Non-specific defenses against disease

Non-specific defenses

work in the same way against all pathogens

Specific defenses

work against a particular pathogen (e.g antibodies and memory cells)

Body's external barriers

Skin, mucous, hairs, cilia, acids, lysozyme, cerumen, movement of fluid

Skin

A protective barrier outside of body.

Skin defenses

- Bacteria live on skin so pathogens can't become established on skin

- Sebum secreted by oil glands, contains substances that kills some pathogenic bacteria and is slightly acidic

- Sweat secreted onto skin, contains salt + fatty acids and lysozyme which prevent growth of microorganisms

Lysozyme

An enzyme that kills bacteria, found in tears, saliva, sweat

Hairs

Found in nose cavity/ears, traps particles

Mucus

Mucous membranes line body cavities that open to the exterior, secrete mucus that traps microorganisms and inhibits entry to organs of body

Cilia

Tiny hair-like projections from cells that have a beating motion, mucociliary escalator - moves mucus containing particles/microorganisms towards throat where it is coughed up/swallowed

Acids

Acidic body fluids kill many bacteria and reduces growth of microorganisms

Stomach acid - pH 2

Urine - pH 6

Sebum - 4.5 - 6

Vagina - pH 3.5 - 5

Cerumen

Ear wax, waxy, hydrophobic and slightly acidic, protects the outer ear from pathogens as it creates a hostile environment where they can't grow

Movement of fluid

The flushing action of urine, tears, sweat and saliva prevents bacterial growth

Protective reflexes

Automatic, involuntary response to stimulus: sneezing, coughing, vomiting, diarrhoea

Sneezing

forceful expulsion of air from lungs carries mucus, foreign particles/noxious gases out through nose/mouth.

Stimulated by irritation of walls of nasal cavity, caused by noxious fumes, dust particles

Coughing

Forceful expulsion of air from the lungs to remove irritant up the trachea and towards the throat and mouth, stimulated by irritation in lower respiratory tract (bronchi/bronchioles)

vomiting

Caused by contraction of abdomen muscles and diaphragm to expel stomach contents, stimulated by psychological stimuli, caused by excessive stretching of stomach or bacterial toxins

Diarrhoea

Caused by increased contraction of the muscles of the wall of intestines so contents move quickly for elimination, stimulated by irritation of small/large intestines by bacteria, viruses or protozoa, produces watery faeces