primary defences against disease Flashcards
1
Q
define inflammation
A
- swelling and redness of tissue caused by infection
2
Q
define mucous membrane
A
- specialised epithelial tissue that is covered by mucus
3
Q
define primary defences
A
- those that prevent pathogens entering the body
4
Q
what do the pathogenic organisms need to do before causing harm ?
A
- they need to enter the body of their host
5
Q
what do selected hosts adapted to do ?
A
- evolution - to defend themselves against such invasions
6
Q
what are the mechanisms that have evolved to prevent entry of pathogens called ?
A
primary defences
7
Q
what are primary defences and they ?
A
non-specific as they prevent the entry of any pathogen
8
Q
what is the main primary defence within the body ?
A
- skin
9
Q
what is the outer layer of skin called and what does ir consist of ?
A
- epidermis and consists of layers of cells
10
Q
what are keratinocytes ?
A
- main cells found in epidermis
- outer layer of skin
11
Q
what is the role of keratinocytes ?
A
- main job is to produce keratin
- strong protein that makes the skin tough,waterproof and protective
12
Q
how do keratinocytes work ?
A
- cells are produced by mitosis at the base of epidermis
- migrate out to the surface of the skin
- as they migrate , they dry out and the cytoplasm is replaced by the protein - keratin
- process is called KERATINISATION (takes about 30 days )
- by the time the cells reach the surface they are NO LONGER ALIVE
- the keratinised layer of dead cells as an effective barrier of pathogens
- eventually the dead cells slough off
13
Q
why are keratinocytes important ?
A
- protection - they create a physical barrier against barrier , UV radiation and injury
- waterproofing - keratin helps prevent water loss from the body
- wound healing - keratinocytes help repair damaged skin by making new cells
14
Q
what does abrasions and lacerations do to the skin ?
A
- damage the skin and open the body to infections
15
Q
what must happen when abrasions and lacerations occur ?
A
- the body must prevent excess blood loss by forming a clot
–> making a temporary seal to prevent infection and repairing the skin
16
Q
what is blood clotting ?
A
- a complex process
17
Q
what is important to do when blood clots ?
A
- important to prevent clots forming in the blood vessels
—> when they are not needed
18
Q
what does blood clotting involve ?
A
- calcium ions and at least 12 factors
–> known as clotting factors
19
Q
where are clotting factors released ?
A
- from platelets and from damaged tissue
20
Q
what do these factors activate ?
A
enzyme cascade
21
Q
could you summarise blood clotting ?
A
- thromboplastin (enzyme) converts prothrombin -> thrombin (active enzyme) in the presence of Ca2+ + vitamin K
- thrombin catalyses conversion of fibrinogen (soluble) -> fibrin (insoluable fibers)
- fibrin forms a mesh , trapping platelets and RBC’s to form a clot
22
Q
could you summarise skin repair ?
A
- clot dries -> forms a scab , protecting wound from pathogens
- fibroblasts migrate -> secrete collage to strengthen new tissue
- stem cells in epidermis divide via mitosis , forming new skin cells
- new capillaries grow ( angiogenesis) to restore blood supply
- scab falls off once tissue is fully repaired
23
Q
what substances must enter our blood ?
A
- oxygen and the nutrients in our food
24
Q
what must the environment be like when the substances enter the body however … ?
A
- the exchange surfaces where this occurs must be thinner and are less well protected from pathogens
25
what may the air and food we taken in bring ?
from our environment may harbour microorganisms
26
what may be at risk at infection as a result ?
airways,lungs and the digestive systems are at risk of infection
27
define microorganisms
a microscopic, single-celled organism, such as bacteria, fungi, viruses, and protoctists, some of which can act as pathogens
28
what are the airways,lungs and digestive system protected by ?
mucous membranes
29
could you summaries the process of mucous membranes ?
1. goblet cells secrete mucus, which traps pathogens
2. ciliated epithelial cells move mucus upwards in the airways (eg. trachea & bronchi) via synchronous beating
3. mucus is swallowed - pathogens are destroyed by stomach acid
4. in other areas (e.g. eyes, genitals,) enzymes like lysosomes in secretions break down the bacterial cell walls
30
where are mucous membranes found also ?
- in the gut,genital areas, anus ,ears and nose
31
areas that are also prone to attack are ...
also sensitive
32
how do they respond to irritation ?
- by the presence of microorganisms or the toxins that they release
33
what are the reflexes as result ?
coughing , sneezing , vomiting
34
what will happen during a cough or a sneeze ?
- the sudden expulsion of air will carry with the microorganism causing the irritation
35
what is a sign that a tissue is infected ?
- swelling and redness known as inflammation
- tissue may be feel hot and painful
36
what are primary defences ?
- eyes are protected by antibodies and enzymes in the tear fluid
- the ear canal is lined by wax , which traps pathogens
- the female reproductive system is protected by a mucus plug in the cervix and by maintaining relatively acidic conditions in the vagina
37
what is the function of histamine and vasodilation ?
- part of the inflammatory response to injury or infection
- helps increase blood flow + immune cell access to affected tissues
38
what is the process of histamine and vasodilation ?
1. mast cells detect damage/infection and release histamine.
2. histamine triggers vasodilation (widening of blood vessels), increasing blood flow.
3. capillary walls become more permeable, allowing white blood cells (phagocytes) & plasma to enter tissues.
4. swelling (oedema) occurs as more fluid leaves the capillaries.
5. increased blood flow brings immune cells to fight infection & remove pathogens.
6. excess fluid drains into lymphatic system, reducing swelling over time.
