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Adaptive Tissue Responses - Coggle Diagram
Adaptive Tissue Responses
Atrophy:
Decreased size and/or no. of cells
Causes
Nutrient deprivation
Loss of hormonal stimulation
Decreased workload (disuse atrophy)
Denervation (esp. skeletal muscle)
Compression
Aging
Autophagy & apoptosis - shrinkage/loss of cells
Atrophy
Fewer mitochondria or organelles
Diminished function
Can by physiological (e.g. thymus) or pathological
Hypertrophy:
Increase in size & volume, due to an increase in cell size
Causes
Compensatory
Increased metabolic demands --> hypertrophy
Increases amount of force each myocyte can generate
Cardiac hypertrophy
Concentric "Pressure overload"
Eccentric "Volume overload"
Hormonal
E.g. Physiologic - pregnancy causing uterine hypertrophy (hypertrophy of smooth muscle)
Mechanisms
Increased workload
, agonists (e.g. hormones) or growth factors initiate
Signal transduction pathways
Increased production of
growth factors
, increased expression of genes that encode muscle proteins
Hyperplasia:
Increase in number of cells in an organ or tissue --> increase in overall size of organ
Compensatory
Action of hormones or growth factors when there is a need for increased functional capacity
Physiologic
Mammary hyperplasia during pregnancy
Pathologic
E.g. Hormonal excess
Prostatic hyperplasia due to excess androgens
Hyperplasia
Dependent on cells being able to divide
Metaplasia:
Reversible replacement of one differentiated cell type by another cell type
Barrett oesophagus
Refluxed gastric acid
Irritation of oesophageal squamous epithelium
Replacement by intestinal-like columnar cells (intestinal metaplsia)
More resistant
Can progress to dysplasia & neoplasia
Dysplasia:
Disordered development; an abnormality in formation of tissue
Atypical features
State of differentiation
Labile
Epithelial surfaces, bone marrow
Stable
Hepatic and renal parenchyma
Permanent
Cardiac myocytes, neurons