Components of Human Blood - Blood Cells, Antibodies & Immunity PDF

Okay, here is the conversion of the provided text into a structured markdown format. ### Topic 7: Components of Blood * Blood consists of red blood cells, white blood cells, platelets and plasma * Over half of the volume of the blood is made up of plasma * The majority of the other half is m...

Okay, here is the conversion of the provided text into a structured markdown format. ### Topic 7: Components of Blood * Blood consists of red blood cells, white blood cells, platelets and plasma * Over half of the volume of the blood is made up of plasma * The majority of the other half is made up of red blood cells * The remaining fraction consists of white blood cells and platelets The image is a blood micrograph showing the composition of human blood, with labels pointing to red blood cells, white blood cells and a platelet. ### Components of the Blood Table | Component | Structure | | :--------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Red blood cells: | Biconcave discs containing no nucleus to maximise the available capacity to carry the protein haemoglobin | | White blood cells: | Large cells containing a large nucleus; different types have slightly different structures and functions | | Platelets: | Fragments of cells | | Plasma: | Clear, straw-coloured aqueous solution | ### Plasma Plasma is a straw coloured liquid which the other components of the blood are suspended within. * Plasma is important for the transport of many substances including: * Carbon dioxide - the waste product of respiration, dissolved in the plasma and transported from respiring cells to the lungs * Digested food and mineral ions - dissolved particles absorbed from the small intestine and delivered to requiring cells around the body * Urea - urea is a waste substance dissolved in the plasma and transported to the kidneys * Hormones - chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body * Heat energy - heat energy (created in respiration) is transferred to cooler parts of the body or to the skin where heat can be lost ### Red Blood Cells * Red blood cells are specialised cells which carry oxygen to respiring cells * They are adapted for this function in 3 key ways * They are full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin * $Haemoglobin + oxygen \rightarrow Oxyhaemoglobin$ * They have no nucleus which allows more space for haemoglobin to be packed in * The shape of a red blood cell is described as being a 'biconcave disc' this shape gives them a large surface area to volume ratio to maximise diffusion of oxygen in and out The image shows a red blood cell, highlighting the cytoplasm containing haemoglobin and the cell membrane. It also describes the biconcave shape due to the lack of a nucleus. ### White Blood Cells * White blood cells are part of the body's immune system * These specialised cells defend against pathogenic microorganisms * There are two main types of white blood cells: ### Phagocytes 1. Phagocytes 2. Lymphocytes * Phagocytes carry out phagocytosis by ingesting pathogens * Phagocytes have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells * Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it * This is a non-specific immune response- The image shows and describes the process of phagocytosis, with labels pointing to: bacterial pathogen, bacteria being engulfed by phagocyte (phagocytosis), cell membrane, granules of digestive enzymes, and digestive enzymes released to destroy bacteria. ### Lymphocytes * Lymphocytes produce antibodies * Antibodies are proteins with a shape that is specific (complementary) to the antigens on the surface of the pathogen * Lymphocytes provide a specific immune response as the antibodies produced will only fit one type of antigen on a pathogen The image shows an illustration about the different kinds of lymphocytes and how each ones creates different antibodies * The body's immune system is highly complex, with white blood cells being the main component * Once a pathogen has entered the body the role of the immune system is to prevent the infectious organism from reproducing and to destroy it * An organism has immunity when they have sufficient levels of antibodies to protect it from a particular disease * As a result, they do not suffer from the disease or its symptoms ### Response to infection The stages of infection and the subsequent immune response are as follows: 1. The pathogen enters the blood stream and multiplies 2. A release of toxins (in the case of bacteria) and infection of body cells causes symptoms in the patient 3. Phagocytes that encounter the pathogen recognise that it is an invading pathogen and engulf and digest (non-specific response) 4. Eventually, the pathogen encounters a lymphocyte which recognises its antigens 5. The lymphocyte starts to produce specific antibodies to combat that particular pathogen 6. The lymphocyte also clones itself to produce lots of lymphocytes (all producing the specific antibody required) 7. Antibodies destroy pathogens 8. Phagocytes engulf and digest the destroyed pathogens ### Tips and Tricks Make sure you know the difference between antigen and antibody: * An antigen is a molecule found on the surface of a cell * An antibody is a protein made by lymphocytes that is complementary to an antigen and, when attached, clumps them together and signals the cells they are on for destruction ### Vaccinations * Vaccines are used to induce immunity to infectious diseases * They have reduced the cases of certain diseases drastically or even eradicated many diseases worldwide * This includes smallpox, measles, mumps and tetanus amongst many others * A vaccine contains harmless versions of a pathogen * There are several different methods by which scientists ensure that vaccines contain harmless pathogens such as: * Killing the pathogen * Making the pathogen unable to grow or divide (attenuated vaccine) * Using fragments of pathogens, rather than whole cells * A vaccine may be administered orally, nasally or via an injection ### How vaccines work * Once in the bloodstream, the antigens contained within the vaccine can trigger an immune response in the following way: * Lymphocytes recognise the antigens in the bloodstream * The activated lymphocytes produce antibodies specific to the antigen encountered * Memory cells are produced from the lymphocytes * Memory cells and antibodies subsequently remain circulating in the bloodstream The image shows different stages in the process of long-term immunity by vaccination, from injecting harmless pathogen in the bloodstream to the generation of memory cell * Future infection by the same pathogen will trigger a response that is much faster and much larger compared to the initial response * Due to the rapid nature of the response, the pathogen is unable to cause disease and the individual is said to be immune The image is a graph showing the number of measles antibodies in the blood following vaccination. The x axis is Time and y axis is Number of Measles Antibodies in the Blood. ### Platelets * Platelets are fragments of cells that are involved in blood clotting and forming scabs * When the skin is broken (i.e. there is a wound) platelets arrive to stop the bleeding * A series of reactions occur within the blood plasma: * Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin * This forms an insoluble mesh across the wound * Red blood cells become trapped, forming a clot * The clot eventually dries and develops into a scab * This process helps to prevent excessive blood loss and protect the wound from bacteria entering until new skin has formed