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THE MCAT-BIO 4
DIGESTION AND EXCRETION
| Question | Answer |
|---|---|
| Digestive tract from start to finish | mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus |
| alpha-amylase | break down starch |
| relationship between pharynx, larynx, and trachea | -pharynx-connect inner nose to throat -larynx-below pharynx that has vocal cords -trachea - below larynx that leads to lungs |
| epiglottis | separates pharynx and larynx to prevent food from entering respiratory tract |
| Describe musculature of esphagus | -starts with striated and ends with smooth (voluntary and involuntary mvmt) |
| cardiac sphincter (lower esophageal) | allows food to pass from esophagus to stomach |
| mucus cells | produce epithelial lining made of sticky glycopx and electrolytes |
| chief cx | secrete pepsinogen |
| function of pepsinogen | digest px |
| parietal cx | -secrete HCl -secrete intrinsic factor |
| Function of HCl in digestion? | -lower pH of stomach and raise pH of blood -kill bacteria -break down intracx bond of food -activate pepsinogen --> pepsin |
| G-cx | secrete gastrin |
| What does gastrin do? | -stimulates parietal cx to secrete HCl -mix stomach contents to produce chyme |
| Function of intrinsic factor in digestion? | helps ileum absorb vitamin B12 |
| How does acetylcholine affect secretion of stomach juices? | increases secretion of all cx types |
| How does gastrin / histamine affect secretion of stomach juices? | increases HCl secretion |
| gastric juice made of? | HCl, pepsinogen, mucus, intrinsic factor, gastrin, BICARBONATE (think homeostasis!) |
| Function of bicarbonate in digestion? | protects mucosa lining |
| ulcer | portion of mucosal lining digested and hole forms |
| What does sphincter connects stomach to small intestine? | pyloric sphincter |
| Where does most digestion occur? most absorption? | -digestion: duodenum -absorption: jejunum and ileum |
| Lining of small intestine is covered with what? | villi |
| What is inside each villi? | capillary network and lymph vessel (lacteal) -some nutrients go into capillary and some into lymph vessel |
| What covers villi? | Microvilli (brush border) aka enterocytes |
| What does brush border have? | -mem-bound digestive enzymes -goblet cx that produce mucus for protection |
| Cryptes of LIeberkunn-where and what does it do? | -located deep between villi -secrete intestinal juice with pH 7.6 and lysozyme |
| lysozyme | regulates bacteria within intestine |
| When food first enters duodenum, what is released? | Cholecystokinin (CCK) |
| What does CCK do and what is it released in response to? | -Causes gallbladder, liver, and pancreas to release substances into duodenum -inhibits gastric emptying and gastric acid secretion -px or fat rich chyme |
| What does pancreas release? | Trypsin, chymotrypsin, amylase, lipase, ribonuclease, deoxyribonuclease |
| What is the pH inside duodenum? | pH = 6 because of bicarbonate |
| Secretin | causes release of pancreatic juice from pancreas |
| What is pancreatic juice? | enzymes in bicarbonate solution |
| At what pH are pancreatic enzymes most active? | 8.5 |
| enterokinase | activates trypsinogen --> trypsin |
| What is importance of trypsin? | activates all other zymogens |
| In what form are peptidases released from pancreas? | zymogens |
| What are examples of pancreatic peptidases? | trypsinogen, chymotrypsinogen, elastinogen, carboxypeptidase |
| What is the exocrine fxn of pancreas? | -secrete pancreatic juice into small intestines -release enzymes from acinar cx through pancreatic duct |
| What is endocrine fxn of pancreas? | releases insulin and glucagon directly into blood |
| How is bile released? | bile stored in gallbladder --> joins with common bile duct --> joins pancreatic duct --> duodenum |
| Where is bile produced and where is it stored? | produced by liver and stored in gallbladder |
| What is bile made of? | bile salts, bile pigments, cholesterol |
| How is bile released? | released in response to hx CCK |
| What is pH of bile | 7.5-8.8 to neutralize acid chyme |
| Why are bile salts important? | hydrolyzes ester bonds to increase SA of fats |
| Does bile breakdown fats? | NO |
| Where does bile go after it has done its job? | reabsorbed by small intestine and transported back to liver |
| Where does bile get its color? | bilirubin (end product of hemo degradation) |
| 2 main functions of large intestine? | 1. water absorption 2. electrolyte abosrption |
| 3 major sections | cecum, colon, rectum |
| cecum | connects small and large intestine -also has appendix |
| colon | absorbs salt and water |
| rectum | storage for feces |
| anus | -where waste is eliminated -has voluntary and involuntary sphincters |
| What gives rise to anus? | blastopore |
| What is function of e.coli in large intestine? | metabolize fiber, produce vitamin K, B12, thiamin, riboflavin |
| Why do most fats bypass liver? | -directly enter circulation w/o going to hepatic portal |
| Where do carbs and a.a. go before they are released to rest of body? | hepatic portal circulation |
| What happens after absorbed fats absorbed through intestinal wall? | -fats reform into triglycerides at smooth ER |
| What happens after absorbed fats are reformed to triglycerides? | packaged into insoluble chylomicrons that enter lymphatic circulation through lacterals |
| What do chylomicrons do? | chylomicrons enter venous circulation and stick to capillary walls and combine with lipoprotein lipase |
| lipoprotein lipase | hydrolyzes triglyercides in the bloodstream --> products of hydrolysis are taken up by liver and repackaged into HDL, LDL, etc. |
| Between meals, 95% of protein is in the form of? | lipoprotein |
| VLDL | transport triglycerides from liver to adipose tissue |
| LDL | transport cholesterol / phospholipid |
| Lacteals converge and dump contents into ___________ that then enters systematic circulation. | thoracic duct |
| What happens to proteins and carbs? | absorbed by blood and taken up by cx (esp. by liver) |
| What causes allergic rxn? | any protein that is not completely broken down |
| What happens inside cx with a.a.? | cx immediately creates px from a.a. so intracell a.a. concentration stays low |
| What happens when cx reach upper limit for px storage? | -a.a. are burned for energy -a.a. are converted to fat for storage |
| Calorie rate for proteins, carbs, fats? | -px - 4 -carbs - 4.5 -fats - 9 |
| How are proteins transported into cell? | transported down conc. gradient of sodium |
| gluconeogenesis | creation of glucose / glycogen in liver from a.a., glycerol, lactic acid |
| What is byproduct of gluconeogenesis? | ammonia |
| How to get rid of ammonia? | liver converts ammonia to urea and excreted in urine by kidney |
| What causes secretin release? | HCl in duodenum -causes bicarbonate release from pancreas (natural antacid) |
| What is main fxn of stomach? | stores food and releases a little at a time to be digested |
| How is glucose transported with sodium into cell? | -sodium is pumped out of enterocyte -resulting low sodium drags sodium and glucose from outside to inside |
| All carbs absorbe din blood are carried to? | liver! |
| Most carbs are turned into? | glycogen --> too full? --> fat |
| What enzymes does small intestinal mucosa release? | maltase, lactase, sucrase, peptidase, dipeptidase, secretin, CCK |
| What enzymes does stomach release? | HCl, pepsinogen, mucus, bicarbonate, water, intrinsic factor, gastrin |
| What does pancreatic juice release? | trypsin, chymotrypsin, amylase, lipase, ribonuclease, deoxyribonuclease |
| secretin vs. CCK | -secretin released in response to H+ and causes pancreatic juice release -->bicarbonate release -CCK released in response to fats/px and causes pancreatic juice and bile release |
| Where is bile derived from? | cholesterol |
| Role of liver and fats | breaks down fats, makes cholesterol, makes lipopx |
| Role of liver and vitamins | stores vitamins B12, A, D and iron |
| Role of liver and detox | metabolize alcohol, transform ammonia --> urea, remove toxins |
| Structure of liver and where does ducts drain to? | -largest gland in the body -duodenum and gall bladder |
| Active transport for glucose. Intestinal lumen has ____ glucose while enterocyte has ______ glucos. | low / high |
| Facilitated diffusion for glucose. Enterocyte has ______ glucose while extracx fluid has _____ glucose. Glucose will enter ______ | high / low / bloodsream |
| Why is bicarbonate from pancreas important for neutralizing acidic chyme? | enzymes would be denatured |
| Does large intestine have folds or villi? | NO |
| Anal sphincter | at end of rectum |
| Name all sphincters | cardiac, pyloric, anal |
| Where does urine go once its made in kidneys? | kidney - calyces - renal pelvis - ureter - bladder - urethra |
| What are 5 parts of nephron? | glomerulus, proximal convoluted tubule, descending and ascending LOH, distal convoluted tubule, collecting duct |
| What is function of kidneys? | 1. excrete wastes 2. maintain homeostasis 3. control plasma pH |
| Glomerulus is surrounded by? | Bowman's capsule |
| renal corpuscle? | glomerulus + bowman's capsule |
| What forces plasma through fenestrations into Bowman's capsule? | hydrostatic pressure |
| How much of blood that passes through glomerulus passes into Bowman's capsule? | 20% |
| What does glomerulus retain and what passes through? | -erythrocytes and plasma px -water, electrolytes, organic solutes (low MW), urea |
| Where does blood go that didn't pass into Bowman's capsule? | efferent arterioles and then vasa recta |
| Where does major reabsorption and secretion take place? | Proximal convoluted tubule |
| What happens in proximal convoluted tubule? | -reabsorb all nutrients,px, and most ions -secrete wastes |
| What does PCT secrete? How does it secrete hydrogen ions? | -ammonia, toxins, hydrogen ions -secrete through an antiport system with sodium |
| What does PCT reabsorb? | glucose, proteins, sodium, calcium through secondary active transport |
| transport maxima | concentration of solute that saturates transport px -when transport max reached, any non-absorbed solute will go into urine |
| What is result of teh PCT? | reduce amount of filtrate while changing solute composition without changing osmolarity |
| How is water reabsorbed in the PCT? | across tight junctions |
| What do diuretics do? | -help body get rid of excess fluids -inhibit reabsorption of sodium |
| What are the 2 types of arterioles in the kidneys? | -afferent - lead to glomeruli -efferent - lead to vasa recta |
| How does LOH differ from PCT in terms of secretion and absorption? | more specific |
| ascending LOH and type of transport | permeable to salt not water - reabsorption of salt -salt passively diffuses out and then actively |
| descending LOH and type of transport | permeable to water not salt - reabsorption of water -water passively diffuses out |
| Where is kidney cortex and what does cortex contain? | -outer shell of kidney -contains convoluted tubules |
| Where is kidney medulla and what does it contain? | -inner part of kidney -LOH |
| What is function for distal convoluted tubule? | -aldosterone acts here to reabsorb sodium and secrete potassium -PTH acts here to reabsorb calcium |
| What is function of collecting ducts? | -ADH acts here to reabsorb water -urea recycling -reabsorb / secrete various ions |
| Regulation of blood pH in kidneys? | -secrete H+ when blood too acidic -secrete bicarbonate when blood to basic |
| Countercurrent multiplier mechanism | -creates osmotic gradient down LOH for collecting duct to concentrate urine |
| What drives creation of countercurrent gradient? | -sodium pump on ascending limb |
| What's the multiplier in the countercurrent multiplier mechanism? | -longer the LOH, more each individual NaCl pump multiplies down length of LOH, more concentrated urine can be produced |
| In the ascending limb, sodium is actively diffused out but chloride ______ diffuses out. | passively |
| The collecting duct goes from the ______ to the ________ | cortex to medulla |
| Urea recycling | urea diffuse out of collecting duct back into LOH to help maintain osmotic gradient |
| What releases Aldosterone? | adrenal cortex in response to decrease in blood pressure |
| What does aldosterone do? | -increases ability of distal tubule to reabsorb sodium -increases blood pressure -increases potassium secretion |
| What does ADH do? | collecting duct becomes permeable to water |
| afferent arterioles constrict, GFR increases / decreases. efferent arterioles constrict, GFR increases / decreases. | - decreases -increases |
| High hydrostatic pressure forces water out / in. High osmotic pressure forces water out / in. | - out - in |
| What happens when you have diarrhea in terms of acid/base homeostasis? | metabolic acidosis |
| How can kidney help metabolic acidosis? | -decrease in pH stimulates DCT to secrete hydrogen and reabsorb as much bicarbonate as possible |
| Juxtoglomerular apparatus | juxtoglomerular cells and macula densa cells |
| What do j.g. cells sense and macula densa cells sense? | -j.g. - sense change in BP -macula dense - sense changes in sodium concentration |
| When sodium concentration goes down in distal tubule, macula densa cells stimulate _____ secretion by j.g. cells | renin |
| What does renin do? | converts angiotensinogen --> angiotensin 1 |
| What does angiotensin 2 do? | increases aldosterone secretion |
| What should ultimately be foudn in urine fluid? | urea, uric acid, sodium, potassium, magnesium, calcium |
| What SHOULD NEVER be in urine? | blood, protein, glucose |
| All blood received by liver will move to? | vena cava |
| What oxygenates the liver? | hepatic artery |
| Where do all nutrients absorbed as well as blood from all other organs travel through? | hepatic portal vein |
| Where are most erythrocytes destroyed? | spleen |
| Where is albumin, prothrombin, and fibrinogen produced? | liver |
| When liver metabolizes fat/proteins for energy, blood acidity ______ | increases |
| What are 2 principal parts of skin | epidermis and dermis |
| epidermis and what is it made of? | -avascular epithelial tissue -stratified squamous epithelial tissue |
| dermis | vascular connective tissue derived from mesodermal cells |
| ADH is also called? | -vasopressin -causes vasoconstriction |
| What is atrial natriuretic peptide and where is it released? | -released from heart -antagonizes aldosterone and causes kidney to release more sodium and water |
| ANP vs. ADH | -vasodilation -vasoconstriction |
| blood osmolarity is determined by _______ | Na Cl |
| what does PTH regulate in kidneys? | calcium absorption and phosphate excretion |
| How are amino acids excreted in kidneys? | amino acids --> ammonia --> urea --> peed out |
| What does the renin-angiotensin pathway respond to? | low blood pressure |
| What does ANP respond to? | high blood pressure |
| Vasoconstriction / dilation when too cold? Too hot? | -vasoconstriction of arterioles decrease blood supply -vasodilation of arterioles increase blood supply |
| What does salt excrete? | -salts -nitrogenous wastes |
| How does hair help insulate the body? | traps air in them |
| Where is fat layer located in skin? | hypodermis |
| Where are sweat glands, blood vessels, and hair follicles located? | dermis |
| What is function of keratin? | -protect against abrasion -waterproof seal -block out pathogens |
| Where is keratin found? | nail, skin, hair |
| How does sweat provide chemical protection? | sweat is acidic and contains antibodies and antimicrobial agents |
| What are benefits of natural flora? | fight of bad bacteria |
| keratinocytes and how are they produced? | -cells that produce keratin -start off like normal cells at bottom of epidermis, get flatter as you go up, and become dead keratin plates at surface |
| melanocytes | cells that make melain |
| Langerhans cells | phagocytes that eat pathogens |
| What is found in epidermis? | keratinocytes, melanocytes, Langerhans cells |
| What is found in dermis? | fibroblasts, hair follicles, sweat glands, oil glands, blood vessels |
| fibroblasts | make fiber and "glue" for extracx matrix that makes up connective tissue |
| Why is skin relatively impermeable to water? | layer of dead, keratin-packed cells sealed with glycolipids -skin oil contributes to some (glands not present in palms and soles) |
| What is the source of energy that forces fluid into capsular space? | blood pressure from heart |
| What would happen if heart stopped with GFR? | fluid in space around glomerulus would flow back into capillary blood |
| Low BP allows for ______ time for GFR | decreased |
| In proximal convoluted tubule, filtrate is _______ to surrounding interstitium | isotonic |
| Tm = | tubular transport maximum |
| What is the major osmoregulatory px in blood? | albumin |
| What is part of the excretory system? | skin, lungs, kidney |
| What is part of the digestive system? | mouth to anus |
| Why are micelles circular? | to minimize exposure to hydrophilic surfacs |
| What makes up the kidney filter system? | glomerulus and Bowman's capsule |
| What is the normal volume of urine? | 1-2L |
| What is the shortest part of the small intestine? | duodenum |
| Where does most absorption occur? | jejunum and ileum |
| What is the beginning of the large intestine? | cecum |
| Describe path of glucose and a.a. during filtration. | Glucose and a.a. are freely filtered and then reabsorbed by PCT and returned to circulation |
| What stimulates aldosterone? (particle) | angiotensin II |
| What does dehydration cause in kidneys and hypo? | release of renin from kidneys and stimulation of osmorx in hypo |
| Where is appendix located? | near cecum (jxn of small intestine and large intestine) |
| What are fat-soluble vs. water-soluble vitamins? | -fat soluble: Vitamins D, A, K, E -water-soluble: Vitamins B, C |
| Hypocalcemia | low blood calcium --> spastic twitches |
| What makes up glomerular capillary BP? | plasma osmotic P + Bowman's capsule hydrostatic pressure |
| What are the proteolytic enzymes from pancreas? | trypsin, chymotrypsin, carboxypeptidase |
| Perineum vs. Peritoneum | -perineum - area between legs that rips during birth -peritoneum - cavity that contains pelvis, stomach, spleen, gall bladder, liver, intestines |
| An ulcer in wall of intestine would allow contents to enter perineum or peritoneum? | peritoneum |
| Digestion of carbs starts in? Proteins? Fats? | mouth / stomach / small intestine |
| liver and pancreas are associated with which system? | digestive |
| What is bile made of? | breakdown of hemoglobin, bilirubin, and bile salts |
| TO have a hydrophilic and a hydrophobic portion? | amphipathic |
| What vitamins do E.Coli produce? | Vit B12 and Vit K |
| Where is appendix located? | continuous with colon |
| What is the shortest and longest part of the small intestine? | duodenum / ileum |
| What stimulates parietal cells? | gastrin, AcH, and histamine |
| What is the best way to inhibit stomach acid synthesis? | inhibit proton pump |
| Is the digestive system a blind tube? | NO |
| What is the most important extracx ion? intracx ion? | Sodium / Potassium |
| What is one of the main nerves of the PNS in digestion? | vagus nerve |
| Where is oxytocin made? | Hypothalamus and stored in posterior pituitary |
| What areh most numerous gastric cell types? | chief cells |
| Main function of hypothalamus? | maintain homeostasis --> BP, body temp |
| Main function of medulla oblongata? | -controls rate of breathing |
| What would long-term lipase inhibition create? | depletion of fat-soluble vitamins (DAKE) |
| What are the digestive accessory organs? | liver, gall bladder, pancreas, salivary glands |
| Cortisol vs. insulin on glycolysis | -cortisol inhibits glycolysis -insulin increases glycolysis |
| sodium / hydrogen antiport system used in kidneys | sodium in, hydrogen out |
| Is urine acidic or basic? | acidic |
| Is the renal filtration membrane negative or positive? | negative |
| somatostatin | inhibits release of insulin and glucagon |
| What test can check for Type 1 diabetes mellitus? Type 2? | -self-antibodies -insulin receptor count |
| What are the main functions of colon? | -secretion of K+ -absorption of Na and water |
| Where are the main targets for aldosterone? | -distal convoluted tubule -large intestine |
| What does ACTH cause the release of? | cortisol and aldosterone and other hx of adrenal cortex |
| The conversion of Vit D to is active form, synthesis of renin, and release of erythropoietin all occur where? | kidney |
| What does erythropoietin do? | activates bone marrow to produce red blood cells |
| primary active transport | moves cpds against concentration gradient with Na/K pump and ATP |
| secondary active transport | symport and antiport |
| Where is bicarbonate most important? | blood an GI tract |
| acinar cells | secrete pancreatic digestive enzymes |
| Does insulin cause hyper or hypoglycemia? | hypoglycemia |
| Where does final disaccharide digestion/absorption occur? | brush border of small intestine |
| Difference btwn cilia and microvilli | microvilli are not motile |
| Is glucose ever secreted under normal circumstances? | NO |
| What does alcohol and caffeine inhibit? | ADH |
| Why do diabetics have glucose in urine? | so much glucose isn't taken up by body that filtrate entering kidneys has a lot of glucose -too much to filter -gets into urine |
| Is the esophagus purely involuntary muscle? | NO --> some voluntary for swallowing |
| What is sucrose made of? | frucotse and glucose |
| In the PCT, the reabsorbed fluid is _____ with the nephron lumenal contents? | isosmotic |
| hyperosmotic? | greater solute concentration in comparison |
| What does angeiotensin-converting enzyme do? | increases BP |
| Where are macula densa cx located? | distal convoluted tubule |
| What releases renin and when does it release it? | macula densa cx in response to low NaCl |
| Diuretics that affect what part of nephron will be most effective? | loop of henle |
| What reaction does dehydration create? | -release of renin from kidneys --> aldosterone -stimulation of osmorx in hypo --> ADH release |
| What does thyroid hx cause? | increase basal metabolic rate and increase metabolism of all nutrients -increase px synthesis |
| Where does most digestion and absorption occur? | jejunum |
| What are the 2 important tasks for large intestine? | water reabsorption and K secretion |
| What is hippocampus for? | emotion and sexuality |
| How are glucose, a.a., and phosphate reabsorbed in PCT? | secondary active transport |
| Is urea ever actively transported? | NO |
| Where does aldosterone act? | distal convoluted tubule, collecting duct, large intestine |
| What does aldosterone do with K and H? | -increases urine K with Na/K pump -increases H in urine |
| Where is bicarbonate reabsorbed in nephron? | PCT |
| What are 2 important properties of hx action? | -receptor specificity -signal amplification |
| When is aldosterone produced in response to? | low sodium / elevated potassium in blood |
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