Cellular Adaptations Flashcards
Define it ..
Adaptations are reversible changes in the number, size, phenotype, metabolic activity or functions of cells in response to changes in their environment.
Two types of adaptations:
Physiologic adaptations: represent response of cells to normal stimulation by hormones or endogenous chemical mediators.
Pathologic adaptations: responses to stress that allow cells to modulate their structure and function and thus escape injury.
E.g of physiologic adaptation
The hormone-induced enlargement of the breast abd uterus during pregnancy
Shrinkage in the size of the cell by the loss of cell substance
Atrophy
Atrophic cells may have diminished function but:
They are not dead, but if the stimulus continues, die often by apoptosis
Atrophy represents a reduction in the structural components of the cell:
The cell contains fewer mitochonria, myofilaments, a lesser amount of endoplasmic reticulum
In atrophy: increase in number of:
Autophagic vaculoes, residual bodies and lipofuscin granules.
Mechanism of atrophy:
– sythesis of protein》 because of reduced metabolic activity
++ degradation of protein
In atrophy: the degradation of cellular proteins occurs mainly by :
The ubiquitin-proteasome pathway.
Mechanism of ubiquitib-proteasome pathway:
Nutient deficiency and disuse may activate ubiquitin ligases
Attach copies of small peptide ubiquitin to proteins》proteasome
The ubiquitin pathway is responsible for :
For the accelerated proteolysis seen in a variety of catabolic conditions, including cancer cachexia
Why atrophic cell shows autophagy:
It is the process in which the starved cell eats its components in an attempt to find nutrients and survive
How do the residual bodies appear?
Some of the cell debris within the autophage vacuole may resist digestion and persist as membrane bound residual bodies that may remain as a sarcophagus in the cytoplasm
Common causes of atrophy:
Reduced workload Inadequate nutrition Ageing Loss of innervation Reduced blood supply Loss of endocrine stimulation
E.g of physiologic atrophy:
Atrophy of ductus arteriosus in infants
Atrophy of thymus in adults
Atrophy of gonads in old age
E.g of generalized atrophy:
Atrophy due to starvation
Senile atrophy due to aging
E.g of ischaemic atrophy:
Small atrophic kidney in atherosclerosis
Atrophy of brain in cerebral atherosclerosis
Prolonged diminshed functional activity is associated with :
Disuse atrophy of tge organ
E.g of disuse atrophy:
Wasting of muscles of limb immobilised in cast
Atrophy of the pancreas in obstruction of panceatic duct.
In neuropathic atrophy interruption in nerve supply leads to:
Wasting of muscles e.g:
Poliomyelitis,, motor neuron disease and nerve section.
Endocrine atrophy:
Loss of endocrine regulatory mechanism results in reduced metabolic activity of tissue and hance atrophy
E.g of endocirne atrophy :
Hypopituitarism may lead to atrophy of thyroid, adrenal and gonads.
Hypothyroidism may cause atrophy of the skin and its adnexal structures
Pressure atrophy:
Prolonged pressure from benign tumours or cyst or aneurysm may cause compression and atrophy of the tissues
E.g of pressure atrophy:
Erosion of spine by tumour in nerve root.
Erosion of skull by meningioma arising from piaarachnoid.
Erosion of sternum by aneurysm of arch of aorta.
Other causes of a small organ ther than atrophy :
Hypoplasia :incomplete growth of an organ.
Agenesis : complete failure of development of an organ in embryogenesis
Aplasia : failure of development of organ.
Hypertrophy:
It is an increase in the size of the cell resulting in increase in the size of organ.
Hyperplasia is characterized by :
An increase in cell number because of proliferation of differentiated cells and replacement by tissue stem cells
T or F
In pure hypertrophy there are no new cells, just bigger cells containing increased amounts of structural protein and organelles.
T
Hypertrophy without accompanying hyperplasia affects:
Mainly striated muscles (heart, skeletal).
Causes of hypertrophy:
It caused by increased functional demand or by hormonal stimulation
E.g of physiol.. hypertrophy:
The massive enlargement of the uterus during pregnancy (estrogen stimulate S.M HT and HP)
Breast enlargement during pregnancy
Skeletal muscle HT due to + workload.
E.g of patho.. HT:
HT of uterine S.M under the influence of estrogen secreted by ovarian tumor.
L ventricle HT due to systemic HTN.
R ventricle HT due to pulmonary HTN.
Limitation of hypertrophy due to:
Limitation of vascular supply to enlarged fibers
Diminished oxidative capabilities of mitochondria ATP.
Alternations in protein synthesis and degeneration.
Hyperplasia :
It refers to increase in number of cells in an organ or tissue.
Causes of hyperplasia:
Hormonal stimulation Tissue loss (remaining tissue undergo hyperplasia to compensate for tissue loss).
Which cell types can undergo hyperplasia?
Labile and stable cells (e.g parenchymal cells of the liver, pancreas, kidney, adrenal, and thyroid)
Types of hyperplasia:
Physio.. :
Hormonal and compensatory hyperplasia
Patholo…
E.g of hormonal hyperplasia
Proliferation of epithelium of female breast at puberty and during pregnancy due to estrogenic stimulation
Proliferation of uterine smooth muscle during pregnancy due to estrogenic stimulation
Compansatory hyperplasia:
It refers to hyperplasia that occurs when a portion of tissue is removed or diseased
E.g of compansatory hyperplasia:
Compansatory hyperplasia of remaining liver after hepatectomy under influence of TGF-Alpha & beta and hepatopoietin produced by remnant hepatic cells.
Hyperplasia of remaining kidney.
E.g of patho.. hyperplasia:
Adenomatous hyperplasia of endometrium after normal menestrual period due to increased estrogen/progesteron ratio.
HP of thyroid follicles in primary huperthyroidism (Grave’s disease)
Hyperplasia that associated with certain viral infections for example :
Papillomaviruses HPV cause skin warts and mucosal lesions composed of mass of hyperplasia epithelium.
Other patholo.. e.g of hyperplasia :
Hyperplasia of prostate gland (BPH)
Hyperplasia of C.T in wound healing
Hyperplasia importance in healing:
HP is an important response of C.T cells in wound healinh, in which proliferating fibroblast and blood vessels aid in repair under these circumstances, growth factors is also involved in the hyperplasia
Clinical significance of hyperplasia:
It may produce clinical disease (e.g : endometrial Bleeding, thyroid hyperfunction)
It increases the risk of neoplasia (e.g: endometrial hyperplasia, HPV).
Metaplasia:
It is a reversible change in which one adult cell type (epithelial or mesenchymal) is replaced by another adult cell type
Causes of metaplasia:
Chronic irritation (cigarette smokers, stone) Chronic inflammation Vit A deficiency
Types of metaplasia:
Epithelial metaplasia
Mesenchymal metaplasia
Atypical metaplasia
Squamous metaplasia:
Replacement of columnar epithelium by stratified squamous epithelium, in respose to irritation or inflammation
Squamous metaplasia occurs in :
Gallbladder, trachea, brochi, bronchioles, endocervical glands, amd excretory ducts of glands
Advantage of metaplasia:
It is protective response and the metaplastic cells are capable of surviving against injurious agent.
Disadvantage of metaplasia:
The protective mechanism of the epithelium is lost (epithelium resulting from squamous MP leads to loss of mucus secretion)
Fertile soil for malignant transformation, for this it is called two edged sword.
Metaplasia of epithelial in respiratory passages and renal calyces & pelvis into ….. epithelium in response to ……
Keratinizing stratified squamous
Vit A deficiency
In the columnar epithelium, In chronic gastric reflux, the normal stratified squamous epithelium of the lower esophagus may undergo metaplastic transformation to gastric or intestinal-type columnar epithelium called :
Barrett esophagus
E.g of mesenchymal metaplasia :
Metaplasia of fibroblast into chondroblast to produce cartilage.
Metaplasia of fibroblast into osteoblast to produce bone in traumatic injury to muscle causing “myositis ossificans”.
Atypical metaplasia:
It refers to disorderd metaplasia,
cell vary in size and shape, and are disoriented and have variation in nuclear size and chromaticity
Difference b/w epithelial &mesenchymal metaplasia:
Epi.. MP is reversible and mesenchymal that form the bone is irreversible.
Dysplasia:
It means ‘disordered cellular development’ often accompanied with metaplasia and hyperplasia.
It refers to loss of uniformity of individual cell & loss of their architectural orientation.
Dysplasia is also defined as :
Atypical hyperplasia
Dysplasia occurs often in :
Epithelial cells
Is dysplasia reversible?
It is reversible upon removal of offending stimulus
Epithelial dysplasia is characterized by :
Cellular proliferation and cytologic changes.
Characteristics of dysplastic cells :
Pleomorphism, ie variation in size & shape
Hyperchromatic (deeply staining) & abnormally large nuclei.
++ mitotic figures with normal pattern.
Mitosis in abnormal location within epithelium.
Architectural anarchy of cells.
++ nuclear cytoplasmic ratio.
Causes of dysplasia:
Protracted chronic irritation
Protracted chronic inflammation
Chronic infection
Common sites of Dysplasia:
Epithelial of cervix, vuvla, gallbladder, respiratory tract & oral cavity.
T or F
Dysplasia and Intraepithelial lesions are synonymous
T
Dyaplasia of cervix, prostate and vulva is known as :
CIN, PIN, VIN
Mild dysplasia or intraepithelial lesion-I:
When dysplasia or intraepithelial neoplasia (IEN) involves one third of epithelium lining thickness.
Moderare dysplasia or intraepithelial lesion-II :
When dysplasia or intraepithelial neoplasia (IEN) involves two third of epithelium linig thickness
Severe dysplasia or intraepithelial lesion-III or carcinoma in situe (CIS) 》(in site).
if the dysplasia involves the full or entire thickness of the lining epithelium and does not cross basement mambrane.
if the dysplasia cells cross the basement membrane :
It is no longer carcinoma in situ but it is infiltrating or invasive cancer.
Clinical significance of dysplasia:
Increased chance of neoplastic transformation and it is considered as precancerous.
