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10.2 |
Circulatory System of Humans |
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Blood composition: |
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Blood |
Cell |
Blood plasma |
Erythrocytes
Leucocytes
- Granulocytes; neutrophils, eosinophils, and basophils
- Agranulocytes; lymphocytes, and monocytes
Platelets
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Dissolved substances
- Protein; albumin, globulin, and fibrinogen
- Nutrients; glucose, amino acids, and vitamins
- Respiratory gases; oxygen and carbon dioxide
- Waste substances
- Enzymes
Water
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Characteristics and functions of red blood cells and white blood cells: |
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Red blood cell (erythrocytes):
- Biconcave disc-shaped.
- Size: 8 µm (diameter) and 2 µm (thickness).
- No nucleus.
- Contains hemoglobin.
- Elastic; allows it to squeeze into thin capillaries.
- 5 million cells/mL.
- Life span 120 days.
- Function: transport oxygenated and deoxygenated blood in the form of oxyhemoglobin and carbaminohemoglobin respectively.
- Produced in the bone marrow.
- Destroyed in the liver and spleen.
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Leucocytes |
Function |
Basophils |
Secretes heparin (inflammatory response) |
Eosinophils |
Inflammatory response |
Neutrophils |
Phagocytosis |
Monocytes |
Phagocytosis |
Lymphocytes |
Produces antibodies |
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The function of blood: |
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- Transport oxygen.
- Transport water.
- Transport heat.
- Transport wastes.
- Transport nutrients.
- Transport hormones.
- Transport carbon dioxide.
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Comparison of blood vessels in humans: |
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Arteries:
- Size of the lumen; small.
- Muscular wall: thick.
- Presence of valve: absent.
- Blood pressure: high.
- Function: transport oxygenated blood except for the pulmonary artery.
- Blood flow: transport blood from the heart to all body parts.
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Capillaries:
- Size of the lumen: absent.
- Muscular wall: one cell thick.
- Presence of valve: absent.
- Blood pressure: higher than veins and lower than arteries.
- Function: the site of exchange for gases and nutrients.
- Blood flow: transport blood from arteries to the veins.
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Veins:
- Size of the lumen: large.
- Muscular wall: thin.
- Presence of valve: present (prevent the backward flow of blood).
- Blood pressure: lower than arteries and capillaries.
- Function: transport deoxygenated blood except for pulmonary vein.
- Blood flow: transport deoxygenated blood from body tissues to the heart.
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The heart structure: |
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- The weight of a human's heart is around 250g until 350g and has the size of a fist.
- The heart is situated at the thorax cavity, above the diaphragm, and protected by the ribcage.
- The heart's muscles are myogenic, which means they contract and relax automatically and are not controlled by the nervous system.
- Covered by pericardium to protect the muscle tissues of the heart.
- The function of the valve is to ensure that the blood flows only in one direction and to prevent the backward flow of blood.
- It has a four-chambered heart; atria (right and left); thinner than ventricles and ventricles (right and left); thicker.
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