What are non-specific defences?
always present and working to prevent against the invasion of pathogens. They target all/a range of pathogens.
How
... [Show More] are non-specific defences classified?
--> Classified as primary (keeping pathogens out) and secondary (getting rid of pathogens)
Are Non-specific defences fast or slow acting?
fast acting
What are specific defences?
specific to each type of pathogen that invades the body and is known as the 'Specific Immune Response'
Are specific defences fast or slow to respond?
slower to respond
What primary defences does the body have?
1) physical barriers to prevent the entry of pathogens
2) expulsive reflexes
3) blood clotting and wound repair
4) inflammatory response
What are the physical barriers?
skin, mucous membranes, lysozymes in tears, lysozymes in urine, HCl in stomach, ear wax, hair and mucus in nose, mucus plug in the cervix
How does the skin act as a physical barrier?
- Prevents the entry of pathogens
- Skin contains a flora of healthy MO's that outcompete pathogens for space on the body surface
- Skin secretes 'sebum oil' an antibacterial substance which prevents pathogen growth
-The epidermis consists of layers of keratinocytes.
--> Keratinocytes migrate to the surface and dry out when their cytoplasm is replaced by keratin.
--> This surface layer of dead hardened cells is low in moisture, somewhat acidic and has a high salinity which prevents MO's from growing and multiplying on the skin
Why are the airways lungs and digestive system always at risk of infection?
because of the constant exposure to air and water/food from the environment and the presence of exchange surfaces
How to mucous membranes act as a physical barrier?
- the airways, lungs and digestive system are lined and protected by mucous membranes that consists of epithelial cells interspersed with mucus secreting cells called goblet cells.
- Mucus traps pathogens. It is sticky as it contains long carbohydrate chains of the glycoprotein molecules.
- Mucus contains lysosomes which destroy bacterial and fungal cell walls and phagocytes which remove remaining pathogens.
- Also found in airways, gut, anus, genital, nose and ears
How do lysozymes in tears prevent infection?
--> Lysozymes break down the cell walls of bacteria
--> Tears also have antibodies in them
How do lysozymes in urine prevent infection?
--> lysozymes break down the cell walls of bacteria
How does HCl in stomach prevent infection?
HCl in stomach is strong enough to kill many bacterial pathogens
How does hair and mucus in nose prevent infection
--> Hairs in your nose and the mucus produced in your nose trap larger particles containing pathogens. When you sniff or swallow the mucus and pathogens move to the stomach.
How are expulsive reflexes triggered?
· Pathogens irritate areas prone to attack when they release toxins. These toxins trigger 'Expulsive Reflexes'
What are the expulsive reflexes and what do they do?
--> Coughs and sneezes eject pathogen-laden mucus from the gas exchange system
--> Vomiting and diarrhoea expel the contents of the cut with any infective pathogens.
Why is bad if the skin is cut? And why is blood clotting needed?
because the skin is breached and pathogens can enter the body. Blood clotting is needed to rapidly seal the wound to prevent infection and blood loss.
What are platelets responsible for?
Platelets are responsible for initiating an 'Enzyme Cascade' that results in the formation of a blood clot.
What triggers the action of platelets? And what do they do?
When platelets come into contact with COLLAGEN in skin or the wall of the damaged blood vessel, they adhere to the damaged area and release...
1.Thromboplastin:
2. Serotonin:
3. Calcium ions:
What is and what does thromboplastin do?
it is an enzymes that triggers a cascade of reactions that lead to a blood clot forming.
What is serotonin and what does it do?
a chemical signaller that initiates vasoconstriction of smooth muscle in the walls of the blood vessel so the muscle narrows and reduces the blood flow to the injured area
What role do calcium ions play in the immune response?
act as the cofactor for the enzymes thromboplastin and thrombin
What is prothrombin? Where is it found? What is it converted into and how?
a soluble protein. Contained in blood plasma. Changed into thrombin if thromboplastin is present to catalyse the reaction (and calcium ions which are the cofactor for thromboplastin)
What is the role of thrombin?
acts as the enzyme that causes fibrinogen to be converted to fibrin whose fibres help to seal the wound forming a clot. (calcium ions act as the cofactor)
What happens when the blood clot is formed?
· It dries out forming a scab that keeps pathogens out.
· Epidermal cells below the scab start to grow, sealing the wound permanently while damaged blood vessels regrow.
· Collagen fibres are deposited to give the new tissue strength.
· Once the new epidermis reaches normal thickness, the scab sloughs off and the wound is healed.
Draw out the enzyme cascade that results in the formation of a blood clot?
...
What is the inflammatory response?
The inflammatory response is a localised response to pathogens (or damage or irritants) resulting in inflammation at the site of the wound.
What is inflammation characterised by?
pain, heat, redness and swelling of tissue.
The presence of pathogens in the _____ is detected by __________ called _____
tissues, specialised WBCs, mast cells
What 2 chemicals do mast cells release?
histamines, cytokines
What do histamines do?
- Trigger vasodilation of blood vessels in area which causes localised heat and redness. The increased temperature helps prevent the pathogen reproducing.
- Trigger an increase in the 'leakiness' of capillaries so more blood plasma is forced out forming more tissue fluid. Tissue fluid causes swelling and pain. Phagocytic WBCs also enter tissue fluid
--> Excess tissue fluid is drained into the lymphatic system where lymphocytes detect pathogens and initiate the SIR
What do cytokines do?
attract phagocytes to dispose of pathogens by phagocytosis
If an infection is _______, the inflammatory response can cause __________
widespread, a whole-body rash [Show Less]