Objectives

• Students should learn:• that urine, containing urea, excess mineral

ions and water, is removed from the body by the kidneys

• that sugar, mineral ions and water needed by the body are reabsorbed into the blood as it passes through the kidneys.

Requirements

• Nephron sheets to label• Colours

Specification

• A healthy kidney produces urine by:• – first filtering the blood• – reabsorbing all the sugar• – reabsorbing the dissolved ions needed by the body• – reabsorbing as much water as the body needs• – releasing urea, excess ions and water as urine.

[B3.3.1 c)]• Controlled Assessment: B4.5 Analyse and interpret

primary and secondary data. [B4.5.3 a)]; [B4.5.4 a) b)]

2 the human kidney

p.248

Starter – Urea

• 1 min to extract bullet point list from p. 248• I got 7… but I knew one from last unit!

Lesson 2: the human kidney

• p.248

What is it? Where is it produced? How is it produced? What transports it? Where to? What happens to it?

Urea

1. Produced in the liver2. Excess amino acids are broken

down3. It is poisonous4. It travels in the blood plasma5. Kidneys filter it out of the blood6. Stored in the urine in the

bladder7. Leaves the body in the urine

Outcomes

• Most students should be able to:• describe how the kidneys produce urine • describe that the kidneys remove urea and

regulate the water content of the body.• Some students should also be able to:• explain the role of the kidney in homeostasis• explain in detail that sugar and dissolved ions

may be actively absorbed against a concentration gradient in the kidney tubules.

Which other organs get rid of waste from the body by excretion?

• Kidney plus 2…• Does not include faeces/digestive system, why

not?• Excretion is not defaecation!!

Waste removal

The lungs remove carbon dioxide.

The liver converts excess protein into urea.

The kidneys remove unwanted substances such as urea, excess water and salt.

Several organs are important in removing waste from the body.

The skin provides a surface for small amounts of water and salt to move out of the body.

Cortex

Medulla

Pelvis

Nephrons

Ureter

What are the different parts of a kidney?

How a kidney produces urineget the sequence right then copy it down

A. reabsorbing the dissolved ions needed by the body

B. reabsorbing as much water as the body needs

C. filtering the bloodD. releasing urea, excess ions and water as

urine.E. reabsorbing all the sugar

How a kidney produces urineget the sequence right then copy it down

A. 3 reabsorbing the dissolved ions needed by the body

B. 4 reabsorbing as much water as the body needs

C. 1 filtering the bloodD. 5 releasing urea, excess ions and water as

urine.E. 2 reabsorbing all the sugar

The blood is filtered

Water dissolved ions (salt), glucose and urea are small enough to pass through

Glucose is selectively reabsorbed into the blood

What dissolved ions (salt ) are needed by the body are taken back into the blood by selective reabsorption

Any water needed by the body is taken back into the blood

Urea, excess ions and water travel to the bladder as urine.

The blood is filtered

Water dissolved ions (salt), glucose and urea are small enough to pass through

Glucose is selectively reabsorbed into the blood

the dissolved ions (salt ) are needed by the body are taken back into the blood by selective reabsorption

Any water needed by the body is taken back into the blood

Urea, excess ions and water travel to the bladder as urine.

How does the kidney work?

What does urine contain?

• 1 min to list from the book

• Why is urine yellow? (extension)• Where have we met something like this on the

course before?

What does urine contain?

• Urea• Excess dissolves (mineral) ions• Excess water

• Urobilins (yellow pigments from the breakdown on haemoglobin in your liver)

• Bile consists of bilirubin and biliverdin, again these are pigments from the breakdown of haemoglobin in the liver

Comparing the composition of blood with urineSubstance Present in

blood?Present in filtrate in kidney tubule?

Present in urine?

Red blood cellsPlatelets

Proteins

Glucose

Amino acids

Urea

water

Mineral ions

Why is urine yellow?

How your kidney responds to drinking

• See graphs p. 249• More water is lost so the concentration of salt

decreases as a result of the greater volume.

Workbook

• P. 115-6

Extension

• Control of water balance by ADH

Controlling water content

Regulating water content

Analysing urineChanges in the colour, clarity, pH and the presence of certain substances in urine can help doctors diagnose medical conditions:

Protein or red blood cells in urine can indicate kidney damage or disease, as these substances would not normally filter through the glomerulus.

Glucose in urine is often an indication of diabetes. A person with diabetes will have a high level of glucose in the blood.