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Part 21

Rapid Review of Renal Physiology

QuestionAnswer
What are some of the functions of the kidney? Form/excrete urine (excrete wastes from body). Regulates volume of blood plasma. Regulates Blood Pressure. Regulates concentration of solutions in the body. Regulates plasma pH.
What is filtering and reabsorption of the kidneys? Kidneys regulate plasma and interstitial fluid by forming and excreting urine. They do this by filtering the blood plasma, reabsorbing some things, and letting some leave in urine. Then they put additional stuff into urine before it leaves body.
People with kidney disease generally have what that goes along with it? Hypertension.
What contains many capillaries and outer parts of nephrons and also the glomeruli? Cortex
What consists of the renal pyramids which have the inner parts of the nephron and collecting ducts? Medulla
Where are all exits/entrances of the kidney? Medulla
Blood enters the kidney through the _______________. Renal artery
Blood exits the kidney through the __________________. Renal vein.
What are some of the inner parts of the nephron? Descending and ascending limbs, loop of Henle.
What is the functional unit of the kidney, responsible for forming urine? Nephron
How many nephrons are there in a kidney? Over 1 million nephrons per kidney.
What does the nephron consist of? Small tubes and associated small blood vessels.
Urine production moves from the _______________ to the _____________. Cortex to the medulla.
How much of the kidney do we really use right now to stay alive? Why does this help us? We need about 1/5 of the kidney to stay alive. This helps us because in 50 or so years, we will lose our kidney functions. Lots of backup nephrons.
90% of the blood that enters the kidney goes where? Where does the other 10% go? 90% heads to the cortex.
Interlobular arteries give rise to _________________ which supply ___________________. Afferent Arterioles which supply glomeri.
A glomerulus is what? A mass of capillaries inside glomerular capsule (Bowman's Capsule)
What is a renal corpuscle? A glomerulus plus Bowman's Capsule.
What do efferent arterioles do? Drain glomerulus and deliver that blood to peritubular capillaries (Vaso recta)
What is another name for peritubular capillaries? Vaso recta
Explain the tubular part of the nephron. Begins with the glomerular capsule, which transitions into the proximal convoluted tubule (PCT), then to descending and ascending limbs of Loop of Henle (LH), and then distal convoluted tubule (DCT).
Tubule ends where it empties into the _____________. collecting duct.
Glomerular capillaries and Bowman's capsule form a filter for ___________. Blood.
What does fenestrated mean? Has large pores between its endothelial cells.
Glomerular capillaries are _______________. Fenestrated.
What do the glomerular capillaries let through its membranes? Big enough to allow any plasma molecule to pass (but not all do!).
Are glomerular capillaries more permeable or are regular capillaries more permeable? Glomerular capillaries are 100-400 times more permeable than other capillaries.
To enter tubule, filtrate must pass through what? Narrow slit diaphragms.
Why are plasma proteins mostly excluded from the filtrate? Because of their relatively large size and negative charge.
Slit diaphragms are lined with __________ which repel ______________. Slit diaphragms are lined with negative charges, which repel negatively-charged proteins.
Some protein, especially _______________, enters the filtrate but then what? Some protein, especially albumin, normally enters the filtrate but then most is reabsorbed by receptor mediated endocytosis.
Defects in the slit diaphragm result in what? Lots of leakage of protein in the filtrate and thus it appears in the urine = proteinuria.
Which plasma proteins are filtered? Green
Which plasma solutes easily enter the glomerular ultrafiltrate? Smaller plasma solutes (purple).
What is the glomerular filtration rate (GFR)? The volume of filtrate produced by both kidneys per minute.
What is the average GFR for women and men? Averages 115 mL/min in women; 125 mL/min in men.
How much filtrate is produced by both kidneys per day? What does this tell us? Totals about 180L/day (45 gallons). So most filtered water must be reabsorbed or death would ensue from water lost through urination.
Regulation of GFR is controlled by ____________ and __________ mechanisms. Extrinsic and intrinsic (autoregulation) mechanisms.
What affects the rate of blood flow to glomeruli and thus affects the GFR? Vasoconstriction or dilation of afferent arterioles.
What is the juxtaglomerular apparatus? (JGA) Is a specialized region in each nephron where afferent arteriole comes in contact with the thick ascending limb LH.
What is renal autoregulation? Defined as the ability of kidneys to maintain relatively constant GFR in the face of fluctuating B.P.
2 mechanisms responsible for renal autoregulation: Myogenic Constriction of afferent arteriole; Negative feedback between afferent arteriole and volume of filtrate.
Myogenic constriction of the afferent arteriole can be due to ________________ responding to ________________________. smooth muscle responding to an increase in arterial pressure.
Myogenic constriction of the afferent arteriole is achieved via effects of ________________________ on __________ part of ________________________________. locally produced chemicals; afferent arterioles; part of tubuloglomerular feedback.
Tubuloglomerular feedback is _________________________ sensed by ___________________________ in ______________________. Increased flow of filtrate. sensed by macula densa (part of JGA) in thick ascending LH.
What does tubuloglomerular feedback signal? Afferent arterioles to constrict.
Reabsorption in PCT returns most ______________ and _____________ from filtrate back to _______________. Reabsorption in PCT returns most molecules and H2O and filtrate back to peritubular capillaries.
How much ultrafiltrate is produced a day? How much is secreted? 180 L/day of ultrafiltrate is produced. Only 1-2 L of urine is excreted in a day.
Urine volume varies according to _______________. Needs of the body.
What is the minimum amount of urine necessary to excrete metabolic wastes (obligatory water loss)? Minimum of 400 ml/day
What is the definition of reabsorption? The transport of molecules out of the tubular filtrate back into the blood.
Water moves by what ? Osmosis
PCT walls consist of ______________________. Single layer of cuboidal cells with millions of microvilli.
What does the wall of the PCT do? Increases surface area for reabsorption.
During reabsorption, ________________________ is transported from _______________________ and into ________________________. Salt, water, and other molecules needed by the body are transported from the lumen through the tubular cells and into the surrounding peritubular capillaries.
What 3 things are reabsorbed in the PCT? Cl-, Na+, water.
In the PCT, Cl is reabsorbed via _________________________. Na+ is reabsorbed via ____________________________. H2O is reabsorbed via ______________________________. Cl- transport (passive). Na+ transport (active). H2O follows salt by osmosis.
After reabsorption in the PCT, fluid is ___________________________ but still ______________________. Reduced to 1/3 the original volume, but is still isosmotic.
__________ % of Na+, Cl-, and water is reabsorbed in PCT and returned to bloodstream. 65%
An additional _______% of Na+, Cl- and water is reabsorbed in _______________. (After the initial 65%) An additional 20% is reabsorbed in descending loop of henle.
So _________% of filtered H2O and salt are reabsorbed early in the tubule. This is ______________ and ______________ of hydration levels. 85%. This is constant and independent of hydration levels.
Energy cost is what percent of calories consumed at rest? 6%
What happens to the remaining 15% of filtrate that is not reabsorbed early on? The remaining 15% is reabsorbed variably, depending on level of hydration.
In order for H2O to be reabsorbed, interstitial fluid must be ________________. Interstitial fluid must be hypertonic.
What is the osmolality of medulla interstitial fluid? What about the osmolality of cortex and plasma? 1200-1400 mOsm. This is 4x that of cortex and plasma. (300 mOsm)
The concentration gradient in kidney results largely from ______________________ which allows ___________________________. Loop of Henle which allows interaction between descending and ascending limbs.
Extrusion of NaCl from ascending limb makes surrounding interstitial fluid _______________. More concentrated.
Countercurrent multiplier system: multiplication of concentration due to descending limb ______________________ to water. Causing fluid to _________________________ as the surrounding interstitial fluid is ______________________. The descending limb is passively permeable to water - cases fluid to increase in concentration as the surrounding interstitial fluid is more concentrated.
What is the osmolality of the deepest region of the medulla? 1400 mOsm.
Descending limb is _____________ to water. Ascending limb has _________________ of Na ions. Cl _____________________, impermeable to water. Descending limb is passively permeable to water. Ascending limb has active transport of sodium ions. Chlorine follows passively, impermeable to water.
Ascending Limb Loop of Henle: has a thin segment in the __________________ and a thick segment _______________________. Deths of the medulla and thick part toward cortex.
The ascending limb loop of henle is _______ to water, __________ to salt. The thick part ________________ salt out of filtrate. Impermeable to water, permeable to salt. The thick part actively transports salt out of filtrate.
Active transport of salt causes filtrate to ____________________ by the end of the LH. (how many mOsm?) Active transport of salt causes filtrate to become dilute (100mOsm) by the end of LH.
Countercurrent flow allows descending and ascending limbs of the LH to interact in a way that causes __________________. Osmolality to build up in the medulla.
Salt pumping in the thick ascending part raises osmolality around ______________________, causing more ____________________________________. Descending limb; causes more H2O to diffuse out of filtrate in the descending limb.
Through salt pumping in the thick ascending limb, osmolality increases in _______________ which causes more ______________ filtrate to be delivered to the ____________________. Osmolality increases in the descending limb which causes more filtrate to be delivered to the ascending limb.
What is an important component of the countercurrent multiplier? Countercurrent exchange in vasa recta.
Vasa Recta is permeable to what? Salt, H2O (via aquaporins) and urea.
Vasa Recta is permeable to water via ___________________. Aquaporins.
The vasa recta recirculates ___________, trapping some ________________________. Recirculates salt, trapping some in the medulla interstitial fluid.
Vasa Recta reabsorbs ______________ coming out of the ____________. Reabsorbs water coming out of the descending limb.
The descending section of the vasa recta has _______________. The ascending limb has _______________. Descending has urea transporters. Ascending section has fenestrated capillaries.
What really is another name for vasa recta? Peritubular capillaries.
Urea diffuses out of ___________________ into _________________ in medulla. It then passes into the ascending limb so it ________________________. Water is __________ by osmosis from _____________. Diffuses out of inner collecting duct into interstitial fluid in medulla. It then passes into ascending limb so it recirculates in interstitial fluid in medulla. Water is reabsorbed by osmosis from collecting duct.
Juxtaglomerular (JG or granular) cells produce and store _____________. Renin
JG is a mechanism of __________ of the kidney. What does this mean? Autocontrol of the kidney. This means the kidney can monitor how well it is doing on its own without the brain.
What is the region of the JGA? Afferent arteriole comes into contact with thick ascending limb LB. Also connects the efferent arteriole.
JGA can sense what? Pressure and concentration (especially chlorine concentrations).
What can cause renin release in JG cells? Decreased wall tension in afferent arteriole or decreased salt delivery to macula densa cells.
A(n) ______________ in pressure leads to a(n) ____________________ in renin release. A decrease in pressure leads to an increase in renin release.
If your afferent arteriole relaxes, what happens? Less pressure. Kidneys assume your systolic pressure is low and JGA releases renin.
What 2 things does renin do? 1. Will increase volume (absorb more from your urine). 2. Will raise blood pressure (HTN).
How do you calculate renal clearance? What is renal clearance? (Filtration rate + secretion rate) - reabsorption rate. Renal clearance is the excretion rate of certain drugs through the body.
What is the type of secretion we deal with when we talk about renal clearance? A way that we have of dumping certain things into the tubular system of the kidney, without the need to filter those things.
How much of the cardiac output goes to the kidneys? 25%, approximately 1200 mL/min
Plasma is ________ % of blood. So how much blood do the kidneys normally see? Plasma is 55% of blood. WE see about 660 mL/minute.
What is the definition of glomerular filtration rate (GFR) 20% of the plasma gets filtered as it passes through the kidneys, or about 125 mL/minute. This is the GFR in a healthy individual.
Reabsorption mostly occurs in the _________. PCT.
_____ is readily filtered and reabsorbed back into the body. So is __________. So we should never see what in the urine? Bicarb is readily filtered and reabsorbed back into body. We essentially reabsorb carbonic acid back into the body (we never pee it out). Should never see glucose in the urine.
What can glucosuria be a sign of? Problem with reabsorption of glucose. We always filter glucose, but it is always reabsorbed back into the body. Also can be hyperglycemia - we cannot reabsorb as much glucose as we are taking in.
Role of ADH is to reasorb ___________. reabsorb pure water.
What happens to the blood that is not filtered each pass through the kidney? 20% is filtered. The rest passes into efferent arteriole and back into the circulation.
Substances that aren't filtered each pass through the kidney can still be cleared by ___________. Active Transport (secretion) into tubules.
__________ is the opposite of reabsorption Scretion
Reabsorption _________ renal clearance; secretion ___________ renal clearance. Reabsorption decreases renal clearance; secretion increases renal clearance.
Filtered glucose and amino acids are normally ___________% absorbed from filtrate. 100%
Where does absorption of glucose and amino acids occur? and How? PCT. by carrier mediated cotransport with sodium.
_________ and _______________ transporters don't ______ under normal conditions. Glucose and amino acid transporters don't saturate under normal conditions.
__________ is readily filtered - always reabsorbed back into the body. We essentially reabsorb ____________ back into the body. Bicarb is readily filtered. We essentially reabsorb carbonic acid into the body (we never pee out carbonic acid).
If we see glucose in our urine, what can potentially be happening? 1. Reabsorption problem. 2. Badly hyperglycemic - cannot reabsorb all the glucose they are taking in.
______________ occurs when hyperglycemia results in glycosuria. Diabetes mellitis.
What does ADH stand for? Antidiuretic Hormone (ADH)
ADH is made in the ____________ and transported to the ________________. Made in the hypothalamus (brain) and transported to the pituitary.
When is ADH secreted and by what? It is secreted by the posterior pituitary in response to dehydration.
Role of ADH: Gets you to reabsorb pure water. Will make you pee less.
Specific target of ADH: Distal convoluted tubule and collecting duct.
ADH stimulates insertion of _______________ in to ________________. Aquaporins (water channels) into plasma membrane of collecting duct.
When ADH is high, what happens? H2O is drawn out of collecting ducts by high osmolality of interstitial fluids and reabsorbed by vasa recta (blood).
Does the volume and/or concentration change with ADH? Explain. ADH regulates concentration of plasma. It drags out water so concentration of urine is increased and volume is decreased. Plasma solution will be more or less concentrated and so will urine.
What is released if you don't need to change concentration of blood, just the volume? Aldosterone.
Target of aldosterone. Proximal and Distal convoluted tubule.
Aldosterone _____________ activity of sodium pumps. This does what? Increases activity of sodium pumps. This pumps sodium back into the body. Chloride and water follows.
Aldosterone involves ______________ but in a different way than ADH. Water absorption.
With release of aldosterone, does concentration and/or volume change? Concentration does not change. Just the volume of the urine. When you are losing volume alone, you released aldosterone.
Kidneys are the key player in________________. Regulation of electrolytes.
Aldosterone is made in and released by the _______________. Adrenal cortex.
Kidneys regulate which ion levels (electrolytic)? They do this by matching ______________ to ____________. Regulate Na+, K+, H+, HCO3-, Cl- and PO4(3-). They do this by matching excretion to ingestion.
Control of plasma Na+ is important in regulation of ____________. Blood volume and pressure.
Control of plasma K+ is important in __________________. Function of cardiac and skeletal muscles.
K+ is almost completely ______________ in ____________. Reabsorbed in proximal tubule.
Under aldosterone stimulation, K is secreted into _______________. Cortical collecting ducts.
All K+ in urine comes from ___________ rather than ________. Secretion rather than filtration.
What is RAAS (Stand for)? Renin-Angiotensin-Aldosterone System
Renin is made and released from ____________ in _________ when ______________. From JG cells in the JGA when volume or salt content is lowered.
Renin is a hormone that is an ___________. Enzyme.
Renin converts _______________ to _____________. Renin converts angiotensinogen to angiotensin 1.
ACE stands for ___________. Angiotensin converting enzyme.
ACE converts ______________ to ____________. Ang. 1 to Ang. 2.
ACE inhibitors do what? Control hypertension. We can treat people with such modest HTN with ACE inhibitors.
ACE is made where? In the lungs
Ang II basically does everything it does to ____________. what 2 things does it stimulate the release of? conserve water. Stimulates release of ADH and aldosterone.
Angiotensin II stimulates the release of ADH from where to do what? Stimulates the release of ADH from the pituitary (increases water reabsorption).
Angiotensin II stimulates release of aldosterone from where to do what? Form adrenal cortex to increase saline reabsorption
Angiotensin II is present when _______ is released and in ______ plasma concentrations. It can have significant ____________ of arteries. This causes what? Present when renin is released. Present in low concentrations of plasma. Can have significant vasoconstriction of arteries. This alone can cause HTN.
ACE inhibitors don't work well in what type of people? African Americans, Mexicans or the elderly. It is used for young white people.
What are ANP hormones? Atrial Natriuretic Peptide = hormones that will unload volume from body.
ANP gets released from ______________. It hits ________ and causes you to _________________________________. It's released from the right atrium. It hits DCT and causes you to decrease sodium pumping back into body. therefore you will pee out more saline as a result of the presence of ANP in body.
With the presence of ANP in the body, you will pee out what? More saline.
Where is the brain natriuretic peptide released? Released in the brain. This senses it better than the right atrium can sense it.
Created by: sam_melillo