Nucleus and Cell Cycle (Physical Therapy) PDF

Cell biology Physical therapy dr. manal m. sayed 1 Dr. Manal M. Sayed  THE NUCLEUS dr. manal m. sayed Dr. Manal M. Sayed 3 What is the nucleus? It is the part of the cell which co...

Cell biology Physical therapy dr. manal m. sayed 1 Dr. Manal M. Sayed  THE NUCLEUS dr. manal m. sayed Dr. Manal M. Sayed 3 What is the nucleus? It is the part of the cell which contains the chromosomes that carry the genetic information. Shape: Nuclei are of different shapes. They may be spherical, oval, indented (kidney – shaped), spiral, multilobed or lobulated or even irregular. Number: Mononucleated in most cells. Binucleated as in liver cell. Multinucleated dr. manal m. sayed e.g. skeletal muscle fibers 4 dr. manal m. sayed Different shapes of nuclei 5 dr. manal m. sayed 6 The site of the nucleus: Central or Eccentric. Appearance of the nucleus: may be deeply stained nucleus or vesicular (open face). Nucleus, always deeply basophilic due to abundance of DNA. dr. manal m. sayed 7  Nucleus Stained by Hematoxylin dr. manal m. sayed 8 Structure of the nucleus: With E.M: the interphase nucleus is composed of a nuclear envelope, chromatin, nucleolus and nuclear sap or nucleoplasm. 1-Nuclear envelope: It forms a selective barrier between the nuclear and cytoplasmic compartments. LM: Dark basophilic membrane which surrounds the nucleus. dr. manal m. sayed 9 EM: Appears as two concentric membranes separated by a narrow (30-50 nm) perinuclear space, so called nuclear envelope. Circular pores are present in the nuclear envelope and allow for the exchange of special substances between the nucleus and the cytoplasm. dr. manal m. sayed 10  Nuclear pore complex Circular pores are present in the nuclear envelope, these pores allow for the exchange of special substances between the nucleus and the cytoplasm. dr. manal sayed 11 2- Chromatin: is the substance of chromosomes. It is present in the nucleus in the following forms: A. Finely granulated chromatin called “euchromatin” or dispersed chromatin representing uncoiled active parts of chromosomes. B. Clumps of chromatin called “heterochromatin” or condensed chromatin, which represent the inactive coiled parts of chromosomes. dr. manal m. sayed 12  Euchromatin Heterochromatin Dispersed chromatin, OR Clumps of chromatin or finely granulated condensed chromatin Uncoiled Coiled parts of chromosomes Active parts of chromosomes Inactive parts of chromosomes Has many types dr. manal sayed 13  Agenda dr. manal m. sayed 14 3-The nucleolus: LM: is a generally spherical, highly basophilic usually seen in most cells. It is not bound by membranes. Ribosomal RNA is formed in the nucleolus. EM: the nucleolus is formed of two definite areas: 1. A central fibrous area (pars fibrosa) containing the chromatin filaments as well as filamentous RNA. 2. The outer portion (pars granulose) is granular and is composed of RNA particles quite similar to ribosomal subunits. dr. manal m. sayed 15  Agenda n Nucleolus dr. manal m. sayed 16 Chromosome is a coiled DNA molecule within the cell’s nucleus that carries an individual’s Genetic code. The number of chromosomes is always fixed in all the different cells of the same species. In most cases, chromosomes exist in pairs. There are two types of chromosomes : - Autosomes( somatic) &Sex chromosomes(gonadal). - At the point of attachment of the 2 arms of the anaphase chromosome, there is a constriction called primary constriction or the centromere. 17 dr. manal sayed Function of the nucleus: 1. The nucleus houses the genetic material. 2. Control all the structural and functional activity of the cell. 3. Cell division. 4. Produces ribosomal subunits in nucleolus and exports them into cytoplasm for assembly into ribosome. dr. manal m. sayed 18 Function of the nucleus: 1. The nucleus houses the genetic material. 2. Control all the structural and functional activity of the cell. 3. Cell division. dr. manal m. sayed 19 dr. manal m. sayed 20 dr. manal m. sayed 21 Cell Cycle  The cell cycle Definition: It is a sequence of events that occur in the cell during its division (mitosis) and during its rest (interphase), that produces new cells. The cell cycle is formed of 2 periods: a. Interphase: Includes Gap 1 phase, Synthesis phase, and Gap 2 phase. b. Mitosis: Includes division of the nucleus (Karyokinesis) and division of the cytoplasm (Cytokinesis). 10/29/2024 23 Dr. mANAL Phases of Cell Cycle: 1- G1 Phase. 2- S Phase. Interphase 3- G2 Phase. 4- M Phase. Mitosis dr. manal m. sayed 24 A. Interphase: It is the interval between two consecutive cell divisions, and during which the cell performs its specialized functions. It is subdivided into three phases: dr. manal m. sayed 25  1. Gap 1 stage (G1): The period starting after the completion of mitosis and during which Agendathe nucleus does not show any increase in DNA content. It is the longest phase. A good amount of protein is formed during this stage. 2. Synthesis (S) stage: Starts after G1 and represents the period of DNA and centrioles duplication. which duplication of DNA **Any cell entering the S-stage must continue the cycle. dr. manal m. sayed 26  3. Gap2 (G2): During this stage, the cells synthesize a great amount of cytoplasmic material such as proteins, Agenda and the organoids are increased in number. Mitosis (M): It the period when the chromosomes shorten, align in the middle of the cell, and separate into two identical sets each of which forms the chromosomal content of the new daughter cell. Note: The time required for a call cycle to be completed ranges from 10 to 30 hours. dr. manal m. sayed 27  Agenda dr. manal m. sayed 28 dr. manal m. sayed 29 1-G1 Phase: is the longest phase. It is a period of active protein synthesis. 2-S Phase: is the period of DNA replication. 3-G2 Phase: is a short period of preparation for mitosis. 4-M Phase (Mitosis): is the period of cell division that results in two new daughter cells. dr. manal m. sayed 31  Cell death: Agenda Cell death can be defined as “the irreversible cessation of vital activities inside the cell”. Cells, like individuals, have a life span i.e., they die. Death result from the normal process of development where certain cells become functionless and their death is necessary, otherwise the function of the individual is altered. dr. manal m. sayed 32  Agenda There are TWO main types of cell death : Apoptosis. Necrosis. dr. manal m. sayed 33 1- Apoptosis: Agenda Is the normal cell death due to internal activities within the cell as a result of genetic information. So, it is called programmed cell death. It is a rapid, highly regulated cellular activity. 2- Necrosis: Is cell death due to exogenous factors such as injury or toxins. dr. manal m. sayed 34  Apoptosis Necrosis Physiological Pathological process process Programmed cell acute cell injury death Cell death The cell shrinks The cell swells The cell forms The cell rupture apoptotic bodies and release its content Does not induce Induce dr. manal m. sayed inflammation inflammation 35 dr. manal m. sayed 36 dr. manal m. sayed 37  Self- exam dr. manal m. sayed 38 1- The outer membrane of the nuclear envelope is continuous with? A. Lysosomes. B. Mitochondria. C. Rough endoplasmic reticulum. D. Smooth endoplasmic reticulum. 2- Which of the following is the period of DNA replication in the cell cycle? A. G1 phase. B. G2 phase. C. M phase. D. S phase. 3- A kind of cell death as a result of disease or injury is called: A. Programmed cell death B. Necrosis C. Cell division. D. Cytokinesis. 4. The normal cell death due to internal activities is termed? A. Mitosis B. Necrosis. C. Apoptosis. D. Cytokinesis. 5-The cell cycle is formed of 2 periods A. Interphase and Apoptosis. B. Interphase and mitosis. C. Necrosis and mitosis. D. Mitosis and S phase. 1.Define a. Interphase. b. Mitosis. c. Cell death. d. Cell cycle. e. Centromere. 2. Enumerate a. Types of chromatin. b. Components of the nucleus. c. Functions of the nucleus. 3. Compare between apoptosis and necrosis. Dr. Manal