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Dr. Suhad Faisal Hatem. CELLULAR ADAPTATIONS. CELLULAR ADAPTATIONS
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Dr. Suhad Faisal Hatem CELLULAR ADAPTATIONS
CELLULAR ADAPTATIONS Adaptations are reversible changes and are divided into physiologic & pathologic adaptations. Physiologic adaptations usually represent responses of cells to normal stimulations e.g., the hormone-induced enlargement of the breast and uterus during pregnancy. Pathologic adaptions, on the other hand, can take several distinct forms. Types of cellular adaptation: The types of cellular adaptation include(atrophy,hypertrophy, , hyperplasia & metaplasia).
A. Atrophy Atrophy is a decrease in both the number and size of the cells. This can lead to decreased size of the organ.Atrophy results from decreased protein synthesis together with increased protein degradation in the affected cells.It can be Physiological atrophy, Example: uterus after labour and atrophy of the ovary after menopause orPathological atrophy Example: a-Ischemic atrophy: due to decrease of blood supply e.g. atherosclerosis. b- Pressure atrophy: due to long continued pressure on a tissue leading to decrease in its blood supply with atrophy of its cells. d-Decreased work load:e.g. immobilized limbas treatment for a bone fracture or after prolonged bed rest. muscular strength is reduced, When normal activity resumes, the muscle's size and function return. c-Neuropathicatrophy:e.g. when a motor nerve supplying a muscle is affected as in poliomyelitis . d-Starvation: leading to generalized atrophy. e-Loss of endocrine stimulation: as in postmenopausal endometrial atrophy (due to decrease in the levels of estrogen after menopause) and testicular atrophy (due to decrease in the production of LH & FSH as in hypopituitarism.
B-Hypertrophy: Hypertrophy is enlargement of individual cells without increase in the number of cells. Increased workload leads to increasedprotein synthesis , size & number of intracellular organelles. This increased in cell size leads to increased size of theorgan.Examples: the enlargement of thepregnant uterusdue to estrogen-stimulated smooth muscle, skeletal muscleof athletes and heart muscles.
C. Hyperplasia Hyperplasia is an increase in the number of cells. It can lead to an increase in the sizeof the organ. It is usually caused by hormonal stimulation. It can be physiological as inenlargement of the breastglandular epithelium during pregnancy or it can pathological as in endometrialhyperplasia.Endometrial hyperplasia: this results from persistent or excessive estrogen stimulation of the endometrium. This hyperplasia is a common cause of abnormal uterine bleeding
D. Metaplasia Metaplasia is the replacement of one differentiated tissue by another cell type of the same tissue. Metaplasia is thought to arise by genetic deprogramming" of epithelial stem cell or of undifferentiated mesenchymal cells in connective tissue. There are 2 different types of metaplasia:
1- Squamous metaplasia It is replacement of adultepithelium cell by another type of epithelium e.g. squamous epithelium. Forexample:pseudostratified ciliated columnar respiratory epithelium due to chronic irritation by habitual cigarette smoking , transitional epithelium of urinary bladder, ureter or renal pelvis due to chronic irritation by bilharziasis or stones. 2- Osseous metaplasia This replacement of a connective tissue by bone, for example at sites of injury. Note:If the influences that induce metaplastic transformation of the epithelium are persistent, they may lead to cancer transformation in the metaplastic epithelium, e.g. squamous metaplasia of transitional epithelium of the urinary bladder by bilharziasis will lead to squamous cell carcinoma. Note:If the influences that induce metaplastic transformation of the epithelium are persistent, they may lead to cancer transformation in the metaplastic epithelium, e.g. squamous metaplasia of transitional epithelium of the urinary bladder by bilharziasis will lead to squamous cell carcinoma.
Pathologic calcification Calcification is abnormal tissue deposition of calcium,iron and mineral salts. This buildup can harden and disrupt your body’s normal processes. Calcium is transported through the blood stream. It is also found in every cell. As a result, calcification can occur in almost any part of the body. about 99 percent of your body’s calcium is in your teeth and bones. The other 1 percent is in the blood, muscles, fluid outside the cells, and other body tissues. Some disorders cause calcium to deposit in places where it does not typically belong. Over time, this can add up and cause problems.
Causes of calcification • Many factors have been found to play a role in calcification,These include: • infections • calcium metabolism disorders that cause hypercalcemia (too much calcium in the blood) • genetic or autoimmune disorders affecting your skeletal system and connective tissues • persistent inflammation • there are two type of calcification • dystrophic calcification is deposition of calcium in degeneration or dead tissues, though serum levels of calcium remain normal(normal calcium metabolism). This type of calcification is seen in: • a-areas of necrosis ,dying and dead tissue. • b-atherosclerotic plaques • c- aging or damaged heart valves.
Metastatic calcificationis deposition of calcium salts in normal living tissue, with elevated serum levels of calcium, which can occur because abnormal calcium metabolism(hypercalacemia). This type of calcification happens when there is body but principally affects the interstitial tissues of the vasculature, kidneys, lungs, and gastric mucosa. These differences in pathology also mean that metastatic calcification is often found in many tissues , whereas dystrophic calcification is localized. Pathogensis of calcification The calcium in the surface of cell member will bind with phospholipid, phosphates enzyme lead to the calcium,phosphates deposite as amicro crystal in the tissue causing calcification. Microscopically Two type of calcification are appear as intracellular and /or extra cellular(bluish) deposites as seed surrounding with ca+ layers.
