What is hypertrophy?
What are two reasons for it?
Increased size of cells by synthesis of cellular components therefore increasing cellular weight
-may happen because there is an increase in functional demand or because there is hormonal stimulation
What is an example of hypertrophy and what is the mechanism of its development?
What is the significant of this example?
An example is cardiac hypertrophy. This involves two triggers - mechanical and hormonal triggers. These two triggers cause hypertrophy, causing an enlarged heart. Once the heart has reached it limit where it can’t compensate (b/c uncoordinated action potentials and because with the pericardium there is no room for the heart to grow out so it grows inwards making less space for blood = decreased CO and SV) then the heart goes into cardiac failure. This results in myocardial cells degenerating via necrosis or apoptosis
What is hyperplasia?
increased number of cells. This is only possible in cells that are capable of mitotic division
Describe physiological hyperplasia?
- hormone induced hyperplasia increases the amount of functional cells when needed (ex endometrial hyperplasia in a pregnant uterus)
- compensatory hyperplasia increases the amount of functional cells after there has been trauma or damage (ex bone marrow hyperplasia after loss of blood)
Describe pathological hyperplasia?
caused by excessive hormone secretion or continuous irritation
- ex/ cystic endometrial hyperplasia in bitch - an exaggerated hyper plastic response because there is estrogen primed endometrium to progesterone
- ex/ formation of calluses due to chronic irritation on skin
Describe the mechanisms of hyperplasia
-there are increased level of growth factor production and growth factor receptors on the cell. There is also increased activation of intracellular signalling pathways which leads to the production of transcription factors, which all lead to increased cellular proliferation
What happens with hyperplasia when the stimulus is removed?
with hyperplasia, there will be a stop in the proliferation response
What is atrophy? how is hypoplasia different?
- atrophy is when a normalized cell shrinks because of a loss of substance.
- hypotrophy is when there is a small cell, but it is because there was a failure of the cell to reach its full size
What are the 8 types of atrophy?
- physiological atrophy - during embryonic development or reproductive cycles of female repro organs
- disuse atrophy - lack of use/workload leads to atrophy (bone or muscle mostly)
- denervation atrophy - damage to the nerve causes fast atrophy to the muscle it innervates
- diminished blood supply causing atrophy
- nutritional atrophy - if there is poor nutrition for long period of time then body has used up all of its energy sources and starts atrophying muscle. In this situation, fat will be replaces with watery, gelatinous fluid (serous atrophy)
- increased or decreased endocrine atrophy - if there is an increased external administration of hormone then the organ that normal produces that hormone atrophies. Or if there is a decreased amount of hormone then there will be atrophy of tissue (ex mammary tissue)
- Senile atrophy - when cells are getting old they under go atrophy
- pressure atrophy - if there is an increase in pressure then there may be diminished blood supply causing atrophy
Describe some reason for serous atrophy in regards to nutritional atrophy
ultimate reason in that the animal is in negative energy balance which can be caused by:
- malnutrition
- poor dentition
- cold environment
- increased energy demands (pregnancy or lactating)
Describe the mechanism of atrophy
there is a decreased size of cell to a size that allows the cell to still remain functional. the decreased size is due to the decreased amount of structural components within the cell. These cells are still alive! they are not dead!!
Describe the 3 proteolytic systems within the mammalian cell
- lysosome that contain acid hydolases degrade proteins that have been engulfed from the extracellular environment and degrade them
- the ubiquitin-proteasome pathway take nucleic and cytosolic proteins and conjugate them into ubiquitin and then degrade them using proteasomes. This pathway is induced by timor necrosis factor.
- autophagy, which is the disposal of damaged organelles within a cell through the formation of autophagic vacuoles. Atrophy increases the amount of autophagic vacuoles
What is metaplasia? Give an example
When a tissue changes from one specialized type to another specialized type. It can be a reversible process if the stimulus if removed
ex/ columnar epithelium to stratified epithelium
Describe connective tissue metaplasia
the formation of cartilage, bone or fat in tissue that normally does not have it. it is typically insignificant because it is normally a very small amount
