CIE Categories Archives: 7. Transport in humans

7. Transport in humans

7.1 The Heart.

Fig.7.1 The structure of the heart.

The thickest part of the cardiac muscle indicates that it is the left part of the heart.

1 . Functions of valves:

  • To allow the blood to flow in one direction only.
  • To prevent the backflow of blood.

2 . The Double circulation:

Fig.7.2 (a) Pulmonary and (b) systemic circuit.

3 . The blood which carries oxygen is called oxygenated blood (from lungs to body).

The blood which doesn’t carry oxygen is called deoxygenated blood (from body to lungs).

4 . The left side of the heart is more muscular and thicker because it pumps blood to all parts of the body.

7.2 The Blood Vessels.

1 . There are three types of blood:Arteries.• Veins.• Capillaries. (smallest)•

  • Arteries.
  • Veins.
  • Capillaries. (smallest)

2 . Differences between arteries and veins:

  • Arteries have smaller central cavity than veins.
  • Arteries have thicker elastic and muscular wall than veins.
  • Veins have valves while arteries don’t have valves.
  • The blood flows slower, smoother and at low pressure than arteries.
  • All arteries carry oxygenated blood except pulmonary artery while all veins carry deoxygenated blood except pulmonary veins.
  • Arteries carry blood away from the heart to the body while veins carry blood to the heart from the body.
  • The blood carried by arteries are bright red in colour while the blood carried by veins are dark red in colour.
  • Blood in arteries flow due to the pumping action of the heart while veins flow due to the contraction of the heart.
  • Veins are big, slow and evil.

7.3 The Blood.

1 . Components of the blood:Plasma.• Blood cells.• Platelets.•

  • Plasma.
  • Blood cells.
  • Platelets.

2 . Plasma is the liquid part of the blood, it contains:

  • Blood cells.
  • Platelets.
  • Water.
  • Blood proteins.
  • Waste products.
  • Hormones.
  • Food substances; glucose, proteins, vitamins, etc.

3 . The blood cells consist of two parts:

  • Red blood cells.
  • White blood cells.

4 . Red blood cells are also known as erythrocytes which have the function of transporting oxygen.White blood cells are also known as

5 . White blood cells are also known as leucocytes which have the function as a defense mechanism.

6 . Platelets which are also known as thrombocytes have the function to clot blood. (involving the use of fibrinogen)

7 . Fibrinogen work together with platelets to form fibrin.

8 . Factors that may cause heart diseases:

1) Smoking.

2) Stress.

3) Malnutrition i.e. obesity.

4) Lack of physical exercise.


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