The Cell - Lectures Outline - PDF

October 24 THE CELL ASSOC. PROF. DR INTAN SHAMEHA A.R., DEPT. OF VET. PRECLINICAL SCIENCES, F...

October 24 THE CELL ASSOC. PROF. DR INTAN SHAMEHA A.R., DEPT. OF VET. PRECLINICAL SCIENCES, FACULTY OF VET. MEDICINE [email protected] This Photo by Unknown Author is licensed under CC BY-NC Lectures Outline  Introduction  Cell Generalities  Terminologies  Shape, size and function  Measurement  Mitosis & Meioisis  Apoptosis & necrosis  Components of cells and its functions  Nucleus  Cytoplasmic organelles  Cytoplasmic Inclusions o Cell Modifications  Cytoskeletons 1  October 24 INTRODUCTION  CELL  small compartment (cella = small room)  Structural and functional unit of the body  The smallest organized unit of living material capable of existing independently Light Microscope vs Electron Microscope SEM Light Microscope TEM 2  October 24 TERMINOLOGIES To describe the position of cytoplasmic organelles or inclusion bodies in the cell SHAPE OF CELLS 1. FLAT/SQUAMOUS 2. CUBOIDAL 3. COLUMNAR 4. ROUNDED 3  October 24 SHAPE OF CELLS 5. STELLATE (STAR-SHAPE) - due to the presence of axons and dendrites - e.g. neurons - irritability & transmission of impulses 6. POLYGONAL - means many sided - e.g. liver cells SHAPE AND FUNCTION  Every shape/ structure related to its function: 1. Motility/movement  E.g. macrophages (phagocytic cells)  Pseudopodia (false foot)  https://histologyguide.com/EM-view/EM-016-macrophage/03- photo-1.html?x=0&y=0&z=-1&page=1 2. Irritability  Response to irritant/stimulus  e.g. nerve cells 4  October 24 SHAPE AND FUNCTION 3. Reproduction  E.g. ovum, testis  Produce ova, undergone mitotic divisions 4. Metabolisme  Catabolism : breakdown of food  Anabolism: uptake of food materials MEASUREMENT  Sizes  Rarely visible to the naked eye  Very large cell = Giant cell @ megakaryocyte (multinucleated) (50-100 µ)  Unit  LM - µ (micron) e.g. diameter of RBC is 6µ  EM – A (Armstrong) e.g. thickness of cell membrane is 80A 5  October 24 MITOSIS  Is the process of cell division that results in the formation of two identical daughter cells  5 distinct stages: 1. Prophase 2. Prometaphase 3. Metaphase 4. Anaphase 5. Telophase MITOSIS 6  October 24 PROPHASE  Chromosomes condense and the nucleolus disappear  Not easy to identify under LM  Nuclear membrane very prominent PROMETAPHASE  Nuclear envelope disappear  Chromosomes arranged randomly throughout the cytoplasm 7  October 24 METAPHASE  begins as the newly duplicated chromosomes align themselves on the equator of the mitotic spindle  Easy to identify  mass of nucleus or ‘jagged’ appearance of the nucleus ANAPHASE  The sister chromatids separate and begin to migrate to opposite poles of the cell, and a cleavage furrow begin to develop  Nucleus had divided 8  October 24 TELOPHASE  terminal phase  Cytokinesis  reconstitution of the nucleus and nuclear envelope  Disappearance of the mitotic spindle  The nucleus far apart MEIOSIS  process in which the parent cell divides twice into four daughter cells containing half the original amount of genetic information, i.e., the daughter cells are haploid.  results in the formation of four daughter cells in each cycle of cell division  formation of sex cells or gametes that are responsible for sexual reproduction. 9  October 24 MEIOSIS  Significance of Meiosis:  Reproduction in animals = the fusion of gametes i.e. two cells fuse together with their genetic material to develop a zygote. If germ cells, which give rise to gametes, also maintains their ploidy during division like the somatic cells, the zygote will have an accumulation of chromosomes in its nucleus. This accumulation will keep on increasing with every subsequent generation.  Meiosis offers a very smart solution to this problem as it reduces the number of chromosomes in the gametes to half of their parent germ cells. Moreover, prophase I of meiosis allows recombination of homologous chromosomes.  This recombination is essential for the variation to be introduced in the genetic makeup of the gametes as this variation only holds the key to evolution through sexual reproduction.  2 Phases of Meiosis: I and II MEIOSIS 1 & 2 Meiosis 1 Meiosis 2  the homologous chromosomes  the sister chromatids separate and separate from each other and two four haploid daughter cells are diploid daughter cells are produced produced  The different stages of meiosis 1  The different stages of meiosis 2 include: are:  Prophase  Prophase II  Metaphase  Metaphase II  Anaphase  Anaphase II  Telophase  Telophase II 10  October 24 APOPTOSIS & NECROSIS  APOPTOSIS  Genetic programming @ programmed cell death which literally mean “falling off”  To balance cell proliferation and cell death in the adult life  NECROSIS  Cell dies because of attack or injury  pathological  Stages of apoptosis - peripheral nuclear chromatin condensation - blebbing of cell membrane Apoptosis - nuclear lobulation - nuclear fragmentation - nuclear fragment deletion or removal by macrophages or cells which turn phagocytic  Apoptotic cell refer to cell with fragmented nucleus This Photo by Unknown Author is licensed under CC BY-SA 11  October 24 APOPTOTIC CELL  https://creativemeddoses.com/topics -list/necrosis-vs-apoptosis-six-major- differences/  The apoptotic cell appears as a round or oval mass with dark eosinophilic cytoplasm and dense purple nuclear chromatin fragments NECROSIS  Necrosis is the death of body tissue resulting from injury, radiation, or chemicals.  It occurs when too little blood flows to the tissue.  Necrosis cannot be reversed. 12  October 24 APOPTOSIS VS NECROSIS (MAJOR DIFFERENCES) DIFFERENCES APOPTOSIS NECROSIS REASON Physiological Pathological CELL SIZE Shrink Enlarge NUCLEUS Break to nucleosome size Pyknosis Pyknosis Fragmentation Fragmentation Karyolysis PLASMA MEMBRANE Remains intact Loss its integrity CELLULAR CONTENTS No leakage Leakage INFLAMMATION Phagocytoses Inflammatory cells involved CYTOLOGY PART 2 13  October 24 COMPONENTS OF CELL AND FUNCTION  NUCLEUS  Nucleus = Latin word; Karyon = Greek word.  Both used e.g. nucleolus, nucleoprotein, perikaryon, eukaryon  Prominent body / structure located in the center of the cell  Off center = eccentrically located e.g plasma cells  Certain cells are non nucleated e.g. RBC NUCLEUS  Number  1 = mononucleate  2 = binucleate  Many = multinucleate This Photo by Unknown Author is Shape licensed under CC BY-SA-NC   Normally spherical  At times, may correspond to the shape of the cell e.g.lobulated in WBC, flat in squamous epithelium 14  October 24 CYTOPLASM & ORGANELLES CELL ORGANELLES 1. Endoplasmic Reticulum 2. Ribosomes 3. Golgi complex 4. Mitochondria 5. Lysosomes 6. Cell membrane* #All have CM except ribosomes 15  October 24 CELL MEMBRANE  Plasma membrane, plasmalemma, cytolemma Protein layers  Under TEM = trilaminar str.  Function:-  Selectively permeable  Have pumps to regulate ion Lipid layer concentration within the cell  Variety of enzymes  Specific receptor sites for Protein layers: Inner important functions e.g. endocytosis, phagocytosis. Outer Endoplasmic Reticulum (ER)  A system of closely set membrane-bound branching and anastomosing channels or cisternae  2 types:  Rough ER (rER) / granular ER – studded with ribosomes on the external surface  Smooth ER (sER) / agranular ER - devoid of ribosomes  Ribosomes  Only organelles NOT surrounded by plasmalemma  RNA materials/granules  Can appear as:  Single = ribosomes  Aggregates = polyribosomes 16  October 24 rER in neuron: Nissl’s bodies Endoplasmic Reticulum (ER)  Functions:  rER : in the synthesis of proteins for extracellular and intracellular use  sER : transitional ER, tubules give rise to transfer vesicles that carry substances synthesized within the rER to other locations especially Golgi apparatus  E.g. steroid hormone synthesis in interstitial cells of testis, Corpus Luteum  Drug detoxification e.g.in the liver cells 17  October 24 Endoplasmic Reticulum Golgi Apparatus @ Golgi Complex  Capital ‘G’ (Camillo Golgi)  Under LM, Golgi complex is visible as clear halo (area), supranuclearly located; known as ‘Negative Golgi Image’  Under TEM : stacks of flattened smooth –surfaced membranous vesicles (saccules), arranged one top of the other 18  October 24 Golgi Apparatus @ Golgi Complex Golgi Apparatus @ Golgi Complex  2 faces:  Cis (forming) – facing the base of the cell  Trans (mature surface) -Facing apex of the cell  Forming transport system  Proteins synthesized in rER – transfer to Golgi Complex (by transfer vesicles) – reach the cis face – protein concentrated in GC might be added with carbohydrate complex = glycoprotein  Move upwards to trans face – free as vacuoles – secretory granules – discharged from the cell (exocytosis) 19  October 24 Lysosomes  Lyso (originate from word lysis)  Membrane bounded granules contain hydrolytic enzymes  2 types:  Primary: only containing hydrolytic enzymes  Secondary: as a result of fusion of 1º lysosomes with a variety of membrane-bounded substrate  e.g. elements of rER, mitochondria or others lose their ability to function ---segregate with 1º lysosomes = autophagosomes. Mitochondria cristae  Under EM seen to be bounded by 2 membranes:  Outer smooth  Inner: folds known as cristae  1= crista, plural = cristae  As energy store house of the cell  Numerous in cells with high metabolic activity e.g. muscle cells 20  October 24 Any Guess? OTHER PARTS OF CELL 1.CYTOPLASMIC INCLUSIONS 2.CYTOSKELETON 3.CELL MODIFICATIONS 21  October 24 CYTOPLASMIC INCLUSIONS  metabolic products that are stored in the cytoplasm  typically in long-lived cells such as hepatocytes, neurons, and cardiac muscle cells.  Examples:  glycogen granules (a storage form of glucose seen as small, dark granules in the cytoplasm in TEM images)  melanin pigment granules  lipid droplets  residual bodies or lipofuscin granules. *Some of these inclusions are visible in routinely prepared, H&E stained sections, and most are visible in electron micrographs. CYTOPLASMIC INCLUSIONS  Inert (no specific function) 1. Glycogen granules  Carbohydrate stored in cells e.g.hepatocytes 2. Lipids  Fat stored cells, e.g. degenerating cells 3. Lipofuschin  Golden brownish pigments in cardiac muscle, liver & nerve cells  Indigestible residues of phagocytosis  End product of lysosomal activity 22  October 24 CYTOPLASMIC INCLUSIONS 4. Melanin  Pigment = black colour of the skin and eyes  In skin, produced by melanocytes 5. Hemosiderin  Resulting from hemoglobin degradation following phagocytosis by macrophages of spleen, liver, lymph node and bone marrow  Golden brown in colour  With EM dense particles of ferritin, an iron containing protein = visible within the hemosiderin Inclusion Bodies  NOT enclosed by a membrane  serve as storage vessels.  Example: Glycogen, which is a polymer of glucose, is stored as a reserve of carbohydrate and energy. 23  October 24 CYTOSKELETON  Microfilaments and microtubules  Form complex meshwork  To maintain cell shape and stability & for cell movement  3 types: 1 INTERMEDIATE FILAMENT 2 MICROTUBULES 3 MICROFILAMENT https://readbiology.com/cytoskeleton-types/ CYTOSKELETON 1. Microfilament  1.o µ long and 5 – 8 nm in diameter  Protein actin  Actin filament are abundance in microvilli and stereocilia = supportive role  In migrating cells e.g. in macrophages; responsible for movement 1 INTERMEDIATE FILAMENT 2 MICROTUBULES 3 MICROFILAMENT 24  October 24 CYTOSKELETON- cont. 2. Intermediate filament  8-10nm in diameter  To maintain cell shape e.g. neurofilaments of nerve cells, glial filaments in astrocytes  Also play a role in cell adhesion CYTOSKELETON- cont. 3. Microtubules  25nm in diameter  Stable, permanent structures in cilia, flagella, centrioles and basal bodies  Essential role in cell division  In nerve cells, important for the transport of various organelles from the perikaryon to the periphery 25  October 24 MICROFILAMENTS INTERMEDIATE FILAMENTS MICROTUBULES support the transportation of vesicles IF play an essential structural role Microtubules give shape to the cell. into and out of a cell. in the cell which is more permanent. makes cell migration possible like cell They maintain the shape and bear Cell and its cytoplasmic organelles motility which is needed to build up tension, and berth the nucleus and movement tissues. other cell organelles in place. involved in endocytosis and exocytosis. Support and maintain the cell transportation of communication signals Microtubules also help the between cells. productions of vacuoles. Muscle contraction is caused by actin It forms cellular outgrowth such and myosin filaments. as cilia and flagella, in some cells. After nuclear division, cleavage is The microtubules control separation brought about by constriction of a ring of of chromatids and chromosomes. microfilament. help in the flow of cytoplasm MT and MF can be assembled or (Cytoplasmic streaming) disassemble and allow cells to contract, migrate and crawl e.g. amoeboid movement. CELL MODIFICATIONS 1. CILIA 2. MICROVILLI 3. STEREOCILIA 26  October 24 CELLS MODIFICATIONS CILIA Short, hair-like structures on cell surface Motile or non-motile No glycoclayx coating Core structure is made up of microtubules (9+2) Function: movement and locomotion Location: respiratory tract, oviduct MICROVILLI STEREOCILIA Bundles of actin filament, branched Non-motile May or not presence of glycoclayx coating Core structure is made up of actin filaments Function: increase conductance of membranes Location: ductus deferens, epididymis, sensory cells of the ears Bristle- like protrusions on cell surface Non-motile Glycoclayx coating Core structure is made up of actin filaments Function: nutrient absorption, secretion Location: surface of small intestines 27  October 24 CILIA 9+2 MICROTUBULES https://www1.udel.edu/biology/Wags/histopage/illuspage/iep/ep itheliumppt.htm 28