Cell/Tissue Proliferation & Repair Flashcards
(35 cards)
What are cell numbers determined by a balance of?
- Cell proliferation
- Death by apoptosis
- Stem cell differentiation
- Tissue repair is affected by these, as well as the growth factors that affect cells
Define: Mitosis
Process where a cell separates chromosomes and nucleus into two identical cells, or “daughter cells,” that are genetically identical to each other and to the “parent cell”
Define: Meiosis
- Cell division necessary for sexual reproduction
- Number of chromosomes reduced to half original number, so when paired with another gamete, the resulting zygote contains the original number of chromosomes
What is the difference between cell proliferation and cell differentiation?
PROLIFERATION: Process of increasing the number of cells by mitosis
DIFFERENTIATION: Process where cell specializes into specific body structure (organ, tissue, etc.) and function; Different types of cells differentiate at different rates and processes
Which type of cells are fully differentiated once the system is fully developed and cannot proliferate any further?
Neurons
What is Gap 1 in the process of mitosis?
- Cells start to prepare for DNA replication and mitosis
- Increased size
What is Synthesis phase?
- DNA synthesis
- Chromosomes replicated
- Lasts 10-12 hours
What is Gap 2 phase?
- Premitotic phase
- ENzymes and proteins needed for cell division are synthesized and move into place
What is Mitosis phase?
Formation of mitotic spindle and cell division
What is Gap O?
- Not part of the “cycle”
- Resting phase after mitosis
- Different cell types act differently here
- Blood cells and GI tract lining cells never enter here but continue to cycle
- Hepatocytes rest but can be stimulated to re-enter cycle when needed
- Neurons leave cycle permanently
What are Cyclins?
- Proteins that control entry and cell movement through the cycle
- Help to regulate repair of DNA at checkpoints if errors occur
What are Checkpoints?
Occur throughout cycle, where cyclins are utilized to prevent genetic errors from occuring
What are Labile tissues?
- Continuously dividing tissue
- Divide and replicate throughout our lives to replace destroyed cells
- E.g. skin epithelium, oral mucous membranes, vaginal/cervical lining, GI/GU tract, bone marrow cells.
What are Stable tissues?
- Replication stops when growth stops
- Rest in Gap0 stage but can be stimulated to regenerate
- E.g. solid organ parenchyma (liver, kidney), smooth muscles, vascular endothelial cells, fibroblasts, wound healing
What are Permanent tissues?
- Terminally differentiated
- E.g. neurons, cardiac muscle, some skeletal muscle.
Define: Stem Cells
Undifferentiated cells that can differentiate when need arises
What are the properties of stem cells?
- Self-renewal (can undergo mitosis while still undifferentiated)
- Asymmetric replication (following division, one cell retains stem-cell characteristics)
- Differential potential (each generation of cell becomes increasingly differentiated)
What are the three phases of Connective Tissue repair?
1) Angiogenesis and ingrowth of granulation tissue
2) Emigration of fibroblasts and depostion of extracellular matrix
3) Maturation and remodeling of fibrous tissue
What happens in the first phase of CT repair?
- Angiogenesis and ingrowth of granulation tissue
- New capillaries induced by growth factors (not well structured, leak causes fluid/edema)
- Inflammatory cells
What happens in the second phase of CT repair?
- Emigration of fibroblasts and deposition of extracellular matrix
- Scar formation on framework of granulation tissue (pale, larely avascular scar)
- 2 Phases: Fibroblasts proliferate; Collagen synthesis
What happens in the third phase of CT repair?
- Maturation & Remodeling of Fibrous Tissue
- Extracellular matrix reorganizes scar tissue to relatively permanent state
- Slow process
What is the difference between primary and secondary intention in wound healing?
PRIMARY: wound closure and healing by sutured surgical incision; well-reduced bone fractures. There is no tissue loss.
SECONDARY: wound closure by scarring (e.g. burns, abrasians). There IS tissue loss.
What happens in the inflammatory phase of cutaneous wound healing?
- Begins at time of injury
- Blood clot (Vasoconstriction, platelet aggregation; vasodilation to allow WBC, etc. to enter)
- Inflammatory cells (phagocytic WBC’s, macrophages arrive and ingest/remove bacteria and cellular debris)
What happens in the proliferative phase of cutaneous wound healing?
- New tissue to fill wound
- Begins within 2-3 days of injury
- Granulation (Fibroblasts synthesized and secrete collagen, growth factors, etc. to begin healing process; Angiogenesis, initially very fragile)
- Epithelialization occurs (formation of new surface layer similar to original)
