Cellular Adaptation Flashcards
Are cellular adaptations normally reversible or irreversible?
Normally reversible.
-unlike cell injury and neoplasia
What are cellular adaptations?
Reversible (usually) changes in cellular size / number / phenotype / metabolic activity / function.
What causes cellular adaptations?
Changes in environment/demand.
What is the purpose of cell adaptations?
Cells acquire steady state of metabolism, and are better equipped to survive in new environment.
What type of cells don’t normally need to adapt?
Fibroblasts.
-survive severe metabolic stress (e.g. absence of O2)
What type of cells adapt easily?
- Epithelial cells
- Labile cell populations
- Stem cells
What type of cells cannot adapt?
Cerebral neurons.
- terminally differentiated / highly specialised
- permanent cell population
- rapidly die when hypoxic
What are the main types of adaptive response? (3)
- Increased cellular activity
- Decreased cellular activity
- Change of function/morphology
How do cells respond to increased demand? (2)
- Hypertrophy
- Hyperplasia
> > increased cell mass
What is the difference between hypertrophy and hyperplasia?
HYPERTROPHY -increase in size of cells
HYPERPLASIA - increase in number of cells
What type of cell population is hypertrophy often seen in?
Permanent cell populations.
-especially cardiac and skeletal muscle
What type of cellular adaptation causes an enlarged uterus during pregnancy?
Hypertrophy.
-increase in cell size
What type of cellular adaptation occurs when the bladder has to work harder due to obstruction (e.g. prostate tumour)?
Hyperplasia.
- increase in cell number
- leads to diverticulum
How do permanent cell populations respond to increased demand?
Hypertrophy.
- can only increase cell size
- e.g. LVH
Give 2 examples of permanent cell populations undergoing hypertrophy to meet increased demands.
- Skeletal muscle cells of a marathon runner
- Cardiac cells due to aortic stenosis (LVH)
What causes left ventricular hypertrophy?
- Hypertension
- Aortic stenosis
- Cardiomyopathy
- Athletic training
How in left ventricular hypertrophy diagnosed?
- Electrocardiogram (ECG)
- Echocardiogram
- MRI
What are the main problems associated with left ventricular hypertrophy?
- Arrhythmias (^ ectopic beats)
- Increased stroke risk
- Increased heart attack risk
- Sudden unexpected death
What is subcellular hypertrophy and hyperplasia?
Increase in size and number of subcellular organisms.
Give an example of subcellular hypertrophy in the liver.
Barbiturates lead to smooth ER hypertrophy in hepatocytes.
|»_space; increased metabolism of other drugs
What is hyperplasia?
An increase in number of cells.
-caused by cell division
What type of cell populations is hyperplasia possible in?
Labile and stable cell populations.
What is gynaecomastia?
Enlargement of male breast due to hyperplasia of glandular and stromal tissue.
Is gynaecomastia physiological or pathological?
Both;
PHYSIOLOGICAL - puberty, due to drugs
PATHOLOGICAL - due to liver cirrhosis
What is compensatory hyperplasia of the kidneys?
Hyperplasia of one kidney due to hypoplasia of the other kidney.
What is the process of cellular adaptation in Graves disease?
Auto-antibody switches on TSH receptor in thyroid
|»_space; uncontrolled hyperplasia of thryroid (HYPERTHYROIDISM).
What does the abnormal healing process of liver cirrhosis lead to?
Hyperplasia nodules.
What is atrophy?
Reduction in the size of an organ/tissue.
-due to decreased cell size/number
Give 2 physiological types of atrophy.
- Embryogenesis
- Uterus after pregnancy / menopause
What are the main causes of pathological atrophy?
- Decreased workload
- Loss of innervation
- Diminished blood supply
- Inadequate nutrition
- Loss of endocrine stimulation
- Pressure
What is another name for atrophy due to decreased workload?
Disuse atrophy.
-e.g. muscles in cast when broken bone
Give an example of atrophy due to inadequate nutrition.
Cachexia.
-wasting of body in severe illness
How does a tumour in the pituitary cause atrophy due to pressure?
Benign pituitary tumour squashes the rest of the pituitary»_space; atrophy.
What happens to the brain with age?
It shrinks.
-bigger sulci, narrower gyri
What does renal artery stenosis cause?
Atrophy of the kidney.
What is the thymus an example of in adults?
Physiological atrophy.
-decreases in size with age
How do steroid therapies lead to adrenal cortex atrophy?
Reduces the ACTH drive to the adrenal»_space; decreased hormonal stimulation.
What are the 2 mechanisms of atrophy?
- Reduction in individual cell volume
- Death of individual cells
What is apoptosis?
Process of programmed cell death that occurs in multicellular organisms.
What is involution?
Physiological atrophy of an organ by apoptosis.
-e.g. womb after childbirth
What are the main developmental abnormalities that lead to a reduced cell mass? (4)
- Agenesis
- Aplasia
- Dysgenesis
- Hypoplasia
What is agenesis?
Failure of an organ to develop during embryonic growth.
- never grows
- due to absence of primordial tissue.
What is aplasia?
The failure of an organ to develop/function normally.
-e.g. may have been primordial tissue, but not organ-specific tissue
What is dysgenesis?
Defective development of an organ.
- especially gonads
- doesn’t grow to full size
What is hypoplasia?
Underdevelopment of an organ/tissue.
What is metaplasia?
Transformation of one differentiated cell type into another.
-can»_space; better adaptation to environment
What is metaplasia caused by?
Transdifferentiation of stem cells.
What tissues can be affected by metaplasia? (2)
- Epithelium
- Mesechymal tissue
What type of epithelium does the cervix have before puberty?
Cervix has stratified squamous epithelium, endocervical canal has collumnar epithelium.
What happens to the cervix at puberty?
Oestrogen causes stratified squamous to descend and replace columnar epithelium.
-PHYSIOLOGIAL METAPLASIA
What can pathological hyperplasia and metaplasia lead to?
Carcinoma.
What pathological metaplastic change can cigarette smoke cause to bronchial epithelium?
Bronchial epithelium;
pseudostratified ciliated»_space; squamous.
What pathological metaplastic change can bladder calculus cause to bladder epithelium?
Bladder epithelium;
transitional»_space; squamous.
What pathological metaplastic change can chronic trauma cause to fibrocollagenous tissue?
Fibrocollagenous tissue»_space; bone.
What pathological metaplastic change can acid reflux cause to oesophageal epithelium?
Oesophageal epithelium;
squamous»_space; columnar (glandular).
What can endometrial hyperplasia due to increased oestrogens lead to?
Adenocarcinoma.
What is the earliest morphological manifestation of neoplasia?
Dysplasia.
What is dysplasia?
Enlargement of an organ / tissue by the proliferation of cells of an abnormal type.
-non-invasive (in-situ)
What test is dysplasia detected in?
Cervical screening test.
-detection before invasice
