non-specific defences against pathogens

How does the skin prevent the entry or pathogens?

Covers the body, has a skin flora of healthy microorganisms that outcompete pathogens for space on the body surface. Also produces sebum, an oily substance that inhibits the growth of pathogens

What are the airways lined with?

Mucous membranes that secrete sticky mucus

What does mucus contain?

Phagocytes which remove pathogens

Where are lysozomes and what do they do?

Tears, urine, stomach acid, help to prevent pathogens getting in

What are explusive reflexes?

Coughing and sneezing, they expel pathogen mucus from the gas exchange system

What is thromboplastin in platelets?

An enzyme triggers a cascade of reactions resulting in the formation of a blood clot

What is serotonin in platelets?

Makes smooth muscles in the walls of the blood vessels contract, so they narrow arterioles, reducing the supply of blood to the area

What happens after a scab forms?

Epidermal cells below the scab start to grow sealing the wound while damaged blood vessels regrow. Collagen fibres are deposited to give the new tissue strength

What does thrombin catalyse?

soluble plasma protein fibrinogen into insoluble fibrin, fibrin forms a network of fibres that traps platelets and blood cells, forming a scab

What do mucous membranes do?

Have epithelial cells and and goblet cells which secrete mucus. Mucus in the airways traps pollen, dust, pathogens. Pathogens moved to back of throat by cilia which beat rythmically

What does the stomach have?

Hydrochloric acid, produced by cells that line the stomach, acid creates a low pH to kill bacteria

What does blood clotting prevent?

Excess blood loss, the entry of pathogens and provides a barrier (scab) for wound healing to occur

Describe inflammation

Local response to infection and tissue damage. Occurs via chemical signalling molecules which cause migration of phagocytes into the tissue and increased blood flow

What do mast cells do?

Respond to tissue damage by secreting the cell signalling molecule, histamine

What does histamine do? (1)

Vasodilation increases blood flow through capillaries, "leaky" capillaries allow fluid to enter the tissues and creating swelling, a portion of the plasma proteins leave the blood

What does histamine do? (2)

Phagocytes leave the blood and enter the tissue to engulf foreign particles, cells release cytokines that trigger an immune response in the infected area

What do cytokines do?

Stimulate inflammation and an immune response

How does wound repair happen?

New blood vessels form, collagen is produced, granulation tissue forms to fill the wound, stem cells move over the new tissue and divide to produce epithelial cells, contractile cells cause wound contraction, unwanted cells die

What is a primary defence?

Inflammation