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Powerpoint Presentation: Defence Against Disease
Powerpoint Presentation: The Immunity
Powerpoint Presentation: The Monoclonal Antibodies

 

Animal Physiology Index

The Nervous System and Movement
Muscle contraction
The Nerve Impluse
The Synapse
The Major Factors controlling the Heartbeat
Reproduction
Digestion
The Alimentary Canal or Gut

Topic Chapters Index

Defence Against Disease Index

Infectious disease
Immunity
Vaccines and Vaccination
Monoclonal Antibodies
PDF download: The Immune System

Skin and Mucous Membranes

  • Skin consists of the epidermis (an outer later of dead, cornified cells on top of a layer of living cells).

  • These are produced continually from a layer of dividing cells at the base (stratum basale).

  • Below this the dermis made up of blood vessels, glands, hair follicles and connective tissues.

  • The dead cells are impregnated with keratin which makes them waterproof (that is why they die).

  • The waterproof layer prevent microbes from entering the skin

  • The sweat glands sweat and oils which permit the skin flora to grow (a mixture of bacteria and yeast)

  • The skin flora occupies a niche on the skin that prevents pathogens from growing and invading.

  • Mucus membranes cover the inner compartments of the body (digestive tract, lungs, and genital tracts).

  • It also consists of cells that are being constantly renewed from below but they are not waterproof.

  • These membranes secrete mucus (mucopolysaccharide), and sugars.

  • A commensal flora grows there too feeding on the secretions.

  • Mucus also traps materials in the airways.

  • HCl is secreted from the stomach mucosa, which acts as an anti-microbial agent.

  • The humidity permits the leucocytes (white blood cells) to leave the blood capillaries and patrol over the surface of the membrane engulfing pathogens by phagocytosis.

  • Secretions of lysozyme (an enzyme which digests bacterial cell walls) are also produced by glands such as tear and salivary glands.

ANIMAL PHYSIOLOGY

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Defence Against Infectious Disease

Phagocytic leucocytes ingest disease-causing organisms in the blood and tissues

  • Revise phagocytosis

  • Leucocytes can act directly upon microbes by phagocytosis (Cell Mediated Immunity)

  • Phagocytes recognise and engulf foreign (non-self) material

  • Pus forms when large numbers of phagocytes die from engulfing microbes

  • The most common phagocytic cells are neutrophils

  • Macrophages also engulf and digest non-self but they are involved in activating the antibody production in lymphocytes

  • Macrophages present antigens from non-self to the lymphocyte T-cells

 

What is the difference between antigen and antibody?

  • Antibodies are proteins produced by B-cell lymphocytes of the immune system

  • They recognise non-self molecules called antigens

  • They call up phagocytes

  • They have two or more antigen binding sites

  • They are very specific: One antibody recognises one antigen molecule

  • The different binding sites can bind to two or more cells clumping them together = AGGLUTINATION.

  • Antigens are molecules found on the surface of non-self cells (e.g. microbes infecting the body)

  • They are usually complex molecules (e.g. glycoproteins)

 

Antibody production

  • Each type of antibody is produced by a specific lymphocyte B-cell

  • B-cells are produced by the red bone marrow

  • The body produces a vast range of B-cells capable of producing different antibody molecules

  • Early on in development the body learns to recognise the difference between self (belonging to the body) and non-self (foreign material)

  • Only non-self recognising lymphocytes are retained

  • Macrophages capture pathogens and present their antigens to helper T-cell lymphocytes

  • Helper T-cell lymphocytes stimulate the appropriate B-cells to multiply forming a clone

  • These B-cells produce the antibodies to fight that particular microbe

  • Antibodies are found in the blood plasma (Humoral Immunity)

  • When the infection is overcome memory cells remain so the immune response is faster the second time the body is infected (natural immunity)

  • The body can be stimulated into producing the memory cells by vaccination/immunisation (artificial immunity)

 

The effects of HIV on the immune system

  • HIV (Human Immunodeficiency Virus) is the virus that causes AIDS (Acquired Immune Deficiency Syndrome)

  • HIV infects the body through transfer of body fluids (blood, blood products, semen) or across the placenta

  • HIV infects one type of the T-cell lymphocyte, helper T-cells.

  • Antibody production cannot be stimulated

  • The immune system fails to respond to an infection by certain bacteria (e.g. pneumonia) and fungi (e.g. Candida) which are normally easily resisted

  • The disease may take 8-10 years to reveal itself

  • This gives time for several cross infections

  • There is no vaccine yet

  • Drugs may stop the disease progressing but do not cure it

 

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