OCR AS Biology Fact Sheets: Primary Defences
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Primary Defences Skin • The skin is the body’s main primary defence. • The epidermis (outer layer of skin cells) are usually keratinocytes. • Keratinocytes are produced by mitosis at the base of the epidermis. • They migrate to the surface of the skin. • As the cells migrate, they dry out and they cytoplasm is replaced with keratin (a protein), which is called keratinisation. • The cells are dead and are an effective barrier to pathogens. The primary defences are those that attempt to prevent pathogens from entering the body. The immune response is the specific response to a pathogen, which involves the action of lymphocytes and the production of antibodies. Mucous Membranes • The barrier between the blood and our environment is reduced (such as in alveoli), there is a greater potential for infection. • These areas are protected by mucous membranes. • The epithelial layers contain goblet cells which secrete mucus and traps any pathogens. • The epithelium also contains ciliated epithelial cells, which waft the mucus layer along. • Most pathogens are killed in the digestive system because of the PHs denaturing the pathogen’s enzymes. Other Primary Defences • The eyes are protected by antibodies in the tear fluid. • The ear canal is lined with wax, which traps pathogens. • Vagina is protected by maintaining relatively acidic conditions. PHAGOCyTES Some pathogens are not killed by the primary defences, and they must be killed before they reproduce and cause disease symptoms. The secondary response is the job of the phagocytes. Neutrophils • Neutrophiles have a multi-loabed nucleus’. • manufactured in the bone marrow. • Travel in the blood. • Squeeze out into the tissue fluid. • Found on epithelial surfaces such as alveoli. • Short lived. • Released in large numbers as result of infection. Macrophages • Macrophages are larger than neutrophils. • Produced in bone marrow. • Settle in body organs. • Particularly in lymph-nodes. • They travel in the blood as monocytes and whilst in the lymph-nodes they develop into macrophages. • Specific responses to invading pathogens.
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Transcript of OCR AS Biology Fact Sheets: Primary Defences
Primary DefencesSkin
• The skin is the body’s main primary defence.
• The epidermis (outer layer of skin cells) are usually keratinocytes.
• Keratinocytes are produced by mitosis at the base of the epidermis.
• They migrate to the surface of the skin. • As the cells migrate, they dry out and
they cytoplasm is replaced with keratin (a protein), which is called keratinisation.
• The cells are dead and are an effective barrier to pathogens.
The primary defences are those that attempt to prevent pathogens from entering the body.
The immune response is the specific response to a pathogen, which involves the action of lymphocytes and the production of antibodies.
Mucous Membranes
• The barrier between the blood and our environment is reduced (such as in alveoli), there is a greater potential for infection.
• These areas are protected by mucous membranes.
• The epithelial layers contain goblet cells which secrete mucus and traps any pathogens.
• The epithelium also contains ciliated epithelial cells, which waft the mucus layer along.
• Most pathogens are killed in the digestive system because of the PHs denaturing the pathogen’s enzymes.
Other Primary Defences
• The eyes are protected by antibodies in the tear fluid.
• The ear canal is lined with wax, which traps pathogens.
• Vagina is protected by maintaining relatively acidic conditions.
PHAGOCyTESSome pathogens are not killed by the primary defences, and they must be killed before they reproduce and cause disease symptoms. The secondary response is the job of the phagocytes.
Neutrophils
• Neutrophiles have a multi-loabed nucleus’.
• manufactured in the bone marrow. • Travel in the blood. • Squeeze out into the tissue fluid. • Found on epithelial surfaces such as
alveoli. • Short lived. • Released in large numbers as result of
infection.
Macrophages
• Macrophages are larger than neutrophils.
• Produced in bone marrow. • Settle in body organs. • Particularly in lymph-nodes. • They travel in the blood as monocytes
and whilst in the lymph-nodes they develop into macrophages.
• Specific responses to invading pathogens.
