The Kidneys by Abhishek Jaguessar

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Excretion by the Kidney

Urea

-nitrogenous waste

-made by liver-excess amino acids in blood

-toxic

Why must nitrogenous waste be excreted?

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1 Filtration by the Kidney

Renal

artery

Ureter

Renal

vein

Supplied with blood

from renal artery

Inside it splits into

many fine capillaries

Each capillary

supplies blood to

hundreds of

thousands of tinyfiltration units called

nephrons

Lets have a

look at a

nephron!!!

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1. Glomerulus brings a largesurface area of bloodcapillaries in close contact

with Bowmans capsule

2. Liquid filtered from bloodunder pressure (filtration)

3. Glomerular filtrate producedcontaining:

-water

-glucose

-salts

-urea

(Protein molecules and red blood

cells do not pass into tubule as

they are TOO BIG!!!!)

Blood from

renal artery

enters wide

capillary

Blood travelthrough

narrow

capillary

towards ren

vein

Glomerularfiltrate

Filtration

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Think

Which feature of the glomerulus helps the

process of filtration?

Which 4 components of unfiltered blood

appear in the glomerular filtrate?

Why do blood cells and protein molecules

not appear in the glomerular filtrate?

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Key Words!!

Nephron: structure in the kidney that acts asa microscopic filtration unit

Glomerulus: dense mass of very fine

blood capillaries at thenephron that act as a filter

Bowmans capusle: cup-shaped part of thenephron that holds a

glomerulus and collects theproducts of filtration from it

Glomerular filtrate: liquid removed from the blood byfiltration in the kidney

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2 Reabsorption by the Kidney

Once the main components of glomerulur filtrate

enter the bloodstream

-they are no longer in bloodstream

If nothing more happened in the nephron then all

the useful stuff would be lost in the urine!

Therefore, glucose, water and some salts need

to be reabsorbed!

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Glucose

reabsorbed

Variable amounts of water

and salts reabsorbed and

filtrate gradually turning intourine

More water

reabsorbed

Final urine

containing:

-excess water

-unneeded salts

-waste urea

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Think.

Which three components of the glomerular

filtrate are reabsorbed?

Why is it important for these to be

reabsorbed?

Which substances are present in the final

urine?

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Summary of kidney function

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2 Controlling Water

Concentration Blood

-important part of internal environment

-constantly changing water concentration-e.g. exercising

drinking lots of water

The body uses negative feedback controlto regulate water content of the blood

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How does it work?

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Control of Water animation