Lecture 1 - Cell and Tissue Adaptations Flashcards
In microenvironment, cells interact with:
- adjacent cells
- extracellular matrix
- vascular elements / blood / fluid
cell/hormone, cell/cell, cell/ECM
List some physical signals cells respond to:
stretch, cold, heat, electricity
Name some labile cells (divide continuously)
skin, hair, mucosa, stem cells (bone marrow)
What are quiescent or stable cells?
Divide only in stress or repair
- liver, glands, stroma, smooth muscle cells, endothelial cells, renal tubular epithelium
Non-dividing cells?
Cardiac muscle, skeletal muscle, nerve cells
Adaptive responses are _______; cell death is not.
REVERSIBLE
List some adaptive responses.
Hyperplasia, hypertrophy, regeneration, atrophy, metaplasia, dysplasia (sometimes)
Hyperplasia:
Increase in cell NUMBER
- labile and stable cell populations
Physiologic: hormonal control
Pathologic: aberrant hormone, HPV (warts)
What is neoplasia?
Irreversible and unregulated cell proliferation; no external signal
Hypertrophy:
Increase in size of cells
- can occur in most all cells
More proteins, organelles, cytoskeletal elements synthesized to support new size
What is scar tissue?
Fibroblasts and collagen
Atrophy:
Loss of cell size OR loss of cells
- cell shrinkage, cell injury, necrosis, apoptosis
List two modes for atrophy; decreasing synthesis and increasing degradation of cellular components.
- Ubiquitin proteosome pathway - mark for destruction
- Increase in autophagic vacuoles (lipofuschin granules / brown atrophy)
Causes of atrophy (6):
- Disuse
- Decreased nutrients/oxygen (ischemia)
- Loss of innervation
- Loss of endocrine stimulation
- Aging
- Pressure
Aplasia / aplastic:
No division
- aplastic anemia: loss of stem cells in marrow
Hypoplasia / hypoplastic:
lack of development
- congenital abnormalities
- marrow that makes some cells, but not enough
Metaplasia:
One adult cell type replaced by another
- usually adaptive in response to chronic infection, irritation, injury
Stratified squamous best at resisting injury
ONLY in dividing tissues
Examples of metaplasia:
- Cigarette smoking: columnar bronchial epithelium to squamous epithelial
- Vitamin A deficiency
- Squamous epithelium to columnar epithelium in Barret’s esophagus (GERD)
- Transitional epithelium to squamous epithelium in Schistosoma haematobium
Dysplasia:
Abnormality of cell morphology and alterations in tissue architecture; often pre-cancerous
Further damage –> neoplasia
In metaplasia, tissue is ___________.
In dysplasia, tissue development is ________.
normal and well-differentiated; NOT normal - altered cell development via genetic alterations
