topic 6 Flashcards
(38 cards)
what does a post mortem examination consist of?
- external examination
- internal examination: incision made down front of body, organs taken out for examination
blood and tissue samples tested for toxins/ infections/ tumours
stomach contents analysed to show when and where person alive
what type of cell are bacteria
prokaryotic (no nucleus or membrane bound organelles and do not produce a spindle during cell division)
bacteria cell walls
gram positive- walls that are thickened with additional polysaccharides and proteins
gram negative- thinner walls with surface layer of lipids for protection
what are viruses made of
1x strand of nucleic acid (RNA or DNA) enclosed within a protein coat
single OR double stranded
how do viruses infect cells
- enter host and use its metabolic systems to reproduce as they lack the internal cells required for growth and reproduction
- normal working of cell disrupted
- new virus particles bud from cell surface or burst out of the cell, causing cell lysis
- cell lysis= cell contents released into surrounding tissues- enzymes + chemicals damage other cells causing disease symptoms
what are viral envelopes
an outer envelope taken from the hosts cell surface membrane- thus contains lipids and proteins.
have glycoproteins from the virus itself. These are antigens; molecules recognised by the host’s immune system
Therefore, the envelope helps virus attach to the cell and penetrate the surface membrane, eg. HIV
how does a virus get inside a host cell
- virus attaches to host cell
- virus inserts nucleic acid
- viral nucleic acids replicate
- viral protein coats synthesised
- new virus particles formed
- cell lysis; viral particles released
examples of bacteria
salmonella food poisoning
cholera
examples of viruses
flu
measles
chicken pox
cold sores
debate about if viruses are living
YES - can reproduce, pass on genetic info from 1 generation to the next
NO- not capable of independent reproduction or energy use
what increases the risk of getting TB
close contact
poor health/ diet
overcrowded living conditions
what fluids transmit HIV
blood
vaginal secretions
semen
breast milk
types of HIV transmission
sharing needles
unprotected sex- breaks in skin, virus enters bloodstream
direct blood to blood- cuts and grazes, police
maternal: last few weeks
reduce- anti HIV drugs during last 3 months
giving birth via caesarean section
difference between non specific and specific immune response
non- ANY invading pathogens, immediate
specific- specific pathogens, delayed
what is an antigen
any foreign molecule the body recognises
3 types of non specific immune response
- lysozome
- inflammation
- phagocytosis
what do lysozomes do
enzyme lysosome kills bacteria by breaking down their cell walls by hydrolysing the polysaccharide
found in: tears, salvia, nasal secretions
what is inflammation
injury enables microbes + foreign material to enter body, so blood clots rapidly to seal the wound. Helps destroy invading microbes
how does inflammation occur
damaged white blood cells and mast cells release HISTAMINE:
- arterioles in area dilate; increasing blood flow in capillaries at infected site
- increases permeability of capillaries; antibodies leak from the blood into the tissue, causing oedema because cells in capillary walls separate slightly
infecting microbes can now be attacked by intact white blood cells
what is phagocytosis
phagocytes (white blood cells) from capillaries engulf bacteria and other foreign matter in blood and tissues
- neutrophils
- macrophages
bacterium with antigens on surface detected and engulfed by neutrophil or macrophage.
Bacterium enclosed in vacuole
Lysosomes fuse with the vacuole, releasing enzymes to destroy foreign material.
action at site of infection; non specific immune response
chemicals released by bacteria and damaged cells at the site of infection attracted pathocytic white cells.
NEUTROPHILS arrive first. engulf 5-20 bacteria before becoming inactive + dying
MACROPHAGES arrive- larger, longer lived cells destroy up to 100 bacteria by phagocytosis and digest debris from damaged cells and foreign matter.
ingested material enclosed in vacuole
Lysosomes containing digestive enzymes fuse with vacuole, enzymes are released which destroy bacteria and other foreign material
how does the body prevent spread of infection in blood and lymph
action of macrophages in lymph nodes, spleen and liver
tissue fluid drains into lymphatic vessels
fluid (lymph) flows along lymph vessels. It passes through lymph nodes and returns to the blood via lymphatic and thoracic ducts.
as lymph passes through lymph nodes, any present pathogens activate lymphocytes and macrophages- which can then destroy the microbes
what are lymphocytes
white blood cells that help defend the body against specific diseases.
Circulate in the blood and lymph and gather in large numbers at site of infection
give 2 types of lymphocytes
B and T cells
both respond to antigens, proteins, other foreign ‘proteins’
