cellular adaptation Flashcards
what is cellular adaptation
this is how cells respond to stress in order to stay alive
what are the five main adaptations
atrophy
hypertrophy
metaplasia
hyperplasia
dysplasia
what are labile cells
those that are constantly replicating and are very mitotically active
what are stable cells
asleep cells that are not copying themselves but can if they need to
what are permanent cells
these never undergo mitosis and cannot copy themselves to repair
what are some permanent cell types
muscle and neural cells
describe atrophy
reduction in cell size
caused by reduction in work demand or due to hormones
decreased size makes the cells more efficient so if they are not being used they will shrink to become more energy efficient
what are the physiological causes for atrophy
muscles in the uterus become large during pregnancy but once hormone levels drop after birth the muscles return to normal size
what are the pathological causes for atrophy
ischaemia - if there is reduced blood flow due to peripheral vascular disease, a reduced blood flow to leg will mean the muscle in the leg will atrophy due to inadequate blood supply
does the number of cells change in atrophy
no, just the size of the cell
which cells are likley to be affected by atrophy
stable or permanent cells - often happens with muscle
describe hypertrophy
this is an increase in cell size
often occurs in skeletal and cardiac muscle cells
stimulus is usually in response to mechanical force or stretch like contraction, hormonal stimulation or growth factor stimulation
describe a physiological cause for hypertrophy
going to the gym and lifting weights will increase mechanical stress on the muscle, so the muscle will respond by increasing the gene expression to make more proteins making the cells larger
describe a pathological cause for hypertrophy
cardiac myopathy where increased muscle in the heart occurs. as muscle increases, the heart can become inefficient and have issues with contraction
which cell types usually experiene hypertrophy
muscle cells - permanent cells
describe hyperplasia
this is when tissue size increases due to an increase in cell numbers rather than cell size
usually occurs in labile or stable cells
cells respond to stress by increasing their number
what are some physiological causes for hyperplasia
inducing agent of hormone levels can lead to hyperplasia of the breast during puberty and pregnancy to increase ability to produce milk
what is a change in stable cells that can be caused by hypertrophy at a physiological level
hepatocytes in the liver, if the liver was ever cut in half the hepatocytes would be activated and increase mitosis so there is more replication and the cell number increases
describe why hyperplasia may occur in an athlete
constant exposure to hypoxia, more red blood cell production in the bone marrow, increased oxygen carrying capability
describe a pathological cause for hyperplasia
prostate gland exposed to androgen hormone can increase the prostate size
papilloma virus causes warts
describe metaplasia
change in cell type or morphology due to chronic irritation or inflammation
when the environment of the cells are exposed long term to inflammation, the cells must change to be more appropriate to the environment so they can survive
give examples of when metaplasia would occur
- if cells are exposed to lower pH, like in barrets oesophagus due to reflux, they would want to be more like cells in the stomach that can withstand the lower pH.
- if exposed to cigarette smoke, the respiratory epithelium would change from cilia to stratified squamous for protection against soot
is metaplasia irreversible
no, cells will return to normal once the stimulus is removed
describe how metaplasia occurs
genes in the cells are activated to cause differentiation, so the cells being affected have to be stem cells like epithelium - bone and muscle cells cannot change their cell type, but epithelial cells can
describe dysplasia
disordered growth, stimulus is chronic irritation or inflammation, the response is deranged growth
increase in cell number and cell shape
precursor for neoplasia
can be reversible but this is unlikely
pathological causes rather than physiological
