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EXOGENOUS AGENTS THAT INJURE CELLS - Coggle Diagram
EXOGENOUS AGENTS THAT INJURE CELLS
HYPOXIA
HYPOXAEMIA
reduced availability of atmospheric O2
e.g. mountain top
ANAEMIA
reduced capacity of O2 in blood
ISCHAEMIA
stagnant circulation
HISTOXIA
tissues unable to use O2
REPERFUSION INJURY
tissues fuse again with blood
if tissues are oxygen deprived, they will enter a mode best designed to cope with low levels of oxygen
blockage released so blood spreads again, more oxygen
surplus of oxygen not anticipated by cells, leads to lots of respiratory activity and lots of free radicals
lag before DNA repair mechanisms required for synthesis of new proteins to be upregulated again
PHYSICAL INJURY
TRAUMA
cells become separated and damaged
blood vessels rupture (CONTUSION=bruise) causing leakage of blood into interstitial space and connective tissue
red blood cells are phagocytosed by macrophages
iron in blood converted to brown haemosiderin
Haemorrhage in a confined space (cranium)
limited space for swelling
pressure rises, closes capillaries
hypoxia, nerve compression
coma
HEAT
exposure to extremes of temperature
extent of damage depends on temperature and duration of exposure
damage may occur to many if not all tissues
causes may be flames, scalds or chemicals
a. PARTIAL THICKNESS (HEAL WELL)
FIRST DEGREE
epidermal, painful
SECOND DEGREE
epidermal and upper dermis, less painful
b. FULL THICKNESS (POORLY HEALING)
THIRD DEGREE
epidermal, dermal, subcutaneous; no pain, hair pulls out
FOURTH DEGREE
same as third degree, plus fascia
muscle and bone appear black and dry
no pain, hair pulls out