ADH Diagram animated

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1

Slide 1

Water content

of the blood normal

Water content of the blood HIGH

Water content of

the blood LOW

Too much water drunk

Too much salt

or sweating

Brain produces

More ADH

Urine output

LOW

Brain produces

Less ADH

Urine output

HIGH

High volume of water

reabsorbed by kidney

Low volume of water

reabsorbed by kidney

(small volume of

Concentrated urine)

(large volume of

dilute urine)

Slide 2

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(then click the mouse button to make it play through)

Slide 3

All land animals need to conserve water.

This is because the external environment is usually drier than the internal environment of the animal’s body. Thus, water will tend to diffuse away from the body.

There is also a need to excrete waste products such as urea, which is dissolved in water. This creates a problem!

In mammals, the kidneys are responsible for both excretion of urea and osmoregulation (the control of body fluid concentration).

So, the kidney must balance the need to excrete with the need to conserve water, in other words it must produce a small volume of highly concentrated urine.

Slide 4

The operating unit of the kidney is called the nephron.

There are about 1 million nephrons in each of the 2 kidneys.

Each nephron comprises 5 segments:

Glomerulus

Proximal (first) convoluted tubule

Loop of Henle

Distal (second) convoluted tubule

Collecting duct

The Loop of Henle allows mammals to produce urine which is more concentrated than body fluids… .

Slide 5

Cortex

Medulla

The nephrons are packed into the kidney:

the glomeruli and convoluted tubules in the cortex,

the loops and collecting ducts extending into the medulla.

All the collecting ducts eventually join up to form the ureter,

emptying urine into the bladder and away!

Ureter

Slide 6

Cortex

Water leaves - ion concentration in filtrate increases

Filtrate reaches maximum concentration

Chloride ions out (sodium follows) -ion concentration in filtrate decreases

Medulla

Increasing concentration

Slide 7

Increasing concentration

To ureter

Collecting duct

Several nephrons empty into one collecting duct.

The collecting duct passes through the progressively more concentrated medulla, losing water by osmosis. This water is reabsorbed by the capillaries.