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Chapter 18 & 19
Kidneys
76
Physiology
Undergraduate 1
04/20/2010

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Term
What does urine production regulate
Definition
  • plasma ion concentrations
    • Na+, K+, Ca2+, Mg2+, C1-, HCO3, HPO4-
  • Blood Ph
  • Plasma volume
  • Plasma osmolarity
  • Removes wastes and foreign substances
  • Retains useful molecules
Term
How does urine production regulate blood Ph
Definition
By regulating the concentration of bicarbonate and hydrogen ions in the plasma, the kidneys partner with the lungs to regulate the pH of the blood
Term
How does urine production regulate plasma osmolarity
Definition
by regulating the total solute concentraiton of plasma
Term
What are the type of wastes found in urine
Definition
  • metabolic wastes
  • urea
  • creatinine
  • ammonia
  • uric acid
Term
The kidneys secrete Erythropoietin, which stimulates _________ to produce ________
Definition
  • bone marrow
  • red blood cell production
Term
Where does urine collect in the kidney
Definition
in calyces and the renal pelvis
Term
How much blood flows through the kidneys
Definition
  • 1200 mL/min
  • 72 L p/hr
Term
Where does the blood return to after it has been processed by the kidneys
Definition
inferior vena cava
Term
What is the function of nephrons
Definition
functional units of the kidnyes, they do the work of filtering the blood and forming the urine
Term
How many nephrons are there in two kidneys
Definition
2.5 million
Term
Where is the capsular space found in the kidney
Definition
inside the renal corpuscle, on the nephron side of the glomerular epithelium
Term
The capsular space funnels into
Definition
the proximal convolute tubule (PCT)
Term
The distal convoluted tubule drains into a
Definition
collecting duct which drains into the renal pelvis
Term
Before the blood is filtered, it enters the ______ via an ________ ___________
Definition
glomerular capillaries via an afferent arteriole
Term
An efferent arteriole exits the glomerular capillary bed and forms the
Definition
peritubular capillary bed, or else a vasa recta, which surrounds the tubules of the nephron or the nephron loop
Term
Filtration
Definition
blood pressure  forces fluid across the filtration membrane, into the capsular space
Term
Reabsorption
Definition
most water and some solutes are removed from the filtrate, and enter the interstitial fluid, and then the bloodstream
Term
Secretion
Definition
some solutes are transported form the ISF across the tubular epithelium, into the flitrate
Term
What are the 3 comonents of filtration
Definition

1) fenestrated capillary

2)  basement membrane

3)  filtration slits 

Term
Fenestrated Capillary
Definition
Endothelial cells with pores
Term
Basement Membrane
Definition
contains large amounts of protein fibers
Term
Glomerular filtrate must cross three barriers to enter the Bowman's capsule, what are they
Definition
  • Capillary endothelial cell layer
  • Surrounding epithelia cell layer
  • Basement membrane the is sandwiched between them
Term
The amount of plasma the two kidneys receive over time is called the
Definition
renal plasma flow
Term
Renal plasma flow mL/min
Definition
625 mL/min
Term
The __________ filtration rate is the rate at which filtrate is produced from plasma
Definition
glomerular
Term
What is the average glomerular filtration rate
Definition

125 mL/min

or

180 L/day

Term
Filtration occurs where
Definition

in the renal corpuscle

it is the bulk of flow of protein-free plasma from the glomerus into Bowman's capsule

Term
Where does reabsorption occur
Definition
along the tubules, is the movement of water or solute from the lumen of the tubules into the peritubular capillaries
Term
Where does secretion occur
Definition
along the tubules, it is the movement of solute from the peritubular capillaries into the lumen of the tubules
Term
Where is the juxtaglomerula appartus located
Definition
located where the initial part of the distal tubule passes through the fork between the afferent and efferent arterioles
Term
What does the juxtaglomerular apparatus do
Definition
regulating blood volume and blood pressure
Term
What do the secretory granules in the juxtaglomerular apparatus contain
Definition
renin
Term
Without regulation, blood pressure increases which would increase the ______, and decreases would decrease _______
Definition
Glomerular Filtration Rate
Term
Myogenic Regulation
Definition
  • Increases MAP - stretchs the afferent arterioles
  • constricts the smooth muscle in the afferent arterioles
  • Decreases BP in the glomerular capillary bed
Term
Tubuloglomerular feedback
Definition
  • increased fluid flow past the macula densa
  • releases paracrine signals
  • constriction of the afferent arteriole
Term
Mesangial Cells
Definition
  • similar to smooth muscle cells
  • respond to increased bp (in a manner similar to myogenic regulation)
  • affect the capillary bed surface area, to affect filtration rates
Term
Active reabsorption of solutes
Definition
Solutes can be actively transported against their concentration gradients across either the basolateral membrane or the apical membrane
Term
Passive reabsorption of water
Definition
active transport increases the osmolarity of peritubular fluid and plasma, creating conditions that enable reabsorption of water via osmosis
Term
Almost all nutrients that were in the filtrate are reabsorbed in the
Definition
PCT
Term
How much of ions and water are reabsorbed in the PCT
Definition

65%

 

about 120 of the 180 liter of filtrate per day

Term
Ascending Limb
Definition

this region of the tubule is impermeable to water and most solutes

 

But Na+, K+, and C1- are actively transported out of the ascending limb (reabsorption)

Term
Medullary Osmotic gradient
Definition

makes extensive water reabsorption possible in the descending limb and collecting duct

 

The descending limb of the loop of Henle is permeable to water, whereas the thick ascending limb is impermeable to water and contains trasnporters for Na+, C1- and K+

Term
Low osmolarity of fluid entering the DCT allows us to generate a very
Definition
diluted urine when the plasma osmoarity is too low as in over-hydrated
Term
The reabsorption in the DCT and collecting duct allows what
Definition
allows us to generage highly concentrated urine when plasma osmolarity is too high as in dehydration
Term
Water is drawn out of the descending limb by
Definition
osmosis
Term
What is the descending limb permeable to
Definition
water not solutes
Term
How much filtrate water is reabsorbed in the descending limb
Definition

15 %

 

25 of the 180 L/day

Term
Does the fluid entering the ascending limb have a high osmolarity or low osmolarity
Definition
High
Term
Countercurrent multiplier system
Definition

works to maintain the high osmolarity of the renal medulla by pumping ions out of the tubular fluid in the ascending limb

 

Term
High osmolarity of the medulla draws water out of the
Definition
descending limb, which actually makes it even easier to remove ions from the ascending limb.
Term
Countercurrent refers to the
Definition
opposite directions of fluid flow in the descending and ascending limb by the reabsorption of water in the descending limb
Term
DCT and Collecting Duct are they impermeable or permeable to water and solutes
Definition
impermeable to water and solutes
Term
What instructs the DCT and collecting ducts to perform reabsorption or secretion
Definition
hormones
Term
Secretion
Definition
some solutes ar transported from the ISF across the tubular epithelium, into the filtrate.
Term
Anti-diuretic hormone is secreted by what
Definition
  • secreted by the hypothalamus
    • ECF osmolarity - high - inceases ADH
    • ECF osmolority - low - decreases ADH
  • Blood Pressure - decreased - stimulates ADH
  • Angiotensin II
Term
How much filtrate volume is reabsorbed in the DCT and collecting ducts under the influence of ADH
Definition

19%

 

34 L/day

Term
If our plasma osmolarity is too high, the additional ADH will instruct the DCT and collecting ducts to
Definition
increase the amount of water that is reabsorbed, so that we may generate as little as 0.4 L/day of urine (as when we are dehydrated)
Term
When our plasma osmolarity is too low, the reduced ADH secretion will allow the DCT and collecting ducts to
Definition
decrease the amount of water reabsorbed, so that we may generate as much as 20 L/day of urine (as when we are over-hydrated)
Term
Aldosterone
Definition
regulates the rates of Na+ reabsorbion and K+ secretion
Term
Aldosterone secretion
Definition
Secreted by cells in the cortex of the adrenal gland
Term
Aldosterone secretion in response to
Definition
  • increased blood K+ levels
  • decreased blood volume or blood pressure, indirectly through the RAAS system
  • decreased blood Na+ levels, indirectly through the RAAS system
Term
Aldosterone actions
Definition
  • binds to intracellular hormone receptors, which stimulates synthesis of Na+/K+ pumps

 

Term
How do the Na+/K+ pumps work
Definition
  • pump Na+ out of the tubular epithelial cells into the ISF
  • pump K+ into the tubular epithelial cells from the ISF
Term
Binding of aldosterone to its receptor also leads to opening of
Definition

ion channels, and stimulates ion channel synthesis.

 

diffusion of the ions across the apical membrane is more rapid

Term
Aldosterone facilitates Na+ reabsorption to maintain
Definition
blood Na+ levels
Term
Aldosterone facilitates K+ secretion to
Definition
decrease blood K+ levels
Term

The RAAS System

(renin-angiotensin-aldosterone system)

Definition

The liver and the juxtaglomerular cells secrete and release angiotensinogen and renin into the blood where renin cleaves amino acids from angiotensinogen to form angiotensinI.

 

Angiotensin convertng enzyme (ACE) located on certain endothelial cells in capillaries cleaves amino acids from angiontensin I to form angiotensin II, which travels in the bloodstream to the adrenal cortex, where it stiumulates the release of aldosterone into the blood.

Term

The liver and the juxtaglomerular cells secrete and release angiotensinogen and renin into the blood where

Definition
renin cleaves amino acids from angiotensinogen to form angiotensinI.
Term

Angiotensin convertng enzyme (ACE) located on certain endothelial cells in capillaries cleaves amino acids from angiontensin I to

Definition
form angiotensin II, which travels in the bloodstream to the adrenal cortex, where it stiumulates the release of aldosterone into the blood.
Term
Renin
Definition
proteolytic enzyme
Term
ACE
Definition
an enzyme that converts angiotensin I to angiotensin II
Term
Angiotensin II
Definition

a hormone the maintains and increases blood pressure

  • stimulates vasoconstriction of systemic arteries (increase MAP)
  • stimulates adreanl cortex to secrete aldosterone
  • stimulates posterior pituitory to secrete ADH
  • stimulates feelings of thirst in hypothalamus
Term
Aldosterone increases
Definition
Na+ reabsorption, which in turn increases water reabsorption (prevents decreases in MAP)
Term
Posterior pituitary Gland secretes ADH
Definition
which increases wate reabsorption (prevents decreases in MAP)
Term
If Na+ is low will blood osmolarity be low
Definition

Yes, reduces ADH secretion, and leads to wate loss to that the body can maintain osmotic balance.

 

Water loss reduces MAP.  Decreased MAP activates the RAAS system above to maintain MAP and increase Na+ reabsorption

Term
Atrial Natriuritic Peptide
Definition
works to decrease blood Na+ levels, and therefore decrease MAP
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