chapter 10 - protection against invaders Flashcards
1
Q
what are pathogens
A
- such disease causing organisms
- non specific defence: external defences (body defences / protective reflexes), internal defences (phagocytes, lymphatic system, inflammatory response, fever)
types: bacteria, viruses, fungi and animal parasites
2
Q
what is disease
A
- communicable / infectious diseases, caused by foreign organisms invading the body and multiplying
- produced by pathogens which produce abnormal pathological conditions and have specific symptoms
3
Q
what is bacteria
A
- living organisms that have a metabolism, DNA and can reproduce on own
- size: single called, classified by cell shape, can be seen with light microscope
- types: cocci, bacilli (with flagella), spirilla, vibrio
- reproduction: conjugation and binary fission
- structure: slime layer (some), cell wall (peptidoglycan), DNA (no nuclear membrane), cell membrane, flagella, cytoplasm (appears granular due to ribosomes, no mitochondria / Golgi body), capsule (protection)
4
Q
reproduction of bacteria
A
- BF: replication of bacterial chromosome (origin of replication), replication continues, origins move to opposite poles, plasma membrane grows inward, new cell wall
- C: direct transfer of DNA in form of plasmid (encodes ability to mate, antibiotic resistance), donor cell (+) and recipient (-)
- do not need host for food / to cause disease
5
Q
what is a virus
A
- not all are harmful, may be dormant, need host to reproduce
- size: smaller than bacteria, only seen with an electron microscope
- reproduction: virus infects cell and the DNA or RNA induces the cell to manufacture more virus particles (hijacks cell)
- structure: core of DNA or RNA surrounded by coat of protein and not contained in nuclear membrane, lipid membrane / lipoprotein envelope
6
Q
explain the viral replication of HIV
A
- HIV (human immunodeficiency virus)
- HIV binds to receptor site on T lymphocyte (cannot reproduce alone, dependent on host for replication)
- uncoated RNA from virus enters lymphocyte (endocytosis)
- virus contains enzyme (reverse transcriptase) which enables it to produce a DNA copy of its RNA
- DNA copy integrates with host cell DNA, host DNA is transcribed and later translated
- new viral RNA and proteins are produced
- budding of new virus particle from t lymphocyte (exocytosis), host cell is destroyed
- new HIV is able to infect other cells
7
Q
what is fungi
A
- most pathogenic fungi causes disease of skin / nails
- some useful fungi
8
Q
what are animal parasites
A
- organisms that live on or in another living thing (host) and gain shelter and food from it, may cause little / no harm
- ectoparasites: live on surface of the body (fleas, lice)
- endo parasites: live inside the body (malaria)
9
Q
how are pathogens transmitted
A
- contact: physical contact (direct / indirect), e.g. skin infections / STI’s
- body fluids: one person to another, blood / other body fluids coming into contact with mucous membranes / blood stream, e.g. HIV, hep B/C
- airborne / droplets: moisture droplets (harbouring pathogens) emitted when breathing / talking, coughing, sneezing, which are then inhaled / digested, e.g. measles, mumps, colds
- ingestion: pathogen contaminated food / drink, e.g. salmonella
- vectors: transfer by animals, direct / indirect, vector specific, e.g. dengue fever (mosquitos), bubonic plague (fleas)
10
Q
what are the external body defences
A
- skin: impervious barrier, ‘good’ bacteria live on skin (difficult pathogens establish), sebum (oily secretion) kills pathogens, sweat inhibits growth
- mucous membrane: line bodies cavities (respiratory, digestive, urinary), inhibits entry of microorganisms (trapped by mucous)
- hairs: nose cavity / ears, traps microorganisms
- cilia: hair like projections, mucous membranes of nasal cavity / trachea, beating of cilia traps particles
- acids: very acidic, kill bacteria, vaginal secretions inhibit growth of pathogens
- lysozyme: kills bacteria, found in saliva, sweat, nasal secretions, tissue fluid, tears (cleansing = inhibits)
- cerumen: ear wax, inhibits growth
- urethra: flushing actions of body fluids inhibit growth
11
Q
what are the protective reflexes
A
- reflex: automatic involuntary response to a stimulus, protects body from injury
- sneezing: irritation of wall of nasal cavity, noxious fumes / dust particles, forceful expulsion of air (mucous, irritant)
- coughing: irritation of lower respiratory tract, air forced from lungs (irritant, mucous, foreign matter)
- vomiting: psychological / excessive stretching of stomach / bacterial toxins, contraction of muscles of abdomen / diaphragm, expels contents
- diarrhoea: irritation of intestines, increased contractions of muscle walls, expelled quickly without water absorption
12
Q
what are internal nonspecific defences
A
- help when pathogens get past external defences and can fight invaders
- phagocytes, inflammatory response, lymphatic system, fever)
13
Q
what are phagocytes
A
- cells that can engulf / digest microorganisms and cell debris
- leucocytes: (WBC), play a part in phagocytosis, secrete substances that destroy bacteria / engulf live bacteria
- macrophages: large phagocytic cells (develop from leucocytes), same processes as leucocytes, eliminate pathogens before infection takes place
14
Q
what is inflammation
A
- a response to any damage to the tissues
- purpose: reduce the speed of pathogens (destroy them, prevent the entry of more pathogens), remove damaged tissue / cell debris, begin repair of damaged tissue
- signs: redness, swelling, heat and pain
15
Q
what is the inflammation response
A
- skin is broken (non-specific inflammatory response begins)
- mast cells (special cells) release histamine (increases BF to area; redness / swelling, BV become more permeable/ leaky; escape of fluid = swelling) heparin (prevents clotting in immediate area, allows clotting around damaged area; prevent more pathogens from entering)
- complement proteins are activated, attract phagocytes, engulf and digest debris / bacteria; abnormal conditions = pain (phagocytes full of bacteria -> die and form pus)
- histamine and complement proteins signal ‘finished’, phagocytes are no longer attracted, new cells produced (mitosis), repair of damaged tissue
