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lecture 6

functions of the kidneys

1.regulation of extracellular fluid volume & BP
2.regulation of osmolarity
3.maintain of ion balance (na+ K+ Ca2+)
4.homeostatic regulation pH
(removal of conservation of H+ or HCO3-)
5.excretion of wastes
6.production of hormones

Production of hormones...

-synthesize erythropoietin (regulates RBS synthesis)
-synthesize renin (regulates hormones involved in Na+ balance and BP homeostasis)

adrenal glands are located

on top of kidneys

nephron

functional unit (cell that does the work)

portal system caries

capilaries to capilaries

80% of nephrons are in the

cortex

20% of nephrons are in the

medulla

Renal portal system

-filter fluid out of the blood and into the lumen of the nephron at the glomerular capillaries.
-to reabsorb fluid from the tubule back into the blood at the at the peritubular capillaries

glomerous+
Bowman's Capsule

Renal
Corpuscle

proximal tubule of the nephron..

reabsorption and secretion

descending limb of nephron

reabsorbs water

ascending limb of nephron

reabsorbs ions

secretion

is more selective than Filtration and uses membrane proteins to move molecules
across the tubule
epithelium

filtration

only takes place in the Renal Corpuscle

filtration

blood to lumen

reabsorption

lumen to blood

secretion

blood to lumen

excretion

lumen to external environment

70% of filtrate is reabsorbed in

the proximal tube

90% of the volume is filtered into Bowman's capsule has been
reabsorbed into

peritubular
capillaries

how do you find out the amount of solute secreted?

amount filtered - the amount reabsorbed + the amount secreted

podocytes used for filtering

Capsule epithelium that surrounds each glomerular
capillary are specialized cells

Glomerularcapillary endothelium

Has negatively charged pores for
secretion; repels negative proteins
and RBCs

Basal lamina

Excludes most plasma proteins

Epithelium of Bowman's Capsule

Podocyteshave foot processes that
wrap around glomerularcapillaries
leaving narrow filtration slits

Substances pass through 3 barriers
before entering the tubule lumen:

Glomerularcapillary endothelium
Basal lamina
Epithelium of Bowman's Capsule

podocyte foot processes......

surround each capillary, leaving slits where filtration takes place

Filtration Fraction

The percentage of total plasma
volume that filters into the tubule

#1 filtration

plasma volume afferent arteriole= 100%

#2 filtration

20% of volume filters (efferent?)

#3 filtration

19% of fluid is reabsorbed

#4 filtration

99% of plasma entereing kidney returns to systemic circulation

#5 filtration

1% of volume is excreted to external environment

Filtration pressure in the renal corpuscle depends on

hydrostatic pressure, colloid osmotic pressure, and fluid
pressure

Hydrostatic pressure

Capillary blood pressure

Capillary colloid osmotic pressure

Glomerularcapillaries higher than Bowman's capsule,
moves fluid back into the capillaries

Capsule fluid pressure

Created by fluid in Bowman's capsule opposes filtration

net filtration measure

10 mm Hg

Autoregulation

maintains a constant glomerularfiltration rate (180 L/day) over a wide range of blood pressures (which provides the hydrostatic pressure that drives glomerularfiltration)

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