أسئلة_الـ_15_باثو_PPPM_قبل_التعديل_

Normal Growth Pattern

• Occurs due to cell division and differentiation.
• Growth has a defined limit.
• Coordination exists among different organs' growth rates.

Developmental Disorders of Growth

• Occur due to defective fetal development in utero.
• Manifest at birth or shortly after.
• Can be hereditary abnormalities inherited from parents (genetic disease).
• Congenital abnormalities result from affection of normal fertilized ovum by adverse factors.
• Nutritional deficiencies like vitamins A and C can have effect.
• Physical agents such as irradiation may impact development.
• Chemical agents like thalidomide are a cause.
• Infections like German measles, congenital syphilis, and toxoplasmosis can impact development.
• Increased maternal age (>35 years) may affect development.

Types of Congenital Anomalies

• Agenesis involves complete absence of an organ, such as a solitary kidney.
• Aplasia means an organ is represented by a rudimentary structure.
• Hypoplasia: organ has a normal structure but fails to reach adult size, e.g., kidney.
• Atresia involves absence of a normal opening or failure of canalization of a hollow organ, e.g., intestine.
• Heterotopia (Choristoma) involves normal tissue in abnormal sites, e.g., pancreatic tissue in the stomach or thyroid tissue in base of tongue.
• Hamartoma refers to formation of a mass of mature tissue in its locality, with abnormal arrangement or quantity.
• Hamartomas manifest at birth or after, cease to grow when body growth stops, and their growth coordinates with surrounding tissue.
• Examples of hamartomas include pigmented naevi, hemangioma, lymphangioma, osteochondroma, lung hamartoma, and multiple neurofibromatosis.

Prognosis of Growth Disorders

• Growth stops at puberty in some cases.
• Some may turn malignant, such as osteochondroma changing into chondrosarcoma.

Cellular Adaptations to Stress

• These adaptations are reversible changes in cell number, size, phenotype, metabolic activity, or functions.
• Cellular adaptation is a state intermediate between a normal, unstressed cell and an injured, over-stressed cell.

Types of Cellular Adaptations

• Physiologic adaptations occur in response to normal stimulation, like hormones or endogenous chemical mediators during pregnancy.
• Pathologic adaptations occur in response to stress, allowing cells to modulate their structure and function to escape injury.

Results of Cellular Adaptations

• Cells achieve a new steady state to preserve viability and function.
• If the adaptive capability is exceeded or the stress is harmful, cell injury develops.

Acquired Disorders of Growth: Atrophy

Definition of Atrophy

• Decreased size and weight of an organ/tissue due to decrease in cell size and/or number.

Classification of Atrophy

• Physiologic atrophy can be general (senile) as part of aging or local due to loss of an organ's physiologic function.
• Pathologic atrophy can be general (senile) like starvation atrophy, or local like ischemic atrophy.

Physiologic Atrophy Details

• General senile atrophy is an aging process.
• Local atrophy involves involution of an organ due to loss of function, as seen after labor in the uterus or after weaning in the breast.
• Causes of general atrophy include anorexia, atherosclerosis, limited intestinal absorption, and hormonal changes.

Pathologic Atrophy Details

• General senile atrophy can occur due to starvation.
• Starvation atrophy is from combined dietary deficiency due to anorexia or malabsorption.
• Toxic atrophy results from increased catabolism as in fever, trauma, major surgery, or chronic diseases such as TB, DM, or thyrotoxicosis.
• Hormonal atrophy can result from pan-hypopituitarism.
• Local atrophy examples are ischemic, neurogenic, disuse, pressure, immunological, thermal, and exhaustion atrophy.

Morphology of Atrophy

• General atrophy affects all organs varyingly; skin is wrinkled, fat is lost, with wasting of liver, muscles, and brown atrophy of the heart.
• Local atrophy shows an organ decreased in size and weight.
• Microscopically, there's a reduction in cytoplasmic mass, nucleus appears normal.
• Spaces from atrophied cells are occupied by fibrous tissue in some organs such as kidney and heart.
• In bone marrow, lymph nodes, thymus and salivary glands, atrophy is replaced by fat.

Hypertrophy

Definition of Hypertrophy

• Increase in size & weight of an organ/tissue due to the increase in size of its constituent cells.

Classification of Hypertrophy

• Physiologic hypertrophy can be hormonal or due to excessive functional demand.
• Pathological hypertrophy is due to excess of growth hormone, leading to gigantism and acromegaly.
• To overcome distal resistance in hollow organs.
• As compensatory hypertrophy in paired organs after removal/absence of the other.

Physiological Hypertrophy

• Hormonal: Smooth muscles of the pregnant uterus.
• Excessive functional demand: Skeletal muscles in manual workers (blacksmith's arm) and athletes.
• Only occur only in skeletal muscles as they can not adapt by cell proliferation.

Pathological Hypertrophy

• Occurs with excess growth hormone of the anterior pituitary, which leads to gigantism and acromegaly.
• To overcome distal resistance: in hollow organs like heart in response to valve lesions or hypertension.
• GI & urinary tracts: in response to prolonged partial obstruction leading to hypertrophy of muscles proximal to obstruction.
• Compensatory hypertrophy in paired organs: the remaining organ undergoes hypertrophy to carry the extra work. Examples: Kidney, lung, adrenal.

Hyperplasia

Definition of Hyperplasia

• Increase in the size and weight of an organ due to an increased number of its component cells.

Classification of Hyperplasia

• Occurs as either physiologic or pathologic.

Physiological Hyperplasia

• Hormonal: Hyperplasia of female breast at puberty and lactation or smooth muscles of gravid uterus.
• Excess demand: Thyroid gland in girls at puberty and pregnancy.

Pathological Hyperplasia

• Hormonal: Due to excessive hormonal stimulation causing adrenal hyperplasia (Cushing’s syndrome) or estrogen-induced endometrial hyperplasia in females.
• Compensatory: Liver cell proliferation after partial surgical excision/destruction.
• Irritative: Occurs in response to local irritation, e.g., lymphoid tissue.

Clinical Significance

• Can manifest as a mass (breast, prostate, thyroid), or abnormal bleeding in endometrial hyperplasia.

Prognosis

• Reversible and stops when the inciting stimulus is controlled.
• Can be precancerous.
• Provides an increased risk for neoplasia, but less than dysplasia and metaplasia.
• May progress to malignancy, especially in surface epithelium, goiter, cirrhosis, and endometrial hyperplasia.

Hyperplasia vs. Neoplasia

• Hyperplasia may be physiological or pathological, while neoplasia is always pathological.
• Hyperplasia may have a useful function, whereas neoplasia has no useful function.
• Hyperplasia is reversible, but neoplasia is irreversible.
• Cells are normal in hyperplasia but abnormal in neoplasia.
• Hyperplasia does not endanger life, while neoplasia may be fatal.

Metaplasia

Definition of Metaplasia

• Transformation of a differentiated tissue into another differentiated tissue of the same category.
• It occurs in tissue containing cells capable of proliferation.

Types of Metaplasia

• Include epithelial, connective tissue, and mesothelial metaplasia.

Epithelial Metaplasia

• Adaptive mechanism where cells more sensitive to stress are replaced by other cells more resistant to stress.
• Occurs in chronic irritation.
• Squamous metaplasia occurs in response to chronic irritation, e.g., in the trachea, gall bladder and uterine cervix.
• Glandular metaplasia occurs as Barrett's Esophagus, a metaplasia of gastric mucosa to intestinal epithelium.

Connective Tissue Metaplasia:

• Connective tissue (fibrous, myxomatous, cartilage, bone, fat) transforms into another.

Mesothelial Metaplasia

• Affects flattened cells lining serous sacs.
• Chronic irritation may change them to cubical, columnar, glandular, or stratified squamous.

Dysplasia

Definition of Dysplasia

• Disordered but non-neoplastic cellular proliferation.

Characteristics

• Loss of individual cell uniformity and normal arrangement within the tissue.

Sites

• Skin, mucous membranes, and liver.
• Difficult to be detected by gross examination.
• Dysplastic cells show varying degrees of cellular atypia observed microscopically.

Morphological Features

• Hyperchromasia, pleomorphism, mitotic activity, and loss of normal orientation (polarity) and disordered maturation (as loss of normal arrangement of epidermal layers).

Grades

• Grade I: changes are restricted to lower third of surface epithelium.
• Grade II: involves the middle third.
• Grade III: involves nearly the whole thickness.