6.3 disease defense Flashcards
2 components of first line of defense (keep pathogens out)
skin and mucosa
how does skin keep pathogens out?
Protects the outer body. Has a thick, dry layer of cells that are mostly dead.
Contains sebaceous glands which secrete sebum, a liquid that contains fatty acids, and acids that help protect the body from microbes.
how does mucosa (mucous membrane) keep pathogens out?
Protects the inner body. Living cells that secrete fluids (mucous, saliva, tears) to wash away pathogens. Some cells are also ciliated to sweep away pathogens.
Cells may also secrete an enzyme/acids to protect from microbial growth
how do clots protect cuts?
Blood clots help seal broken skin to prevent access into the body by pathogens.
how are blood clots formed?
Platelets
Fibrin strands
Red blood cells
Blood clots are formed through a series of reactions known as the coagulation cascade.
coagulation cascade
- When blood vessel is cut, platelets in circulating blood bind to the exposed collagen and become active. They release a variety of chemicals called “clotting factors”
- The clotting factors signal the activation of more platelets as well as cause blood vessels to constrict, reducing blood flow to the area.
- Clotting factors also activates prothrombin. It becomes the active enzyme thrombin.
- Thrombin catalyzes the conversion of water soluble fibrinogen into water insoluble fibrin.
- Fibrin meshes around the platelets plugging the cut and form a blood clot.
Coronary thrombosis
The formation of a blood clot in the coronary artery as a result of atherosclerosis
examples of pathogens
bacteria, virus, fungi, parasite
toxin
disrupts metabolic processes
antigen
An antigen is a molecule (peptide, polysaccharide, lipid) that the body recognises as foreign and that will elicit an immune response
antibody
An antibody is a protein that is specific to a given antigen. One side of the antibody binds to the antigen.
The other side of the antibody serves as a recognition site for immune cells so they can destroy the pathogen.
pathogen
an infectious agent
Leukocyte/Leucocyte
A white blood cell. 5 broad types: monocytes & neutrophils (which are phagocytes), eosinophils, basophils, lymphocytes (B cells, T cells, NK cells)
2 key immune systems
innate immune system and adaptive immune system
phagocytosis
the ingestion of pathogens by a cell via endocytosis
innate immune system
- Phagocytes (ex: macrophages, neutrophils) circulate throughout the blood
- During chemical infection, chemical signals (ex: histamine), signal phagocytes to a certain location (chemotaxis).
- Pathogens are engulfed by the phagocyte and enter the cell in a vesicle.
- A lysosome fuses with the vesicle and the lysozyme enzymes digest the cell.
- Antigens from the pathogen may be sent to the cell surface to trigger the adaptive immune system.
lines of defense
1: skin and mucosa
2: innate immune system
3: adaptive immune system
adaptive immune system
Involves the production of antibodies that are pathogen (antigen) specific (immune response).
Involves immunological memory - upon re-exposure to a pathogen it can respond rapidly.
There are two types of lymphocytes:
* B-cells - produce antibodies
* T-cells
describe adaptive immune system response
- phagocyte engulfs a pathogen & presents its antigen on its surface
- the phagocyte presents the antigen to a helper T cell at the lymph node
- the helper T cell activates a B cell (it releases cytokines)
- activated B cells clone themselves, clones are plasma cells & they create+secrete specific antibodies
- antibodies in blood bind to antigens on pathogens to mark them for phagocytosis
- some plasma cells are converted to memory B cells to provide a faster adaptive response upon re-infection
antibiotics
Target prokaryotic cells (bacteria) and structures that are unique to them.
Antibiotics either kill the bacteria or prevent its ability to reproduce (binary fission)
Block processes such as:
- DNA replication
- Transcription
- Translation
- Cell wall formation
As viruses do not have a metabolism, antibiotics do not work on viruses.
penicillin
Derived from the saprotrophic fungus Penicillium which compete with saprotrophic bacteria for food.
Discovered accidentally by Alexander Fleming in 1928.
what did Florey and Chain do for penicillin
Florey and Chain developed a method to grow the fungus so that it would secrete penicillin. They then infected 8 mice with the Streptococcus bacterium.
After successful results with the mice, they tested on humans subjects.
HIV
Human Immunodeficiency Virus
HIV infect T-cells. It replicates inside the cell and destroys it. It then goes on to infect other T-cells.
This leads to immunodeficiency (the inability to fight infection from pathogens) and can result in acquired immunodeficiency syndrome (AIDS).
HIV is transmitted through specific bodily fluids: blood, semen, vaginal fluids, and breast milk.
antibody structure
Antibodies are made up of four polypeptide chains, two heavy and two light chains.
order of coagulation cascade events
clotting factors released from platelets – clotting factors convert prothrombin to thrombin – thrombin converts fibrinogen to fibrin
Clotting factors are released from platelets when a blood vessel is injured. Clotting factors cause inactive prothrombin to be converted to thrombin. Thrombin converts soluble fibrinogen to insoluble fibrin, which forms a mesh over the site of injury.
Which clotting factor is missing in people suffering from hemophilia?
Clotting factor VIII
Hemophiliacs have a mutation which means that clotting factor VIII is not produced correctly by the body, therefore the blood cannot clot correctly.
