Cell adaptations

Cell Adaptations

Homeostasis ?

Cellular Response To Stress

Causes Of Injury Hypoxia Physical Agents Chemicals Infections Immunological Reactions Genetic Errors Nutritional Imbalances

Types Of Cell Adaptations Hyperplasia Hypertrophy Atrophy Metaplasia

Hypertrophy Non dividing cells Physiological Pathological Cells not capable of replication Mechanisms mechanical triggers trophic triggers Ex :hypertrophy of heart uterus in pregnancy Skeletal muscle in body builders

Mechanism Of Hypertrophy

Increased production of structural proteins

Switch of contractile proteins from adult to fetal

Expression of fetal genes

Hyertrophy

Hyperplasia Cells capable of replication Increase in no of cells Increase in size of the organ Physiologic and pathologic

Physiologic Hyperplasia Hormonal Compensatory

Mechanisms of hyperplasia local production of growth factors

activation of intra cellular pathway stem cells

Pathologic Hyperplasia Excessive hormonal stimulation Bph , endometrial hyperplasia Fertile soil for cancerous proliferations

Atrophy Shrinkage in cell size by loss of substances Organ shrinkage Physiologic or pathologic

Physiologic Atrophy

Ex : 1. Development – notocord , thyroglossal duct

2. uterus after parturition

Pathological Atrophy Decreased workload Loss of innervation Diminished blood supply Inadequate nutrition Loss of hormonal stimulation Senile atrophy

Mechanism Imbalance between protein production

and utilization Ubiqutin proteosome pathway

Atrophy

Metaplasia Reversible change Replacement of one adult cell by other type Mc – columnar to squamous Seen in respiratory epithelium Ducts of glands impacted by stones Vitamin A deficiency Malignant transformation on chronic stages Barrets esophagus Connective tissue metaplasia Cervical metaplasia

Mechanism Stem cell reprogramming Uncoordinated growth factors Vit A deficiency Cytostatic drugs Virus

Metaplasia