Interview
Internal body bio
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Interview of 4 pages for the course Biology at 12th Grade (Muscles and kidneys)
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6.3Understandings:
■ The skin and mucous membranes form a primary defence against pathogens
that cause infectious disease
○ First line of defence
■ Skin
● ( protects external structures when intact (outer body areas)
● Consists of a dry, thick and tough region composed of dead
surface cells [epidermis]
● Contains bio chemical defense agents ( secretes chemicals
and enzymes which inhibit microbial growth on skin
● The skin also secretes lactic acid and fatty acids to lower the
pH (skin pH is roughly~5.6-6.4
■ Mucous Membrane
● Protects internal structures (i.e. externally accessible cavities
and tubes – such as the trachea, oesophagus and urethra)
● Consists of a thin region of living surface cells that release
fluids to wash away pathogens (mucus, saliva, tears, etc.)
● Contains biochemical defence agents (secretions contain
lysozyme which can destroy cell walls and cause cell lysis)
● Mucous membranes may be ciliated to aid in the removal of
pathogens (along with physical actions such as coughing /
sneezing)
Nasal cavity trachea stomach vagina
■ Cuts in the skin are sealed by blood clotting
■ Clotting factors are released from platelets
■ The cascade results in the rapid conversion of fibrinogen to fibrin by thrombin
○ Clotting (haemostasis) is the mechanism by which broken blood vessels
are repaired when damaged [prevent blood loss]
○ Clotting factors cause platelets to become sticky and adhere to the
damaged region to form a solid plug
○ These factors also initiate localised vasoconstriction to reduce blood flow
through the damaged region
○ Additionally, clotting factors trigger the conversion of the inactive zymogen
prothrombin into the activated enzyme thrombin
○ Thrombin in turn catalyses the conversion of the soluble plasma protein
fibrinogen into an insolube fibrous form called fibrin
○ The fibrin strands form a mesh of fibres around the platelet plug and traps
blood cells to form a temporary clot
○ When the damaged region is completely repaired, an enzyme (plasmin) is
activated to dissolve the clot
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