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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. 

    9.4.1 Human Activities that Endangered an Ecosystem (Structured Question 1 & 2)

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    Question 1:
    (a) Diagram I shows the effects of farming activities near a pond.


    Explain how the farming activities cause the death of the aquatic plants and the fishes in the pond.
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    (b)     Diagram II shows a new industrial area situated near a residential area.


    Discuss the good and the bad effects caused by the industrial activities on human and environment in years to come.


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    Answer:
    (a)
    - Farmers use fertilisers that usually contain nitrates and phosphates.
    - Fertilisers which contain nitrates/ phosphates may leach into the pond when it rains.
    - Algae in the lake grow faster.
    - They may grow so much that they completely cover the water.
    - Black out the light for plants growing beneath them.
    - Photosynthesis rate is reduced.
    - Dissolved oxygen also reduced.
    - Plants on the top of the water and beneath the water eventually die.
    - Their remains are a good source of food for bacteria.
    - Bacteria decomposed the dead plant rapidly.
    - The large population of bacteria respires, using up oxygen, so there is very little oxygen left for other living organisms.
    - BOD increased.
    - Water population increases.
    - Those aquatic plants and fish which need oxygen die.

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    (b)
    Advantages:
    - More job opportunities
    - More economic activities and development projects
    - Attract tourists
    - Improve infrastructure

    Disadvantages:
    - Can cause respiratory problems/ asthma/ bronchitis/ irritates the eye
    - Crime rate increases

    Environment:
    - Industries emit poisonous gases such as sulphur dioxide/ oxides of nitrogen/ smoke/ fine solid particles
    - Contribute to air pollution
    - Oxides of nitrogen and Sulphur dioxide dissolve in rain water to form acid rain.
    - Makes the soil acidic and unsuitable for the cultivation of crops
    - Smoke and haze reduce light intensity reaching stomata and cause the rate of photosynthesis to decrease
    - Which subsequently reduces crop yield
    - Carbon dioxide leads to the greenhouse effect, resulting in an increase in the atmospheric temperature
    - Cause the extinction of organisms


    8.7.1 The Abiotic and Biotic Components of the Environment (Structured Question 1 & 2)

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    Question 1:
    R, S and T in Figure below show three types of interactions between organisms.


    (a)(i)     Name the type of interaction represented by R and S.

    (ii)     Describe the interaction represented by R.
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    (b)(i)     In the interactions represented by S and T, what terms are used to describe organisms X and Y?

    (ii)     State one characteristics of organism X that adapts it for the interaction.

    (c)     The rubber tree in the interaction represented by S dies.
    Explain what will happen to organism X.

    (d)     Saw dust can be used in the interaction represented by T for the commercial cultivation of mushrooms.
    Explain how mushrooms can grow on saw dust.


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    Answer:
    (a)(i)
    Organism R: Mutualism/ symbiosis
    Organism S: Commensalism

    (a)(ii)
    Nitrogen-fixing bacteria in the root nodules fix nitrogen to form ammonia which is used by the plant while Rhizobium bacteria get shelter from the plant.
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    (b)(i)
    X: Epiphyte
    Y: Saprophyte

    (b)(ii)
    The presence of aerial roots which absorb moisture from the air

    (c)
    X continues to grow because it photosynthesises.

    (d)
    Mushrooms grow on dead organic matter.
    Mushrooms secrete enzymes which digest the complex organic matter to simple substances.


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    7.7.2 Respiratory Structure and Breathing Mechanisms in Humans and Animals (Structured Question 1 & 2)

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    Question 1:
    Figure I represents a model of the human lungs in the respiratory mechanism.


    (a)     Based on the model of the lungs in Figure I, what are the equivalent structures to the glass tube and the bell jar in the human respiratory system?
    Glass tube: __________
    Bell jar: ____________
    (2 marks)

    (b)(i)     The thin rubber sheet represents the diaphragm in the human respiratory system.
    What is the function of the thin rubber sheet in the model of the lungs? (1 mark)

    (ii)     The balloons represent the human lungs.
    Explain one characteristic of the balloons which is similar to the human lungs. (2 marks)
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    (c)(i)     The string in the model of the lungs is pulled down.
    Draw the changes to the thin rubber sheet and the balloons in Figure II below. (1 mark)


    (ii)     Observe your drawing in (c)(i).
    Explain the relationship between the changes in the model of the lungs you have drawn and the real human respiratory system. (3 marks)
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    (d)(i)     The percentage of oxygen and carbon dioxide gases in inspired and expired air is determined by using the J-tube.
    Why is the end of the J-tube dipped in potassium hydroxide solution and then followed by potassium pyrogallol solution? (1 mark)

    (ii)     Table below shows the result of a study on the content of inspired and expired air.


    Explain why there is an increase in percentage of carbon dioxide in the expired air. (2 marks)

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    Answer:
    (a)
    Glass tube: Bronchi/ trachea
    Bell jar: Rib cage/ ribs

    (b)(i)
    To control the volume/ pressure of the air in the bell jar

    (b)(ii)
    Balloons are elastic and can expand and contract

    (c)(i)

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    (c)(ii)
    The diaphragm muscles contract causing the volume of the thoracic cavity to increase. This causes the pressure in the lungs to decrease. Air from the outside is forced in.

    (d)(i)
    Potassium hydroxide solution absorbs carbon dioxide only whereas potassium pyrogallol solution absorbs both oxygen and carbon dioxide.

    (d)(ii)
    Carbon dioxide is the product of cellular respiration in the body. Carbon dioxide diffuses out of the cells to be transported to the lungs.


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    Question 2:
    (a) Sugar is oxidized during respiration.
    Explain the process. (4 marks)

    (b)     After an athlete finished running a race, his breathing is still fast and deep for several minutes. (6 marks)
    Explain why.

    (c)     State the similarities and differences between the human and the grasshopper’s respiratory system based on the structural adaptation to maximize the rate of gaseous exchange. (10 marks)

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    Answer:
    (a)
    - During respiration, oxygen taken in is transported by the blood circulatory system to the body cells.

    - In the cells, sugar (glucose molecules) are oxidized by the oxygen to release energy in the form of ATP.

    - Other products of this oxidation process are carbon dioxide and water.
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    (b)
    - He needs to breathe in fast and deep in order to inhale more oxygen.

    - This is because during running, the rate of oxygen being used by the muscles exceeds the amount of oxygen supplied by the blood.

    - The muscles are in a state of oxygen deficiency.

    - An oxygen debt is incurred.

    - The muscles obtain the extra energy (ATP) from anaerobic respiration, because oxygen is not available.

    - The excess oxygen inhaled is used by the body to oxidise the accumulated lactic acid to carbon dioxide and water.

    - When all the lactic acid is removed, the oxygen debt is paid off.
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    (c)
    Similarities:
    - Both respiratory systems have structures which have a large surface area to volume ratio for efficient gaseous exchange.

    - The cells that lining the respiratory structures are thin. This allows gas diffusion to take place efficiently.

    - The surfaces for gaseous exchange are constantly moist because they are covered by a film of water which allows the respiratory gases to dissolve in it.