1. The Kidney – structure and function
Mrs Tagore

2. Key words
Nephron
Collecting ducts
Renal tubule
Glomerular capsule
Glomerulus
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Afferent arteriole
Efferent arteriole
Reabsorption

4. Urinary system
The system responsible for osmoregulation is called the urinary system.
urethra

5. Task
Use page 125 of your textbook to help you label your diagrams

7. Reabsorbtion of important substances.
Part
Function
Kidney
Filtration of blood.
Reabsorbtion of important substances.
Bladder
Stores urine.
Ureter
Transports urine from kidney to bladder
Urethra
Carries urine from bladder to external environment.
Renal artery
Carries unpurified blood into the kidney.
Renal vein
Carries purified blood away from the kidney.

8. Urea Urea is made in the liver.
Urea is made by breaking down excess amino acids (remember that this process is known as deamination!)
Urea is transported to kidney in the blood by the renal artery.
Urea is removed from the body as urine.

9. Filtration By The Kidney
Blood enters the kidney via the renal artery (red) and leaves via the renal vein (blue)

10. The kidney Main organ of osmoregulation. 3 main functions:
Filtration of blood
Reabsorption of useful materials e.g. glucose, water, amino acids and some salts
Production of urine

11. Structure of the kidney
The renal artery which contains unpurified blood enters the kidney and divides into many tiny branches.
The blood in each tiny branch is filtered in a special filtering unit called a nephron.

12. Structure of the kidney
Each kidney is made up of about 1 million tiny filtration units called NEPHRONS
Nephrons filter the blood and then reabsorb the useful substances.

13. The start of the nephron – where blood is filtered
Kidney
The start of the nephron – where blood is filtered

14. The Role of the Nephron
The nephron reabsorbs useful substances such a glucose back into the blood vessels.
Tiny blood vessels then join up as they leave the kidney. This forms the renal vein.
The renal vein carries purified blood back to the body.

15. Structure of the Nephron
Renal artery divides into about a million tiny branches.
Each branch leads to a glomerulus (a tiny knot of blood capillaries).
The glomerulus is surrounded by a cup-shaped glomerular capsule which leads to a long tubule.

17. The Nephron – A Filtration Unit
Glomerular capsule
Glomerulus
Collecting duct
Blood capillaries

19. Knot of blood capillaries called a GLOMERULUS
Renal artery
Knot of blood capillaries called a GLOMERULUS
The glomerulus sits inside a cup-shaped GLOMERULSR CAPSULE

20. Filtration
Blood vessels that enter the glomerulus are wider than those that leave.
Blood inside these vessels are under pressure (being squeezed).
This means that only the small molecules in blood are squeezed out of the tiny spaces in the capillary wall and collect in the Bowman's capsule.
This liquid is now called glomerular filtrate.
Blood cells and plasma proteins are too big to fit through the pores so remain in the blood.

21. The structure of the Bowman’s capsule is explained

22. Bowman’s Capsule

23. Bowman’s Capsule

24. Capillary network – many small diameter blood vessels presents a large surface area for filtration to occur
Bowman’s Capsule

25. Glomerulus (Capillary network)
Bowman’s Capsule

26. Note the different diameters of the blood vessels entering and leaving
The pressure generated by the heart beat is intensified by the narrowing of the capillary

29. The pressure increases as the blood flows through the capillary network. This is because the diameter of the blood vessels are decreasing

30. The sieve-like membrane of the capsule is shown

31. The membrane between the capillaries and the capsule acts like a sieve

32. This sequence shows which of the blood’s components can pass through into the filtrate

33. Glomerulus
Bowman’s capsule

38. Glucose and amino acid molecule pass through into the filtrate

39. Na+
Na+
H2O
H2O
Cl-
Na+
H2O
Cl-
H2O
H2O
H2O
Cl-

40. Na+
Na+
H2O
H2O
Na+
H2O
Cl-
Cl-
Cl-
H2O
H2O
H2O

41. Na+
H2O
H2O
Na+
Cl-
Na+
H2O
Cl-
H2O
H2O
H2O
Cl-

42. Na+
Cl-
H2O
H2O
Na+
Na+
H2O
H2O
Cl-
Cl-
H2O
H2O

43. Na+
Na+
Cl-
H2O
H2O
Cl-
Na+
water molecules & ions pass through into the filtrate
H2O
H2O
H2O

44. urea
urea
urea
urea

45. urea
urea
urea
urea

46. urea
urea
urea
urea

47. urea
urea
urea
urea
urea molecules pass through into the filtrate

49. protein molecules are too large to pass through into the filtrate

51. Red blood cells are too large to pass through into the filtrate

53. White blood cells are too large to pass through into the filtrate

54. Reabsorption By Kidney
All glucose and variable amounts of water, amino acids and salts are reabsorbed back into the blood
No urea is reabsorbed – expelled as urine (excess water dilutes urea)
Water is absorbed again by collecting duct

55. Excretion By The Kidney
Urine is a nitrogenous waste product. It must be removed from the body because it is toxic
Urea must be excreted as urine so that urea can be removed from the body