Cell Adaptation Flashcards
Cell adaptation
Occurs when the cell homeostasis is distorted by stress or pathologic stimuli
In this stage: cells preserve viability and function
It is reversible
Adaptation may be physiological (normal) or pathological (abnormal)
Five types: atrophy, hypertrophy, hyperplasia, dysplasia, metaplasia
Atrophy
Decrease in size and/or number of the cells and their metabolic activity after normal growth has been reached
Cells are not dead
Decrease protein synthesis and increase protein degradation in cells
A diminution in the size of a cell, tissue, organ or part that was properly developed
Atrophy causes
Decrease workload Denervation Decrease blood supply or ocygen Inadequate nutrition Loss of endocrine stimulation Aging
Atrophy examples
Muscle disuse in a limb that is in a cast
Sedentary atrophy
Atrophy of adrenal cortex by reduction of ACTH stimulation (steroid therapy)
Atrophy in tissues adjacent to a tumor due to pressure and compromised blood supply
Physiologic atrophy (non-lactating mammary gland)
Hypoplasia
Incomplete development or underdevelopment of an organ or tissue; it is less severe in degree than aplasia
It is a congenital condition
Aplasia
Lack of development of an organ or tissue
Hypertrophy
Increased size of cells often leading to increased tissue/organ size
Synthesis of more organelles and structural proteins: bigger cells
More common in cells with little replication
-Stable cells (bone, cartilage, and smooth muscle) or permanent cells (neurons and cardiac and skeletal muscles myocyes)– less common in labile cells (epidermis, intestinal epithelium, and bone marrow
Hypertrophy examples- physiologic
Physiologic: Pregnant uterus, weightlifter
Mechanical stress, agonists, and growth factors all lead to:
-induction of embryonic/fetal genes
-synthesis of contractile proteins
-production of growth factors
Increased workload
Hormon stimulation
Example of how adaptation to stress can progress to functionally significant cell injury if stress isn’t relieved
Cardiac hypertrophy (different causes/mechanisms) Limit beyond which enlargement of muscle mass is no longer able to cope with the increased burden Several regressive changes occur in the myocardial fibers (lysis and loss of myofibrillar contractile elements) Extreme case=myocyte death
Hypertrophy examples- pathologic
Cardiac hypertrophy from hypertension or aortic valve disease
Concentric hypertrophy or eccentric hypertrophy
Increased resistance
Physical obstruction
Hyperplasia
Increase in the number of cells of an organ often leading to increased size of tissue/organ
Cells capable of replication
May occur concomitantly with hypertrophy
Labile cells, Permanent cells, Stable cells
Labile cells
Those that routinely proliferate in normal circumstances such as those of the epidermis, intestinal epithelium, and bone marrow
Readily become hyperplastic
Permanent cells
Neurons and cardiac and skeletal muscle myocytes have very little capacity to regenerate or become hyperplastic in most situations
Stable cells
Bone, cartilage, smooth muscle
Intermediate in their ability to become hyperplastic
Physiologic hyperplasia examples
Hormonal: mammary gland during pregnancy
Compensatory: Hepatectomy
