Non-Specific Defences

What is a non-specific defence?

Work against all pathogens

Name the 8 external defences

• Skin

• Mucus

• Hairs

• Cilia

• Acids

• Lysozyme

• Cerumen

• Movement of fluid

Outline how the skin is an effective barrier

• if not broken, effective barrier against micro-organsisms

• openings have special protection (e.g. mouth, eyes, anus)

• large number of bacteria live on the skin (pathogens stuggle to establish presence)

• secrete sebum

  • produced by oil glands

  • contains substance that kills bacteria

• sweat

  • salts + fatty acids prevent micro-organism growth

Outline how mucus is an effective barrier

• mucous membranes line body cavities (openings to interior of body)

• traps particles (inhibits micro-organisms)

Outline how hairs are an effective barrier

• found in nasal cavity (nose + ears)

• in combination with mucus, trap 90% inhaled particles

Outline how cilia are an effective barrier

• tiny hair-like projections from cells

• beating motions

• found in nasal cavity, trachea, etc.

• moves mucus containing trapped particls to throat (coughed up/swallowed)

Outline how acids are an effective barrier

• stomach juices

• kills many bacteria consumed/inhaled

• urine + sweat

• vagina

Outline how lysozyme is an effective barrier

• enzyme

• kill bacteria

• found in saliva, sweat, tears (protects eyes)

Outline how cerumen is an effective barrier

• (ear wax)

• protects outer ear

• slightly acidic + contains lysozyme

Outline how the movement of fluid is an effective barrier

• flushing action

• e.g. urine through urethra (cleansing)

  • prevent bacteria entering bladder/kidneys

• e.g. tears, sweat, saliva

• females have incresed urinary tract infection rates due to shorter urethra

What is a relex?

• automatic, involuntary response to stimulus

• protect body

• e.g. blink reflex, vomiting

what are the 4 main types of reflexes that help protect the body?

• sneezing

• coughing

• vomiting

• diarrhoea

Briefly outline the sneezing reflex

• stimulated by the irritation of nasal cavity walls

  • noxious fumes, dust particles

• forecful explusio of air from lungs

  • mucus, gases, foreign particles

Briefly outline the coughing reflex

• stimulated irritation in lower respirtatory tract

  • bronchi, bronchioles

• air + foreign substances + mucus out

Briefly outline the vomiting reflex

• psychological stimuli

  • excessive stretching of the stomach

  • bacterial toxins

• contraction of the abdomen and diaphragm muscles

Briefly outline the diarrhoea reflex

• irritated small and large intestines

  • bacteria, viruses, protozoans

• causes: increased contractions of muscle wall intestines

• purpose: remove irritant quickly

  • doesn’t stay in large intestine long, resulting in watery faeces (water not absorbed)

What is phagocytosis?

• specialised white blood cells (phagocytes) that engluf + digest micro-organisms/cell debris

What are the types of phagocytes?

• monocytes + macrophages

• neutrophils

• dendritic cells

Breifly outline how monocytes + macrophages work

• tissue infected/inflamed

  • monocytes from bloodstream go to tissue

    • monocytes differentiate into macrophages (large phagocytic cells)

• some macrophages look + destroy pathogens, others wait for pathogens

• macrophages important, remove microbes and dying cells

Breifly outline how neutrophils work

• 1st cell to respond to tissue destroying pathogen

• short life span

  • make up large portion of puss

• most abundant leukocytes (white blood cell)

  • 55%-70%

• identified by: granuales visible in cytoplasm

Breifly outline how dendritic cells work

• projections from cytoplasm

• detect, engulf, process foreign paricles

  • information collected is used for specific immunity

What is the purpose inflammatory response?

• reduce pathoge spread (destroy + prevent entry)

• remove damaged cells/tissue

• begin repair of damaged tissue

What are the four signs of inflammation?

• redness

• swelling

• heat

• pain

What is sequence of events in the inflammatory response?

1. mechanical damage or local chemical changes

• cause mast cells to be activated (specialised leukocytes) by complement proteins

  • causes release of histamine, heparin, etc. into tissue fluid

2. histamine increases blood flow in area

• causes vasoldilation

  • capillary walls also more permeable

• causes heat + redness, escaped fluid = swelling

3. heparin prevents clotting

• fluid clot forms around damaged area

  • slows spread of pathogen

4. complement system proteins and chemicals attract phagocytes (neutrophils especially)

• consume micro-organisms + debris

5. abnormal conditions in tissue stimulate pain receptors

6. pagocytes die

• filled with bacteria, debris, dead cells

  • in comination with tissue fluid, form pus

7. new cells produced (mitosis)

• repair of damaged tissue

what does histamine do in the inflammatory response?

histamine increases blood flow in area

• causes vasoldilation

  • capillary walls also more permeable

• causes heat + redness, escaped fluid = swelling

what does heparin do in the inflammatory response?

heparin prevents clotting

• fluid clot forms around damaged area

  • slows spread of pathogen

What is a fever?

• increase in body temperature caused by the hypothalamus

what causes the hypothalamus to increase body temperatur (fever)?

• pyrogens act on hypothalamus

  • released by leukocytes during inflammatory response

What causes the body to actually get warmer during a fever?

• thermoreceptors detect changed body thermostat

  • vaconstriction and shivering to preserve and generate heat

Is a fever quick or a slow onset?

ususally a gradual onset, sometimes rapid

What is meant by ‘fever breaks’?

• thermostat reset to normal temperature (hypothalamus)

  • vasodilation and sweating (looks flushed, feels hot)

What is the purpose of a fever?

• inhibit growth of some bacteria and viruses

• increase chemical reactions (allows cells to repair quicker)

What happens if a fever gets too high? What is the temperature?

• conolusions and brain damage

• 44.4-45.5°C = death

What does the lymphatic system consist of?

• network of lymph capillaries and larger lymph vessels

• lymph nodes (located on lymph vessels)

What does the lymphatic system collect and return?

• fluid escaped from blood and returns to cirulatory system

What do lymph nodes contain?

lymphoid tissue

• lymphoid tissue cells are criss-crossed by a network of fibres

What happens to lymph in the lymphatic system?

• lymph enters contaning micro-ogranisms, cell debris, etc.

• large paricles are trapped in the meshwork of fibres as the lymph flows through the spaces in the nodes, macrophages ingest and destroy these particles (phagocytosis)

What happens to lymph nodes when there is an infection?

• swollen and sore