Principles of Histology PDF

Professor of histology  Principles of microscopic and macroscopic structures Methods of studying cells and tissues Prof. Soha Soliman Professor of histology  Learning objectives Recognize Discuss List Differentiate...

Professor of histology  Principles of microscopic and macroscopic structures Methods of studying cells and tissues Prof. Soha Soliman Professor of histology  Learning objectives Recognize Discuss List Differentiate Discuss List the Differentiate Recognize between the the the normal methods structure of light and structure electron of the cell. of the cell. studying the cell microscope. list Define Describe list the Define the Describe component of the cytoskeleton , the structure of the cell, and types of cytosol, cell membrane and membranous and endocytosis & nonmembranous correlate it to the exocytosis function. organelles.  What is Histology Histology – is the science that studies microscopic structures and functions of the human organism, the organization of the tissues and organs. Cytology – is the science that studies the structure and functions of the cell. CYTOLOGY  Cell and Tissue Culture Definition: is the maintenance and study of live cells and tissues outside the body in culture (in vitro). *Uses: 1. Cell culture allows the direct observation of living cells. 2. Experiments which are technically impossible to perform in the body (in vivo) can be accomplished in culture (in vitro). 3. In research on cell structure and function. 4. For genetic or chromosomal analyses. 5. To study molecular changes that occur in cancer  Staining cells and ECM components 1.General 2.Specific 4.Histochemical 3.Vital histological (special) and staining methods histological cytochemical methods methods methods haematoxylin stains the nucleus and one dye stains stains enter cells For identification of other structures in only one structure either by fat or enzyme in the cytoplasm. - or substance e.g., diffusion or by cells or tissues by Eosin stains basic orcein stains only phagocytosis and using either cell components elastic fibers. stain cellular physical or chemical such as most components procedures on cytoplasm proteins without harming histological sections (e.g. mitochondria). the cell. 4.Histochemical and cytochemical methods: a definite substance such as fat or enzyme is identified and localized in cells or tissues by using either physical or chemical procedures on histological sections a)Chemical methods e.g. identification of glycogen by using the periodic acid schiff (P.A.S) b) Physical methods due to certain physical properties of staining affinity for substances e.g., fluorescent substances (vitamin A)  The cell Cells are the structural and functional units (the smallest living parts) of the body. Cells can be eukaryotic or prokaryotic: 2.Prokaryotic cells e.g. human & animal cells e.g. bacteria Large small Have plasma membrane Have cell wall outer to the plasma membrane. Have a definite membrane-limited nucleus. Lack nuclei. The cytoplasm contains membrane- Lack membrane-limited limited organelles. organelles.  The cell Cells are the structural and functional units of human where cells tissues organs systems human. Shape of cells: may be round, oval, flat, cubical or columnar. Size of cells (4-150 μm): may be small (as cerebellum), medium (as liver) or large (as ovum). Function of cells: absorption, digestion and excretion - respiration, ion transport and secretion - sensation, conduction and contraction.  Beams apply Beams of to the electrons passing surfaces of through tissue cells, tissues, sections and organs Electron-lucent = White (Bright) areas The surface of the specimen is spray-coated through which electrons passed with a very thin layer of heavy metal (often Electron-dense = Dark areas where gold) → Reflects electrons in a beam scanning electrons were absorbed or deflected the specimen. The reflected electrons are captured → 3D- Black & white image.  Structure of the eukaryotic cell 1. Cell Membrane 2- Nucleus 3- Cytoplasm Cell membrane  Cell membrane light microscope (LM) It couldn’t be seen but can be inferred due to deposition of dyes. Special stains: can be stained by PAS or Ag electron microscope (EM) It appears as two electron dense bands separated by electron lucent one; trilaminar membrane or unit membrane of 8-10 nm thickness. ) nucleus Lipid bilayer Cell membrane Molecules ?? Molecular structure of cell membrane Carbohydrate (10%) Lipid 30% Protein (60%)  lipid Phospholipid molecule cholesterol 1-Integral membrane protein 2-Peripheral protein membrane protein  Integral and peripheral proteins (ion channels, receptors, enzymes, transporters\carrier) Ion carrier Receptor (signaling) channel Marker Cell Gated Enzyme (glycoprotein) adhesion channel  Gel state Fluid mosaic model of Singer & Nicolson  Lipid lipid carbohydrate protein protein  MEMBRANE TRANSPORT SIMPLE DIFFUSION FACILITATED DIFFUSION Osmosis (for water) (FOR SUGARS AND AMINO (FOR GAS, IONS ) ACIDS) protein channels ACTIVE TRANSPORT EXOCYTOSIS AND (NEEDS ENERGY) SELECTIVE PERMEABILITY (BY RECEPTORS IN CELL COAT) ENDOCYTOSIS protein channels  MODIFICATIONS IN CELL MEMBRANES Microvilli Cilia Flagella Increased surface area Move particles above movement e.g: Tails of e.g: Absorptive cells in cell membrane e.g: sperms small intestine Removal of dust from inspired air in respiratory passages  What is the Function of the trans-membranous protein ? 1- osmoregulation 2- act as receptors 3-act as Ion channels 4- act as barrier 1 2 3 1 2