Chapter 32: The Excretory System Flashcards
what is the excretory system?
the excretory system is a passive biological system that removes excess, unnecessary materials from the body fluids of an organism, so as to maintain internal chemical homeostasis and prevent damage to the body
what is the excretory system also called?
the urinary tract
what is homeostasis?
the tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes
why do organisms use homeostasis?
to maintain a ‘steady state’ or internal balance regardless of external environments
what 3 things are maintained at a constant level in the human body?
body temperature, blood pH, and glucose concentration
how is homeostasis regulated?
through negative feedback
what is negative feedback?
a control mechanism that reduces the stimulus. in other words, the body does not want us to do it.
how to animals achieve homeostasis?
by maintaining a variable at or near a particular value, or set point
what is a stimulus?
a detectable change in the physical or chemical structure of an organism’s internal or external environment. fluctuations above or below the set point serve as a stimulus.
what are stimulus’ detected by?
they are detected by a sensor
what is a sensor?
detects changes in internal or external environment
what does the sensor trigger? what does that do?
triggers a response. the response returns the variable to the set point
does homeostasis eliminate changes in the internal environment?
no, only moderates the internal environment.
is positive feedback a thing? what is an example?
yes, the most common example is pregnancy labor.
what does a shared system mediate?
a shared system mediates osmoregulation and excretion in many animals
what is osmoregulation?
the general term for the processes by which animals control salt concentrations in the interstitial fluid and balance water gain and loss. aka it keeps cells from expanding and contracting too much.
what is interstitial fluid?
thin layer of fluid which surrounds the body’s cells
what do cells require a balance of?
uptake and loss of water
what is osmolarity? what does it determine?
the solute concentration of a solution. determines the movement of water across a selectively permeable membrane. basically the net concentration of everything in a solution
what does isosmotic mean?
the movement of water is equal in both directions
what does hypoosmotic mean?
solution with a lesser concentration of solute
what does hyperosmotic mean?
solution with the greater concentration of solute
what if 2 solutions differ in osmolarity?
the net flow of water is from the hypoosmotic to the hyperosmotic solution
what is the main type of human waste?
nitrogenous wastes
what affects an organisms water balance?
the type and quantity of an animal’s waste products
what do nitrogenous products break down?
products of proteins and nucleic acids
what compound do some animals convert to a less toxic version of before excretion?
ammonia (NH3)
what type of secretion is most common in aquatic organisms? why is it easy for them to do?
ammonia excretion. It requires a large amount of water, so since they are surrounded by water, it is easy to get rid of
what compound do vertebrates excrete?
urea
what is urea?
a conversion product of ammonia, which is much less toxic than ammonia
what is urine? why is it different from urea?
urea is the compound that is released. urine is the combination of all substances secreted out of the body. It is a liquid byproduct of metabolism.
what do birds, reptiles, land snails, and insects secrete?
uric acid. it is released as semi-solid paste. it gets rid of nitrogen.
how do animals produce urine?
by refining a filtrate
what is filtrate?
the fluid filtered from blood. it is derived from body fluids
what are the key functions of the excretory system?
- filtration
- reabsorption
- secretion
- excretion
what is filtration?
filtering of body fluids (by size)
what is reabsorption?
reclaiming valuable solutes
what is secretion?
adding nonessential solutes and wastes from body fluids to the filtrate
what is excretion?
releasing processed filtrate containing nitrogenous wastes from the body
what does renal refer to?
kidney
what is the posterior vena cava?
the largest vein in the body, carrying blood from the lower half of the body to the right atrium of the heart
what is the kidney?
the kidney filters about 1/2 cup blood every minute, removing wastes and extra water to make urine
what is the renal artery?
carries blood from the heart to the kidneys to get filtered
what is the renal vein?
veins that drain the kidney. carry blood filtered by the kidney
what is the aorta?
the main artery that carries blood away from your heart to your body
what is the ureter?
tube that carries urine from the kidney to the urinary bladder. there are 2 - one for each kidney
what is the urinary bladder?
muscular sac in the pelvis. it stores urine
what is the urethra?
thin tube that begins at the lower end of the bladder. used to remove urine from the bladder
what are the 3 main layers of the kidney?
renal cortex, renal medulla, and renal pelvis
what is the renal cortex?
outer layer of the kidney
what is the renal medulla?
inner layer of the kidney
what is the renal pelvis?
takes urine away from the kidney via ureter
what is the difference between an artery and vein?
arteries are blood vessels that carry oxygenated blood away from the heart to the body. veins are blood vessels that carry deoxygenated blood to the heart from the rest of the body to reoxygenate it.
explain the excretion system step by step.
notes
what are arterioles?
small branch of an artery leading into the capillaries.
what is pressure filtration?
process of separating a suspended solid from the liquid in which it is already suspended by straining it-under pressure-through a porous medium that can be penetrated easily by liquid
what are peritubular capillaries?
tiny blood vessels that travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron
what is the largest macromolecule?
proteins
what is bulk flow?
the movement of proteins or other large molecules from the interstitial into the blood
what is countercurrent-exchange?
transport of NaCl (without water) in the thin and thick ascending limb of the loop of Henle results in an interstitial osmoal gradient from 285 mosmol/ kg (in the cortex, similar to plasma) to >1200 mosmol/ kg in the medulla at the tip of the renal papilla
what is the glomerulus? what is its function? where does it go after?
the glomerulus are thin capillaries that help with the filtration process. it is permeable to anything that fits through it (size-wise) - called bulk flow. however, it doesn’t allow blood cells or proteins to go through it. whatever enters is now called filtrate. it then goes to the bowman’s capsule.
what is filtrate made of?
filtrate is made of salts, glucose, amino acids, vitamins, nitrogenous wastes (urea), and other small molecules
what is bowman’s capsule? where does it go after?
capsule-shaped membranous structure surrounding the glomerulus of each nephron in the kidneys of mammals that extract wastes, excess salts, and water from the blood. it then goes to the proximal tubule
what is the proximal tubule? what is its function? where does it go after?
the proximal tubule is named proximal because it is in close proximity to the beginning. it does a majority of the reabsorption (65%) of ions, water, and nutrients. the molecules are transported actively and passively from the fluid into the interstitial fluid and the capillaries. some toxic materials are actively secreted into the filtrate. it then goes to the descending limb in the loop of Henle.
what substances are transported out of the proximal tubule? how?
glucose and amino acids use active transport. Na+ sometimes uses active transport. since Na+ is reabsorbed, Cl- follows, as well as H2O. Both Cl- and H2O use passive transport.
what is the descending limb of the loop of Henle? what is its function? where does it go after?
reabsorption of water continues through channels formed aquaporin proteins. movement is drive by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate. the filtrate becomes increasing concentrated all along its journey down the descending limb, so there is less water. it then goes to the ascending limb in the loop of Henle
what is reabsorbed in the descending limb? how?
water through passive transport.
what is the ascending limb of the loop of Henle? what is its function? where does it go after?
the ascending limb has a transport epithelium that lacks water channels. here, NaCl, but not water, is able to move from the tubule into the interstitial fluid. the NaCl is in high concentration in the limb, but its increasingly dilute as it moves up to the cortex. since its in high concentration, the NaCl/ filtrate diffuses out until its low concentration. goes to distal tubule next.
what is reabsorbed in the ascending limb? how?
NaCl through active transport
what is the distal tubule? what is its function? where does it go after?
the distal tubule is in charge of homeostasis. it regulates pH by either absorbing or secreting HCO3 and either absorbing or secreting H+. it is either absorbed of secreted depending on the pH of the blood. it also regulates the K+ and NaCl levels in the body by secreting K+ and absorbing Na+. if the body needs more of a particular substance, it will absorb more of it. it also has secretions of hormones and drugs. the distal tubule measures and regulates the substances - it’s the final place to decide what needs to be excreted vs reabsorbed. it goes the collecting duct.
what is the collecting duct? what is its function?
the collecting duct carries filtrate through the medulla to the renal pelvis. most of the water, and nearly all sugars, amino acids, vitamins, and other nutrients are reabsorbed into the blood. called urine because its a mixture of substances actually leaving the body.
is urine hypo or hyperosmotic?
it is hyperosmotic to body fluids because its more concentrated going down because Na+ = active transport, and Cl- and H2O = passive transport
what is the key adaption of mammalian kidneys?
the ability to conserve water.
what inputs regulates the osmoregularity function of the kidney?
nervous and hormonal
what do inputs in the kidney help maintain homeostasis in?
blood pressure and volume through their effect on amount and osmoregularity of urine
what is anti-diuretic hormone? (adh)
reducing urine output. anti-pee hormone
what happens if there is high blood osmolarity?
if there is high blood osmolarity, it is detected by the hypothalamus. the hypothalamus releases ADH. the adh goes to the collecting duct in the nephron. the collecting duct becomes more permeable to water, so more water is reabsorbed. then there is a decrease in blood osmolarity. this returns it back to homeostasis.
what happens if there is low blood osmolarity?
if there is low blood osmolarity, it is detected by the hypothalamus. the hypothalamus stops the release of ADH. the adh doesn’t go to the collecting duct, and it becomes less permeable to water, so less water is reabsorbed. then there is in a increase in blood osmolarity. this returns it back to homeostasis.
what does high blood osmolarity result in?
high blood pressure because you’re dehydrated (cells lose H2O to blood because of high to low concentration)
why is blood pressure important?
it is important because substances need to be pushed into the glomerulus. nutrients and oxygen need to be moved around the body.
what is RAAS?
renin-angiotensin-aldosterone system
what happens if there is low blood pressure?
if there is low blood pressure detected in the juxtaglomerular apparatus, there is a release in renin enzyme. the release of renin triggers the formation of angiotensin II. this closes the capillaries. it also releases aldosterone, which increases reabsorption of Na+. this results in increase of reabsorption of H2O. it then reaches homeostasis.
what happens if there is high blood pressure?
if there is high blood pressure, it is detected in the juxtaglomerular apparatus. there is no release of renin. this doesn’t trigger the angiotensin II, so capillaries open and dilate. this stops the release of aldosterone. there is a decrease in reabsorption of Na+, so decreases in the reabsorption of H2O. this brings it back to homeostasis.
