Cellular Adaptation Flashcards
Define cell adaptation
Reversible changes in number size phenotype metabolic activity or functions of cells in response to changes in their environment
Classify adaptations
Hyperplasia
Hypertrophy
Atrophy
Metaplasia
Hyperplasia def and classify
Increase in the no of cells in an organ or tissue usually resulting in increased volume of organ or tissue in response to stimulus
Types
Physiological:
1.hormonal
2. Compensatory
Pathological
Causes of hyperplasia
Physiological
1. Hormonal: glandular tissue of female breast during pregnancy puberty or lactation
Uterine endometrium during pregnancy
2. Compensatory
In partial hepatectomy of liver
Remaining kidney after unilateral nephrectomy
Pathological
Endometrial hyperplasia in granulosa tumor of ovary
Benign prostatic hyperplasia
Clinical imp of hyperplasia
Constitutes a fertile soil in which cancerous proliferation may eventually arise
Causes of hypertrophy
Physiological..
Increased workload ie bulging muscles of body builders 1.Hormone induced
Uterus during pregnancy breast during lactation
2. Pathological hypotrophy hypertrophy of cardiac muscle in hypertension
Both hypertrophy and hyper
Plasia
Uterus during pregnancy
Metaplasia def and examples
It is a reversible change in which one differentiated cell type is replaced by another cell type of similar nature
it is of 2 types
epithelial Metaplasia
Connective tissue metaplasia
Epithelial metaplasia:
Squamous-
columnar to sq( resp tract in chr irritation cigarette smokers ciliated columnar to strat sq)
Transitional to sq( urinary bladder in long standing chr inflammation calculi)
Columnar
Sq to columnar( barette esophagus)
Columnar to columnar( epitheium of stomach is replaced by intestinal type epithelium)
Metaplasia is a double edged sword
Metaplasia Causes two harmful effects at the same time
they are:
1. in respiratory tract although the epithetial lining becomes more durable, important mechanisms of protection against infection like mucous secretion And ciliary action of epithelial cells is lost.
2.the influences that predispose to metaplasia if persistent can initiate malignant transformation in metaplastic epithelium. Eg scc in resp tract can occur from metaplastic sq cell
Mechanism of metaplasia
- Reprogramming of local tissue stem cells
- Colonization of differentiated cell populations from adjacent sites
Condition where fibromlast is converted to osteoast
Myositis ossificans
Define atrophy with examples of types of atrophy. Why atrophy of brain occurs in elderly
It is defined as reduction in size of an organ or tissue to due decreased cell size and number
Types
1. Physiological atrophy
. During early fetal development eg notochord
. Atrophy of uterus after parturation
Pathological
. Localized; eg denervation atrophy, pressure atrophy
. Generalized; due to starvation, senile atrophy
Why in elderly
In late adult life ; Brain undergo progressive atrophy mainly because of reduced blood supply as a result of atheroschlerosis in cerebral vessels. This is called senile atrophy.
Mechanism of atrophy
- Decreased protein synthesis
Due to reduced trophic signals which enhance uptake of nutrients and increase mRna synthesis
- Increased protein degradation in cells
. Lysosome
. Ubiquittin proteasome pathway
. Inc no of autophagic vacuoles
Clinical imp of metaplasia
Metaplasia makes cells better able to withstand stress
It may result in reduced functions and increased risk for malignant transformation
Adv and disadv of metaplasia
- It helps the cells to withstand adverse environment
Eg in resp tract due to chr irritation in cig smokers
Columnar ep changed into squamous type. The stratified sq ep is more rugged and durable.
Disadvantage
Alteration of normal physiological function: due to sq metaplasia of in resp tract , protective func like mucous secretion and ciliary func are lost
- Malignant transformation
Sq cell carcinoma can arise from metaplastic sq cell in resp tract
Intracellular accumulation
It is a metabolic derangement in which there is intracellular accumulation of various substances
Which are
1. Normal cellular components
Water, lipid, protein and carbs
2. Abnormal substances
a. Exogenous:
carbon particles in coal miners
Silica in silica factory workers
b. Endogenous
Lipofucin
Melanin
Hemosiderin
Bilirubin
Mechanism of intracellular accumulation
- Inadequate removal of normal substance eg fatty change in liver
- Accumulation of abnormal endogenous substance eg mutated forms of a1 antitrypsin
- Failure to degrade metabolite eg storage diseases
- Deposition and Accumulation of abnormal exogenous substance eg carbon or silica
Mechanism of fatty change in the liver
Excess accumulation of triglycerides in the liver may result from the defects in any one of the events from fatty acid entry to lipoprotein exit.
The mechanism is
1. Fatty acid
2. Esterified to TG
3. Converted to cholesterol or phospholipids or oxidation of ketone bodies
4. Release of TG requires association with apoproteins
5. Form lipoprotein
6. Transported from blood to tissue
