1. Kidney in Detail

2. Excretion by the Kidney
Urea
-nitrogenous waste
-made by liver
-excess amino acids in blood
-toxic
Why must nitrogenous waste be excreted?

3. 1 – Filtration by the Kidney
Supplied with blood from renal artery
Inside it splits into many fine capillaries
Each capillary supplies blood to hundreds of thousands of tiny filtration units called nephrons
Renal artery
Lets have a look at a nephron!!!
Renal vein
Ureter

6. 2. Liquid filtered from blood under pressure (ultra-filtration)
Glomerulus brings a large surface area of blood capillaries in close contact with Bowman’s capsule
2. Liquid filtered from blood under pressure (ultra-filtration)
Glomerular filtrate produced containing:
-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 travels through narrow capillary towards renal vein
Filtration
Glomerular filtrate

7. 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?

8. Key Words!!
Nephron: structure in the kidney that acts as a microscopic filtration unit
Glomerulus: dense mass of very fine blood capillaries at the nephron that act as a filter
Bowman’s capusle: cup-shaped part of the nephron that holds a glomerulus and collects the products of filtration from it
Glomerular filtrate: liquid removed from the blood by filtration in the kidney

9. 2 – Reabsorption by the Kidney
Once the main components of glomerulur filtrate enter the nephron
-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!

10. More water reabsorbed
Variable amounts of water and salts reabsorbed and filtrate gradually turning into urine
Final urine containing:
-excess water
-unneeded salts
-waste urea
Glucose reabsorbed

11. 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?

12. 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 control to regulate water content of the blood

13. How does it work? Negative Feedback

14. Control of Water animation