Circulatory System

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Slide 12

The Vein

Veins carry blood towards from the heart.

thin muscle and elastic fibres

veins have valves which act to stop the blood from going in the wrong direction.

body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel.

Slide 13

The Capillary

Capillaries link Arteries with Veins

the wall of a capillary

is only one cell thick

they exchange materials between the blood and other body cells.

The exchange of materials between the blood and the body can only occur through capillaries.

Slide 14

artery

vein

capillaries

body cell

The CAPILLARY

A collection of capillaries is known as a capillary bed.

Slide 15

what’s in

red blood cells

white blood cells

platelets

plasma

carbon dioxide

digested food

waste (urea)

hormones

oxygen

Blood

Slide 16

The Blood

plasma

red blood cell

white blood cell

platelets

Slide 17

Red Blood Cells

contain haemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it.

can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries.

a biconcave disc that is round and flat without a nucleus

Slide 18

White Blood Cells

there are many different types and all contain a big nucleus.

the two main ones are the lymphocytes and the macrophages.

some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them.

other lymphocytes make antitoxins to break down poisons.

macrophages ‘eat’ and digest micro-organisms .

Slide 19

Platelets

Platelets are bits of cell broken off larger cells.

Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot.

Slide 20

Plasma

A straw-coloured liquid that carries the cells and the platelets which help blood clot.

carbon dioxide

glucose

amino acids

proteins

minerals

vitamins

hormones

waste materials