Biology 30S - Wikispaces E-Notes... · cannot normally be penetrated by bacteria and ... H2, and...
Transcript of Biology 30S - Wikispaces E-Notes... · cannot normally be penetrated by bacteria and ... H2, and...
Non-Specific Defence Mechanisms
Skin and Mucous
Membranes (the 1st line of
defence)
• Skin is a physical barrier that when intact
cannot normally be penetrated by bacteria and
viruses
• secretions from oil and sweat glands give the skin
a pH ranging from 3 to 5 which is acidic enough
to prevent the growth of most microorganisms
• BUT, skin can be damaged (cuts and scrapes)
which can allow foreign material into body tissues
• Mucous Membranes are physical barriers that
line and protect organ systems in the body
• These membranes secrete Mucous and other
fluids (saliva, tears, lysozymes) that trap, wash
away and/or destroy potential invaders.
The Inflammatory
Response (The 2nd Line of
Defence)
• Should the physical protective barriers of
the body be breached by foreign material
the body, this slightly more vicious line of
defence is called to action and triggers an
Inflammatory Response
• The cells involved in this line of defence are
primarily White Blood Cells and use
Phagocytosis to eliminate foreign material
(they basically “eat” it)
• There are 6 types of cells involved in the
Inflammatory Response
1. Mast Cells (The Thin Blue Line)
• “local law enforcement”
• These cells are found in skin tissue, joints,
connective tissue, muscle and blood vessels
• Mast Cells are NOT blood cells. They
don’t circulate in the blood stream
• These cells will trigger an inflammatory
response when a physical protective barrier
has been breached, damaged, infected or
encounters a toxin
• These cells also coordinate the bodies
allergic responses and wound healing
2. Basophils
• the early warning cells
• these White Blood Cells patrol the blood
• during an “injury” blood vessels dilate
(widen) carrying more blood to the injured
area
• Basophils detect foreign material and
release Histamine and other chemical
signals which begins the inflammatory
response
3. Neutrophils
• The “Soldiers”
• 60 – 70% of all white blood cells
• attracted to chemical signals
produced by the Basophils
• enter infected tissue and “self
destruct” destroying foreign invaders
• average life span is a few days
4. Monocytes
• 5% of all white blood cells
• the “heavy artillery”
• when these cells detect foreign
material they develop and enlarge
into Macrophages (“big eaters”)
• as Macrophages, they attach to and
ingest (“eat”) foreign material and
destroy them with digestive enzymes
5. Eosinophils
• the “big game” hunters
• these white blood cells attack larger
parasites and worms using an arsenal
of destructive enzymes
6. Natural Killer Cells
• the “executioners”
• these cells destroy infected cells, cells
harbouring viruses and abnormal
cells that could develop into tumours
“The Immune System”
Specific Defence Mechanisms
(The Last Line of Defence)
• There are a number of parasites,
viruses and diseases that the body
cannot deal with using non specific
methods
• The Immune System defends the
body against specific invaders
• The Immune System uses 2 Specific
Defence Mechanisms:
1. Cell Mediated Immunity (CMI)
• Bone Marrow (Labelled A1) produces
Immature T – Lymphocytes (Labelled B)
which mature in the Thymus (labelled C)
• They emerge from the Thymus as Mature T
–Lymphocytes (labelled D1) or Helper T –
Lymphocytes (labelled D2) and are stored in
the lymph nodes
• Each T-Lymphocyte has a receptor (labelled
D3)
• T- Lymphocytes are stimulated by Antigens
(labelled E) from foreign chemical substances
(such as viruses, bacteria, cancer cells, fungi
etc.)
• When a foreign substance enters the body,
the antigen is eventually detected by a T-
Lymphocyte with a specific receptor that
matches the antigen
• when this happens the T- Lymphocyte is
activated (with the help of a Helper T –
Lymphocyte) into a Cytotoxic T –
Lymphocyte (Labelled F)
• The Cytotoxic T – Lymphocytes then
circulate through the blood seeking and
destroying cells that contain the antigen
2. Antibody Mediated Immunity (AMI)
• Bone marrow produces Mature B –
Lymphocytes (labelled H) which are stored
and replicate in the Lymph Nodes
• Like T – Lymphocytes, B- Lymphocytes
have receptors (Labelled H1, H2, and H3)
that bind to specific Antigens
• Antigens (Bacteria, Fungi, Viruses)
stimulate that production of B –
Lymphocytes
• Eventually the antigen is detected by a B –
Lymphocyte with a specific receptor that
matches the antigen
• when this happens the B – Lymphocyte
activates and turns into a Plasma Cell
(labelled J)
• the Plasma Cell releases a large number
of Antibodies (labelled K) which attach
to the antigens
• the antibodies attract phagocytes which
engulf and destroy the foreign material
• the antibodies stay in circulation for
years which results in long-term
immunity