quiz 9 Flashcards
what causes swelling/edema?
- swelling/edema caused by extra fluid in interstitial space
- common reasons:
- vascular damage (leaking)
- increased hydrostatic pressure (damage to area causes greater flow)
where and what is the lymphatic system?
- follows along cardiovascular system; “second circulatory system”
- delivers excess water in interstitial space back to circulatory system
what is the primary driver of water movement across capillaries?
- vascular hydrostatic/osmotic pressure is main driver (high hydrostatic at start; high osmotic at end)
- interstitial pressures have only slight impact
classification of digestive systems based on what organisms eat
- herbivore
- carnivore
- omnivore
monogastric vs polygastric
- carnivores and omnivores (and a few herbivores) are monogastric
- one “true stomach” with acid and pepsin enzymes for digestion
- herbivores are polygastric
- highly specialized stomach components
role of true stomach, small intestine, and large intestine
true stomach: secretes enzymes for digestion
small intestine: absorption of nutrients
large intestine: absorption of water; some nutrients
what organisms can digest cellulose?
- no carnivores
- some omnivores
- all herbivores
herbivore digestive tract
- herbivores have the longest digestive tracts because they are ruminant animals
- the materials they consume take longer to digest before they can be assimilated
differences in dentition between animals
- herbivores have flat teeth for grinding
- carnivores have large/sharp teeth for ripping/tearing/cutting
- omnivores have “leatherman” teeth that are multipurpose
how do we prevent food from being inhaled
- epiglottis is a flap of tissue that closes the trachea while we swallow, preventing aspiration
role of salivary glands
- salivary glands release saliva to lubricate food during mastication
- contain amylase to begin digesting carbs but overall little enzymatic activity
peristalsis
enteric nervous system controls peristalsis movement of bolus down the esophagus
- circular muscles contract behind food mass
- longitudinal muscles contract ahead of food mass, shortening the tube in front of the mass
- circular muscles contract to move bolus forward
*** esophageal problems with age
upper esophageal sphincter: trouble swallowing (opening/closing epiglottis)
lower esophageal sphincter: GERD
what is GERD? what problems does it cause? solutions?
- gastroesophageal reflux disease
- lower esophageal sphincter gets acidic as stomach acid sloshes up
- continued acid washing increases risk of esophageal cancer
- solution: proton pump inhibitors reduce stomach acidity, but reduces pepsin (it needs low pH to activate)
stomach anatomy
- fundus at the top
- body in the middle
- antrum and them pylorus at the bottom
- lumen is made up of gastric glands which have many cell types!
cells in gastric glands
- goblet cells: at top; bicarbonate-rich mucus protects stomach lining from acid
- parietal cells: gastric acid production by proton pumps (active)
- chief cells: produce pepsinogen (protease precursor)
- D cells and G cells: regular acid secretion
importance of acid production in the stomach
- kills bacteria
- gastric juice pH in humans is 2, in some carnivores like vultures it’s 1
- carnivorous birds spit up acidic stomach contents onto talons before feeding on decaying flash, pre-sterilizing them from bacteria
protein digestion in the stomach
- chief cells produce pepsinogen, an inactive protease precursor
- pH in stomach turns pepsinogen into pepsin, which partially digests proteins into small peptide fragments
- important to use inactive precursors because they can be stored/secreted without breaking down proteins in the secretory cell
what is food called in the esophagus vs stomach
esophagus: bolus
stomach: chyme
functions of the pancreas
endocrine functions:
- release insulin from beta cells
- release glucagon from alpha cells
exocrine functions:
- acinar cells release bicarbonate and proteases to duodenum
endocrine vs exocrine
endocrine: release hormones to the bloodstream
exocrine: release material to small intestine lumen via a duct
exocrine role of the pancreas
acidic chyme from the stomach must be neutralized in the duodenum
- low pH stimulates secretin from duodenum cells, which signals acinar cells in pancreas release bicarbonate (base) to neutralize pH
- lipids/fats induce release of cholecystokin (CCK) from duodenum cells which signals release of digestive enzymes (including trypsinogen)
role of trypsinogen
- inactive precursor to a protease released by acinar cells (in response to CCK)
- enzymes in duodenum lining convert it to trypsin
- trypsin activates other inactive precursors for protein digestion (cascade)
*important because more gut absorption is in the duodenum!
role of bile in the duodenum
- bile produced by the liver, stored by the gall bladder
- emulsifies fats (with the help of pancreatic lipase)
- CCK secretion by duodenum (response to fats in chyme) induces release of bile by causing the gall bladder to contract
upper GI tract anatomy
- uvula: blocks off nasopharynx
- nasopharynx
- oropharynx
- laryngopharynx
- epiglottis: covers trachea when swallowing
- salivary glands: parotid, submandibular, sublingual
- upper esophageal sphincter
esophageal anatomy
- circular and longitudinal muscles
- enteric nervous system controls peristalsis
- lower esophageal sphincter
how does bile work on fats?
- bile emulsifies fats with the help of pancreatic lipase
- fats enter duodenum as triglycerides, broken down into monoglycerides and fatty acids
- mix of fats form small droplets called micelles to be absorbed
functions of the large intestine
- absorb water and salts
- produce and absorb vitamins
- form/propel feces
how are different substances absorbed in the small intestine?
- fatty acids and micelles: simple diffusion
- water: osmosis; through aquaporins
- glucose and fructose: SGLT (with sodium) or GluT transporters; both facilitated diffusion
- amino acids or di/tripeptides: active transport
problems with long-term asprin use
- asprin increases acid production from parietal cells and decreases bicarbonate production in mucus layer
- stomach relies on bicarbonate-rich mucus to keep pH 2 away from stomach lining
- long-term asprin use erodes the mucus layer, leading to gastric ulcers
how do our carbohydrate levels fluctuate?
- blood glucose levels vary, but the body attempts to maintain a stable blood glucose level between meals
- absorption of glucose from food raises it, glucose must exit the bloodstream and enter cells to lower it
role of insulin
- high blood glucose after meals promotes the release of insulin
- beta cells in pancreas are always sensing glucose levels; in response to high blood glucose they release insulin which has 2 roles:
- stimulate glucose uptake from blood to cells (triggers reservoir of glucose channels to be put in cell membranes)
- triggers glycogen formation in the liver
binding of insulin ***
- binds to tyrosine kinase receptors, causing them to dimerize (pair)
- dimerization triggers auto-phosphorylation of kinases (using ATP) which can then phosphorylate more receptors or protein targets (kinase activity)
what are kinases?
enzymes that allow you to phosphorylate a target
what does insulin binding do to the cell? (pathway) ***
- insulin binds to tyrosine kinase receptors, activating them to phosphorylate things
- phosphorylation leads to activation of many signaling molecules, which cause different processes
- anabolic events like protein synthesis
- GLUT4 transporters sent to membrane to bring in glucose
what happens to glucose after entering the cell?
- can be burned or stored as glycogen
- osmotic load of cell is reduced when its stored as glycogen compared to glucose (only 1 molecule); stored this way so the cell isn’t fighting the inward movement of water
role of glucagon
- helps regulate blood glucose between meals
- produced by alpha cells in the pancreas; induces glucose release from glycogen stores in the liver
- liver is the only organ that can release glucose into the blood!!
- small amount of insulin also released (needed for glucose uptake into cells)
