98. General atrophy: definition of the concept, causes. Macro- and microscopic changes in organs with local atrophy, outcomes, clinical significance.

Atrophy is a lifetime decrease in the volume of cells, tissues, and organs with a decrease or cessation of their function.

Causes of general atrophy:

1. starvation or severe metabolic disorders (alimentary exhaustion)

2. toxic effect of the tumor on the body (cancerous cachexia)

3. Simmonds disease (pituitary cachexia)

4. hypothalamus lesion (cerebral cachexia)

5. severe chronic infections (tuberculosis, chronic dysentery)

Morphology of general atrophy (cachexia, exhaustion):

• sharp emaciation, lack of subcutaneous fat, brown color of subcutaneous fat due to lipochrome

• muscles are atrophic, skin is dry, flabby, osteoporosis

• the internal organs are reduced in size

• the phenomena of brown liver and myocardial atrophy (due to the accumulation of lipofuscin in cells)

• atrophy and dystrophy of the endocrine glands

• areas of dead neurons in the brain

Microscopic changes in organs and tissues during atrophy. They are manifested by a decrease in the size of predominantly parenchymal cells, a densification of the cytoplasm and, to a lesser extent, nuclear structures (simple atrophy). In atrophying cells, the nuclear-cytoplasmic ratio increases, secretion products and spare nutrients disappear in conditions of oxygen deficiency, products of incomplete combustion, autooxidation and peroxidation, lipofuscin accumulate in increased quantities. This pigment is light-optically detected in the form of golden or brown grains in the cytoplasm of cells near the nuclei.It is especially found in the liver, in the fibers of skeletal muscles, in the cells of the central and autonomic nervous system, where it occurs normally, and accumulates with age. Attention is drawn to the preservation of the nucleus and the main organelles of the cytoplasm with a closer location in the cell, a decrease in their size and number, especially mitochondria and the granular cytoplasmic network containing a relatively small number of ribosomes, which indicates a decrease in protein synthesis.

As atrophic changes increase, cell nuclei are increasingly involved in the process; they decrease in volume, condense, note the accumulation of chromatin in the nuclear membrane, a decrease in the size of nucleoli In these cases, not only the volume of cells decreases, but also their number (numbering atrophy). Parenchymal cells of adipose tissue shrink during atrophy. The intercellular substance thickens, undergoes destruction, or serous fluid accumulates in it. Atrophied cells are stained more intensively with histological dyes. Collagen and elastic fibers deform and acquire basophilic properties.

The significance and outcomes of atrophy: a) reversible in the initial stages after the elimination of the causal factor b) far-reaching atrophic phenomena are irreversible

99. Metaplasia, definition of the concept, causes, role in the development of tumor growth, examples.

Metaplasia is a pathological process in which one differentiated tissue is replaced by another differentiated tissue within the histione.

Metaplasia is always preceded by proliferation of undifferentiated cells.

a) chronic inflammation of the respiratory tract, hypovitaminosis a  the transition of the prismatic epithelium to the flat bronchi (reverse transition - prosoplasia)

b) chronic gastritis  metaplasia of the gastric epithelium into the intestinal epithelium (enterolysis of the gastric mucosa)

c) metaplasia of connective tissue into cartilage or bone - in scars, aortic wall in atherosclerosis, in the capsule of healed foci of primary tuberculosis

d) myeloid metaplasia of the spleen, L.U., extramedular foci of hematopoiesis are also a special type of metaplasia.

It is more common in the epithelium and connective tissue. The transition of one tissue to another is observed strictly within the limits of one germ leaf and develops with the proliferation of young cells.

EPITHELIAL METAPLASIA

Epidermal metaplasia (epithelial metaplasia-) the transition of the prismatic epithelium to the keratinizing flat.observed in the gut.paths with chronicinflammation, lack of vit A, in the pancreas, prostate.mammary and thyroid glands.Metaplasia begins with the multiplication of cambial cells, differentiating in the direction of the multilayer squamous epithelium.The transition of a multilayer flat non-corneating epithelium into a cylindrical one. It's called prosoplasia.

Intestinal metaplasia-metaplasia of the epithelium of the stomach into the intestinal

Gastric metaplasia-metaplasia of the intestinal epithelium into the gastric epithelium

METAPLASIA OF THE CONNECTIVE TISSUE

with the formation of cartilage and bone, it occurs in scars, the wall of the aorta (with atherosclerosis), in the stroma of the muscles, the capsule of healed foci of primary tuberculosis, in the stroma of tumors.This is preceded by the proliferation of young connective cells.tissues differentiating into chondro- and osteoblasts.

MYELOID METAPLASIA of the spleen, lymph nodes, the occurrence of foci of extracostomosebral hematopoiesis.