renal Flashcards
what are the main functions of the kidneys?
- regulation of water, Na/K balance and blood pH
- removal of metabolic from the blood and their excretion in the urine
- removal of foreign chemicals from the blood
- hormone/enzyme production
what types of hormones are produced by the kidneys?
erythropoietin
renin
1,25 dihydroxyvitamin D3
what is the function of erythropoietin?
production of RBC
What is Renin
enzyme that controls the formation of angiotensin and influence sodium balance.
what is the function of vitamin d in the kidneys
influences calcium balance, precursor enters the kidneys to be activated
how big are each kidney?
size of fist, 150g
where are the kidneys located?
Behind the peritoneum on either side of the vertebral column against the posterior abdominal wall
what is the outer layer of the kidneys?
renal cortex
what is the inner layer of the kidneys?
renal medulla
how is the renal medulla divided into?
pyramids
what do the renal pyramides converge into?
renal pelvis
where is the renal A relative to the renal vein?
A is above V
what is the first arterial branch of the renal a
interlobar A
how does the interlobar A travel?
turns 90 degrees and artery, turns back 90 degrees
what does the interlobar A branch off into?
into the interlobular
what branch gives blood to the nepheron
afferent arteriole
how many nepherons are contained in each kidnet
~1 million
what is the nepheron composed of?
tubule renal corpuscule (glomerulus and bowman’s capsule)
how does the nephron get blood supply?
afferent arteriole –> glomerulus –> efferent arteriole
where is the bowman’s spae located?
around the glomerulus in the bowman’s casule
in what does urine travel through?
through the tubule
how does urine travel through the tubule
proximal tubule in the cortex will then enter the medulla in the loop of henle, will leave the medulla and will come in contact with the arterioles and enter the distal convoluted tubule which will merge with other nephrons into a collecting duct system found in both the cortex and the medulla.
where is renin formed in the kidneys?
Juxtaglomerular apparatus
what are the holes found in the glomerular capillary wall?
Fenestrae
what covers the holes of the glomerular capillary wall?
podocytes
what is the function of the glomerular capillary wall?
acts as a filtration barrier
where are the fenestrae located?
in the endothelial cells of the glomerular capillary wall
how does blood circulate through the glomerular capillary wall (pathway)
capillar lumen > endothelial cells > glomerular basement membrane > visceral glomerular epithelial cells
what is another name given to the glomerular epithelial cells?
podocytes
what is the function of the glomerulus?
filter blood to produce urin
what is another name given to the tubule epithelial cells?
peritubular capillaries
what are the 3 basic processes of urine formation?
- glomerular filtration
- tubular secretion
- tubular reabsorption
what is the function of glomerular filtration?
filtration of plasma from the glomerular capillaries into Bowman’s space
what is glomerular filtrate ?
fluid found in bowman’s space which is cell free but contains substances or plasma except for large proteins
what is the function of tubular secretion?
peritubular capillaries to tubules blood becomes urine
what happens are the glomerular filtrate passes through the tubules?
As the glomerular filtrate passes through the tubules, its composition is altered by movements of substances.
what does tubuar reabsorption invole
reabsorbin urine into the blood by the tubule to the peritubular capillaries
what is the amount of urine excreted?
its the sum of the amount filtered + amount secreted - amount reabsorbed
where does everything get filtered?
at the glomerular capillaries.
how is glucose filtered?
100% reabsorbed
how is sodium and water filtered?
reabsorbed to some extent and then the rest is secreted
how is PAH filtered?
what isnt filtered continues in the blood and gets fully secreted
what does the rate of filtration, reabsorption and secretion depend on?
physiological state of the body such as (When the body content of a substance goes above or below normal, homeostatic mechanisms can regulate the substance’s bodily balance by changing these rates)
what gets filtered in the bowman’s space of the glomerulus?
filtrate
what type of molecules are freely filtered?
Water and low-molecular weight substances
what type of molecules are not freely filtered?
Not freely filtered: cells, proteins (i.e. albumin, globulins), protein-bound substances (i.e. 1/2 of Ca ion, fatty acids)
what are the main forces involved in filtration?
PGC = glomerular capillary blood pressure is the favoring filtration force. PBS = fluid pressure in bowman’s space, an opposing filtration force. piGC = Oncotic pressure = osmotic force due to proteins in plasma, the other opposing filtration force.
what is the net glomerular fitration pressure?
PGC – PBS – piGC
~16 mm Hg
what is the Glomerular filtration rate (GFR)?
the volume of fluid filtered from the glomeruli into
Bowman’s space per unit time
how if GFR regulated?
net filtration pressure (only one accounted for in this class but also memebrane permeabiluty and surface area availible for filtration)
what is the normal GRF in a standard patient?
180L/day
how often is the entire plasma of a person filtered daily?
over 50 times
how can GRF be decreased?
- Constrict the afferent arteriole, thus less blood flowing per time, decreasing PGC.
important) - Dilate efferent arteriole, thus decreasing the PGC
how can GRF be increased?
- Constrict Efferent arteriole, slowing down the blood flow away from glomeruli, increasing PGC. 2. Dilate afferent arteriole, more blood arrives at the same time, increasing PGC.
what is the filtered load?
total amount of any freely filtered substance per unit time. GFR x plasma concentration of the substance (if freely filtered)
what happens if filtered load > amount excreted?
net reabsorption has occurred
what happens if filtered load < amount excreted?
net secretion has occurred
where does reabsorption take place?
from the tubular lumen to the peritubular capillary
what keeps the tubular epithelial cells together?
tight junctions
what faces the tubular lumen?
the tubular membrane
what faces the peritubular capillaries
basolateral membrane
how do parcellular solvents travel?
go between the cells from tubular lumen to peritubular capillary
how do transcellular solvents travel?
go through the cells from tubular lumen to peritubular capillary
what has the highest percentage of reabsorption?
Water, sodium and glucose
why are urine and potassium not fully reabsorbed?
urine is a waste product (44% reabsorbed)
potassium if found in large doses may be toxic (86.4%)
is reabsorption of waste products complete?
no, relatively incomplete
is reabsorption of most useful plasma components complete?
yes
is the regulation of glucose and AA regulated?
no
is the reabsorption of water and inorganic ions regulated?
yes
are the filtered loads big or small?
they are enormous
through what process does reabsorption occur?
diffusion and mediated trabsort
how does reabsorption by diffusion function/?
ften across the tight junctions connecting the tubular epithelial cells. Secondary to sodium diffusion.
what happens when urea is reabsorbed through the proximal tubules?
- ->In the proximal tubule, water reabsorption occurs and urea follows water.
- ->Urea concentration in the tubular fluid becomes higher.
- ->Urea diffuses into the interstitial fluid and peritubular capillaries.
how does reabsorption by mediated transport function?
occurs across tubular cells Requires the participation of transport proteins in the plasma membrane of tubular cells.
what is reabsorption by mediated transport usually coupled with?
Na+ reabsorption
how does mediated transport function?
Na/K-atpase pumps Na from the cell into the capillary and K from the capillary to the cell. Low Na in the cell drives Na+ in the lumen of the cell
Na/glucose cotransporter allows for Na and Glucose to drive into the cell
Na/AAs channels allow Na to drive in with AAs
Glucose/AAs channels let glucose and AAs diffuse out into the ISF and eventually back into the capillaries
what is the transport maximum attained?
When the membrane transport proteins become saturated causing the tubule to be unable to reabsorb anymore
how is Tm exceeded in diatbetic patients?
uncontrolled diabetes= high [glucose] in plasama, where filtered load > capacity of tubules to reabsorb glucose causing glucourea
what is moved by tubular secretions?
moves substances from peritubular capillaries into the tubular lumen
what is tubular secretion mediated by?
diffusion and transcellular mediated transport.
what are the most important substances secreted by the tubules?
H+ and K+
what is tubular secretion generally coupled with?
eabsorption of sodium
what is the function of the proximal tubule?
reabsorbs most of this filtered water and solutes. It is also a major site of secretion for various solutes, except K+.