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THE MCAT-BIO 4

DIGESTION AND EXCRETION

QuestionAnswer
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
Created by: 507935299 on 2012-06-21



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