Human Anatomy Lecture 2: The Cell Cycle PDF

PAS 313 – Human Anatomy Lecture 2 The Cell Part 2: The Cell Cycle Dr. Joseph Costa, PhD Department of pathology and Science Photo Library anatomical sciences  The Cell Cycle In humans, 100 BILLION cells die every 24 hours and must be replaced! How is this accomplished? ...

PAS 313 – Human Anatomy Lecture 2 The Cell Part 2: The Cell Cycle Dr. Joseph Costa, PhD Department of pathology and Science Photo Library anatomical sciences  The Cell Cycle In humans, 100 BILLION cells die every 24 hours and must be replaced! How is this accomplished?  Stages of the Cell Cycle: Principal Events I. Interphase A. G1 Phase Normal cellular activities. Cell growth & duplication of organelles. Protein synthesis. B. S Phase: DNA replication C. G2 Phase: Synthesis of proteins, microtubules II. Mitotic Phase: Nuclear division Cytokinesis: Cytoplasmic division  General Information A. Possible fates of “daughter” cells: Differentiate (specialize), age, or die Rest as an “uncommitted” Enter a new cell cycle immediately B. The capacity to grow and divide varies with the cell type, as does rate of these processes.  Three Major Categories of cells based on their ability to divide: 1. Cells which are extremely specialized and have lost their ability to divide: Neuron (nerve cell) Skeletal Muscle cell Mature red blood cells (may increase in size, not in number)  2. Cells that normally do not divide but can be induced to do so by an appropriate stimulus Liver cells Lymphocytes (white blood cells)  3. Cells which continually undergo cell division cells which are subject to frequent destruction, for example, those destroyed due to exposure, friction, etc. Also, where cells are reproduced to be circulated elsewhere in the body Skin (constantly replaced) Cells of the esophagus Bone marrow cells Terminology Related to Cell Division Chromosome: Dark-staining, threadlike body in the nucleus composed of DNA & protein Contains genetic information Single strand Chromatid: duplicated chromosome Gene: Unit of DNA found at particular “locus” (location) Provides the instructions for the production of a specific protein  Centrioles Composed of microtubules 2 Cylindrical structures Serves as organizing center for the mitotic spindle Karyotype = Number and type of chromosomes an individual has A Normal human Karyotype contains 23 pairs of chromosomes = 2(23) = 46 22 pairs are autosomes and 1 pair of sex chromosomes: Females have XX / Males have XY Haploid n Diploid 2n  The Cell Cycle Notice lengths of Interphase vs Mitotic Phase  The Cell Cycle 1. Interphase Non dividing stage of cell cycle Focus on DNA replication and growth S Phase: DNA replication Highly regulated Cell is very vulnerable during this phase Potential for damage to DNA very high Rapidly dividing cells (skin, GI tract, etc.) are especially vulnerable. G2 Phase: continued growth and protein synthesis 2. Stages of Mitosis: A. Prophase Distinguishing Features Nuclear membrane disappears Chromosomes become condensed Centrioles migrate to opposite poles of the cell Stages of Mitosis: B. Metaphase Distinguishing Feature Paired chromosomes line up along the equator of the cell 2. Stages of Mitosis: C. Anaphase Distinguishing Features The chromosomes separate & migrate to opposite sides of the cell 2. Stages of Mitosis: D. Telophase Distinguishing Features The nucleus divides into two identical cells that have the same composition of DNA Cytokinesis occurs: Division into two daughter cells  Results of Mitosis Two identical daughter cells are produced. These cells will then enter the phases of the cell cycle and... May divide again Liver cells will replicate rapidly following organ damage “Rest” Remain permanently in interphase Mitosis Meiosis  Mitosis vs. Meiosis Mitosis Meiosis 1. Occurs in most cells of the body 1. Occurs in “sex cells” (ova and sperm) located in the gonads (ovary and testes) 2. Results in 2 daughter cells 2. Results in 4 daughter cells 3. Daughter cells contain DNA identical to parent cell 3. Daughter cells contain ½ the DNA content of parent cell – 23 chromosomes 4. Each has 23 pairs of chromosomes = 46 total Mitosis Meiosis  Cellular Adaptations Cells undergo changes in response to stimuli or injury to adapt to unfavorable conditions. Normal Hypertrophied 2 Examples: cardiac muscle cardiac muscle Hypertrophy Increase in size of cells Hypertrophied skeletal muscle  Atrophy Decrease in size of cells Skeletal muscle atrophy Hyperplasia Increase in mitotic activity and number of cells Metaplasia Changes in cell in response to disease or chronic irritation which result in the transformation of the cell into a different cell type Neoplasm “New cell mass” Rapid multiplication Benign vs. Malignant Up Next: Tissue 1 in the lecture hall