1. The role of the kidney Dissecting the kidney

2. Learning Outcomes
1. recall that the lungs, kidneys and skin are organs of excretion (2.68)
2. describe the structure of the urinary system, including the kidneys, ureters, bladder and urethra (2.70)

3. Review Questions
The blood is to the circulatory system as ________ is to the lungs.
The _______ is to the circulatory system as lungs are to the respiratory system
Amino acids are to proteins as _______ are to carbohydrates

4. Organs of Secretion: Skin
Role of the skin:
Protection against damage
Preventing entry of disease
Sense organ
Controlling heat loss

5. Organs of Excretion: Lungs
The lungs take in oxygen from the air and remove Carbon Dioxide (excretion)

6. The function of the kidney
The kidneys are essentially blood filters. Blood is brought to the kidneys to be filtered by the renal artery. After filtering, the blood is taken away again by the renal vein.
The kidneys have four functions:
Maintaining the water balance in the body by a process called OSMOREGULATION
Reabsorption of useful substances into the blood
Adjustment of the levels of salts and ions in the blood
Excretion of urea and other metabolic wastes
Write this in the front of your books

7. Water Balance:
State three ways in which the body gains water and three ways in which the body loses water
What is the difference between the amount of water lost and the amount of water gained by the body?
Why is this important? What is maintained in the body by keeping this balance?

8. Kidney Location in Human
Two kidneys – each about the size of a fist, and lie at waist level at the back of the body.
Humans have two kidneys. They are bean-shaped organs, approximately 11.5 cm long, situated in the abdominal cavity, just below the ribcage, one on either side of the spine. They are embedded in fatty tissue for protection.

9. A closer look at the kidney
This is a human kidney. You have 2, but can survive with only 1.

10. Diagram of the Kidney
A longitudinal section through a kidney shows three distinct areas:
an outer region called the cortex
a middle region called the medulla, and
an inner region leading to the ureter, called the pelvis.

11. Dissecting a Kidney: What to look for

12. Blood Supply to Kidney Renal artery supplies blood to kidney.
Renal vein takes blood away from kidney.
Ureter connects kidney to bladder
Urethra connects bladder to outside of body it is where urine leaves the body.

13. Excretion of Urea
Urea is a waste product from the breakdown of proteins.
If more protein is eaten than is needed the body will have an excess of amino acids, which cannot be stored by the body.
The excess amino acids are broken down by the liver, with urea as a by-product.
Urea is toxic, and must be excreted from the body, so it is passed into the blood to be filtered out by the kidneys.
It is then passed to the bladder for storage as urine, before leaving the body.
Write this in the front of your books

14. Production of urine

15. How the kidneys work Blood enters the kidneys (renal artery)
Millions of nephrons (mini-filtering systems) sieve the blood
Needed substances are reabsorbed and the waste products are removed in the form of urine
Clean blood returned to the blood (renal vein)
Urine carried to the bladder by tubes called ureters
When the bladder is full, urine passes out of the body via the urethra

16. Structure of the nephron
Ultra Filtration- all small molecules and lots of water
Blood high in urea
Blood low in urea
Selective reabsorption- useful substances back into blood from tubules (water sugar ions)
Excretion of waste- excess ions and water plus all urea as urine
Urine to bladder

17. Water balance
Our bodies control the amount of water in our blood and tissues through the endocrine system (hormonal system)
Like thermo-regulation, water balance is a negative feed back system that relies on the hypothalamus in the brain.
Anti Diuretic Hormone (ADH) is released in the blood to control how much water the kidneys release in urine.

18. If body has to little water

19. If body has too much water

20. Control of water hypothalamus Kidneys excrete more water in urine
Kidneys excrete less water in urine
+ water in blood
- water in blood
Pituitary gland produces less ADH
Pituitary gland produces more ADH
Blood enters brain

21. Water balance Healthy kidneys filter the blood to:
Remove waste products (from metabolism of the food we eat and body cells).
Remove excess fluid to balance fluid levels in the body

22. And Finally……
Homework; 1. Revise for module test 2. Visit work your way through the section on kidneys and try the higher tier test.