Adaptive disorders

 Atrophy is an adaptive disorder in which the number and the size of the parenchymal cells of an organ or its parts decreases once it was normal is called atrophy.

Causes of the atrophy-

Atrophy may caused by the physiological changes or the pathological changes in the body.

A. Physiological atrophy- atrophy is an normal process as per the ageing in some of the organs where the size and the number decreases as per the increasing age.

• atrophy of lymphoid tissues
• atrophy of the thymus gland
• atrophy of the brain with ageing
• atrophy of the gonads after menopause
• osteoporosis

B. Pathological atrophy- this occurs because of the any kind of the diseases which makes the parenchymal cells weaker and the number and the size decreases.

• ischemic atrophy in atherosclerosis
• renal atrophy
• starvation atrophy in depletion of carbohydrates
• neuropathy atrophy in motor neuron diseases, poliomyelitis, muscular weakness
• atrophy of thyroid gland in hypothyroidism
• atrophy of endocrine glands in hypopituitarism.
• pressure atrophy
• myopathies
• testicular atrophy
• 
  

  In atrophy  the organ is small, often shrunken.

 Th e cells become smaller in size but are not dead cells. Shrinkage in cell size is due to reduction in cell organelles, chiefly mitochondria, myofilaments and endoplasmic reticulum.

 Th ere is often increase in the number of autophagic vacuoles containing cell debris.

Hypertrophy

Hypertrophy is an increase in the size of the parenchymal cells resulting in the enlargement of the particular organ or its parts.

Hypertrophy may be because of the physiological or pathological causes.

A. Physiological hypertrophy- enlarged size of the uterus in the pregnancy's is the physiological hypertrophy.

B. Pathological hypertrophy - because of any diseases the abnormal size of the organs increases.

• Hypertrophy of the cardiac muscles.
• hypertrophy of the smooth muscles.
• hypertrophy of the skeletal muscles

 Th e affected organ is enlarged and heavy.  

A hypertrophied heart of a patient with systemic hypertension may weigh 700-800 g as compared to average normal adult weight of 350 g.

There is increased synthesis of DNA and RNA, increased protein synthesis and increased number of organelles such as mitochondria, endoplasmic reticulum and myofibrils.

Hyperplasia

Hyperplasia is the increases in the number of the parenchymal cells of an organ or tissue.

Neoplasia differs from hyperplasia in having hyperplastic growth with loss of growth-regulatory mechanism due to change in genetic composition of the cell, while hyperplasia persists so long as stimulus is present.

Hyperplasia is caused by the physiological changes in the body or because of the pathological by any kind of the diseases or the pathogen that effects the cells of the organ.

A. Physiological hyperplasia- two most common are the influenced by the hormones or the compensatory.

Hormonal hyperplasia -

• hyperplasia of the female breast in puberty o the lactation period.
• hyperplasia of the pregnant uterus.
• prostatic hyperplasia in the old age.

Compensatory hyperplasia- in this compensation of the particular in removal of the paired organ or its parts where the growth of the cells reoccur.

• regeneration of the liver cells after partial hepatectomy.
• regeneration of the skin cells after abrasions.
• removal of the one kidney after nephrectomy.

Th ere is enlargement of the affected organ or tissue and increase in the number of cells. This is due to increased rate of DNA synthesis and hence increased mitoses of the cells.

Metaplasia

Metaplasia is the reversible change of the epithelial or the mesenchymal cells in another epithelial or mesenchymal  when any kind of abnormal  stimulus is provided but becomes in normal state as previously when the abnormal stimulus is removed.

Metaplasia is mainly divided into two parts

• epithelial metaplasia
• mesenchymal metaplasia

Epithelial metaplasia-this type is the most common in squamous and columnar epithelium.

Squamous- bronchus, endocervix. gall bladder, prostate.

columnar metaplasia-gastric ulcer, in esophagus layers,

Mesenchymal metaplasia -this is rare form and mainly present in the bony and the cartilaginous tissues.

• osseous metaplasia-myositis ossificans, arterial walls, cartilages of the larynx and the bronchus.
•  cartilaginous metaplasia-during healing of fractures, cartilaginous metaplasia may occur where there is undue mobility.

Dysplasia

 Dysplasia means ‘disordered cellular development’, often preceded or accompanied with metaplasia and hyperplasia.

It is therefore also referred to as atypical hyperplasia. 

Dysplasia occurs most often in epithelial cells.   

Epithelial dysplasia is characterized by cellular proliferation and cytologic changes-

• Increased number of layers of epithelial cells
• Disorderly arrangement of cells from basal layer to the surface layer
• Loss of basal polarity i.e. nuclei lying away from basement membrane
• Cellular and nuclear pleomorphism
• Increased nucleocytoplasmic ratio
•  Nuclear hyperchromatic
• Increased mitotic activity.

The most common changes of dysplasia is mostly seen in the uterine cervix and the respiratory tract.