Pathology CAM235 Unit 2 CELLULAR ADAPTATION Dr. Moattar Raza Rizvi

Cellular Adaptations ■ 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.

Atrophy 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 prolonged bed rest, disuse of limbs or tissue, poor tissue nutrition and ischemia.

Atrophy can be physiologic or pathologic. Physiologic atrophy: 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

Atrophy

PATHOLOGIC ATROPHY 3 Physiologic atrophy of the brain in an 82-year-old male. The meninges have been stripped Normal brain of a 36-year-old male.

Hypertrophy 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.

HYPERTROPHY Physiologic: The most common stimulus for hypertrophy of muscle is increased workload. 5 Belgian Blue bull bulging muscles of bodybuilders

HYPERTROPHY 11 Rounded heart due to chronic hypertrophy Pathologic: Hypertension causes hypertrophy of the heart, specifically of the left ventricle

Hypertrophy Physiologic hypertrophy Pathologic hypertrophy

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

Can be (A) Physiologic or (B) Pathologic. الفسيولوجية والمرضية HYPERPLASIA Increase in the number of cells in an organ or tissue, usually resulting in increased volume of the organ or tissue. Can be (A) Physiologic or (B) Pathologic. الفسيولوجية والمرضية Physiologic hyperplasia can be divided into: Hormonal hyperplasia, which increases the functional capacity of a tissue when needed, and Compensatory hyperplasia, which increases tissue mass after damage or partial resection.

PHYSIOLOGICAL HYPERPLASIA Hormonal hyperplasia: Proliferation of the glandular epithelium of the female breast at puberty and during pregnancy Occurs in the pregnant uterus. Compensatory Hyperplasia: Partial hepatectomy --- proliferation of residual liver cells and regeneration of the liver. After unilateral nephrectomy--- when remaining tissue grows to make up for partial tissue loss Hormonal hyperplasia---- Proliferation of the glandular epithelium of the female breast at puberty and during pregnancy Occurs in the pregnant uterus. Compensatory Hyperplasia: The experimental model of partial hepatectomy has been especially useful in examining the mechanisms that stimulate proliferation of residual liver cells and regeneration of the liver. After unilateral nephrectomy, when the remaining kidney undergoes compensatory hyperplasia (when remaining tissue grows to make up for partial tissue loss)

PATHOLOGIC HYPERPLASIA 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). Hormonal hyperplasia---- Proliferation of the glandular epithelium of the female breast at puberty and during pregnancy Occurs in the pregnant uterus. Compensatory Hyperplasia: The experimental model of partial hepatectomy has been especially useful in examining the mechanisms that stimulate proliferation of residual liver cells and regeneration of the liver. After unilateral nephrectomy, when the remaining kidney undergoes compensatory hyperplasia (when remaining tissue grows to make up for partial tissue loss)

Hyperplasia

Metaplasia 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.

Metaplasia 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.

Dysplasia 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.

Unit 2 Objectives How do the cells adapt themselves? Define Atrophy? What is the important of atrophy? Give the cause of atrophy? Give the example of physiologic atrophy? Give the example of pathologic atrophy? Define disuse atrophy? Define hypertrophy? In what kind of cell does hypertrophy takes place? Define the different types of hypertrophy with example? Define compensatory hypertrophy? Define hyperplasia and name the types of hyperplasia? Write the division of physiologic hyperplasia?

Unit 2 Objectives Define hormonal hyperplasia? Define compensatory hyperplasia? Write the types of pathologic hyperplasia? Define Metaplasia? Write about physiologic hyperplasia with example? Write about pathologic hyperplasia with example? Pathologic hyperplasia is irreversible? Is this true? Define Dysplasia? Give an example of dysplasia?