L1 Histology BMS 122 - GALALA University, Fall 2024

Textbook guide General Histology for Dental Students BMS 122 Faculty of Dentistry Junqueira's Basic Histology,...

Textbook guide General Histology for Dental Students BMS 122 Faculty of Dentistry Junqueira's Basic Histology, Text and F A L L 2 0 2 4 Atlas. Mescher, 15th Edition, 2018 T H E F U T U R E S T A R T S H E R E  Exams and evaluation of BMS 122 Assessment Measures Weight Time Course Activities (Assignments, Quizzes, Weekly 20% Presentations) basis Midterm Exam 10% 7th Week Practical Exam 30% 14th Week Final Exam 40% 15th Week Total 100% 2025 -2024 ‫رابط مجموعة التيليجرام اسنان‬ https://t.me/+3pi-mlHYpb8zOWI0  INTENDED LEARNING OBJECTIVES (Ilos) By the end of this lecture, the student should be able to:  Define Histology and cytology.  Identify different types of microscopes.  Identify different methods of microtechniques.  Explain the general structure of the cell.  Enumerate the components of the nucleus.  Define the different structures of the nucleus and their functions.  Enumerate components of the cytoplasm.  Define cytoplasmic organelles  Identify the histological structure of the cell membrane  Histology is the science of studding the microscopic structures of normal tissues, (Microscopic Anatomy).  Cytology means the study of cells.  The cell is the structural and functional unit of the organism.  Cells are too small to be seen by naked eye, so Basic tools are: 1- Microscopes: Light microscope (LM) & Electron microscope (EM). 2- Microtechniques: Methods of preparing microscopic slides.  Types of Microscopes: 1. Light Microscope 2. Electron microscope a- Transmission Electron Microscope (TEM) b- Scanning Electron Microscope (SEM)  Three main Microtechniques: 1- Paraffin technique: the most common method. 2- Celloidin technique: the most ideal method. 3- Freezing technique: the most rapid method.  CELL Cell. - It is the structural and functional unit of any tissue. - Cell is composed of protoplasm, which consists of nucleus and cytoplasm.  THE NUCLEUS It is the largest component of the cell, It contains the genetic information necessary for cell activities. binucleated Shape: it has different shapes; rounded, oval or flat. Position: it may be central, basal, peripheral or eccentric Number: cells are usually mononucleated but some cells may be binucleated or multinucleated. LM: vesicular - It appears as dark blue (basophilic stains) - It appears vesicular in active cells and dark in inactive cells dark  Nucleus Heterochromatin Outer nuclear membrane Euchromatin Inner nuclear membrane Nuclear Sap Nuclear pores Components of nucleus are Nucleolus A. Nuclear envelope B. Chromatin (Eu. &Hetero.) C. Nucleolus D. Nuclear Sap  1- Nuclear envelope: - It surrounds the nucleus - EM: it is formed of two membranes separated by perinuclear space. -The nuclear envelope is interrupted by nuclear pores which is closed by diaphragm which allow some molecules to inter the nucleus & RNA to pass from the nucleus to cytoplasm  2- chromatin  In non-dividing nuclei: Chromatin is the chromosomal material in uncoiled state.  In dividing nuclei: the chromatin starts to be condensed and form chromosomes. EM: (according to the activity of the cell) chromatin is divided to: A- Euochromatin (active) :extended chromatin filaments B- Heterochromatin (inactive): the condensed chromatin filaments are arranged as: a- Peripheral chromatin (close to the inner side of the nuclear membrane) b- Chromatin islands c- Nucleolus associated chromatin, it surround the nucleolus Functions of chromatin: 1- Stores genetic information. 2- Synthesis of protein and formation of RNA. Euchromatin Heterochromatin  3. Nucleolus LM: Nucleus contains single or double nucleoli that appear as rounded basophilic structure EM: Sponge like structure of dense areas together with light areas. Function: formation of ribosomal RNA 4. Nuclear sap It is a colloidal solution between nucleolus and chromatin. Formed of nucleoprotein, enzymes, sugar, Ca and phosphorous  Cytoplasm 1. Cytosol  Semifluid cytoplasmic matrix - This is the part of cytoplasm between the organelles and the inclusions. - It is a colloidal solution composed of soluble proteins, amino acids, carbohydrates, enzymes, minerals and ions. 2. Organelles 3. Inclusions  Living  Non-Living  Permanent  Temporary  Essential  Not essential  Active  Inert  Have vital  Metabolic functions products  2. cell organelles Definition: these are specialized intracellular living structures permanently present in the cell to perform specific functions. Classification: organelles are classified into membranous and non-membranous. Membranous organelles Non-membranous organelles 1. The cell membrane 1. Ribosomes 2. Mitochondria. 2 Cytoskeleton A- Microtubules 3. Endoplasmic reticulum(rER &sER) (Centriole& cilia) 4. Golgi apparatus. B- Filaments 5. Lysosomes. (thin and thick) 6. Secretory vesicles.  A. Membranous Organelles 1- The Cell Membrane (plasmalemma or plasma membrane) Definition: It is the outer limiting membrane of the cell. LM: Not visible with the light microscope because it is very thin. Its thickness 8- 10 nm. which is below the resolution power of LM, except, if cut oblique sections or when stained with PAS stain, which stain carbohydrates of the cell coat EM appearance: It is composed of an outer and inner dark layers, separated by a middle light layer (trilaminar appearance). Its thickness is 8- 10 nm. Such arrangement is called unit membrane. Covered by: cell coat (glycocalyx).  The molecular structure of cell membrane: It is formed of a lipid bilayer, proteins and carbohydrates. Lipid contents:(30%) It is formed of phospholipids and cholesterol molecules.  Protein content: (60%) a. Intrinsic or integral membrane proteins. b. Extrinsic or peripheral membrane proteins. The carbohydrate content (10%) - In the form of glycoprotein and glycolipids (Cell coat or Glycocalyx). - Which is responsible for: Cell recognition, protection and intercellular adhesion.  Cell coat Cell coat Cell coat protein Lipid  Functions of the cell membrane 1-It protects the cell. 2. Exchange of material between the cell and its environment by several ways: A. Passive diffusion: enter the material according the concentration gradient on either sides of the membrane e.g. water & gases. B. Active transport: this needs energy e.g. amino acids, and fatty acids. C. Selective transport: due to the presence of specific receptors to certain substances on the outer aspect of the cell membrane. D. Bulk transmit: through exocytosis and endocytosis. 1. Endocytosis engulf of material from the surrounding environment into the cytoplasm. - This includes phagocytosis, pinocytosis and receptor mediated endocytosis. a- Phagocytosis: the processes in which the membrane engulf solid particles within a vesicle forming phagosomes b- Pinocytosis: The cell engulfs a small amount of fluid forming pinocytic vesicle. c- receptor mediated endocytosis. 2. Exocytosis: It is the extrusion of the contents of a membranous vesicle from inside cell to the extra-cellular fluid.  Bulk Transport Endocytosis Exocytosis 1A 1A Phagocytosis Cell eating 1B 1B Pinocytosis Cell drinking Outside Inside the cell the cell