•THE ROLE OF THE KIDNEY•DISSECTING THE KIDNEY

THE KIDNEY

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)

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

ORGANS OF SECRETION: SKIN

• Role of the skin:• Protection against damage• Preventing entry of disease• Sense organ• Controlling heat loss

ORGANS OF EXCRETION: LUNGS

• The lungs take in oxygen from the air and remove Carbon Dioxide (excretion)

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:1. Maintaining the water balance in the body by a process

called OSMOREGULATION2. Reabsorption of useful substances into the blood 3. Adjustment of the levels of salts and ions in the blood 4. Excretion of urea and other metabolic wastes

Write this in the front of your books

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?

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.

A CLOSER LOOK AT THE KIDNEY

This is a human kidney. You have 2, but can survive with only 1.

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.

DISSECTING A KIDNEY: WHAT TO LOOK FOR

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.

EXCRETION OF UREA

1. Urea is a waste product from the breakdown of proteins. 2. If more protein is eaten than is needed the body will have

an excess of amino acids, which cannot be stored by the body.

3. The excess amino acids are broken down by the liver, with urea as a by-product.

4. Urea is toxic, and must be excreted from the body, so it is passed into the blood to be filtered out by the kidneys.

5. It is then passed to the bladder for storage as urine, before leaving the body.

Write this in the front of your books

PRODUCTION OF URINE

vena cava aorta

renal arteryrenal vein

kidney

bladder

sphincter muscle

urethra

ureter

cortex

renal artery

renal vein

ureter

pelvis

medulla

pyramid

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 urineClean 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

Blood high in urea

Blood low in urea

Structure of the nephron

Ultra Filtration- all small molecules and lots of water

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

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.

IF BODY HAS TO LITTLE WATER

Hypathalmus detects low blood water concentration

Pituatory gland produces more ADH

Kidney re-absorbs more water into blood

Less volume of urine produced (more concentrated

Sensor Response Result

IF BODY HAS TOO MUCH WATER

Hypathalmus detects high blood water concentration

Pituatory gland produces less ADH

Kidney re-absorbs less water into blood

higher volume of urine produced (less concentrated

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

WATER BALANCE

• Healthy kidneys filter the blood to:1. Remove waste products (from metabolism of

the food we eat and body cells). 2. Remove excess fluid to balance fluid levels in

the body

AND FINALLY……

Homework;1. Revise for module test2. Visit

http://www.bbc.co.uk/schools/gcsebitesize/biology/humansasorganisms/6homeostasisrev5.shtml.work your way through the section on kidneys and try the higher tier test.