(IGP) GS Paper 1 – General Science – “Lymphatic System & Immunity”

Integrated Guidance Programme of General Studies for IAS
(Pre) – 2013

Subject – General Science
Chapter : Lymphatic System & Immunity

Lymphatic System

  • The lymphatic system is composed of lymph vessels, lymph
    nodes, and organs. The functions of this system include the absorbtion of
    excess fluid and its return to the blood stream, absorption of fat (in the
    villi of the small intestine) and the immune system function.

  • Lymph vessels are closely associated with the circulatory
    system vessels. Larger lymph vessels are similar to veins. Lymph capillaries
    are scatted throughout the body. Contraction of skeletal muscle causes
    movement of the lymph fluid through valves.

  • Lymph organs include the bone marrow, lymph nodes,
    spleen, and thymus.

  • Bone marrow contains tissue that produces lymphocytes.
    B-lymphocytes (B-cells) mature in the bone marrow.

  • T-lymphocytes (T-cells) mature in the thymus gland.

  • Other blood cells such as monocytes and leukocytes are
    produced in the bone marrow.

  • Lymph nodes are areas of concentrated lymphocytes and
    macrophages along the lymphatic veins.

  • The spleen is similar to the lymph node except that it is
    larger and filled with blood.

Immunity

  • Immunity is the body’s capability to repel foreign
    substances and cells.

  • The nonspecific responses are the first line of defense.

  • Highly specific responses are the second line of defense
    and are tailored to an individual threat.

  • The immune response includes both specific and
    nonspecific components. Nonspecific responses block the entry and spread of
    disease-causing agents.

  • Antibody-mediated and cell-mediated responses are two
    types of specific response.

  • The immune system is associated with defense against
    disease-causing agents, problems in transplants and blood transfusions, and
    diseases resulting from over-reaction (autoimmune, allergies) and
    under-reaction (AIDS).

General Defenses

Barriers to entry are the skin and mucous membranes:

  • The skin is a passive barrier to infectious agents such
    as bacteria and viruses. The organisms living on the skin surface are unable
    to penetrate the layers of dead skin at the surface. Tears and saliva
    secrete enzymes that breakdown bacterial cell walls. Skin glands secrete
    chemicals that retard the growth of bacteria.

  • Mucus membranes lining the respiratory, digestive,
    urinary, and reproductive tracts secrete mucus that forms another barrier.
    Physical barriers are the first line of defense.

Specific Defenses

  • The immune system also generates specific responses to
    specific invaders.

  • The immune system is more effective than the nonspecific
    methods, and has a memory component that improves response time when an
    invader of the same type (or species) is again encountered.

  • Immunity results from the production of antibodies
    specific to a given antigen (antibody-generators, located on the surface of
    an invader).

  • Antibodies bind to the antigens on invaders and kill or
    inactivate them in several ways.

Vaccination

Vaccination is a term derived from the Latin vacca (cow,
after the cowpox material used by Edward Jenner in the first vaccination). A
vaccine stimulates the antibody production and formation of memory cells without
causing of the disease. Vaccines are made from killed pathogens or weakened
strains that cause antibody production but not the disease. Recombinant DNA
techniques can now be used to develop even safer vaccines. The immune system can
develop long-term immunity to some diseases. Man can use this to develop
vaccines, which produce induced immunity. Active immunity develops after an
illness or vaccine. Vaccines are weakened (or killed) viruses or bacteria that
prompt the development of antibodies.

Disorders of the Immune System

The immune system can overreact, causing allergies or
autoimmune diseases. Likewise, a suppressed, absent, or destroyed immune system
can also result in disease and death.

  • Allergies : Allergies result from immune system
    hypersensitivity to weak antigens that do not cause an immune response in
    most people. Allergens, substances that cause allergies, include dust,
    molds, pollen, cat dander, certain foods, and some medicines (such as
    penicillin).

  • Autoimmune diseases : The immune system usually
    distinguishes “self” from “nonself”. The immune system learns the difference
    between cells of the body and -foreign invaders. Autoimmune diseases result
    when the immune system attacks and destroys cells and tissues of the body.
    Juvenile diabetes, Grave’s disease, Multiple sclerosis, Systemic lupus
    erythematosus, and Rheumatoid arthritis are some of the autoimmune diseases.

  • Myasthenia gravis : Myasthenia gravis (MG) is a
    muscle weakness caused by destruction of muscle-nerve connections. Multiple
    sclerosis (MS) is caused by antibodies attacking the myelin of nerve cells.
    Systemic lupus erythematosis (SLE) has the person forming a series of
    antibodies to their own tissues, such as kidneys (the leading cause of death
    in SLE patients) and the DNA in their own cellular nuclei. In systemic lupus
    erythematosus (SLE), the immune system attacks connective tissues and major
    organs of the body.

  • Immuno deficiency diseases : Immunodeficiency
    diseases result from the lack or failure of one or more parts of the immune
    system. Affected individuals are susceptible to diseases that normally would
    not bother most people. Genetic disorders, Hodgkin’s disease, cancer
    chemotherapy, and radiation therapy can cause immunodeficiency diseases.

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Blood: The Vital Fluid

  • Blood looks like a homogenous red fluid to the uncover
    edge. But when spread into a thin layer, it is found to be a suspension of
    different type of cells in a liquid called the ‘plasma’. Most of the cells
    are faint yellow and without a nucleus. A dense accumulation of these cells
    is responsible for the red colour of the blood. These cells are called
    ‘erythrocytes’ or red blood cells. These are also another two types of
    cells—the ‘leucocytes’ or white blood cells and ‘thrombocytes’ or platelets.

  • Plasma : is a straw coloured liquid, about 90
    percent of which is water. The chief salt dissolved in plasma is sodium
    chloride, or common table salt. The salinity of plasma is one-third that of
    sea water.

  • Fibrinogen is a protein which is essential for clotting
    of blood, another protein globulins aid in the defense mechanisms of the
    body.

  • Red Blood Cells : are the most numerous of the
    blood cells, they neither have a nucleus nor mitochondria, RBC are a reddish
    coloured protein containing iron.

  • It is hemoglobin which makes it possible to deliver
    oxygen to tissue which need it.

  • The normal quantity of hemoglobin present in blood in
    12-15 g in every 100 ml of blood. A decrease in this quantity is called
    ‘anemia’.

Facts from N.C.E.R.T

  • Ball and Socket Joints : The rounded end of one
    bone fits into the cavity (hollow space) of the other bone. Such a joint
    allows movements in all directions.

  • Pivotal Joint : The joint where our neck joins,
    the head is a pivotal joint. It allows us to bend our head forward and
    backward and turn the head to our right or left.

  • Hinge Joint : The elbow has a hinge joint that
    allows only a back and forth movement.

  • Fixed Joint : There are some bones in our head
    that are joined together at some joints the bones cannot move at these
    joints. Such joints are called fixed joints.

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