THE KIDNEY Organ of osmoregulation and excretion © 2008 Paul Billiet ODWSODWS.

THE KIDNEY

Organ of osmoregulation and excretion

© 2008 Paul Billiet ODWS

The urinary system

Kidney

Ureter

Aorta

Renal vein

Bladder

Renal artery

Vena cava

Urethra


The Kidney

Pelvis

Ureter Medulla organised in pyramids

Cortex

Outer membrane

Renal Vein

Renal artery

Urine

Nephrons(2 million)


The blood supply


The cortex (view x100)

Tubule

Malpighian or renal corpuscles© 2008 Paul Billiet ODWS

The Malpighian corpuscle (view x400)

Glomerulus – a ball of capillaries

Bowman’s capsule© 2008 Paul Billiet ODWS

Medulla (view x400)

Tubules

Capillaries


The nephron

In the cortex

In the medulla


The nephronBowman’s capsule

Glomerulus

Proximal convoluted tubule

Capillary

Loop of Henlé

Collecting duct

Distil convoluted tubule

Branch of renal vein

Branch of renal artery


Filtration in the glomerulus Blood enters the glomerulus

from a branch of the renal artery

This blood is under high pressure

The capillary walls are one cell thick

They are pierced with openings (fenestrations)

The plasma filters though the membrane under pressure

Proteins do not pass

Southern Illinois School of Medicine


Filtration in the glomerulus

A membrane surrounds each capillary of the glomerulus

The blood plasma is filtered at about 150 litres per day



Filtration in the glomerulus

The filtration membrane is held in place by specialised podocytes

Auer Lab Life Sci Div Lawrence Berkley National Lab



Blood plasma v Filtrate

Component Plasma

/ mg 100cm-3

Filtrate

/ mg 100cm-3

Urea 0.03 0.03

Glucose 0.10 0.10

Amino acids 0.05 0.05

Salts 0.72 0.72

Proteins 8.00 0


The nephron functions

Variable permeability to water

Impermeable to water

Freely permeable to water


The nephron osmoregulation




Na+ Na+ Na+

Active reabsorption

H2O H2O

Passive osmosis

80% of water reabsorbed

Ultrafiltration under pressure





The nephron osmoregulationM

ore an

d m

ore salty

H2O

H2O

H2O

H2O

H2O

H2O

Co

llecting

d

uct

Loop of

Henlé

H2O

H2O

Na+

Na+

Na+



The blood concentration is monitored by osmoreceptors in the hypothalamus

If the concentration rises the hypothalamus releases ADH

ADH makes the collecting duct walls more permeable

More water is reabsorbed from the filtrate as the ducts pass through the salty tissues of the medulla



The urine released into the pelvis is more or less concentrated depending upon the blood concentration

Excessive sweating and eating salty food will produce concentrated urine

Drinking and cold weather will produce dilute urine


Kidney reabsorption

Component Filtrate

/ mg 100cm-3

Urine

/ mg 100cm-3

Urea 0.03 2.00

Glucose 0.10 0

Amino acids 0.05 0

Salts 0.72 1.50

Proteins 0 0


Reabsorption

Microvilli on cuboidal epithelial cells

Kidney tubule with brush border

Dr Millet USC Med schooll


The proximal tubules reabsorb:

80% of water All of the glucose All of the amino acids Blood pH is regulated Blood salt levels are regulated Urea is left behind and even secreted into the

tubules Reabsorbed molecules pass into the surrounding

capillaries


THE KIDNEY Organ of osmoregulation and excretion © 2008 Paul Billiet ODWSODWS.

Documents

Transcript of THE KIDNEY Organ of osmoregulation and excretion © 2008 Paul Billiet ODWSODWS.