what are the three funcitons of the urinary system?

excretion elimination and homeostatic regulation

how does the urinary system help regulate blood volume and blood pressure?

by adjusting the volume of water lost in the urine and releasing erythropoietin and renin

how does the urinary system help regulate plasma ion concentration?

by controlling quantities of sodium potassium and chloride ions lost in urine and by controlling calcium levels through syntesis of calcitriol

how does the urinary system help stabilize blood pH?

by controlling loss of hydrogen ions and bicarbonate ions in urine

how does the urinary system conserve valuable nutrients?

by preventing excretion while excreting organic waste products

what does the urinary system assist the liver with?

detoxifying poisons

what is the renal cortex? what color and texture is it?

the superficial portion of kidneys in contact with renal capsule; reddish brown and granular

what are renal pyramids?

6 to 8 distinct conical or triangular structures in renal medulla

where are the base and tip found

base is abuts the cortex and the tip (renal papilla) project into renal sinus.

how much of the total cardiac output does the kidneys recieve?

20%-25%

what are the two types of nephrons?

cortical and juxtamedullary

which type of nephron make up 85% of all nephrons?

cortical

where are the cortical nephrons located?

within the superficial cortex of kidneys

compare the nephron loop (loop of henle) of the cortical to the one of the juxtamedullary

the cortical nephron is relatively short while the one of the juxtamedullary extends deep into the medulla

what does the efferent arteriole of the cortical nephron do?

delivers blood to a short network of peritubular capillaries

what do the peritubular capillaries of the juxtamedullary nephron do?

connect to vasa recta

what does a large loop mean?

more concentrated urine

what are the two segments of the renal tubule and where are they located?

proximal convoluted tubule and distal convoluted tubule; cortex

what are the segments of the renal tubule seperated by?

nephron loop

what is the nephron loop?

a u-shaped tube that extends partially into the medulla

is filtration at the renal corpuscle active or passive?

passive; no atp is necessary

what kind of solutes enter capsular space during filtration?

metabolic waste and excess ions like glucose, free fatty acids, amino acids, and vitamins

what is reabsorption and where does it occur

when useful materials that are recaptured before filtrate leaves kidneys and it occurs in proximal convoluted tubule

what is the first segment of the renal tubule and where is the entrance to this segment?

proximal convoluted tubule; opposite to the point of connection of afferent and efferent arterioles with glumerulus

describe the epithelial lining of PCT. what does it do?

simple cuboidal with microvilli on apical surfaces. the fuunction is reabsorption and it secretes substances into lumen

what is the nephron loop

renal tubule that turns toward renal medulla

what are the two limbs of the nephron loop? what does each contain?

descending and ascending; thick and thin segement

what does the thick descending limb do? what is its function similar to?

pump sodium and chloride ions out of tubular fluid; PCT

where is the ascending limb? what does it do?

juxtamedullary nephron in the medulla; it creates high solute concentrations in peritubular fluid

what are the thin segments permeable to? what dos the movement of this help?

water only,not solute; helps concentrate tubular fluid

where does the thick ascending limb end?

at a sharp angle near the renal corpuscle where DCT begins

what arethe three organic waste produces?

urea, creatine and uric acid

where are organic waste dissolved, when are they eliminated, and what does their removal include?

dissolved in bloodstream, eliminated only while dissolved in urine and removal is accompanied by water loss

what are the three components of the membrane involved in glomerular filtration

capillary endothelium, dense layer, and filtration silts

what type of capillary are glomerular capillaries? what do their pores do?

fenstrated; prevent passage of blood cells and allow diffusion of solutes including plasma protiens

what is glomerular filtration governed by?

the balance between hydrostatic pressure and colloid osmotic pressure on either side of capillary walls

what is glomerular hydrostatic pressure? what does it tend to do?

blood pressure in glomerular capillaries; push water and solute molecules out of plasma into filtrate

why is the hydrostatic pressure significantly higher than capillary pressure in systemic circuit.

arrangement of vessels at gloerulus

where does blood leaving glomerular capillaries do? how does the diameter of this arteriole compare to the other

flow into an efferent arteriole with a diameter smaller than afferent arteriole

what does the efferent arteriole produce? what does this require?

resistance; relatively high pressure to force blood into it

what is capsular hydrostatic pressure? what does it do? what does it result from?

capsular hydrostatic pressure that opposes glomerular hydrostatic pressure; pushes water and solutes out of filtrate into plasma; resistance to flow along nephron and conducting system (avg is 15 mm Hg)

what is the net hydrostatic pressure?

difference between glomerular hydrostatic pressure and capsular hydrostatic pressure

what is colloid osmotic pressure?

osmotic pressure resulting from the presence and capsular hydrostatic pressure

what does blood colloid osmotic pressure tend to do?

draw water out of filtrate into plasma. opposes filtration (avg is 25 mm Hg)

what is net filtration pressure?

average pressure forcing water and dissolved materials out of glomerular capillaries into capsular spaces

what is there a difference between at the glomerulus?

hydrostatic pressure and BCOP accross glomerular capillaries

what is the creatinine clearance test used for?

to estimate GFR

how much flitrate is generated in glomeruli each day? where is 99% of it reabsorbed?

180 liters; renal tubules

wht three interacting levels control the GFR

autoregulation, hormonal regulation, and autonomic regulation

what are the hormonal regulations of the GFR?

renin-angiotensin system and natiutic peptides (ANP and BNP)

what three stimuli causes the juxtagloumerular complex to relesase renin?

1. decline in blood pressure at glomerulus due to decrease in blood volume fall in systemic pressures, or blockage in renal artery or tributaries
2. stimulation of juxtaglomerular cells by sympathetic innervation
3. decline in osmotic concentration of tubular fluid at macula densa

what does angiotensin II activation do?

constricts efferent arterioles of nephron elevating glomerular pressure, stimulates reabsorption of sodium ions and water at PCT, stimulates secretion of aldosterone by adrenal cortex, stimulates thirst, and triggers release of ADH which stimulates reabsorption of water in distal portion of DCT and collecting system

what does angiotension II do?

increases sympathetic motor tone, causes a brief powerful vasconstriction, and elevates arterial pressures throughout the body

was do the increase of sympathetic motor tone by angiotensin II cause to happen?

mobilizes the venous reserve, increases cardiac output and stimulates peripheral vasoconstriction

what does aldosterone do?

accelerates sodium reabsortion in DCT and cortical portion of collecting system

what are natriuretic peptides? what do they do?

hormones that regulate GFR; trigger dilation of afferent arterioles and constriction of efferent arterioles and elevate glomerular pressure and increase GFR

where are natriuretic peptides released and when?

by the heart in response to stretching walls due to increased blood volume or pressure

what are the two types of natriuretic hormones and where are they released?

atrial natriuretic peptide (ANP) released by the atria and Brain natriuretic peptide (BNP) released by ventricles

what does reabsorption do?

recover useful materials from filtrate

what does secretion do?

ejects waste products, toxins, and other undesirable solutes

where does reabsorption and secretion occur? what changes from segment to segment with these two things?

in every segment of nephron except renal corpuscle; relative importance

how much of the filtrate produced in the renl corpuscle does the PCT cells usually reabsorb? where does this reabsorbed material go?

60-70%; it enters the peritubular fluid and diffuse into peritubular capillaries

what are the five functions of the PCT?

reabsorption of organic nutrients, active reabsorption of ions, reabsorption of water, passive reabsorption of ions, secretion

what is important in every pct process?

sodium ion reabsorption

how do sodium ions enter tubular cells?

diffusion through leak channels; sodium lined cotransport organic solutes, and countertransport for hydrogen ions

how does the nephron loop reabsorb around half the water and 2/3 of the sodium an chloride ions remaining in tubular fluid

by the process of countercurrent exchange

what is countercurrent multiplication?

the exchange that occurs between the two parallel segments of loop of henle- the thin descending limb and the thick ascending limb

what does countercurrent refer to?

the exchange between tubular fluids moing in opposite directions ( fluid n descending limb flows toward renal pelvis and fluid in ascending limb flows toward cortex)

what does multiplication refer to?

the effect of exchange hat increases as movement of fluid continues

what are the parallel segments of the nephron loop separated by? how do their characteristics compare?

peritubular fluid; they are very different

describe the permeability to the thin descending limb

permeable to water and relatively impermeable to solutes

describe the permeability of the thick ascending limb. what does it contain?

relatively impermeable to water and solutes. it contains an active transpor mechanism that pumps Na+ and Cl- from tubular fluid into peritubular fluid of medulla

what do sodium and chloride pumps do?

elevate osmotic concentration in peritubular fluid around thin descending limb and causes osmotic flow of water out of thin descending limb and into peritubular fluid which increases solute concentration in thin descending limb

where does the concentrated solution arrive and what does it cause?

thick ascending limb and accelerates Na+ and Cl- transport into peritubular fluid of medulla

what does solute pumping at ascending limb cause?

and increase solute concentration in descending limb which accelerates solute pumping in ascending limb

where does contercurrent multiplication occur? what does it move and where does it move it?

apical surface; Na+, K+, and Cl- out of tubular fluid

what is the carrier protein used in contercurrent multiplication

Na+-K+/2Cl-

describe the route for potassium ions.

pumped into peritubular fluid by cotransport carriers, removed from peritubular fluid by sodium- potassium exchange pump,and diffuse back into lumen of tubule through potassium leak channels

describe the route for sodium and chloride ions.

removed from tubular fluid in ascending limb which elevates osmotic concentration of peritubular fluid around thin descending limb

what happens as tubular fluid flows along thin descending limb?

osmosis moves water into peritubular fluid, leaving solutes behind. osmotic concentration of tubular fluid increases

where are 2/3 of Na+ and Cl- in tubular fluid pumped out before reaching DCT causing the solute concentration to decline and why?

thick ascending limb because of the highly effectie pumping mechanism

what is the osmotic concentration of tubular fluid at the DCT?

100 mOsm/L

what is the rate of ion transport across thick ascending limb proportional to?

ion's concentration in tubular fluid

where are more Na+ and Cl- pumped into medulla?

at the start of thick ascending limb near cortex

what does the regional difference in the ion transport rate cause?

concentration gradient within medulla

what is the maximum solute concentration of peritubular fluid near the turn of the nephron loop? how much of this is from Na+ and Cl- pumped out of ascending limb? what is the remainder?

1200 mOsm/L; 2/3; from urea

what locations are impermeable to urea?

thic ascending limb, DCT, and collecting ducts

what happens to the concentration of urea as water is reabsorbed?

the concentration rises

how many mOsm/L of urea are found in tubular fluid reaching papillary ducts?

450

what is permeable to urea?

papillary ducts

what are two benefits of contercurrent multiplication?

efficiently reabsorbs solutes and water before tubular fluid reaches DCT and collecting system and it establishes a concentration gradient that premits passive reabsorption of water form tubular fluid in collecting system.

what is aldosterone and what all does it do?

a hormone produced by the adrenal cortex that controls ion pump and channels, stimulates synthesis and incorporation of Na+ pumps and channels in plasma membranes along DCT and collecting ducts and reduces Na+ lost in urine

what is produced by prolonged aldosterone stimulation and dangerously reduces plasma concentration?

hypokalemia

what opposes secretion of aldosterone and its actions on DCT and collecting system?

natriuretic peptides (ANP and BNP)

what regulates calcium ion reabsorption at he DCT?

parathyroid hormone and calcitriol

what is contained in blood entering peritubular capillaries?

undesirable substances that did not cross filtration membrane at glomerulus

what causes the rate of K+ and H+ secretions to rise or fall and how?

the concentrations in peritubular fluid. higher concentration and higher rate of secretion

how do potassium ions diffuse into lumen?

through potassium leak channels

what do tubular cells exchange?

Na+ in tubular fluid for excess K+ in body fluids

what generates hydrogen ion secretions?

dissociation of carbonic acid by the enzyme carbonic anhydrase

what does hydrogen ion secretion do? what causes it to accelerate?

acidifies tubular fluid,elevates blood pH, and accelerates when blood pH falls

what is acidosis and when does it develop?

lactic acidosis and develops after exhaustive muscle activity

what causes ketoacidosis to develop?

starvation or diabetes mellitus

what controls blood pH? what are these important to?

H+ removal and bicarbonate production at kidneys; homeostasis

what is alkalosis? what can cause it?

abnormally high blood pH; prolonged aldosterone stimulation which stimulates secretion

what are the responses to acidosis?

PCT and DCT deaminate amino acids, ammonium ions are pumped into tubular fluid and bicarbonate ions enter bloodstream through peritubular fluid

what do PCT and DCT deaminate amino acids do?

ties up H+ and yields ammonuium ions (NH4+) and bicarbonate ions (HCO3-)

what are some benefits of tubular deamination?

provides carbon chains for catabolism and generates bicarbonate ions to buffer plasma

describe reabsorption and secretion at collecting ducts?

receives tubular fluid from nephron and carries it toward renal sinus

how is water and solute loss regulated in the collecting system?

by aldosterone and ADH

what does aldosterone control? what is it opposed by?

sodium ion pumps and actions are opposed by natiuretic peptides

what does ADH control and what is it suppressed by?

permeability to water; natriuretic peptides

what is reabsorbed in the collecting system?

sodium ions, bicarbonate, and urea

what is secreted in the collecting system and why?

hydrogen or bicarbonate ions. it controls body fluid pH

what happens when there is a low pH in peritubular fluid.

carrier protiens pump H+ into tubular fluid and reabsorbs bicarbonate ions

what happens when there is a high pH in peritubular fluid.

collecting system secretes bicarbonate ions and pumps H+ into peritubular fluid

how is urine volume and osmotic concentration controlled?

through control of water reabsorption

how is water reabsorbed?

through osmosis in proximal convoluted tubule and descending limb of nephron loop

what does ADH cause to appear in apical cell membranes and why?

water channels (aquaporins) to increase the rate of osmotic water movement

what does higher levels of ADH increase?

number of water channels and water permeability of DCT and collecting ststem

what happens if there is no ADH?

water is not reabsorbed and all fluid reaching DCT is lost in urine producing large amounts of dilute urine

what causes DCT and collecting systems to always be permeable to water?

the hypothalamus is continuously secreting ADH

how much urine does a healthy aduly produce per day?

1200 mL with osmotic concentration o 800-1000 mOsm/L

what is diuresis? what does it typically indicate?

the elimination of urine typically indicating production of large volumes of urine

what is diuretics?

drugs that promote water loss in urine

what does diuretic therapy reduce?

blood volume, blood pressure and extracellular fluid volume

what is the function of the vasa recta?

to return solutes and water reabsorbed in medulla to general circulation without disrupting the concentration gradient

what is the osmotic concentration of blood entering the vasa recta?

300 mOsm/L

when does the osmotic concentration of blood to increase? what does it involve?

as the blood descends into the medulla. it involves solute absorption and water loss

what does blood flowing toward the cortex do? what does it involve?

gradually decreases with solute concentration of peritubular fluid. it involves solute diffusion and osmosis

what does the vasa recta carry out of the medulla and why?

water and solute; balances solute reabsorption and osmosis in medulla

what are the seven steps of renal function

1. glomerulus
2. proximal convoluted tubule
3. PCT and descending limb
4. thick ascending limb
5. DCT and collecting ducts
6. DCT and collecting ducts
7. vasa recta

what has the same composition as blood plasma?

filtrate produced at renal corpuscle

what happens during step two of renal function?

active removal of ions and organic substrates (produces osmotic water flow out of tubular fluid that reduces volume of filtrate and keeps solutions inside and outside tubule isotonic

what happens during step three of renal function?what is there a reduction in and why?

water moves into peritubular fluids, leaving highly concentrated tubular fluid. a reduction in volume occurs by obligatory water reabsorption

what happens during step four of renal function? what accounts for a higher proportion of total osmotic concentration?

tubular cells actively transport sodium and chloride out of tubule. urea account for higher proportion of total osmotic concentration.

what happens during step five of renal function? what is adjusted and how?

final adjustments in composition of tubular fluid; osmotic concentration through active transport

what happens during step six of renal function? what is exposed here and what does it determine?

final adjustments in volume and osmotic concentration of tubular fluid; ADH, final urine concentration

what happens during step seven of renal function? what does it maintain?

absorbed solutes and water reabsorbed by nephron loop and the ducts; concentration gradient of medulla