Urine formation Flashcards by Miranda Holder

ChlorineTo produce urine, nephrons & collecting ducts do 3 things -

glomerular filtration
tubular reabsorption
tubular secretion

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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

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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

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Filtrate contains (6)

water
glucose
amino acids
electrolytes/ions
urea &amp; other wastes
hormones

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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

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how else is glomerular filtration efficient?

pores in glomerular capillaries 50 times more leaky

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summary of how glomerular filtration is adapted for fantastic filtration

greater blood pressure

more permeability

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what happens if systolic BP is above 200

the kidneys are damaged

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what happens if systolic BP is below 80 (e.g. shock)

nephron filtration is impaired

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how does blood flow through nephrons remain constant despite normal changes in systolic BP?

diameter of arterioles (bringing blood to kidneys) is adjusted

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albuminaria

damage to glomerular capillaries leading to plasma protein loss - leaks into filtrate

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lowered albumin in blood makes it

hypotonic - fluid leaks from blood to tissues

blood volume decreases & interstitial fluid volume increases causing Oedema

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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

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4 substances reabsorbed during tubular reabsorption

water
amino acids & small proteins
glucose
electrolytes

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what is tubular secretion

tubule & duct cells also SECRETE certain materials so can be removed from blood and excreted via urine

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what materials are secreted in tubular secretion

waste products - creatinine, ammonium ions, urea
certain drugs - penicillin
Excess ions - H+, K+

Sodium

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