ANIMAL NUTRITION & TRANSPORT IN MAN

Circulatory System: Blood

What you are supposed to learn / know

• Describe how blood acts as a transport medium

• Identify different types of blood cells

• State the functions of each component of

blood.

Blood

What is ‘blood’?• Blood is made up of a liquid called plasma (yellow in

colour). It contains blood cells (red and white) and small bits of cells called platelets.

Human body has about 5 litres of blood. (55% plasma, 44% red blood cells and 1% white blood cells and platelets)If you lose more than 2 litres of blood you could die.

Can you identify this?

RED BLOOD CELL

WHITE BLOOD CELL

Red Blood Cell

Why does blood look red?• Red blood cell is a biconcave, flattened disc with

no nucleus.• It contains a red pigment called haemoglobin

(Hb) which gives the blood colour red.• Red blood cells are made in bone marrow. (the

soft centre in the bone).• They live for about 3 – 4 months only.• Worn out blood cells are destroyed and replaced.

What does red blood cell do?• Red blood cell contains haemoglobin, which combines

with oxygen and carries it round the body.• It combines with the oxygen from the lungs

Oxygen + haemoglobin oxyhaemoglobin• The red blood cells are bright red in colour when they

carry oxygen.• At the tissue, low concentration of oxygen causes the

oxyhaemoglobin to break down and its oxygen.• Haemoglobin is a protein which contains iron. A person

with insufficient haemoglobin will not be able to transport oxygen fast enough and often, that person will look pale and breathless.

Checkpoint

1. What are the three parts of the human circulatory system?

2. What does human blood consist of?3. a) Name the three kinds of blood vessels

b) Which blood vessels carry blood from the heart?c) Which blood vessels carry blood towards the heart?

White Blood Cells• There are fewer than red blood cells• They are colourless, are larger than red blood

cells and have nuclei• Also made in the bone marrow.• White blood cells only live for a few days.• Worn out cells are destroyed by the active white

blood cells and replaced.• There are two different types of white blood

cells: phagocytes and lymphocytes• White blood cells protect the body against

germs that causes diseases.

Platelets

• Tiny pieces of blood cells.• No nucleus.• Made in bone-marrow.• Help blood to clot when we bleed.• Produced fibrinogen and converts it to fibrin• Fibrinogen is a protein that is present in plasma. • Fibrin is a network of threads that forms across

the wound.

What is ‘plasma’?

• A pale yellow liquid consists of 90% water and many dissolved substances.

• Plasma transports useful substances (digested food from the small intestine and hormones) to all the body tissues and removes waste materials (urea and carbon dioxide) produced by the body tissues to the kidneys and lungs respectively.

Quick checkpoint

• Name the component of blood that is described by each of the following statements.

a) They produce antibodies.b) They help to clot blood.c) They live for only four months.d) They are made up of pieces of broken-up cytoplasm.e) They transport oxygen from the lungs to the body cells.