Growth Disturbances and Cellular Adaptations

Flashcards testing definitions, causes, examples, mechanisms, and microscopic features of growth disturbances and cellular adaptations based on the lecture notes by Dr. Praggaya Priya Lakra.

What is cellular homeostasis?

It is the healthy steady state in which cells maintain the ability to handle physiologic demands.

What are the three ways cells respond to altered physiological demands or stimuli?

Cells respond via cellular adaptations, degeneration or intracellular/extracellular accumulations, and cell death.

How is cellular adaptation defined?

It is a state lying between the normal (unstressed) cell and the injured (over-stressed) cell, where reversible changes occur that allow the cell to return to normal if the stress is eliminated.

What are the seven types of cellular adaptation mentioned in the notes?

Aplasia, Hypoplasia, Atrophy, Hyperplasia, Hypertrophy, Metaplasia, and Dysplasia.

What is aplasia and when does it occur?

Aplasia is the failure of an organ or tissue to develop, occurring as a developmental disturbance in the embryo or foetus in utero.

What tissue is present in place of an organ in aplasia?

Rudimentary tissue composed of fat and connective tissue.

What is hypoplasia?

It is the failure of cells, tissues, or organs to attain their mature size.

What are the gross and microscopic characteristics of hypoplasia?

Grossly, the organ is smaller in weight, volume, or measurement than adult size. Microscopically, cells are fewer in number than normal.

What are the four causes of hypoplasia listed in the lecture?

Congenital anomalies (e.g., genetic mutation affecting proper differentiation and cell migration), inadequate blood supply, inadequate innervation, and malnutrition.

How is atrophy defined?

Atrophy is the shrinkage in the size of cells from loss of cell substance, occurring after cells have attained full normal growth.

What are four examples of physiological atrophy?

Involution of the thymus on attaining puberty, uterine involution after parturition, involution of the mammary gland after lactation, and atrophy of the endometrium during anaestrous.

What causes neurotropic atrophy in horses leading to shoulder muscle atrophy (sweeny)?

Injury to the suprascapular nerve.

What causes neurotropic atrophy of the laryngeal muscle in horses?

Injury to the left recurrent laryngeal nerve.

How do Strongylus larvae cause angiotrophic atrophy of the hind limb in horses?

By causing parasitic ischaemia through the occlusion of the femoral artery.

What effect does prolonged steroid therapy have on the adrenal gland?

It leads to endocrine atrophy of the zona fasciculata of the adrenal gland.

What two main cellular mechanisms drive the pathogenesis of atrophy?

(i) Autophagocytosis with destruction of senile cytoplasmic organelles like ribosomes, mitochondria, and lysosomes; and (ii) the ubiquitin-proteasome pathway where cytosolic and nuclear proteins combine with ubiquitin and are destroyed by proteasomes.

What causes the brownish discolouration seen in brown atrophy?

Undigested cell debris that persists inside membrane-bound residual bodies as lipofuscin granules.

What is hypertrophy?

An increase in the size of cells or an organ without an increase in the number of cells.

Why do cardiac and skeletal muscle cells only undergo hypertrophy and not hyperplasia?

Because as permanent/stable adult cells, they cannot divide in response to increased demand.

What are two examples of compensatory hypertrophy?

Hypertrophy of one kidney following the loss of the other, and right ventricular hypertrophy due to pulmonary stenosis.

What is hyperplasia?

An increase in the number of cells in an organ or tissue.

What tissue response occurs in the esophagus of chickens during vitamin A deficiency?

Hyperplasia and hyperkeratinization of the epithelium.

What is metaplasia?

A reversible change in which one adult cell type (epithelial or mesenchymal) is replaced by another cell type.

What metaplastic change occurs in the gall bladder due to irritation from gall stones?

The gall bladder epithelium changes from columnar to stratified squamous epithelium.

What is dysplasia and what are its microscopic characteristics?

Dysplasia is a disorderly, non-neoplastic proliferation marked by loss in cell uniformity and architectural orientation. Microscopically, cells vary in shape and size, are deeply stained, and show abundant mitotic figures.

What is anaplasia and how does its reversibility compare to dysplasia and metaplasia?

Anaplasia is a reversal in differentiation (dedifferentiation) or loss of structural and functional differentiation of normal cells. Unlike metaplasia and dysplasia, anaplastic changes are not reversible and are characteristic of cancerous tumours.