pt 6 Flashcards
(50 cards)
What does ‘cellular adaptation’ mean in the context of pathology?
Cellular adaptation refers to the ways cells adjust their structure and function in response to increased or decreased demands or stress, often to avoid injury or keep functioning.
Under what circumstances does a cell typically undergo hypertrophy vs. hyperplasia?
Hypertrophy: When cells increase in size, due to synthesis of more structural components (often seen in tissues with limited cell division, e.g., muscle). Hyperplasia: When cells increase in number via cell division (e.g., epithelial or glandular tissues).
Define hyperplasia, and how does it differ from cancerous growth?
Hyperplasia: A controlled increase in the number of cells, leading to tissue/organ enlargement. Cancerous growth: An uncontrolled proliferation that does not respond to normal regulatory signals.
What are the main molecular mechanisms that can trigger hyperplasia?
- Increased local production of growth factors. 2. Increased expression of growth factor receptors on cells. 3. Enhanced intracellular signalling pathways that lead to gene transcription and cell proliferation.
What is hypertrophy, and what are common examples of physiological vs. pathological hypertrophy?
Hypertrophy: Increase in cell size (and thus organ size) due to increased synthesis of structural proteins. Physiological example: Skeletal muscle hypertrophy from exercise. Pathological example: Cardiac hypertrophy in response to hypertension or valve disease.
Summarize the two main biochemical pathways leading to muscle hypertrophy.
- Physiological: IGF-1 → PI3K → Akt pathway (e.g., muscle growth from exercise). 2. Pathological: Ang II, ET-1, or NA → G-protein-coupled receptors (Gαq/11) → MAPK/PKC/PKA → excessive or maladaptive hypertrophy (e.g., heart under high blood pressure).
Differentiate hyperplasia from hypertrophy with a simple example.
Hyperplasia: Four cells → eight cells (cell number doubles, same size). Hypertrophy: Four cells → four enlarged cells (cell size increases, number unchanged).
What is atrophy, and why can it be considered an adaptive process?
Atrophy is the shrinkage (reduced size) of a tissue or organ due to decreased cell size and number. It’s adaptive because it helps cells/tissues minimize energy demands or resources if stimuli (e.g., blood flow, nutrition) are reduced.
List some common causes of atrophy.
- Decreased workload (disuse) 2. Loss of innervation (denervation) 3. Diminished blood supply (ischemia) 4. Inadequate nutrition 5. Loss of endocrine stimulation 6. Pressure (compression)
What is metaplasia, and when might it occur?
Metaplasia is when one mature cell type changes to another mature cell type better able to endure new conditions (e.g., respiratory epithelium changing to squamous in a smoker’s airways).
Define ‘healing responses’ after injury and how regeneration differs from scar formation.
Healing is the body’s way of restoring tissue integrity post-injury. Regeneration fully replaces damaged cells with original cell types, preserving function. Scar formation (fibrosis) uses collagen and fibrous tissue to patch damage, potentially losing normal function.
What factors determine whether healing occurs primarily by regeneration or by fibrosis (scar formation)?
- Tissue’s intrinsic ability to regenerate (e.g., labile vs. stable vs. permanent cells). 2. Extent of the injury (smaller or superficial injuries more likely to regenerate; extensive damage often leads to scarring).
Give examples of tissues that exhibit continuous (labile), stable, and permanent cell turnover.
Labile (continuous): Skin epidermis, GI tract epithelium, hematopoietic cells. Stable: Liver, kidney tubule cells (can regenerate if needed). Permanent: Neurons, cardiac muscle (minimal to no regenerative capacity).
Why is stem cell function crucial for tissue regeneration?
Stem cells can self-renew and differentiate into needed mature cells, making them vital for replacing lost or damaged cells in regenerative tissues (e.g., skin, gut lining, bone marrow).
Compare embryonic stem cells (ES) with adult (somatic) stem cells.
ES cells: Pluripotent, can form all tissue types; found in the inner cell mass of blastocysts. Adult stem cells: Typically multipotent or more lineage-restricted, reside in specific niches (e.g., bone marrow, basal layer of skin).
What are induced pluripotent stem cells (iPSCs), and why might they overcome some ethical or rejection issues?
iPSCs are adult somatic cells (e.g., skin fibroblasts) genetically reprogrammed to pluripotent status. Because they originate from the patient’s own cells, they sidestep many immune rejection and ethical problems associated with embryonic stem cells.
What is the main safety concern in using stem cells for regenerative therapy?
Their intrinsic capacity for rapid proliferation and self-renewal can, if dysregulated, lead to tumorigenesis (i.e., formation of teratomas or other malignancies).
Why is understanding stem cell biology important for advancing medical research and therapy?
- Elucidates developmental signals and differentiation steps. 2. Aids in creating knockout models for disease study. 3. Enables potential regeneration of damaged organs (e.g., cell-based transplant therapies).
What is ‘growth’ in the context of tissue biology?
Growth is the process by which a tissue increases in size through the synthesis of specific cellular components.
How is ‘differentiation’ defined?
Differentiation is the process by which a cell develops a specialized function or morphology that distinguishes it from its parent cells.
What does ‘tumour differentiation’ refer to?
It refers to the extent to which neoplastic cells resemble the normal cells of the tissue from which they arise, both morphologically and functionally.
Define ‘anaplasia.’
Anaplasia is the loss of cellular differentiation—a reversion from a highly differentiated state to a less specialized, primitive state—and is a hallmark of malignant transformation.
Name one morphological change seen in anaplastic cells.
Pleomorphism, which is marked variation in cell size and shape.
Give another example of a change associated with anaplasia.
Abnormally large nuclei that contain an abundance of DNA relative to the cell size.
