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urinary system
| Question | Answer |
|---|---|
| what is the main function of the urinary system? | to maintain homeostasis within the body by producing urine |
| what is urine? | a highly concentrated liquid produced by the kidneys that contains waste products to be removed from the body |
| 4 functions that contribute to the maintenance of homoeostasis: | excretion of metabolic wastes (urea, ammonium); maintenance of water-salt balance (blood volume associated with salt balance); maintenance of acid-base balance (eliminate H+ ions); secretion of hormones (renin -> aldosterone from adrenal cortex on kidney) |
| kidney | produces urine, filters out wastes from blood, maintain healthy blood volume/pressure |
| ureter | tube that carries urine from kidney -> bladder |
| urethra | tube that takes urine from bladder -> outside body. UTIs occur here; common in females cuz their tube is shorter |
| urinary bladder | stores urine up to ~600 mL, we pee when this is ~halfway |
| renal cortex | outer granulated layer of kidney |
| renal medulla | consists of cone-shaped tissue masses (renal pyramid), inner layer of kidney, salty |
| renal pelvis | central cavity that collects urine; continuous with ureter |
| nephron | produces urine. a kidney is made of over a million nephrons, each with their own blood supply. |
| glomerulus | knot of capillaries where blood is filtered out due to high hydrostatic pressure (large input, small output) |
| bowman's capsule | collects glomerulus filtrate ex. water, urea, salts, glucose |
| afferent arteriole | renal artery -> afferent arteriole -> glomerulus. Afferent Arrives |
| efferent arteriole | glomerulus -> efferent arteriole -> peritubular capillary network. Efferent Exits |
| peritubular capillary network | surrounds rest of nephron, at the end blood -> renal vein |
| proximal convoluted tubule | (PCT). packed with microvilli to increase surface area for reabsorption of nutrients. 2/3 of glomerulus filtrate is reabsorbed |
| distal convoluted tubule | (DCT). contain mitochondria for active transport of molecules from blood in/out of tubule. adjusts to the body's needs |
| collecting duct | collects urine from many nephrons and carries it to renal pelvis |
| loop of henle | narrow loop that extends deep into the renal medulla. it has an ascending and descending limb. it allows for water reabsorption . |
| processes of urine formation | 1. glomerular filtration 2. tubular reabsorption 3. tubular secretion |
| where & what is glomerular filtration? | occurs at the glomerulus when blood enters afferent arteriole, AKA pressure filtration |
| what is filtered at the glomerulus? | water, Na+, Cl-, urea, glucose, creatinine, amino acids |
| what escapes glomerulus filtration? | formed elements (blood cells, platelets) & plasma proteins |
| components that are not filtered by the glomerulus leave by the... | efferent arteriole and enter the peritubular capillary network |
| why is the composition of urine not the same as glomerular filtrate? | because the body would continuously lose water, salts & nutrients if we didn't reabsorb them. |
| where & what is tubular reabsorption? | occurs at the PCT. molecules & ions are passively & actively absorbed from the nephron into the blood |
| passive transport | the movement of molecules ACROSS a diffusion gradient |
| active transport | the movement of molecules AGAINST a diffusion gradient. requires energy (ATP) |
| at the PCT, what is actively reasborbed? passively reabsorbed? | actively: Na+ ions. Passively: Cl- ions (follow Na+), water (follow osmolarity gradient created by Na+ reabsorption) |
| at the PCT, how are glucose and amino acids reabsorbed? | the reabsorption of glucose & amino acids is a selective process using specific carrier proteins. hence if the concentration of one outweighs the amount of carrier proteins available, it will show up in the urine (ex. excess glucose indicating diabetes) |
| what passes through the PCT (is not reabsorbed fully)? | water, urea & excess salt |
| why does diabetes cause excess glucose in the blood? | the liver & muscles have failed to store it as glycogen |
| how does diabetes affect the kidneys? | the kidneys cannot reabsorb all of the excess glucose and it increases osmolarity in the filtrate, causing less water to be reabsorbed. these cause frequent urination and glucose to appear in the urine |
| where & where is tubular secretion? | occurs at the DCT. it removes substance from the blood & adds them to the tubular fluid by active transport. |
| what is removed from the blood at the DCT? | H+, K+, creatinine and drugs in the blood |
| in the end urine contains: | 1. substances that have undergone glomerular filtration but have not been reabsorbed 2. substances that have undergone tubular secretion |
| urine is hypertonic, meaning... | it is more concentrated than the blood |
| how do we produce a hypertonic urine? | water is reabsorbed in the loop of Henle and collecting duct |
| steps of reabsorbing water | 1. reabsorption of salt 2. establishment of a solute gradient dependent on salt & urea before 3. water is reabsorbed |
| how much sodium is reabsorbed into the blood? | ~99% |
| what does it mean when blood volume is too LOW? | water needs to be reabsorbed into the blood |
| what does it mean when blood volume is too HIGH? | water needs to be removed from the blood |
| what is the juxtaglomerular apparatus? what does it do? | specialized region of the kidney that regulates nephron function. it detects when blood volume is too low and secretes renin. |
| what is renin? | a hormone that is a vasoconstrictor (increases blood pressure). it stimulates the adrenal cortex to release aldosterone |
| what is ANH? | atrial natriuretic hormone secreted by the atria of the heart when blood volume is too HIGH. it inhibits the secretion of renin & aldosterone and promotes the excretion of Na+. opposite of aldosterone |
| what is aldosterone? | a hormone released by the adrenal cortex when stimulated by renin (blood volume is too LOW). it targets the DCT and promotes the excretion of K+ and reabsorption of Na+. opposite of ANH |
| what happens in the ascending limb of the loop of Henle? | lower portion: NaCl passively diffuses out upper portion: actively extrude NaCl out |
| why doesn't water follow the salt in the ascending limb of the loop of Henle? | water cannot leave the limb because it is impermeable to water, helping establish a concentration gradient. |
| what & where is the osmotic gradient in the kidney and how is it established? | the concentration of salt is greater in the inner medulla because salt passively & actively leaves the Loop of Henle and urea leaks from the collecting duct, adding to the high solute concentration. |
| why does water leave the descending limb of the loop of Henle? | because of the osmotic gradient maintained by salt leaving passively |
| what happens when urine reaches the DCT (osmolarity)? | it is above the osmotic gradient of the medulla and becomes hypotonic to the cells of the renal cortex |
| how does urine change when it travels down the collecting duct? | it passes through the renal medulla and encounters the same osmotic gradient, causing water to diffuse out of the duct and make a hypertonic urine. |
| what is ADH? | antidiuretic hormone secreted by the posterior pituitary gland when we are dehydrated. it targets the collecting duct, making it permeable to water and allowing water to diffuse out into the renal medulla |
| regulatory functions of the kidneys | 1. water-salt balance, using hormones aldosterone & renin to regular absorption of Na+ 2. blood volume/pressure by hormone ADH to regulate absorption of water 3. acid-base balance (pH) |
| what is normal blood pH? | ~7.4 (slightly basic) |
| what are the conditions for rise/lower of blood pH? | alkalosis - high blood pH; acidosis - low blood pH |
| things that can upset the acid-base balance in the body: | foods we eat, metabolism, lactic acid |
| mechanisms the body has to regulate blood pH: | acid-base buffers, respiratory centre, kidneys |
| main buffer system in the blood: | combination of carbonic acid & bicarbonate ions |
| how does the respiratory centre help maintain blood pH? | it can increase breathing rate if blood is too acidic (too much H+). this removes more CO2 and thus removes excess H+ from the blood |
| why do we need the kidneys to help regular blood pH? | acid-base buffer systems in the blood & respiratory centre cannot expel acidic or basic substance from the blood, but the kidneys can |
| how do the kidneys affect blood pH? | they can rid the body of a wide range of acidic or basic substances. they're slower acting but more powerful than blood or respiratory buffer systems |
| if the blood is too acidic, the kidneys... | excrete H+ and reabsorb HCO3- |
| if the blood is too basic, the kidneys... | do not excrete H+ and do not reabsorb HCO3- |
| equation of ammonia pH buffering | NH3 + H+ --> NH4+ |
| what & where is ammonia produced? what does it do to urine? | the liver breaks down amino acids, producing NH3 which gives urine its odour. |
| why is the control of blood pH important for all of the body? | it's important to control pH because enzymes can't continue to function if the pH is off-balance |
| after filtration, reabsorption and secretion, what is left in the urine and what pH is it? | water, urea, Na+, Cl-, K+, H+, creatinine. it is pH 6. |
Created by:
AntBanana
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