Urine Formation Flashcards
What are the three stages of urine formation
1) glomerulus filtration
2) reabsorption
3) tubular secretion
Where does glomerulus filtration occur
bowman capsule + glomerulus
How much of the blood content is squeezed into the capsule and why
20% otherwise blood would be too thick to move
why is fluid forced out during filtration
as the afferent arteriole has a wider diameter than the efferent, narrowing increases resistance to flow of blood and produces higher pressure in the glomerulus, which is relieved by squeezing fluid out into capsule
What is the name of the fluid forced out during filtration?
filtrate
What does filtrate contain
water, salts, amino acids, glucose, fatty acids, urea, uric acid, creatinine, ions (K, Cl, Na)
What does filtrate not contain and why?
RBC, WBC, proteins= too large to pass through membrane
Where does reabsorption take place
PCT and Loop OF H
How much filtrate is reabsorbed into the body?
99%
What materials are reabsorbed into the body during reabsorption and by what process and why?
(water) ions (K, Na, Cl), glucose, some urea, creatinine , amino acids
by diffusion due to concentration grad.
How is water absorbed during reabsorption
osmosis
Where does tubular secretion take place?
DCT
Is secretion in tubular secretion active or passive
both, depends on concentration
What is the main function during tubular secretion?
control of pH
What happens in the DCT?
control of pH, water content controlled
Why is water not considered secretion?
processed by facilitated diffusion
How is the pH of the blood controlled
secretions of hydrogen and ammonia into tubule to balance
What determines the amount of water absorbed in the distal convoluted tubule
depends on how much water consumed- will change permiablity of tubule (controlled by hormone that recognises levels in body)
What will happen to water absorption in DCT when dehydrated?
reabsorb lots= little urine at high concentration of ammonia resulting in dark yellow colour and strong odour
What, besides water ammonia and hydrogen is removed from the blood into the tubule
creatinine, urea
What does it mean if glucose is found in the urine
means too much in Prox. CT, and can’t be reabsorbed therefore meaning body is making too much = sign for diebetes
Why isn’t protein found in the urine
too large to pass through into capsule
What shouldn’t be in urine?
glucose, protein
What makes the amber colour of urine
presence of bile pigments
Name the define features of the kidneys (5)
1) efferent artery smaller diameter than afferent leading in= raises b.p. so more fluid is filtered in
2) capsule almost surrounds glomerulus= collected squeezed fluid
3) millions of nephron= SA for reabsorption and secre
4) peritubular cap. surround tubule= close blood supply
5) two sets of convo. tubule and long loop= SA + long time to reab.
