Transport in Humans

Components of Circulatory System
1. Heart
  1. A muscular pump, which ensures blood keeps flowing through the blood vessels.
2. Blood Vessels
  1. Arteries
    1. Function: Transports oxygenated blood away from the heart.
      1. Exception: Pulmonary Artery - carries de-oxygenated blood from the heart to the lungs
    2. Structure: Thick, elastic muscular walls to withstand blood from the heart, which is at higher pressure
    3. Lumen: Smaller lumen relative to diameter
    4. Valves: Semi-lunar valves are present
  2. Veins
    1. Function: Transports de-oxygenated blood towards the heart
      1. Exception: Pulmonary Vein - carries oxygenated blood from the lungs to the heart
    2. Structure: Thin, slightly muscular walls as flow of blood is slower and lower in pressure
    3. Lumen: Larger lumen relative to diameter
    4. Valves: Semi-lunar valves are present
  3. Capillary
    1. Function: Capillaries connects arteries to veins
      1. Allows exchange of materials between blood and tissues
    2. Structure: Have one-cell thick walls that enable exchange of substances to occur rapidly via diffusion
    3. Lumen: No lumen
    4. Valves: Semi-lunar valves are absent
3. Blood
  1. Blood flows through the blood vessels, carrying materials around the body
  2. Components of Blood
    1. Plasma
      1. 55% of blood
      2. A pale yellowish liquid
        90% of plasma is water
        10% includes proteins, mineral salts and dissolved food
      3. Function: Soluble proteins which play a part in clotting of blood
    2. Red Blood Cells
      1. About 5 million red blood cells in 1mm (cube) of blood
      2. Function: Transports oxygen from lungs to all parts of the body
    3. White Blood Cells
      1. Function: Involved in phagocytosis (engulfing of foreign particles)
        Function: Production of antibodies
      2. About 5000 - 10000 white blood cells in 1mm (cube) of blood
        Irregular in shape
        Nucleus is present
        Haemoglobin is absent
      3. Types of White Blood Cells
        Phagocytes
        Produced by bone marrow
        A lobed nucleus
        Involved in the ingestion of foreign particles like bacteria and digesting them
        Lymphocytes
        Produced by lymph glands or lymph nodes
        A large and round nucleus
        Involved in the production of antibodies which neutralises toxins produced by the bacteria
    4. Role of Blood in Transport and Defence
      1. Blood performs many important functions
        It acts as a transport medium for various useful substances from one part of the body to another (e.g. transport of oxygen by RBC), metabolic wastes (e,g. transport of CO2 by plasma), as well as disease-causing microbes like viruses and bacteria
        Substances Transported
        Oxygen (in RBC) from lungs to all parts of the body
        Digested food (glucose, etc.) from small intestine to other parts of the body
        Metabolic waste products (urea, CO2) from all parts of the body to kidneys
        Hormones from glands to target organs
        Heat from respiring blood tissues to all parts of the body (maintain temperature)
        Protecting the body against disease-carrying organisms by:
        i) Ingesting and digesting disease-causing organisms such as bacteria
        ii) Producing antibodies that protect us by neutralising the toxins produced by bacteria
        iii) Blood clotting at wounds. Blood clot by the platelets seals the wound and prevent entry of bacteria and further loss of blood
  3. Blood Donation
    1. Components of blood that donated blood can be separated into:
      1. Platelet
      2. Plasma
      3. Red blood cell
    2. Uses of separated components
      1. Plasma: replace clotting factors which may be depleted in bleeding or infection
        Red blood cell: Replace loss of RBC in accidents, surgeries, etc.
        Platelets: Treatment of dengue, leukaemia and cancer patients
    3. Blood Diseases that require regular blood transfusion
      1. aplastic anemia
      2. thalassaemia
      3. myelofibrosis
    4. Growing need for blood donation in Singapore
      1. As the need for blood in Singapore is growing, with demand expected to rise by 3 to 5 per cent yearly in tandem with the ageing population.
4. Valves
  1. Function: Valves close to prevent a backflow of blood.
  2. Only present in veins where blood pressure is lower
Need for Transport System
1. Unicellular Organisms
  1. No part of cell is too far from external environment
  2. Exchange of substances occurs by diffusion
  3. Oxygen and nutrients diffuse through cell surface membrane and easily reach all parts of the cell. Metabolic waster products such as carbon dioxide can be rapidly removed from cell by diffusion
  4. Unicellular organisms do not need transport system
2. Multicellular Organisms
  1. Cells are situated deep in the body, far from external environment
  2. Diffusion alone is too slow to bring enough oxygen and nutrients to cells or remove metabolic waste products from cells fast enough
  3. Transport system in humans is needed to carry substances from one part of the body to another
Diffusion and Osmosis in Transport System
1. In the cells of living organisms, the cell membrane is partially permeable. It controls the movement of substances in and out of the cell. The following are examples of diffusion and osmosis occurring in the transport system of living organisms
  1. a) In unicellular organisms, oxygen and nutrients can diffuse through cell surface membrane and easily reach all parts of the cell. Metabolic waste products such as CO2 can also diffuse out and be removed from the cell rapidly
    1. b) In the human transport system, substances are transferred between capillaries and tissue cells via diffusion. Oxygen and dissolved food substances diffuse from blood capillaries in tissue fluids and cells. Metabolic waste products diffuse from the cells into tissue fluid and then into blood capillaries
      1. c) The cells in our body must be surrounded by fluid in relatively constant water potential. For example, a red blood cell will:
        1) swell if it is in a solution of higher water potential than its cytoplasm and will burst if left at long periods
        2) shrink if it is in a solution of lower water potential than the cytoplasm. Little spikes will appear on the cell surface membrane. This process is called crenation. The cell will become dehydrated and eventually die
2. Diffusion: Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration
3. Osmosis: Osmosis is the net movement of water molecules from a solution of higher water potential to a solution of lower water potential through a partially-permeable membrane
Transport-related Technology & Techniques
1. Cardio-Pulmonary Resuscitation (CPR)
  1. In Singapore, about 2400 people develop an acute heart attack annually, with 1000 people suffering from sudden cardiac arrest in an out-of-hospital environment also known as "sudden death". The chances of survival drops by 7% to 10% every minute.
  2. What happens to victims during cardiac arrest?
    1. Victim loses consciousness; heart stops beating and breathing stops
      1. Blood circulation ceases
        Organ death begins to occur
        Most sensitive organ is the brain. If circulation to the brain is not restarted within 4 to 6 minutes, permanent and irresversible damage can occur
  3. When mouth-to-mouth ventilation is done during CPR, there is just sufficient oxygen in the exhaled air to keep the victim alive. Chest compression squeezes the heart between the breastbone and the spine and helps to circulate the blood and deliver this oxygen to the vital organs, especially the brain, heart and kidneys
  4. If CPR is performed promptly and correctly...
    1. 1) heart function may be restored
      1. 2) circulation may be maintained until other life support measures are available
2. Automated External Defibrillator (AED)
  1. The AED is a device that delivers electrical shock to restart the pumping action of the heart. It can increase the survival rate of victims suffering from sudden cardiac arrest
3. Heart Transplants
  1. The National Heart Center, Singapore (NHCS) set up the heart transplant program in 1990. It is the only healthcare institution in Singapore that carries out heart transplantations
  2. Heart transplants are for patients suffering from end-stage heart failure
  3. A key factor in heart transplant is organ availability
    1. A heart transplant involves the replacement of a patient's diseased heart with a healthy heart from a donor who has suffered brain death
  4. The Human Organ Transplant Act (HOTA) allows for the kidneys, liver, heart and corneas to be recovered in the event of death from any cause for the purpose of transplantation. Singapore Citizens and Permanent Residents above 21 years of age and of sound mind are included under HOTA unless they have opted out

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Transport in Humans

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	Created by CHUA ZHE LEI student about 5 years ago