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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