Adaptations Of Cell Growth: Cell Injury Flashcards
The cell’s response may be a change in 4 things
number
size
phenotype
metabolism
Etc
● Adaptations are a cell’s response to?
changes in its environment.
4 types of adaptation and slight explanation
• Hyperplasia : increase in cell number
● Hypertrophy : increase in cell size
● Metaplasia : change in cell phenotype
● Atrophy : reduction in cell size/number
Hypertrophy
● Increase in cell size which leads to?
● Seen in cells which?
- increase in the size of the organ.
- cannot multiply by division
May also be seen in cells which undergo division (hyperplasia/hypertrophy)
Hypertrophy Occurs as a result of
synthesis of increased structural elements in the affected cells
Can be physiologic or pathologic
● Physiologic hypertrophy results from ______ or ______
increased stimulation of the cell by hormones or increased functional demand.
E.g.
skeletal muscle in weightlifters
growth of the uterus in pregnancy.
● Pathologic hypertrophy is a response to _____
Examples include?
Disease
In aortic stenosis,
hypertension,
also in hypertrophic cardiomyopathy
when the heart muscle pumps against resistance in certain disease conditions
What is the mechanism of Hypertrophy
Increased synthesis of intracellular proteins
The combined actions of _____, ______and g_____ lead to generation of signals which are transmitted into the cell through signal transduction pathways. These signals activate transcription factors which increase?
Mechanical sensors
Vasoactive agents
Growth factors
the synthesis of muscle proteins.
Other adaptive changes can occur in hypertrophy. For example?
change from alpha to beta isoform of myosin heavy chain, increases expression of atrial natriuretic factor gene in states of cardiac hypertrophy.
Hypertrophy has its limits beyond which the enlargement of muscle mass cannot cope with the stimuli. This may lead to ____ &____
fibrosis and myocyte death.
Hyperplasia is?
It may occur together with hypertrophy if the cell is capable of?
Increase in the number of cells in a particular organ/tissue
Dividing
Physiologic hyperplasia there’s 2 types
Give examples
● Functional: when there is a need to increase functional capacity e.g. breast in puberty/pregnancy.
● Compensatory: need to replace function of damaged cells e.g. liver post-resection and bone marrow after blood loss.
Pathological hyperplasia results from excessive or inappropriate actions of _____ or _____.
Pathologic hyperplasia may be _____
hormones or growth factors
Pre cancerous
3 examples of pathologic hyperplasia
Endometrial hyperplasia due to increase in estrogen
○ Benign prostatic hyperplasia due to androgen effects
Skin changes in response to viral infections (warts in Human Papillomavirus infections)
Mechanism of hyperplasia
Growth factor driven proliferation of existing cells
Increased output of new cells from stem cells
Atrophy is ?
● Maybe physiologic or pathologic.
Reduction in the size of a tissue or organ due to a reduction in cell size and number
Example of physiologic atrophy
in regression of uterus to normal size post pregnancy.
6 types of pathologic atrophy and explanation
DDINEP
- Decreased workload (disuse atrophy): e.g. muscle atrophy following fracture/ prolonged bed rest
- Denervation atrophy: muscles need nerve stimulation to metabolism and function
- Ischaemia : due to atherosclerosis. E.g. senile atrophy in the brain & heart
- Inadequate nutrition: skeletal muscle proteins may be used as energy source.
- Loss of endocrine stimulation: e.g. breast, uterus
- Pressure effects: tissue compression for long periods of time.
E.g. by a tumour or POP cast (fracture)
The purpose of atrophy is to?
create a new balance between the cell’s demands and its supply of nutrients/oxygen.
3 mechanisms of atrophy
- Increased degradation and reduced synthesis of proteins.
- Protein synthesis is reduced due to the reduction in metabolism
- Degradation of protein occurs through the
ubiquitin-proteasome pathway and through autophagy.
Metaplasia is a reversible cell change in which?
But it really is ?
one differentiated cell type is replaced by another cell type.
The reprogramming of stem cells to differentiate along a new pathway
It is an adaptive change to stress such that_____ replaces _____
● However, the functional effects of the original cell may be lost and these changes may be ______
the cell better able to withstand the stress
the cell sensitive to the stress.
Pre cancerous
Give the 3 metaplasmic changes and their examples
- Columnar to squamous epithelial changes:
- Respiratory tract e.g smokers, Vit A deficiency/excess
- Excretory ducts e.g. salivary glands, bile duct - Squamous to columnar changes:
- Oesophagus (Barett’s oesophagus) - Connective tissue metaplasia
- Myositis ossificans
Mechanism of metaplasia is
Reprogramming of stem cells found in that tissue or of undifferentiated mesenchymal cells in surrounding tissues.
The environmental stimulants program these cells towards a differentiation pathway
These precursor cells differentiate along a new pathway due to the expression of genes induced by external stimuli and transcription factors
Effects of metaplasia
Fertile ground for development of malignancy.
E.g. is Barrett’s oesophagus leading to sq
