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5.1 The immune system

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THE IMMUNE SYSTEM
THE IMMUNE SYSTEM SUMMARIZED IN A VIDEO
PATHOGENS
• = disease causing micro-organisms
• bacteria
• virus
• fungi,
• protozoa,
• parasite,
• prion
FIRST LINES OF DEFENCE
saliva
antibacterial
enzymes
skin
prevents
entry
stomach acid
low pH kills
harmful
microbes
tears
antibacterial
enzymes
mucus linings
traps dirt and
microbes
“good” gut
bacteria out
compete bad
SECOND LINES OF DEFENCE
• Involve white blood cells
• Non-specific response
• invading pathogens are
targeted by macrophages
• Specific response
• lymphocytes produce chemicals
called antibodies that target
specific pathogens
NON-SPECIFIC RESPONSE
Phagocytes
PHAGOCYTES
• Monocytes and macrophages
• Provide a non-specific response to
infection
PHAGOCYTOSIS
• Stages in phagocytosis
1. Phagocyte detects chemicals released by a
foreign intruder (e.g. bacteria)
2. Phagocyte moves up the concentration
gradient towards the intruder
3. The phagocyte adheres to the foreign cell
and engulfs it in a vacuole by an infolding of
the cell membrane.
4. Lysosomes (organelles which are rich in
digestive enzymes & found in the
phagocytes cytoplasm) fuse with the
vacuole & release their contents into it.
PHAGOCYTOSIS
5. The bacterium is digested by the
enzymes, and the breakdown products
are absorbed by the phagocyte.
 During infection, hundreds of phagocytes
are needed.
 Pus is dead bacteria and phagocytes!
PUS
An accumulation of : -
• dead phagocytes
• destroyed bacteria
• dead cells
SPECIFIC RESPONSE
LYMPHOCYTE
LYMPHOCYTES
Provide a specific immune response to infectious diseases.
There are 2 types: - T-cells
- B-cells
They produce antibodies.
ANTIGENS
• all cells have surface markers
called antigens.
• body can recognise these as
self or non-self (foreign)
SPECIFIC RESPONSE
• Lymphocytes detect presence of foreign antigens
• Stimulated to produce
specific proteins called
antibodies.
• antibodies combine with their specific antigen (like a lock and
key)
• this renders the pathogen harmless.
• = primary response
IMMUNITY
• = the bodies ability to resist infection
• can be natural or acquired
IMMUNOLOGICAL MEMORY
• after an infection is fought off some lymphocytes
become memory cells.
• if same pathogen returns memory cells stimulate
the produce the specific antibody very rapidly.
• the infection is fought off before symptoms
appear = secondary response
• vaccines can stimulate same response
IMMUNE SYSTEM
Can you…
• Outline the stages in phagocytosis?
• Describe how antibodies work and how they are
specific?
CRASH COURSE IMMUNE SYSTEM
• Answer the questions as you watch this video
INFLAMMATION RESPONSE
• What is inflammation?
LYMPHATIC SYSTEM
• The lymphatic system transports and filters lymph before returning it to the blood
• Parts:
• Lymph
• Lymph Vessels and
• Lymph Nodes
• Spleen
Capillary exchange
LYMPH
• The word "lymph" comes from the Latin word lympha, which means "connected to
water,"
• Clear colorless fluid
• Contains white blood cells
• Plasma leaves the body's cells once it has delivered its nutrients and removed debris.
• Most of this fluid returns to the venous circulation through tiny blood vessels
called venules and continues as venous blood. The remainder becomes lymph
LYMPH VESSELS
• Transport Lymph
• Only carries it in one direction, up and towards the neck.
• Lymph re-enters the circulatory system at the sub-clavien veins located on either
side of the neck near the collar bones.
LYMPH NODES
• Filter the lymph
• Major sites of B and T cells and other white blood cells.
• Many located throughout the body (500-700)
• Act as filters for foreign particles and cancer cells
SPLEEN
• Acts as a filter for blood as part of
the immune system
• Recycles old red blood cells
• Stores platelets and white blood cells
• Helps fight certain kinds of bacteria that
cause pneumonia and meningitis
THYMUS
• Irregular-shaped gland in the top part of the chest, just under the sternum
and between the lungs
• The thymus serves a vital role in the training and development of Tlymphocytes or T cells, an extremely important type of white blood cell.
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