L6 Cell Cycle & Stem Cell - Delta University PDF

# Faculty of Medicine - Delta University for Science and Technology ## Level 1, Semester 1 - Module (Basic science) ## The Cell Cycle & Stem Cell - Contact: prof. Dr. Samar Asker - Department: Histology - Official email: [email protected] - Academic hours: - Saturday: 9:00 AM -3:00 PM -...

# Faculty of Medicine - Delta University for Science and Technology ## Level 1, Semester 1 - Module (Basic science) ## The Cell Cycle & Stem Cell - Contact: prof. Dr. Samar Asker - Department: Histology - Official email: [email protected] - Academic hours: - Saturday: 9:00 AM -3:00 PM - Wednesday: 9:00AM-3:00 PM By the end of the lecture, the students will be able to: 1. Identify the cell cycle. 2. Demonstrate the regulation of the cell cycle 3. Define the stem cell and know their structure. 4. Determine the types of stem cells. ## Cell cycle Series of events within the cell that prepare the cell to divide into two daughter cells. ### Interphase (20 hrs) ### Mitosis (1 hrs) - Prophase - Metaphase - Anaphase - Telophase ## Interphase - Period between two successive cell divisions. - Very long about 20 hours. - Divided into 3 phases: - G1(1st gap) stage (longest 25 hours): - Cell ↑size - RNA & protein synthesis to restore the size of mother cell - 46 of S-chromosomes. - S synthesis stage (8 hours): - DNA replication - Duplication of the centrioles. - 92 of S- chromosomes. 46 of d – chromosomes - G2(2nd gap) stage (4 hours): - Energy for mitosis is stored. - RNA & Protein required for cell division. - Analysis for any DNA error & correction for these errors. ## Regulation of the Cell Cycle in Interphase 1. Regulatory proteins are called cyclins which control the cell cycle at checkpoints: - G1 **checkpoint**: decides whether cell will divide. - S **checkpoint**: determines if DNA has been properly replicated. - Mitotic spindle **checkpoint**: ensures chromosomes are aligned at mitotic plate. ## What happens when checkpoints fail? - **Cancer** (uncontrolled growth of cells) can occur. - Mutation missed by checkpoint → disfunction in the cells ## Tissue Renewal 1. **Non-Renewing Cells**: - These cells cannot divide. - They are NOT replaced by new cells after their death as nerve cells and cardiac muscle 2. **Potentially - Renewable Cells**: - These cells are normally not dividing, but at a time of need they can divide and restore their normal number, as endocrine cells, and liver cells. 3. **Continuously Renewing Cells**: - These cells unable to divide; but when die, they are replaced by Stem Cells of the same family. ## The Histological structure of Stem Cells - **LM**: - Cytoplasm: deep basophilic - **EM**: - Increased ribosomes for protein synthesis to restore the size of the cells after division **Function:** They are responsible for: - Organ development during embryogenesis - Cell renewal in different organs after birth ## Types of Stem Cells - Stem cells are classified according to: - Their origin: - Their ability to differentiate ### Origin - **Adult**: - Less potent - Tissues with continuous cellular turnover - **Embryonic**: - Blastocyst of embryo - Pluripotent all types of cells ### Ability to differentiate - **Totipotent**: any other cell = embryo (1-3 days) - **Pluripotent**: almost all cells = blastocyst (5-14 dys) - **Multipotent**: closely related family of cells = UMC → CT cells - **Unipotent**: only a single cell type = male germ cells, keratinocytes of skin, satellite cells of skeletal muscle ## Therapeutic application - Tissue regeneration - Cardiovascular disease treatment - Brain disease treatment - Cell deficiency therapy - Blood disease treatments ## It's MCQ Time ## Which phase of the cell cycle involves DNA replication? a) G1 b) S phase c) G2 d) Mitosis ## What is the function of cyclins in the cell cycle? a) Destroy damaged cells b) Repair DNA c) Control the cell cycle at checkpoints d) Produce energy for mitosis ## What type of stem cell can differentiate into any type of cell? a) Unipotent b) Multipotent c) Totipotent d) Pluripotent