastric emptying into the duodenum
What is the duodenal ampulla and where is it located?
1. Chamber located about halfway along the length of the duodenum
2. Receives bile from liver and pancreatic secretions through the pancreatic duct and the common bile duct
What are the endocrine and exocrine portions of the pancreas?
1. Endocrine: Pancreatic islets, release insulin or glucagon into the blood
2. Exocrine: Pancreatic acini, secrete pancreatic juice into small intestines (alkaline mixture of water, ions and digestive enzymes)
Which part of the small intestine is most likely to develop a gastric ulcer from exposure to gastric juice?
2. Because it receives chyme with a pH of 1-2
HCl in the stomach is neutralized by what in the small intestine?
Sodium bicarbonate in the pancreas
What is pancreatic juice and what does it do?
1. An alkaline mixture of digestive enzymes, water and ions
2. Released into the small intestines through the pancreatic duct
3. Breaks down carbohydrates, lipids and proteins
What are the pancreatic enzymes?
1. Pancreatic alpha amylase (carbohydrase): breaks down starches similar to salivary amylase
2. Pancreatic lipase: break down certain complex lipids, releases products that can be easily absorbed
3. Nucleases: break down RNA and DNA
4. Proteolytic enzymes: break apart certain proteins, includes proteases for large complex proteins and peptidases for small peptide chains
What are the multiple characteristics of serosa of the intestinal wall?
1. Contributes to the mesentery of the small intestine
2. Part of the visceral peritoneum
3. Composed of simple squamous epithelia
What are the 3 distinctive physical characteristics of the colon?
1. Haustra: pouches that allow the colon to expand and elongate
2. Taeniae Coli: 3 longitudinal bands of smooth muscle, muscle tone in the taeniae coli create the haustra
3. Epiploic (fatty) appendages: teardrop sacs of fat lining the serosa
What is the digestive function of lacteals?
1. Lymphatic vessels
2. Transport products of fat digestion
What is the absorptive state of digestion?
1. The period following a meal when nutrient absorption is underway
2. Liver cells form glycogen
3. Absorbed nutrients are used for growth, maintenance, and energy reserves
What is the post absorptive state of digestion?
1. The period when nutrient absorption is not underway
2. The body relies on internal energy reserves for energy demands
3. Liver cells conserve glucose and break down lipids and amino acids
4. Lipid and amino acid catabolism generates acetyl-CoA
5. Increased concentration of acetyl-CoA results in the formation of ketone bodies
What happens in your body as a result of starvation?
1. Muscle proteins and lipids are used as energy sources
2. Lipid and amino acid catabolism generates acetyl-CoA which forms ketone bodies
3. Ketone bodies dissociate in solution releasing hydrogen ions
4. results in ketonemia
What are ketonemia and what complications does it cause?
1. The appearance of ketone bodies in the blood
2. Lowers blood pH and causes ketoacidosis
3. Blood pH can fall to as low as 7.05 resulting in coma, cardiac arrhythmias and death