Urine formation Flashcards
ChlorineTo produce urine, nephrons & collecting ducts do 3 things -
glomerular filtration
tubular reabsorption
tubular secretion
what happens to water & small molecules in glomerular filtration
they pass through pores in the glomerular capillaries into the bowman’s capsule ready to be processed by the kidneys
what happens to blood cells, plasma proteins and other large molecules during glomerular filtration
they stay in the capillaries as unable to filter through so go back to bloodstream
Filtrate contains (6)
water glucose amino acids electrolytes/ions urea & other wastes hormones
how is the pressure increased for filtration
efferent arteriole diameter (exit) is smaller than afferent arteriole (entrance) thus increases pressure - forces thte filtrate out of capillaries and into the capsule space
how else is glomerular filtration efficient?
pores in glomerular capillaries 50 times more leaky
summary of how glomerular filtration is adapted for fantastic filtration
greater blood pressure
more permeability
what happens if systolic BP is above 200
the kidneys are damaged
what happens if systolic BP is below 80 (e.g. shock)
nephron filtration is impaired
how does blood flow through nephrons remain constant despite normal changes in systolic BP?
diameter of arterioles (bringing blood to kidneys) is adjusted
albuminaria
damage to glomerular capillaries leading to plasma protein loss - leaks into filtrate
lowered albumin in blood makes it
hypotonic - fluid leaks from blood to tissues
blood volume decreases & interstitial fluid volume increases causing Oedema
describe tubular reabsrption
as filtrate moves along renal tubules & collecting ducts tubule cells reabsorb about 99% of the filtrate and are returned to the bloodstream
4 substances reabsorbed during tubular reabsorption
water
amino acids & small proteins
glucose
electrolytes
what is tubular secretion
tubule & duct cells also SECRETE certain materials so can be removed from blood and excreted via urine
what materials are secreted in tubular secretion
waste products - creatinine, ammonium ions, urea
certain drugs - penicillin
Excess ions - H+, K+
Na
Sodium
Ca
Calcium
HCL
Hydrochloric acid
Which 5 hormones affect kidney reabsorption of Na, Cl, Ca & water as well as secretion of K
Angiotensin 2 Aldosterone Antidiuretic hormone Atrial natriuretic peptide Parathyroid hormone
What do kidneys do if blood pressure is too low which inhibits effective blood filtering
secrete an enzyme called RENIN
what does Renin convert
angiotensinogen from the liver into angiotensin 1
how is angiotensin 1 converted into its active form angiotensin 2
via angiotensin Converting Enzyme (ACE)
secreted by lungs & kidneys
Angiotensin 2 does 3 things -
triggers vasoconstriction
triggers pituitary gland to release ADH
Stimulates Adrenal Cortex to produce Aldosterone
Aldesterone does what
causes kidneys to retain Na and excrete K
- causes water retention, increases BV and BP
Summary of Renin-Angiotensin-Aldosterone System
BP too low - kidneys secrete RENIN converts ANGIOTENSINOGEN from liver into ANGIOTENSIN 1 - converted into ANGIOTENSIN 2 by ANGIOTENSIN CONVERTING ENZYME (ACE) from lungs/kidneys Vasocontriction ADH released from pituitary ALDOSTERONE produced by adrenal cortex sodium retained, potassium extreted water retention - blood volume/pressure increased!!!
ADH, released by posterior pituitary is triggered by
dehydration! (reduced water volume in blood)
reduced blood volume (haemorrhage)
How does ADH rebalance the osmotic pressure of the blood by increasing water re-absorption in the kidneys
increases permeability od distal convoluted tubules - reabsorb more water = INCREASE in blood volume/pressure
what feedback mechanism regulates ADH secretion
negative
ANP
Atrial Natriuretic Peptide
when/where is ANP released
from heart when INCREASE in blood volume/pressure
What change does ADH bring about to blood volume/pressure
INCREASES
what change does ANP bring about to blood volume/pressure
DECREASES
how does ANP decrease blood volume/pressure
inhibits reabsorption of na/water in renal tubules
supresses ADH and aldosterone
increased excretion of Na (K retention) in urine and increased urine output - decreases BV & BP
PTH
parathyroid hormone
what stimulates parathyroid glands to release PTH
LOW blood calcium
how does PTH act on kidney sot raise blood calcium
Stimulates kidney tubules to reabsorb more calcium
inhibits phosphate reabsorption
