DR. MOHAMED SEYAM

 Cells are able to adapt to changes in work demands or threats to survival by changing their
 size (atrophy and hypertrophy),
 Number (hyperplasia), and
 Form (metaplasia).
■ Normal cellular adaptation occurs in response to an appropriate stimulus and ceases once the need for adaptation has ceased.

 Decrease in size of a cell or tissue.
 Decreased size results in decreased oxygen consumption and metabolic needs of the cells and may increase the overall efficiency of cell function.
 Atrophy is generally a reversible process, except for atrophy caused by loss of nervous innervation to a tissue.
 Causes of atrophy include
1.
2.
3.
4.
prolonged bed rest, disuse of limbs or tissue, poor tissue nutrition and ischemia

 Some embryonic structures, such as the notochord and thyroglossal duct, undergo atrophy during fetal development.
 The uterus decreases in size shortly after parturition

 Pathologic atrophy: Shrinkage of our brains as we age
 Disuse atrophy: Essentially when an organ is underused, it undergoes atrophy.
 Another example of this is an immobilized limb, which undergoes muscle wasting upon casting.
 Local atrophy: Most often the result of decreased blood flow to that area

 Increase in cell size and tissue mass.
 Occurs when a cell or tissue is exposed to an increased workload.
 Occurs in tissues that cannot increase cell number as an adaptive response.
 The three basic types of hypertrophy are physiologic, compensatory, and pathologic.

 Physiologic hypertrophy reflects an increase in workload that is not caused by disease —
 for example, the increase in muscle size caused by hard physical labor or weight training.

 Pathologic hypertrophy is a response to disease.
 An example is hypertrophy of the heart muscle as the muscle pumps against increasing resistance in patients with hypertension.
 Compensatory hypertrophy takes place when cell size increases to take over for nonfunctioning cells.
 For instance, one kidney will hypertrophy when the other is not functioning or is removed.

 Hyperplasia is an increase in the number of cells caused by increased workload, hormonal stimulation, or decreased tissue density.
 Increase in the number of cells in an organ or tissue, usually resulting in increased volume of the organ or tissue.
 Like hypertrophy, hyperplasia may be physiologic , compensatory , or pathologic .

Physiologic hyperplasia can be divided into:
 Hormonal hyperplasia , which increases the functional capacity of a tissue when needed,
1. Proliferation of the glandular epithelium of the female breast at puberty and during pregnancy
2. Occurs in the pregnant uterus.
 Compensatory hyperplasia , which increases tissue mass after damage or partial resection.
1. Partial hepatectomy --- proliferation of residual liver cells and regeneration of the liver.
2. After unilateral nephrectomy--- when remaining tissue grows to make up for partial tissue loss

 Caused by excessive hormonal stimulation or growth factors acting on target cells.
 Endometrial hyperplasia: Increase in the amount of estrogen.
 Benign prostatic hyperplasia: Induced by responses to hormones (androgens).

 Pathologic metaplasia is a response to an extrinsic toxin or stressor
 and is generally irreversible.
 • For example, after years of exposure to cigarette smoke, stratified
 squamous epithelial cells replace the normal ciliated columnar
 epithelial cells of the bronchi.
 • Although the new cells can better withstand smoke, they don't
 secrete mucus nor do they have cilia to protect the airway.
 • If exposure to cigarette smoke continues, the squamous cells can
 become cancerous.

 derangement of cell growth that leads to tissues with cells of varying size, shape and appearance.
 Generally occurs in response to chronic irritation and inflammation.
 Common examples include dysplasia of epithelial cells of the cervix or the respiratory tract.

 Metaplasia is the replacement of one cell type with another cell type.
 A common cause of metaplasia is constant irritation or injury that initiates an inflammatory response.
 Almost exclusively occurs in epithelial cells.
 Metaplasia may be either physiologic or pathologic.
 Physiologic metaplasia is a normal response to changing conditions and is generally transient.
For example, in the body's normal response to inflammation, monocytes that migrate to inflamed tissues transform into macrophages.

 Pathologic metaplasia is a response to an extrinsic toxin or stressor and is generally irreversible.
 For example, after years of exposure to cigarette smoke, stratified squamous epithelial cells replace the normal ciliated columnar epithelial cells of the bronchi.
 Although the new cells can better withstand smoke, they don't secrete mucus nor do they have cilia to protect the airway.
 If exposure to cigarette smoke continues, the squamous cells can become cancerous.

 A derangement of cell growth that leads to tissues with cells of varying size, shape and appearance.
 Generally occurs in response to chronic irritation and inflammation.
 Common examples include dysplasia of epithelial cells of the cervix or the respiratory tract.

 1. How do the cells adapt themselves?
 2. Define Atrophy?
 3. What is the important of atrophy?
 4. Give the cause of atrophy?
 5. Give the example of physiologic atrophy?
 6. Give the example of pathologic atrophy?
 7. Define disuse atrophy?
 8. Define hypertrophy? In what kind of cell does hypertrophy takes place?
 9. Define the different types of hypertrophy with example?
 10. Define compensatory hypertrophy?
 11. Define hyperplasia and name the types of hyperplasia?
 12.Write the division of physiologic hyperplasia?

 13. Define hormonal hyperplasia?
 14. Define compensatory hyperplasia?
 15.Write the types of pathologic hyperplasia?
 16. Define Metaplasia?
 17.Write about physiologic hyperplasia with example?
 18.Write about pathologic hyperplasia with example?
 19. Pathologic hyperplasia is irreversible? Is this true?
 20. Define Dysplasia?
 21. Give an example of dysplasia?