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BIO170 - Obj 2
BIO170 - Obj 2 - Cellular Adaptation & Injury
| Question | Answer |
|---|---|
| What is the difference between mitosis and cytokinesis? | mitosis is division of organelles; cytokinesis is division of the cytoplasm |
| What is the difference between chromatin and chromosomes? | chromatin is the genetic material in a cell prior to division; during G2, the chromatin condenses into chromosomes |
| What are the phases of the cell cycle? | interphase (G1, (G0), S, G2) & mitosis (prophase, metaphase, anaphase, telophase) |
| Compare mitosis to interphase | interphase is considered a resting phase, in that the cell is not dividing as it is in mitiosis; however, the cell is quite active during interphase |
| What is G1 called? What occurs during this phase? | G1 is gap 1, or the post-mitotic growth phase; the cell regains its normal size, produces RNA, & synthesizes protein; the cell is very active metabolically and is functioning |
| What are some examples of normal cell activity in G1? | endocrine cells secrete hormones; epidermal cells absorb foodstuffs, etc. |
| How long is a normal cell in G1? | G1 is the most variable phase in terms of time; shortest time is about 10 hours (epithelial cells & hemoccytoblasts); longest is days or even weeks (cartilage & dense regular tissue) |
| What are examples of dense regular connective tissue? What is the implication of the amount of time these cells spend in G1? | tendons, ligaments, and aponeuroses have a very long G1 phase; injuries to these tissues take a very long time to heal |
| What is the S phase called? What occurs during this phase? | S is the synthesis phase; the cell lmanufactures a 2nd set of chromosomes in preparation for mitosis |
| How many chromosomes are in a cell at the beginning and end of S phase? | at the beginning of S phase, there are 46 chromosomes (23 pairs; 23 from each parent); after S phase there are 92 chromosomes; the daughter cells will contain the exact same chromosome set |
| What is G2 phase called? What activities happen during this phase? | G2 is the pre-mitotic growth (or 2nd gap) phase; the cell produces the additional organelles & cytoplasm it will need to divide; also, the centrioles are replicated which is essential for mitosis |
| What is phase G0? | A stage where some cells go until cell division is required; some cells will remain forever in G0 |
| What types of cells are always in phase G0? | amitotic cells (=w/o mitosis); these cells permanently stop dividing after a short time period during embryonic & fetal life |
| What are examples of amitotic cells? What happens when these cells are destroyed? | myocardial cells & functional neurons; if these are destroyed, they are replaced with non-functional "scar tissue" type cells |
| What happens during mitosis? Which phase of the cell cycle is it? | mitosis is the division of the cell into 2 equal daughter cells; it is phase M |
| What are the 5 phases in mitosis? | prophase, metaphase, anaphase, telophase, and cytokinesis |
| What occurs during prophase? (4) | 1) chromatin condenses into chromosomes 2) the replicated chromosomes pair up with the original chromosomes 3) the nucleoli & nuclear membrane disappear 4) the pairs of centrioles move to opposite poles of the cell |
| How are the paired chromosomes held together? | the paired chromosomes are held together by a structure called the centromere; each centromere is made from 2 centrioles |
| What are the 2 tibes of microtubules and what are their functions? | short microtubules (astral fibers) anchor the centrioles; longer microtubules (spindle fibers) strech from the centriole to the centromere on each DNA strand |
| What occurs during metaphase? Describe the arrangement of the chromosomes during this phase | the chromosome pairs line up in the center of the cell, called the metaphase plate; each chromosome is attached by its spindle fibers to a centriole anchored at the border of the cell |
| What occurs during anaphase? How is this accomplished? | the spindle fibers will contract and shorten, like muscle proteins during muscle contraction; this shortening moves the chromosomes to the opposite poles of the cell |
| What occurs during telophase? | the prophase events are reversed: 1) nuclear membrane reforms around the nucleus; 2) the nucleoli are re-assembled; 3) the chromosomes become chromatin |
| What is a binucleate cell? When does this occur? | a cell with 2 nuclei; this occurs briefly between telophase and cytokinesis |
| What is cytokinesis? What occurs during this phase? | cytokinesis is the cytoplasmic division; it is the actual division of the cell into 2 identical daughter cells |
| When the cell is actually dividing, what is the separation line called? | the cleavage furrow |
| How does most disease begin? | with cell injury |
| What is it called if the injured cells recover? if the injured cells (or entire tissue) dies? | reversible (sub-lethal) injury is when injured cells recover; irreversible (lethal) injury is when the cells or tissue dies |
| What is the most common mechanism for cellular injury? | Hypoxic injury |
| What are some causes for hypoxic injury? | 1) less O2 in the atmosphere; impaired lung function; impaired heart function; decreased RBCs; decreased hemoglobin in the RBCs, etc 2) poisoning of the cytochromes in the mitochondria |
| What are the 2 main categories of mechanisms which cause injury to the cell? | chemical poisons (street drugs, alcohol, heavy metals, oxygen free radicals) and mechanical (wounds caused by gunshots, burns, radiation) |
| What is usually common to all forms of cellular injury? | cellular apoxia |
| What is cellular adaptation? | after minor cellular/tissue damage, cells can and do adapt and recover |
| What is an example of cellular adaptation? | minor cuts: bleeding was stopped by hemostatic mechanisms; damaged cells and invading microbes were removed by phagocytic WBCs; new skin growth occurred to repair the injury |
| Is cellular adaptation the same in all humans? | no; cellular injury may be reversible in some and irreversible in others; factors include age, nutritional status, severity of the injury, etc |
| Is an adapted cell normal or injured? | an adapted cell is neither normal nor injured; it is in-between |
| What are the 4 typical steps in cellular death? | 1) hypoxia; 2) failure of aerobic metabolism; 3) failure of cell transport mechanisms; 4) cell swelling & lysis |
| What is reduced blood supply called? | ischemia |
| What is most commonly the start of cellular death? | hypoxia; it is caused by disruption of blood supply; results in cellular injury and ultimately cellular death |
| What happens to a cell when its oxygen supply is disrupted? | aerobic (oxidative) metabolism slows drastically and the cell converts to anaerobic metabolism |
| What are the disadvantages of anaerobic metabolism? | it's not efficient - produces only 2 molecules of ATP per glucose molecule; also produces a toxic waste product, lactic acid (lactate), which causes the cytoplasm of the cell to become acidic |
| What happens to the cell after aerobic metabolism fails? | next comes the failure of cell transport mechanisms, which require ATP; sodium & calcium diffuse into the cell and potassium diffuses out, because the Na+/K+ pump fails |
| What happens after the failure of cell transport mechanisms? | water follows the sodium & calcium ions into the cell; first the endoplasmic reticulum, followed by other cell organelles swell, then the entire cell swells, and finally cell lysis occurs |
| What are the 5 causes of altered cellular & tissue biology? | 1) adaptation; 2) injury; 3) neoplasia; 4) aging; 5) death |
| What is hypertrophy? What are its causes? | hypertrophy is enlargement of individual cells; it can be caused by hormonal triggers or by functional demand |
| What is an example of physiologic hypertrophy? | occurs in skeletal muscle by increase in exercise; muscle cells increase in size because of an increase in the workloda |
| What is an example of patholic hypertrophy? | in cardiac muscle, if there is an increase in workload placed upon the heart, the heart cells grow larger; for example, in a person w/chronic hypertension |
| What cells are particularly susecptible to hypertrophy? | skeletal muscle, heart, and kidneys |
| What accumulates in cells that have hypertrophied? | increased accumulation of protein |
| What is hyperplasia? What causes it? | hyperplasia is an increase in the numbers of normal cells; it is caused by hormonal triggers or by functional demand |
| What is an example of hormonal hyperplasia? | growth of the uterine lining or endometrium during the latter stage of the menstrual cycle or during pregnancy |
| What is an example of hyperplasia in response to functional demand? | a callus is hyperplasia due to a mechanical stimulus and therefore in response to functional demand |
| What are examples of cells that are susceptible to hyperplasia? | liver tissue, epithelial tissue, bone and bone marrow stem cells, and fibroblasts are all capable of hyperplastic growth |
| What is atrophy? What are its causes? | atrophy is a decrease in the size of individual cells, and if it occurs to a large extent, the entire tissue may decrease in size; atrophy has physiologic and patholic causes |
| What is physiologic atrophy? What is an example? | Physiologic atrophy occurs as a normal part of development; for example, the thymus gland shrinks in size as a person ages |
| What is pathologic atrophy? | Pathologic atrophy occurs because of disuse, decrease in nervous or blood supply, decreased hormonal stimulation, or decreased nutrition |
| What are examples of pathologic atrophy? | muscle tissue in a limb immobilized by a cast will shrink from disuse; the same muscle in a paraplegic will atrophy from the lace of nervous stimulation and disuse |
| What is metaplasia? | the reversible replacement of a mature cell by another mature (or less mature) cell |
| What is an example of metaplasia? | in smokers, ciliated cells in the bronchi and bronchioles are replaced by stratified squamous cells which are better suited to the chronic irritation caused by cigarette smoke, but don't protect the lungs like ciliated cells |
| How does metaplasia harm smokers? | there is a protective layer of mucus covering the trachea, bronchi, & bronchioles which traps inhaled pollutants; ciliated cells move the layer of mucus upwards to be coughed up & swallowed/spat; this protective mechanism is absent in smokers |
| What is dysplasia? | aka atypical hyperplasia, it is a change in a mature cell in response to chronic irritation; it is not a true adaptive process to an injury; it is not a true adaptive process to an injury |
| Describe the cell changes in dysplasia | the cells are abnormal in size, shape, or organization; also there is an increase in number; dysplasia is often a pre-cancerous change in the cell |
| What is an example of dysplasia? | actinic keratosis (exposure to the UV rays of the sun) is a dysplastic change in the skin, which converts to malignancy if left untreated |
| What is anaplasia? | the loss of differentiation; cells revert to a more primitive condition, similar to the condition seen in the cell's precursor during embryonic development |
| Describe anaplastic cells | the may behave like embryonic cells or they may exhibit bizarre behavior, unique to themselves; they are pleomorphic and do not resemble the tissue of origin |
| What is pleomorphic? | irregular (weird) shape |
| What is the relationship between anaplastic cells and cancerous cells? | cancerous cells usually display some degree of anaplasia; this difference in appearance is used to diagnose the cancer. Cells can be both dysplastic and anaplastic; the most malignant cells have the most anaplasia |
| What is neoplasia? | an abnormal cell growth which is not responsive to normal controls for growth |
| What is another name for a neoplasm? | a tumor |
| What is a benign neoplasm? | it does not invade other tissue and spread throughout the body; it can still be dangerous if it impinges on a structure which is vital to life; ex: a benign neoplasm putting pressure on the cardiovascular/respiratory centers in the brainstem |
| What is a malignant neoplasm? | one than can spread throughout the body |
| Which types of cell changes are adaptive changes? Which ones are not normal? | adaptive processes: hyperplasia, hypertrophy, atrophy, metaplasia; non-adaptive changes: dysplasia (atypical hyperplasia, anaplasia, neoplasia |
Created by:
debmurph
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