Histology Module 1: Cell and Introduction PDF

MODULE 1: Introduction to Cell Structure and Functions Mary Judith S. Rebosa, MD, FPPS UNIT EXPECTED OUTCOMES Appreciate the basic unit of life Define terms and comprehend the brief history of the cell Discuss the ultrastructure and functions...

MODULE 1: Introduction to Cell Structure and Functions Mary Judith S. Rebosa, MD, FPPS UNIT EXPECTED OUTCOMES Appreciate the basic unit of life Define terms and comprehend the brief history of the cell Discuss the ultrastructure and functions of the cell Interpret the histological pictures of the cell  PART I: Introduction to Histology and Generalities INTRODUCTION TO HISTOLOGY ❖ “Histos” – tissue ❖ “-logos” – study of ❖Understanding of the structure and function of cells, tissues, organs, and organ systems DEFINITION OF TERMS CYTOLOGY: study of individual cells MICROSCOPIC ANATOMY: integrated exploration of cells, intercellular materials, and structures, tissues, and organs using a microscope ORGANOLOGY: study of organs or groups of tissues arranged in a specific pattern characteristic for that particular organ LEVELS OF ORGANIZATION LEVELS OF ORGANIZATION: ORGANISM CELLS TISSUES ORGANS ORGAN SYSTEMS Smallest basic Groups of cells of Several tissues Several organs structure capable similar function that, when of independent and origin that combined, form existence form functional an organism units; rarely work alone LEVELS OF ORGANIZATION LEVELS OF ORGANIZATION: TISSUES LEVELS OF ORGANIZATION: TISSUES LEVELS OF ORGANIZATION The body is comprised of different levels of organization, with increasing levels of complexity. Each level has an important role in maintaining the physiologic homeostasis of the body. METHODS OF HISTOLOGY AND CYTOLOGY Direct observation -phase contrast microscope METHODS OF HISTOLOGY AND CYTOLOGY Direct observation Cell, tissue, and organ culture METHODS OF HISTOLOGY AND CYTOLOGY Direct observation Cell, tissue, and organ culture Mechanical micromanipulation and microdissection -technique of performing mechanical operations under high magnification through the use of specialized tools METHODS OF HISTOLOGY AND CYTOLOGY Direct observation Cell, tissue, and organ culture Mechanical micromanipulation and microdissection Use of radiation probes -microbeams of protons and beams of ultraviolet -selective irradiation of small areas of living cells METHODS OF HISTOLOGY AND CYTOLOGY Direct observation Cell, tissue, and organ culture Mechanical micromanipulation and microdissection Use of radiation probes Cinematography METHODS OF HISTOLOGY AND CYTOLOGY Differential centrifugation -can isolate pure fractions of nuclei, nucleoli, mitochondria, lysosomes, ribosomes, pigment granules, and secretory granules METHODS OF HISTOLOGY AND CYTOLOGY Differential centrifugation Microincineration a technique employing high temperatures (as 600–650°C) for driving off the organic constituents of cells or tissue fragments leaving the inorganic matter for chemical identification METHODS OF HISTOLOGY AND CYTOLOGY Differential centrifugation Microincineration Frozen section method a portion of tissue mass is removed which is then frozen in a cryostat machine, cut into a thin film with a microtome, and then stained with various dyes so that it can be examined under the microscope METHODS OF HISTOLOGY AND CYTOLOGY Differential centrifugation Microincineration Frozen section method Use of stains PREPARATION OF HISTOLOGICAL SECTION FIXATION: preserves tissues and prevents structural change or breakdown of components of the tissues Fixatives: stabilize or denature protein (e.g. Formaldehyde) METHODS OF FIXATION ✓ Heat fixation ✓ Perfusion ✓ Immersion ✓ Vapour method ✓ Phase partition method  SIMPLE FIXATIVES FORMALIN ✓ Most commonly used fixative ✓ Prepared by mixing 40% Formaldehyde gas in 100 w/v of distilled water ✓ Resultant mixture is 100% Formalin ✓ Routinely, 10% Formalin is used which is prepared by mixing 10mL of 100% formalin in 90mL of distilled water  COMPOUND FIXATIVES MICROANATOMICAL FIXATIVES ✓ Used to preserve the anatomy of the tissue CYTOLOGICAL FIXATIVES ✓ Used to fix intracellular structures HISTOCHEMICAL FIXATIVES ✓ Used to demonstrate the chemical constituents of the cell FIXATION FIXATION FIXATION PREPARATION OF HISTOLOGICAL SECTION DEHYDRATION: immersion of tissue block in increasing concentrations of ethyl alcohol CLEARING: made transparent Chemicals used: xylol, chloroform, or benzene EMBEDDING: encased in paraffin wax SECTIONING/MICROTOMY: sections of the tissue embedded in the wax block are cut on a MICROTOME. Paraffin sections are then affixed to a slide and the paraffin dissolves DEHYDRATION AND CLEARING EMBEDDING  EMBEDDING PROCEDURE ✓ Place tissue cassette in melted paraffin ✓ Fill mold with paraffin ✓ Place tissue in mold ✓ Allow to cool  SECTIONING/MICROTOMY PROCEDURE ✓ Sections of the tissue embedded in the wax block are cut on a MICROTOME ✓ Paraffin sections are then affixed to a slide and paraffin dissolves PREPARATION OF HISTOLOGICAL SECTION STAINING: most commonly used is Hematoxylin and Eosin PERMANENT MOUNTING: ✓ Stained sections are placed on a slide in a gummy medium that hardens ✓ A thin coverslip is placed over the section to protect it  KINDS OF STAINING ACIDIC STAINS BASIC STAINS NEUTRAL STAINS ✓ Colored organic ✓ Colored organic ✓ Colored organic acid combined base combined acid is linked with a metal with uncolored chemically to a ✓ Dissolved in water acetate, chloride, colored organic or alcohol or sulfate radical base ✓ Stain the ✓ Stain the NUCLEUS ✓ Dissolved in CYTOPLASM absolute alcohol UNITS OF MEASUREMENT IN MICROSCOPY SI SYSTEM (SYSTEM INTERNATIONAL D’UNITIES) ✓ MICROMETER: 1um = 0.001mm = 10,000A ✓ NANOMETER: 1nnm = 0.001um = 10A ✓ ANGSTROM: 1A = 0.1nm = 0.0001um  MICROSCOPY OPTICAL MICROSCOPE: uses visible light ✓ Phase Contract Microscope ✓ Interference Microscope ✓ Polarizing Microscope ✓ Fluorescence Microscope ✓ Darkfield Microscope ULTRAVIOLET MICROSCOPE X-RAY MICROSCOPE ELECTRON MICROSCOPE  PART II: Cell Structure  CELL Basic morphological and functional unit of all living things Capable of independent existence EUKARYOTIC CELL PROKARYOTIC CELL CELL  CELL THEORY All organisms are made up of one or more cells The cell is the basic unit of all organisms All cells come from cells  CELL FUNCTIONS Cell metabolism and energy use Synthesis of molecules Communication Reproduction and inheritance  PRINCIPAL CELL PARTS Cell membrane Cytoplasm Nucleus  CELL MEMBRANE TRIMALINAR STRUCTURE: consists of 2 electron-dense sheets that sandwich a thin electron-lucent layer ✓ Protective covering the delimits the cells from its surroundings ✓ Selectively permeable membrane ✓ Provides attachment for the skeleton of the cell  CELL MEMBRANE TRIMALINAR STRUCTURE: consists of 2 electron-dense sheets that sandwich a thin electron-lucent layer ✓ Provides binding sites and receptors for enzymes and other substances ✓ Cell-to-cell recognition ✓ Forms specialized junctions with the cell membrane of adjacent cells  CELL MEMBRANE: PARTS LIPIDS: trilaminar structure consisting of 2 layers of phospholipids ✓ Globular polar hydrophilic head ✓ 2 slender nonpolar hydrophobic tails  CELL MEMBRANE: PARTS PROTEINS ✓ Integral Proteins: embedded within the lipid bilayer ✓ Transmembrane proteins: span entire thickness of the membrane ✓ Peripheral Membrane Proteins: attached to the inner or outer surfaces of the membrane CELL MEMBRANE: FLUID MOSAIC MODEL Membranes are fluid and have the consistency of vegetable oil Lipids and proteins are always in motion Proteins form patterns or mosaics CELL MEMBRANE: CARBOHYDRATES Key role in cell-cell recognition: ability to distinguish one cell from another (e.g. antigens) Important in organ and tissue development Basis for rejection of foreign cells by immune system CELL MEMBRANE: PHOSPHOLIPIDS ✓ HEADS: consists of glycerol ✓ TAILS: ✓ Straight chain saturated fatty acid ✓ Unsaturated fatty acid CELL MEMBRANE: OTHER COMPONENTS ✓ Cholesterol, glycolipids, glycoproteins, and other polysaccharides ✓ Cholesterol molecules stabilize and regulate the fluidity of the phospholipid bilayer ✓ Glycocalyx is involved in cell-cell recognition, cell-cell adhesion, and immunological response  CYTOPLASM Living material surrounding the nucleus Homogenous substance (cytoplasmic matrix) that fills the cell Formed elements are embedded in it  CYTOPLASM Consists of the following: ✓ Organelles: permanent fixtures that perform specific functions within the cell ✓ Inclusions: temporary structures ✓ Fibrillar elements: supporting framework and maintain the shape and internal organization of the cell  CYTOPLASM The cytosol (cytoplasmic matrix) is made up of water ✓ Viscid translucent and colloidal ✓ 70% water ✓ Inorganic ions and organic molecules dissolved here ✓ Site of biochemical processes Divided into: ✓ Endoplasm: sol phase ✓ Exoplasm: gel state  CYTOPLASM: ORGANELLES MITOCHONDRIA ✓ Generation of energy ✓ 0.5-1um x 10um ✓ Motile and can replicate ✓ Abundant in cells with high energy requirements (e.g. parietal cells of stomach, kidney tubule cells, hepatocyte, adrenal cortex)  CYTOPLASM: ORGANELLES MITOCHONDRIA ✓ STAINS: iron hematoxylin, supravital stain (Janus green) ✓ Phase contrast microscopy, electron microscopy ✓ Matrix contains: DNA, Ribosomes, mRNA, tRNA CYTOPLASM: ORGANELLES MITOCHONDRIA: Structure  CYTOPLASM: ORGANELLES RIBOSOMES ✓ Where proteins are produced ✓ 15-30nm ✓ Polyribosomes: connected by mRNA ✓ Free ribosomes ✓ Attached ribosomes ✓ Large and small subunit  CYTOPLASM: ORGANELLES ENDOPLASMIC RETICULUM ✓ Complex network of tubules, vesicles, and flattened sacs (cisternae) ✓ Seen by Fluorescent dyes and Electron Microscope ✓ ROUGH ER: ✓ with attached ribosomes for protein synthesis ✓ SMOOTH ER: ✓ Synthesis of cholesterol, phospholipids, steroid hormones ✓ Transport of fatty acids and lipids CYTOPLASM: ORGANELLES ENDOPLASMIC RETICULUM  CYTOPLASM: ORGANELLES GOLGI COMPLEX ✓ Arranged in stacks ✓ Processes, concentrates, sorts, and packages proteins it receives from the ER ✓ Secretory vesicles ✓ Concave surface (trans): ✓ Related to nucleus ✓ Maturing face ✓ Convex surface (cis): ✓ Forming face  CYTOPLASM: ORGANELLES GOLGI COMPLEX ✓ Components: ✓ Cisternae ✓ Small vesicles ✓ Larger vacuoles ✓ Light microscope: ✓ Silver salts/osmium ✓ Negative Golgi image (pale region adjacent to the nucleus)  CYTOPLASM: ORGANELLES LYSOSOMES ✓ Small dense bodies, 0.05-0.8um ✓ Enveloped by membranes ✓ Contains hydrolytic enzymes for intracellular digestion ✓ Found in ALL cells except Erythrocytes ✓ Observed by Histochemical method (Gomori’s technique)  CYTOPLASM: ORGANELLES LYSOSOMES ✓ Primary lysosomes: resting ✓ Secondary lysosomes: phagolysosomes (active) ✓ Heterophagy ✓ Lysosomal digestion within the cell of a particular material from the extracellular environment ✓ Leaves residual bodies called Lipofuscin Pigments ✓ Autophagy ✓ Digestion of unneeded or senescent cell organelles  CYTOPLASM: ORGANELLES PEROXISOMES ✓ Membrane-bound pouches containing oxidases and catalases ✓ Synthesized in the free ribosomes ✓ Catalyze metabolic reactions ✓ Catalyze conversion of hydrogen peroxide to oxygen and water ✓ Numerous in hepatocytes  CYTOPLASM: ORGANELLES CENTROSOMES ✓ Microtubule organizing center ✓ 0.2 x 0.5 um ✓ Assembly of microtubules ✓ Consists of a pair of centrioles surrounded by centriolar satellites ✓ DIPLOSOME ✓ pair of centrioles, lying perpendicular to each other ✓ CENTRIOLES ✓ Form mitotic spindles during mitosis ✓ Sources of cilia and flagella CYTOPLASM: ORGANELLES CENTROSOMES  CYTOPLASM: INCLUSIONS Fat Droplets Glycogen Zymogen granules Pigment granules: melanin, hemosiderin Crystals: interstitial cells of Leydig and Sertoli Lipochrome pigments: Lipofuscin pigments Dust particles  CYTOPLASM: INCLUSIONS Fat Droplets ✓ AKA Lipid Droplets ✓ Round clear areas by light microscope ✓ Glutaraldehyde and osmic acid ✓ Lipid droplets appear as gray or black-staining globules  CYTOPLASM: INCLUSIONS Fat Droplets  CYTOPLASM: INCLUSIONS Glycogen Granules ✓ Storage form of carbohydrates ✓ Abundant in liver and muscle cells ✓ Periodic Acid-Schiff stain ✓ Alpha Particles ✓ Beta Particles  CYTOPLASM: INCLUSIONS Zymogen Granules ✓ Secretory granules ✓ Release contents to extracellular space  CYTOPLASM: INCLUSIONS Pigment Granule: Hemosiderin ✓ Product of lysosomal digestion of hemoglobin ✓ Seen with stains that selectively stain iron  CYTOPLASM: INCLUSIONS Pigment Granule: Melanin ✓ Gives brown color of the skin  CYTOPLASM: CYTOSKELETON ✓ Structural support or framework of the cell ✓ Components: ✓ Microfilaments ✓ Intermediate filaments ✓ Microtubules  CYTOPLASM: CYTOSKELETON MICROFILAMENTS ✓ Thinnest: 5-7nm ✓ Actin – F-actin, G-actin ✓ For cellular movement ✓ Endocytosis ✓ Exocytosis ✓ Maintenance of cell shape ✓ Contraction of myoepithelial cells and muscle cells ✓ Locomotion of certain cells  CYTOPLASM: CYTOSKELETON INTERMEDIATE FILAMENTS ✓ 10-12nm in diameter ✓ Examples: ✓ Desmin: smooth muscle cells ✓ Keratin: epithelial cells in the epidermis ✓ Vimentin: mesenchymal cells (fibroblasts, muscle cells) ✓ Neurofilament: internal support for neurons ✓ Glial filament: CNS CYTOPLASM: CYTOSKELETON INTERMEDIATE FILAMENTS  CYTOPLASM: CYTOSKELETON MICROTUBULES ✓ Rod-like or pipe-like tubules 25um in diameter ✓ Made up of 13 tubulin (protofilaments) molecules arranged around a lumen ✓ Tubulin: small globular proteins which comprise the wall of microtubules CYTOPLASM: CYTOSKELETON MICROTUBULES  NUCLEUS ✓ Largest structure inside the cell ✓ Data bank of the cell ✓ Consists of ✓ Nuclear envelope ✓ Chromatin ✓ Nucleolus  NUCLEUS: NUCLEAR ENVELOPE Nuclear Lamina ✓ Consists of fine protein filaments bound to integral membrane proteins in the inner surface of the nuclear envelope ✓ Point of attachment of chromatins  NUCLEUS: CHROMATIN Chromatin ✓ Coiled strands of DNA bound to basic proteins called histones ✓ Nucleosome ✓ Basic structural unit of chromatin ✓ 4 pairs of histone molecules ✓ Heterochromatin ✓ Condensed form of inactive DNA ✓ Euchromatin ✓ Portion of DNA being transcribed ✓ Active in producing RNA NUCLEUS: CHROMATIN DNA  CHROMOSOMES Chromosomes ✓ Humans cells have 46 chromosomes ✓ Structural unit of the genetic material of the cell ✓ PREPARATION FOR CELL DIVISION ✓ Chromatin decondenses ✓ Molecules of DNA reorganized into chromosomes ✓ KARYOTYPE ✓ Number and length of chromosomes distinctive to each species CHROMOSOMES CHROMOSOMES  NUCLEUS: NUCLEOLUS Nucleolus ✓ Basophilic structure located eccentrically in the nucleus ✓ Numerous in cells actively synthesizing RNA and proteins ✓ Synthesizes ribosomal subunits ✓ THREE AREAS ✓ Nucleolar organizing region: where rRNA are transcribed ✓ Pars fibrosa ✓ Pars granulosa NUCLEUS: NUCLEOLUS NUCLEUS: NUCLEOLUS  CELL REPRODUCTION Mitosis ✓ Nuclear division of vegetative cells ✓ Includes: ✓ Prophase ✓ Metaphase ✓ Anaphase ✓ Telophase  CELL REPRODUCTION Cell Cycle MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE DIFFUSION MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE PASSIVE TRANSPORT ✓ Movement of substances from area of higher concentration to an area of lower concentration without the need for energy ✓ Simple diffusion ✓ Osmosis ✓ Carrier-mediated transport mechanism ✓ Facilitated diffusion ✓ Filtration MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE PASSIVE TRANSPORT: SIMPLE DIFFUSION ✓ Movement of solute from an area of higher concentration to an area of lower concentration of that solute in solution MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE PASSIVE TRANSPORT: OSMOSIS ✓ Diffusion of water across a selectively permeable membrane MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE PASSIVE TRANSPORT: FACILITATED DIFFUSION ✓ Passive movement of molecules across the cell membrane with the aid of a membrane protein MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE PASSIVE TRANSPORT: FILTRATION ✓ Passive movement of water and molecules across the cell membrane due to hydrostatic pressure ✓ Depending on the size of the membrane pores, only solutes of a certain size can pass through MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE ACTIVE TRANSPORT ✓ Movement of substances through a membrane against a concentration gradient ✓ Requires energy ✓ Endocytosis ✓ Phagocytosis ✓ Pinocytosis ✓ Exocytosis MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE ACTIVE TRANSPORT: ENDOCYTOSIS ✓ Process by which large molecules, parts of a cell, or even a whole cell are ingested by another cell MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE ACTIVE TRANSPORT: EXOCYTOSIS ✓ Process by which membrane- bound vesicles containing cellular molecules are transported to the cell membrane to be brought outside of the cell MOVEMENT OF MATERIALS ACROSS CELL MEMBRANE ACTIVE TRANSPORT: EXOCYTOSIS  REFERENCES “Microincineration.” Merriam-Webster.com Medical Dictionary, Merriam- Webster, https://www.merriam- webster.com/medical/microincineration. Accessed 7 Sep. 2021. Mescher, Anthony L. (2018) Junquiera’s basic histology: text and atlas (13th ed.) NewYork: McGraw-Hill/Medical. THANK YOU!