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Cell membrane - about
- CA cells do not have a cell membrane
- Cell membranes protect the cell
- Limits cell growth
- Determines what type of cell its gonna be
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What is CA?
Malignant neoplasm - new growth or formation
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All normal cells share:
- Nutrients
- Oxygen
- Carry out metabolism
- Carry out excretion
- Undergo a reproductive process
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Hypertrophy
Increase in size of normal cells (heart muscle)
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Hyperplasia
Increase in number of cells
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Cell growth - neoplasia
Any new or continued cell growth NOT NEEDED for normal development or replacement of dead or damaged tissues is termed NEOPLASIA and is always considered abnormal
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Benign neoplasm
- Slow growing
- Localized
- Encapsulated with well-defined borders
- Easily removed
- Non-malignant
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Malignant neoplasm
- Aggressive growths that INVADE and DESTROY surrounding tissues
- Can lead to death unless interventions taken
- Own blood supply
- Rapid growth
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Normal cell characteristics
- *Have limited cell division
- Undergo mitosis to develop normal tissue & replace lost or damaged normal tissue
- Divide only when optimal body conditions & nutrition exist
- *Show specific morphology
- Each cell type has a distinct & recognizable appearance, size, & shape
- *Have a small nuclear-cytoplasmic ratio
- The nuclear space is small in proportion to the cytoplasmic space
- *Perform specific differentiated functions
- Every cell must perform at least one special function to contribute to whole body homeostasis
- *Adhere tightly together
- Cells make & secrete cell-surface proteins that allow cells to bind closely & tightly together (cling together)
- *Are nonmigratory
- Cells do not wander from one tissue to another
- Exception - erythrocytes & leukocytes
- *Are contact inhibited
- A cell will divide only as long as it hase some surface that is not in direct contact with another cell
- It no longer ungoes mitosis if it is in direct contact on all surface areas with another cell membrane
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Cell Cycle
- G0 Phase: Resting - not in cell cycle
- G1 Phase: preparing for division - taking extra everything - 18 hours
- S Phase: DNA duplicates - DNA synthesis - 20 hours
- G2 Phase: Protein & RNA synthesis
- Mitosis: prophase, metaphase, anaphase, telophase - single cell splits into 2 identical cells
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Differentiation
- Differentiated during embryonic development
- This is a normal cell characteristic
- Daughter cells - look just like mom - same characteristics
- Increased specialization of cells & tissues
- From immature to complex
- A well-differentiated cell is mature & functions properly - looks like mom
- An undifferentiated cell is immature & does not do its work - malignant
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Cancer Etiology
Carcinogenesis - Activation of proto-oncogenes into oncogenes
- Suppressor genes -
- *Prevents cells from dividing
- *Take control over proto oncogenes
- *Maintains control over cell cycle
Carcinogen meets up with suppressor gene DNA - alters it - turns proto oncogene into oncogene
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Proto-oncogenes
- Genetic research has focused on proto oncogenes
- These are genes that promote rapid growth in the undifferentiated cell of the fetus - as the cells begin to differentiate, these genes are "turned off"
- They have no other apparent function in the life cycle
- Mutation of proto oncogenes produces oncogenes
- An oncogene (small segment of the DNA) can transform normal cells into malignant ones and activate the process of cell division
- Proto oncogenes can be activated to become oncogenes by two processes
- *Viral related - certain viruses can alter cell DNA control of the proto-oncogenes
- *Carcinogenesis - some proto-oncogenes can become active oncogenes when spontaneous or chemically induced initiation occurs - this results in uncontrolled reproduction of mutant cells during the promotion phase
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How Does Cancer Develop
The process of changing a cell with normal appearance & function into a cell with malignant characteristics (malignant transformation)
- 4 Steps:
- Initiation
- Promotion
- Progression
- Metastasis
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Pathophysiology Carcinogenesis: Initiation
- Initiators such as chemicals, physical factors, and biological agents escape normal enzymatic mechanisms and cause alterations in the genetic structure of the cellular DNA
- Alterations are irreversible but usually not significant until the second step
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Pathophysiology Carcinogenesis: Promotion
- Repeated exposure to promoting agents causes the expression of abnormal or mutant genetic information
- The cells then begin to produce mutant cell populations
- Agents that promote or initiate cellular transformation are referred to as carcinogens.
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