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

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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