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14. Kidney Function
N/A
115
Physiology
Undergraduate 2
10/30/2012

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Cards

Term
What are the three forms of nitrogenous wastes that animals produce?
Definition

ammonia, urea, and uric acid

 

Term
Urea is formed from the _______________ cycle.
Definition
ornithin-urea
Term
What types of animals excrete ammonia?
Definition
mostly aquatic animals (ammonotelic)
Term
What types of animals excrete urea?
Definition
adult amphibians and mammals (ureotelic)
Term
What types of animals excrete uric acid?
Definition
insects, birds, reptiles (uricotelic)
Term
What are kidneys shaped like and where are they located?
Definition
bean or hert shaped, located on either side of the backbone
Term
How much of an animal's total body weight do kidneys make up?
Definition
.5%
Term
What percentage of areterial blood pumped fromt he heart do the kidneys recieve?
Definition
20-25%
Term
Which artery do the kidneys recieve blood from?
Definition
the renal artery which comes from the aorta
Term
Kidneys are innervated by (sympathetic/parasympathetic) nervous system.
Definition
sympathetic
Term
What is the functional unit of a kidney?
Definition
nephron
Term
How many nephrons does each kidney have?
Definition
4 million
Term
What do the kidneys produce? What happens to this product?
Definition
urine; it goes from the ureter to the bladder and then via the urethra to the exterior
Term
The kidney concentrates ________.
Definition
urine
Term
Kidneys function in eliminating ______.
Definition
waste
Term
Kidneys are involved in ________ balance.
Definition
acid-base
Term
What is one of the main hormones that acts on the kidneys?
Definition
antidiuretic hormone (ADH) (vasopressin)
Term
Renin-aldesterone are used to control ________ and ______.
Definition
Na+, blood pressure
Term
What hormone do the kidneys secrete to control production of red blood cells?
Definition
erythropoietin
Term
What is the function of calcitriol?
Definition
it provides vitamin D for Ca2+ and phosphorus regulation
Term
What are the four steps involved in renal excretion?
Definition
  • glomerular filtration
  • tubular secretion
  • tubular reabsorption
  • osmoconcentration
Term
What happens during glomerular filtration?
Definition
solutes are separated from a solution by passing through a boundary
Term
Is glomerular filtration selective or nonselective?
Definition
nonselective
Term
8
Definition
Term
What happens during tubular secretion?
Definition
specific solutes are transported into the tubule lumen for secretion
Term
8
Definition
Term
What happens during tubular reabsorption?
Definition
specific solutes and water may be transported back into the body from the lumen
Term
Is tubular reabsorption involve active or passive transport?
Definition
active
Term
What happens during osmoconcentration?
Definition
water is removed from the lumen fluid while leaving solutes behind, producing more concentrated fluid than the body fluid
Term
What is the purpose behind osmoconcentration?
Definition
it conserves water
Term
What types of nephrons go through osmoconcentration?
Definition
avian and mammalian
Term
if the kidneys form the urine, what carries the urine?
Definition
the remainder of the urinary system: the bladder and rest of the duct work
Term
11
Definition
Term
12
Definition
Term
14
Definition
Term
What does the length of the loop of Henle determine? Give an example.
Definition
it determines how much the urine can be concentrated; for example, desert animals have longer loops of Henle because they want to concentrate their urine mor ein order to conserve water 
Term
What is the Bowman's capsule and where is it located?
Definition
it is located at the closed end; it is the part where the wall of the nephron is pushed in, forming a double-walled chamber
Term
What is the glomerulus?
Definition
it is a capillary network within the Bowman's capsule
Term
Where does blood leaving the glomerulus go to?
Definition
it passes into a second capillary networksurrounding the proximal convoluted tubule
Term
What is the proximal convoluted tubule?
Definition
it is a coiled structure that is lined with cells carpeted with microvilli and stuffed with mitochondria
Term
What is the vasa recta?
Definition
capillaries associated with the long loops of Henle 
Term
What is the loop of Henle?
Definition
it is a loop that goes down, makes a heirpin turn, and then comes back up; it's length is related to its ability to concentrate urine
Term
What is the distal convoluted tubule?
Definition
it is a highly coiled structure that is surrounded by capillaries
Term
What is the collecting tubule?
Definition
it leads to the pelvis of the kidney from where urine flows to the bladder and periodically is excreted
Term
What are juxtaglomerular cells?
Definition
granulose cells near the distal tubule and arteriole that release rennin that leads to aldosterone and control of blood pressure and Na+ regulation
Term
What is the function of the juxtamedullary nephron?
Definition
it concentartes and dilutes urine
Term
What is the function of the cortical nephron?
Definition
it excretes and has a regulatory function
Term
What is the structural difference between juxtamedullary nephrons and cortical nephrons?
Definition
juxtamedullary nephrons have a loop of Henle that extendsfurther into the medulla of the kidney
Term
How permeable is the glomerular membrane compared to capillaries?
Definition
it is 100 times more permeable
Term
What are the three main structures of the glomerular membrane that make it so permeable?
Definition

endothelial cells, basement membrane, podocyte

 

Term
How do the endothelial cells of the glomerular membrane help permeability?
Definition
they have many pores 
Term
How does the basement membrane help permeability of the glomerular membrane?
Definition
collagen and glycoprotein repel plasma proteins from filtration
Term
How do podocytes help permeability in the glomerular membrane?
Definition
they provide passage to fluids
Term
18
Definition
Term
What is the major force responsible for inducing glomerular ultrafiltration?
Definition
glomerular capillary blood pressure
Term
What does plasma colloid osmotic pressure have to do with glomerular filtration?
Definition
the remaining plasma proteins induce osmotic pressure for water to favor moving into the capillary
Term
Bowman's capsule _______ and _______ pressure also play a role in inducing glomerular ultafiltration.
Definition
hydrostatic, osmotic
Term
Which forces oppose glomerular filtration?
Definition
plasma colloid osmotic pressure and bowman's capsule hydrostatic pressure
Term
Which forces favor glomerular filtration?
Definition
glomerular capillary blood pressure and net filtration pressure (difference between force favoring filtration and forces opposing filtration)
Term
20
Definition
Term
What is GFR?
Definition
glomerular filtration rate
Term
What is the most common factor resulting in a change in the GFR?
Definition
an alteration in the glomerular capillary blood pressure
Term
What happens when blood flow to the glomerulus is decreased through vasoconstriction?
Definition
  • glomerular capillary blood pressure decreases so net filtration decreases which leads to a decrease GFR
Term
What happens when blood flow to the glomerulus is increased through vasodilation?
Definition
glomerular capillary blood pressure increases which causes net filtration pressure to increase which increases GFR
Term
Tubular reabsorption is _______, ________, and ___________.
Definition
tremendous, highly selective, variable
Term
How much water is reabsorbed in the kidneys?
Definition
99%
Term
How much sodium is reabsorbed in the kidneys?
Definition
99.5%
Term
How much glucose is reabsorbed in the kidneys?
Definition
100%
Term
What are the two waste products produced by the kidney?
Definition
urea and phenol
Term
How much urea is reabsorbed in the kidneys?
Definition
50%
Term
How much phenol is reabsorbed in the kidneys?
Definition
0%
Term
How much amino acid is reabsorbed in the kidneys?
Definition
100%
Term
Tubular reabsorption involves ___________ transport.
Definition
tranepithelial
Term
What is essential for Na+ reabsorption?
Definition
and energy dependent Na+ K+ ATPase transport mechanism in the basolateral membrane
Term
What are the steps of transepithelial transport?
Definition
  • the filtarte passes through the luminal membrane
  • cytosol
  • basolateral cell membrane
  • interstitial fluid
  • capillary wall and into the plasma in the capillaries 
Term
Glucose and amino acids are reabsorbed through ____________ transport.
Definition
Na+ dependent secondary active
Term
What products are released through tubular secretion?
Definition
hydrogen ions, potassium, and organic anions and cations 
Term
What is osmoconcentration? What does it depend on?
Definition
the ability to excrete urine of varying concentrations which depends on the medullary countercurrent-miltiplier system and vasopressin
Term
What is the vertical osmotic gradient like in the human kidney?
Definition
in the center of the medulla, the concentartion is 1200 mOsm and goes down to 600 mOsm. In the cortex, the concentration is 300 mOsm 
Term
What is the purpose of the concentration gradient in the kidney?
Definition
  • it enables the kidney to produce urine that ranges from less than 100 mOsm to highly hypertonic
  • it permits excretion of differing concentrations by means of vasopressin controlled, variable H2O reabsorption from the collecting duct
Term
32
Definition
Term
What does countercurrent exchange within the vasa recta enable?
Definition
it allows the medulla to be supplied with blood while conserving the medullary osmotic gradient
Term
34
Definition
Term
How does vasopressin work in the kidney (explain the steps)?
Definition
  • blood-borne vasopressin binds with its receptor sites on the basolateral membrane of a distal or collecting tubule cell
  • this binding activates the second messenger cyclic AMP system within the cell
  • cyclic AMP increases the opposite luminal membrane's permeability to water by promoting the insertion of water channels in this membrane. This membrane is impermeable to water without the presence of vasopressin
  • water enters the tubular cell from the tubular lumen through the water channels and sunsequently enters the blood, in this way being reabsorbed
Term
Different osmoconcentrating abilities among species depend on __________ and ___________.
Definition
nephron anatomy, matabolic rates
Term
A kidney with a thick medulla will be able to concentrate urine (more/less). Why?
Definition
more; because the loop of Henle goes deeper
Term
What steps are involved in the fromation of urine up to just before it enters the proximal tubule?
Definition
  • blood enters the glomerulus under pressure 
  • this causes water, small molecules (not macromolecules like proteins) and ions to flow through the capillary walls into the Bowman's capsule 
  • this fluid collects within the Bowman's capsule and then flows into the proximal tubule
Term
What is the fluid called that collects in the Bowman's capsule?
Definition
nephric filtrate
Term
What happens to nephric filtrate in the proximal tubule?
Definition
  • all of the glucose, and amino acids, less than 50% of urea, 60% of inorganic salts are reabsorbed by active transport 
  • as these solutes are removed from the nephric filtrate, water follows them by osmosis 
Term
What controls active transport of Na+ out of the proximal tubule?
Definition
angiotensin II
Term
What supresses active transport of phosphate? 
Definition
parathyroid hormone
Term
How much water is reabsorbed in the proximal tubule?
Definition
80-85% of the 180L filtered by the Bowman's capsule every day
Term
What steps are involved in urine formation in the loop of Henle?
Definition
  • as the fluid flows into the descending segment of the loop of Henle, water continues to leave by osmosis because the interstitial fluid is very hypertonic
  • this is caused by the active transport of Na+ out of the tubular fluid as it moves up the ascending segment of the loop of Henle 
Term
What happens during urine formation in the distal tubules?
Definition
more Na+ is reclaimed by active transport anmd still more water follows by osmosis
Term
What happens when the body becomes dehydrated?
Definition
  • the osmotic pressure of the blood is increased
  • turns on the ADH, V2 receptors, aquaporin pathway
Term
How much urine will remain from the 180 L/dasy of nephric filtrate?
Definition
as little as .5 liters/day
Term
What is the concentration of salts in the urine like compared to the blood?
Definition
it can be as much as four times that of the blood 
Term
Why does sea water dehydrate the body more than it helps?
Definition
because the kidneys cannot concentrate the urine more than sea water 
Term
What happens if the blood becomes too dilute?
Definition
  • ADH secretion is inhibited
  • a large volume of watery urine is formed (with a salt concentration as little as 1/4 that of the blood)
Term
What happens when the pH of the blood starts to drop?
Definition
more hydrogen ions are secreted 
Term
What happens when the blood becomes too alkaline?
Definition
secretion of H+ is reduced 
Term
If the pH of the blood is maintained within normal limits, what pH of urine can the kidneys produce?
Definition
as low as 4.5 or as high as 8.5
Term
What are the hormones of the kidney?
Definition
renin, erythropoietin, and calcitriol
Term
What is the function of calcitriol?
Definition
  • it is the active form of vitamin D
  • it inhibits the release of calcitonin
Term
What is the tubuloglomerular feedback mechanism?
Definition
the macula densa detects GFR and releases vasoactive paracrines (endothelin, bradykinin) to control the filtration
Term
What types of cells produce renin?
Definition
glomerular cells
Term
Explain how angiotensin II is formed?
Definition
  • angitensinogen is released by the liver 
  • renin is released by the kidney which activates angiotensinogen and makes it angiotensin I
  • angiotensin converting enzyme is released by the lungs, making angiotensin I into angiotensin II
Term
What does angiotensin II do?
Definition
  • it stimulates vasopressin, thrist, and arteriolar vasoconstriction
  • it also stimulates the adrenal cortex to release aldosterone 
Term
What is the function of the renin-angotensin-aldosterone system in mammals?
Definition
the whole process is meant to increase blood volume and pressure 
Term
What stimulates renin to be produced by the kidney?
Definition
a decrease in NaCl, ECF volume, or arterial blood pressure
Term
What is the function of aldosterone? What does this cause?
Definition
  • it stimulates the kidney to increase Na+ reabsorption by the kidney tubules (Cl- reabsorption follows passively)
  • this causes H2O to be conserved and relieves the original stimulus that caused renin to be released by the kidneys
Term
What does the stimulation of thrist and arteriolar vasoconstriction cause?
Definition
they both relieve the original stimulus that caused renin to be released by the kidneys
Term
What kind of drug is often used to decrease blood pressure? Why?
Definition
ACE (angiotensin converting enzyme) inhibitor; it prevents ACE from being rleased so it cannot tuen angiotensin I into angiotensin II
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