defense against infectious disease 6.3 Flashcards
what is the first line of defence against pathogens?
how?
skin and mucous membranes.
skin: physical barrier. Skin has a slighty acididc pH and is dry which prevents bacteria from growing. secretes antimicrobial fatty acids.
sebaceous glands in skin: secrete sebum through hair follices which provides a layer of defense by helping seal off the pore of the hair follice, preventing bacteria from invading sweat glands and surrounding tissues.
Mucous membranes: lines the eyes, ears, inside the nose, etc. it secretes mucus which is a thick protective fluid that traps pathogens.
State two benefits of blood clotting when skin is cut.
Help to stop infections from entering the body
Prevent blood loss when the skin breaks open
Describe the blood clotting cascade, including the role of platelets, clotting factors, thrombin, fibrinogen and fibrin.
- damaged cells of the blood vessels walls release clotting factors.
- clotting factors are released from activated platelets.
- prothrombin is converted into thrombin
- thrombin converts soluble fibrinogen into the unsoluble protein fibrin.
- fibrin fibres collect at the site of damage
- the network of fibrin fibres traps blood cells and forms a clot.
what is the second line of defence?
white blood cells
Outline the function of phagocytic white blood cells in defense against pathogens.
Phagocytic white blood cells circulate in the blood and move into the body tissue in response to infection.
Damaged tissues release chemicals which draw white blood cells to the site of infection
Pahthogens are engulfed when cellular extensions surround the pathogen and then fuse to form an internal vesicle.
Vesicle is then fused to a lysosome and the pathogen is digested
Define “specific immune response.”
Production of antibodies by lymphocytes in response to particular pathogens - this gives specific immunity.
Contrast antigen and antibody.
Antigens
Proteins on the surface of pathogens.
They are foreign substances that stimulate the production of antibodies
Antibody
Are Y-shaped proteins called immunoglobulins, made of four polypeptide chains.
Bind to antigens to defend the body against pathogens stimulating their destruction.
State the function of plasma cells and memory cells.
Both are B cells.
Plasma cells: produce antibodies which bind onto the antigens of the pathogens
Memory cells: long-lived, bearing receptors for the specific antigen. It is able to replicate and create anti-bodies for the organism’s entire life.
Define antibiotic. Outline the mechanisms by which antibiotics kill bacteria.
Antibiotics are compounds that inhibt the growth of microbes by targeting prokaryotic metabolism (such as ribosomes which make proteins or cell wall synthesis).
Explain why antibiotics are ineffective against viruses.
viruses dont have the targeted structures or metabollic pathways such as cell wall, ribosomes or proteins, no cell memebrane, and do not replicate their own DNA.
List five measures that can be taken to avoid the development of antibiotic resistance.
Explain why multiple drug antibiotic resistance is especially dangerous.
State an example of a multidrug resistant bacteria.
- only use antibiotics for serious bacterial infections.
- complete full dose of prescribed antibiotcs.
- prevent cross infection with resistant strains
- avoid unneccessary antibiotc use in agriculture.
- develop and use new antibiotcs when resistance develops.
multi antiobiotc resistant infections may not have a treatment which could results in an epidemic.
ex. tuberculosis
Describe the consequences of the HIV on the immune system.
Targets the helper T lymphocytes which regulate the adaptive immune system.
Following infection, the virus has a period of inactivity while infected T cells reproduce.
Virus becomes active again and begins to spread, destroying the T lymphocytes.
A reduction in the number of T cells means that antibodies are unable to be produced, lowering immunity.
Body becomes susceptible to infections, resulting in death if the condition is not managed.
Outline the relationship between HIV and AIDS.
AIDS is the late stage of HIV infection that occurs when the body’s immune system is badly damaged because of the virus.
List ways the HIV virus is spread.
sexual contact, childbirth, breastfeeding, injection drug use, blood transfusion or organ transplant.
