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)•
- 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.•
- Blood cells.
2 . Plasma is the liquid part of the blood, it contains:
- Blood cells.
- Blood proteins.
- Waste products.
- 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:
3) Malnutrition i.e. obesity.
4) Lack of physical exercise.