Excretion

a nethra original

Nephron Adaptations for Filtration

capillaries 1 cell thick

large surface area

pressure is higher than normal blood (efferent narrower than afferent) allows some molecules to be forced out of the blood

Location of Nephron

Cortex and medulla of kidney

Functions of Nephron

Filtration: Filters waste from blood

Absorption: Reabsorb water/nutrients

Secretion: Gets rid of excess substances as urine

Nephron-Glomerulus function

filters blood(except blood cells and large proteins) to form urine.

Bowman’s Capsule function

Collects filtered fluid (filtrate)

Proximal covulated tubule

reabsorbs glucose amino acids and water from filtrate into blood.

loop of henle

concentrates filtrate by reabsorbing salts/water

descending lets water out

ascending lets salt out (dilute)

distal convulated tubule

finetunes salt and ph levels

collecting duct

final water reabsorption, sends urine to the bladder

how blood enters and leaves the nephron

aorta-renal artery-afferent arteriole-glomerulus-efferent arteriole-renal vein

Filtration

blood entering nephron has waste

substance filtered in glomerulus and forced out into bowmans capsule(glomerular filtrate)

Nephron reabsorption

water salts useful substances

in the proximal covulated tubule 80% of the water is reabsorbed by osmosis

all glucose/amino acids due reabsorbed due to active transport or diffusion

active transport energy( ATP) used transport molecules from high to low concentrations

Nephron Reabsorption adaptations

thin walled

long,lots of infoldings-increased surface area

correct numbers of mitochondria (for active transport)

Secretion

located in cortex of kidney

substance (potassium/hydrogen ions) secreted from blood to nephron through distal convoluted tubule

Controlling H ion concentration, help control pH of blood

Functions of the kidneys

excretion-metabolic waste blood to urine

control water/salt concentration-osmoregulation(varies salt/water content in urine)

blood concentration=concentration inside cell

controls the pH of body fluids(blood pH 7.4)

Bowman’s capsule glomerular filtrate has more…

water

useful substances e.g. glucose and amino acids, than urine (collecting duct)