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Transport

1.2.5b The Heart

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(Image by unknown author under Creative Commons Attribution-Share Alike 3.0 Unported license.)

Structure

  1. The human heart consist of four compartment:
    1. two upper chambers (left atrium and right atrium) 
    2. two lower chambers (left ventricle and right ventricle)
  2. The chamber to the right is separated from the chamber to the left by a wall called septum.

The Atria and Ventricles

  1. The atria are smaller and have thinner wall compare to the ventricles.
  2. The ventricles have thicker wall because they have to pump the blood to other organs of the body with greater pressure.
  3. Also, the wall of the left ventricle is thicker than the right ventricle because the right ventricle only has to pump blood to the lungs whereas the left ventricle has to pump blood to all parts of the body. 

The Valves

  1. The function of the valves in the heart are to prevent the back flow of blood.
  2. There are 4 valves in human heart (as shown in figure above):
    1. the tricuspid valve
    2. the bicuspid valve
    3. the semi-lunar valve
    4. the aortic valve

Contraction of Heart

  1. The wall of the heart is made up of cardiac muscle, which is myogenic.
  2. Myogenic contraction is the contraction of muscle without nervous stimulation.
  3. Contraction of heart is started by sinoatrial node (also known as the pacemaker)


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1.2.5a The Blood Vessels

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  1. Three types of blood vessels
    1. artery
    2. vein
    3. capillary
  2. Artery: Carries blood from the heart to other parts of the body.
  3. Vein: Carries blood from other parts of the body back to the heart.
  4. The arteries divides into smaller branches called arterioles.
  5. The veins receives blood from smaller branches called venules.
  6. Capillaries: Blood vessels connect the arterioles and venules.
  7. Around the capillaries are body cells.

(Image derived from the work of Kelvinsong and is shared under the Creative Commons Attribution-Share Alike 3.0 Unported license.)



Comparison

Artery Vein Capillary
Main function Carries oxygenated blood from the to ather parts of the body Carries dexoygenated blood from the other parts of the body to the heart. Connect arterioles and venules.
Allows exchange of materials between the blood and the cells.
Blood Carries oxygenated blood except pulmonary artery Carries deoxygenated blood except pulmonary vein
Valves No valves except pulmonary artery All have valves except pulmonary vein No valves
Blood pressure High Low Very low
Blood flow Rapid Slow Very slow
Diagram
Wall Thick muscular wall Thin wall and less muscular Thin wall, only one-cell thick
Size of lumen Small lumen Big lumen Very small lumen
Branches Arterioles Venules No


(All 3 images in the table above are derived from the work of Kelvinsong and is shared under the Creative Commons Attribution-Share Alike 3.0 Unported license.


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1.2.5 Circulatory System in Humans

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  1. The circulatory system in humans is made up of two main circulation:
    1. pulmonary circulation (between heart and lung)
    2. systemic circulation (between heart and other body parts)
  2. This is known as a double closed and complete circulatory system.

Pulmonary Circulation

  1. Pulmonary circulation is the part of the circulation of blood in human body which carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated (oxygen-rich) blood back to the heart.

  1. Figure above shows the illustration of the pulmonary circuit.
  2. The deoxygenated blood (blue in colour) is pumped out from the right ventricle into the left and right pulmonary arteries and then to the left and right lungs.
  3. At the lungs, the deoxygenated blood receives oxygen and becomes oxygenated blood (red in colour). 
  4. The oxygenated blood is then transported from the lungs to the  pulmonary veins and then the left atrium of the heart.

(Passage of the blood in pulmonary circulation)


Systemic Circulation

  1. Systemic circulation is the part of the circulation of blood in human body which carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart.
  2. During a systemic circulation, oxygenated blood from the left atrium of the heart is pumped into the left ventricle and then pumped out of the heart through the aorta.
  3. From aorta, the oxygenated blood is pumped to all the body tissues through arteries.
  4. Oxygen is released whereas carbon dioxide is collected from the body cells. The blood is then become deoxygenated.
  5. The deoxygenated blood is pumped back to right atrium through the vein and vena cava.

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1.2.4 Types of Circulatory System

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Circulatory system can be classified into two types:

  1. closed circulatory system
  2. open circulatory system

Closed Circulatory System

  1. Usually found in large animals such as vertebrates.
  2. Medium of transport is blood
  3. The blood  flows continuously in blood vessels
  4. Exchange of gases, nutrients and waste products occurs between the blood in the capillary and the body cell.

    Open Circulatory System

    1. Usually found in smaller animals such as insects and shellfish.
    2. Medium of transport is haemolymph.
    3. Haemolymph is pumped from the heart into the cavity around the body cells.
    4. Exchange of nutrients and waste products occurs directly between  and the body cells the blood around it.
    5. The haemolymph  is then pumped back to the heart.

    Close Circulatory System vs Open Circulatory System

    Open Circulatory System Close Circulatory System
    Circulating fluid Haemolymph Blood
    Occurrence Small animals such as insects Large animals such as vertebrate
    Control of fluid flow Low level of control High level of control
    Presence of valve No Yes
    Pressure of circulating fluid Relatively low Relatively high


    1.2.3 Function of Haemolymph in Transport

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    1. Haemolymph is a fluid in the circulatory system of insects.
    2. As blood, haemolymph is the medium of transport that transport substances such as hormone and nutrient to the cells.
    3. For most insects, haemolymph is not used for oxygen transport because these animals respirate directly from their body surfaces to air.
    4. Unlike blood in human's circulatory system,the haemolymph does not flow in closed blood vessels.
    5. It is pumped out of the heart to fill the spaces between the body cells and then drawn back toward the heart through open-ended pores.

    1.2.2 Function of Blood in Transport

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    Blood is an important medium in
    1. transport of oxygen and carbon dioxide
      1. In blood, oxygen combines with haemoglobin in the red blood cell to form oxyhaemoglobin.
      2. Oxygen is transported in the form of oxyhaemoglobin to the body cells which lack of oxygen.
      3. At the body cells, oxyhaemoglobin breaks down to release the oxygen to the body cells for cell respiration.
      4. Carbon dioxide is transported by the blood in ion hydrogen carbonate (ion bicarbonate) in the blood plasma carbaminohaemoglobin in the red blood cell.
    2. transport of water
    3. transport of digested food, minerals and vitamins
    4. transport of excretion
    5. transport of chemical substances such as hormones
    6. transport of heat

    1.2.1 Composition of Human Blood

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    (This image is shared under Creative Commons Attribution 3.0 Unported license. You can click on the image to enlarge it)
    Human blood consist of
    1. cellular components
    2. plasma


    Cellular Components

    There are three types of blood cells:
    1. erythrocytes (red blood cell)
    2. leucocytes (white blood cell)
    3. platelets

    Erythrocyte (Red blood cells)

    (Image by BruceBlaus under
    Creative Commons Attribution 3.0 Unported license)
    1. Biconcave disc-shaped. Can move quickly in blood capillaries and increases the TSA/V ratio to facilitate the exchange of gases.
    2. Carry large amount of haemoglobin.
    3. Haemoglobin is responsible for the transport of oxygen in the form of oxyhaemoglobin and carbon dioxide in the form of carbaminohaemoglobin.
    4. No nucleus when matured. This enables it to contain more haemoglobin to carry more oxygen.
    5. Produced in the bone marrow.
    6. Life span about 120 days. After that they are destroyed in the spleen and liver.

    Leucocyte

    1. Has no fixed shape.
    2. Less than the erythrocytes, but bigger in size.
    3. Has a nucleus
    4. The function is to protect the body from diseases.
    5. There are two types of leucocytes:
      1. granulocyte
      2. agranulocyte

    Granulocytes
    1. With granules in the cytoplasm.
    2. With lobed nucleus.
    3. Formed in red bone marrow.
    4. There are three types of granulocytes
      1. neutrophil (carry out phagocytosis to engulf invading bacteria)
      2. eosinophil (involve in regulating the allergic responses)
      3. basophil (produce heparin to prevent the blood clotting）

    Agranulocytes
    1. Have no granules in the cytoplasm.
    2. There are two types of agranulocytes:
      1. lymphocytes (responsible for producing antibodies to protect the body against diseases.)
      2. monocytes (carry out phagocytosis to engulf invading bacteria)

    Platelet (Thrombocytes)

    1. Platelets, or thrombocytes , are cell fragments (i.e. cells that do not have a nucleus) of larger cells in the bone marrow called megacaryocytes.
    2. The average lifespan of a platelet is normally just 5 to 9 days.
    3. Platelets circulate in the blood of mammals and are involved in hemostasis, leading to the formation of blood clots.

    (Image by BruceBlaus under Creative Commons Attribution 3.0 Unported license)

    Plasma

    1. Plasma is the liquid part of the blood.
    2. Plasma is a pale yellowish liquid consisting of water, plasma protein and other dissolved substances.
    3. Plasma without plasma protein is called blood serum.

    Plasma Protein

    1. The plasma protein consist of 
      1. albumins, 
      2. immunoglobulins and 
      3. fibrinogen.
    2. The albumin controls osmitic pressure of blood and acts as buffer against pH changes.
    3. Immunoglobulins are antibodies involve in body's defense mechanism.
    4. Fibrinogen is a substance important in blood clotting.

    Water and Dissolved Substances

    1. Other than plasma protein, the dissolved substances in plasma include
      1. products of digestion
      2. excretory products
      3. hormones
      4. minerals
      5. vitamins.
      6. dissolved gases such as carbon dioxide, oxygen and nitrogen.



    1.2 The Concept of Circulatory System

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    1. The circulatory system is an organ system that permits blood and lymph circulation to transport nutrients, oxygen, carbon dioxide, hormones, blood cells, etc. to and from cells in the body.
    2. The circulatory system in human and animals consists of blood, blood vessels and heart.
    3. Blood is the medium of transport in the circulatory system in human and animal.
    4. In SPM, you need to know
      1. the composition of human blood
      2. the function of blood and haemolymph in transport
      3. the types of circulatory system
      4. the circulatory system in humans
      5. the regulation of blood pressure



    1.1 The Importance of Transport System in Multicellular Organisms

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    1. The transport system in humans and animals is the circulatory system.
    2. The transport system in plants is the vascular tissues.
    3. The vascular tissues consist of 
      1. xylem tissues and 
      2. phloem tissues.

    Live Process of Cells

    1. Every cell in an organism need to obtain nutrients and oxygen from the environment and at the same time, is able to remove the waste products from the cell.
    2. Unicellular organisms obtain their nutrients and oxygen across the plasma membrane directly from the environment by diffusion.
    3. Unicellular organisms are small in size. As a result, they have a large total surface area to volume (TSA/V) ratio. This enables the exchange of substances to occur rapidly by diffusion.

    Why the Transport System is Important for Multicellular Organism?

    1. Multicellular organisms are bigger and hence have a small total surface area to volume (TSA/V) ratio. As a result, the rate of diffusion of substances is low. The larger the organism, the more difficult it is for the substances to diffuse in and out of the body cells.
    2. Also, as the size of an organism increases, the amount of nutrients and oxygen gas needed also increases. So does the metabolic waste products. As such, diffusion alone is not sufficient to fulfill the needs of the body cells and to remove the waste products from the body.
    3. Other than that, for a multicellular organism, the cells are located further in the body. They are not directly in contact with the environment.
    4. Therefore, multicellular organisms need special transport systems to transport the nutrients to all the body cells and at the same time to remove the metabolic waste from the body cells.