How does the body protect itself from foreign substances? In this IBDP Biology blog we will learn:
- The definition of a Pathogen
- The three modes of defenses
- Blood clot preventations
- What are antibiotics and how are they made
Pathogen and Defences
Definition: An organism or virus that cause a disease (viruses, bacteria, protozoa, fungi and worms etc)
Primary Defense:
1. Skin
- Continuous
- (hard to find an opening)
- Many layers- Outer layers are tough providing a physical barrier
- Dry
- pH
- is not favourable to pathogen- Sebaceous glands secrete lactic acid and fatty acids making skin surface more acidic
- Lysozomes
- enzymes breakdown pathogens
- Natural organisms - competitive exclusion by non-harmful microbes
2. Mucous Membranes
- Sticky
- mucus
- traps invaders
- pH
- not favourable to pathogens
- Lysozome - enzymes breakdown pathogens
- Natural organisms - competitve exclusion by non-harmful microbes
Secondary Defense (NON SPECIFIC)
1. Phagocytes
- Phagocytes ingest pathogens by
- endocytosis
- Pathogens are then
- killed and digested by enzymes
- from Lysosomes
- Antigens on the surfaces of cells and viruses allow for recognition
- If a cell is
not recognised - Phagocyte engulfs and ingests the pathogen by phagocytosis and lysosomes digests the pathogens
Non-specific Immunity: Does not distinguish between pathogens (ingests any pathogen)
- Phagocytes are in the blood and squeeze out through the walls of capiliaries and move through tissues to infection sites
- If Phagocyte response is not enough and infection spreads - Lymphocytes are called in to help
Tertiary Defense (SPECIFIC IMMUNITY)
Antigens: Molecule found on cell or virus surface that causes antibody formation
Antibodies: Globular protein that recognizes a specific antigen and binds to it as part of an immune response
Plasma cells: Clones of identical cells
Memory Cells: Quickly reproduce to form plasma cells
- Antibodies bind to Antigens
and are specific to Antigens
- Antigens
stimulate the production of Antibodies
- Each Lymphocyte can only make
one type of antibody. Each Lymphocyte puts some of the antibodies it can make on the cell surface membrane
- When a pathogen enters its antigen binds to the antibody of that Lymphocyte
- This makes the Lymphocyte active and
divides by mitosis and produces
- Plasma cells produce a lot of the
same antibody
- Antibody binds to the antigens on the surface of the pathogens and stimulates its destruction
- After the infection most Lymphocytes dissapear but some are kept as
memory cells
- if a pathogen with the same antigen is encountered again
Antibody Production
Humans have different types of B lymphocytes, which produce a relatively small number of one type of antibody each. However, our immune response can produce more antibodies:
1. Antigen is identified.
2. B lymphocyte is identifies to produce an antibody which will bind to the antigen.
3. B lymphocytes clone themselves (mitosis) to increase in number.
4. The “army” begins antibody production.
5. Antibodies eventually find their antigen match.
6. Antibodies eliminate the pathogen.
7. Clones B lymphocytes remain and give immunity (memory cells).Many different Lymphocytes exist)
And we're done!
References
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.pinterest.com%2Fpin%2Fbrown-friends-intense-stickers309904018110618952%2F&psig=AOvVaw0MuRNvxpCB4irWgHaj6y2i&ust=1624951834450000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCIi1iLrnufECFQAAAAAdAAAAABAD
https://www.google.com/url?sa=i&url=https%3A%2F%2Fbiology-igcse.weebly.com%2Fimmune-system---antibody-tissuerejection.html&psig=AOvVaw1IYYDpPCNIK1rb6ZHO4jln&ust=1624951377415000&source=images&cd=vfe&ved=0CAoQjRxqFwoTCNivrODlufECFQAAAAAdAAAAABAD
Written by Venetia (Biology)