Cytology - First Lecture - PDF

First lecture cytology by Dr Rahma Kamal El Dine  Introduction Histology: science that deals with the microscopic study of normal tissues. Correlate structure with function. Tissues (numerous cells) are aggregated to form organs which aggregate to form different systems in living body. ...

First lecture cytology by Dr Rahma Kamal El Dine  Introduction Histology: science that deals with the microscopic study of normal tissues. Correlate structure with function. Tissues (numerous cells) are aggregated to form organs which aggregate to form different systems in living body. Albino rat Fixative Paraffin technique Commonly used microscopic types: Light Electron microscope Microscope Comparison between Light & electron microscopes Light microscope Electron microscope (LM) (EM) Source of Day or electric Beam of illumination light electron Stain used Many stain Only osmic acid with many with grey color colors Magnification Up to 1500 Up to 100,000 power times Field Many cells 1 or 2 cells examined Histology Department/ Faculty of Medicine/ Cairo University Histology Department/ Faculty of Medicine/ Cairo University Common Histological stain used for LM: Hematoxylin and Eosin stain (H&E) Hematoxylin: basic (blue color), stain acidic components of cell (basophilic) as nucleus (rich in DNA & RNA) & may cytoplasm Eosin: acidic (red color), stain basic components of cell (acidophilic) as cytoplasm  Cytology Science that deal with the microscopic study of cells. Cells are the structural & functional unit of living body. Cells have different shapes, sizes & functions. Cell is made of: 1.Nucleus 2. Cytoplasm  Cytoplasm contains: -matrix: viscous solution of proteins, carbohydrates, lipids & enzymes. -Inclusions: temporary& not essential for cell vitality as lipid, glycogen & pigment. -Organelles: permanent & essential for cell vital functions of cell as respiration, digestion,.…..  Non-membranous organelles: They are not surrounded by membranes, include: Ribosomes (rRNA): Non membranous cytoplasmic organelles. Formed in the nucleolus, then pass to the cytoplasm. They can be stained by H&E causing basophilia of cytoplasm. Ribosomes They may scattered in the cytoplasm (so called free ribosomes) or ribosomes may attached to surface of rough endoplasmic reticulum. Function: ribosomes act as factories of protein synthesis: Free ribosomes form proteins used within cell as glycolytic enzymes. Ribosomes  Attached ribosomes form proteins secreted by cells as hormones  Cytoskeleton: It is a complex network of protein molecules forms skeleton of cell. It include the microtubules, thin filaments and intermediate filaments.  Membranous organelles Cell membrane (plasma membrane) Mitochondria Endoplasmic reticulum Golgi apparatus Lysosomes.  Membranous Organelles 1. Cell Membrane: Transport Light microscope (LM): difficult to be seen. Stained by silver or PAS Electron microscope (EM): Trilamellar membrane (2 dark layers &1 pale in-between) Molecular Biology of cell membrane: 1- Lipid component: consists of: a) Phospholipid molecules: arranged in 2 layers (bilayer), each molecule has: Polar hydrophilic head: directed outwards, they are found on outer and inner surfaces of cell membrane. Non-polar hydrophobic tail: directed inwards, to centre of cell membrane. b) Cholesterol molecules: incorporate in- between hydrophobic phospholipid 2- Proteins: a) Intrinsic (Integral): Small or large (trans-membrane) protein molecules that traverse the lipid bilayer. b) Peripheral protein: loosely attached molecules, on both membrane surfaces. 3-Carbohydrates: Glycoproteins & glycolipids forming cellcoat (glycocalyx) on external surface of cell membrane, has specific receptors 5 Functions: 1- Passive transport: The particles move across cell membrane according to concentration gradient (from the area of higher to the area of lower concentration). This process is not require energy It includes: Simple diffusion: pass through phospholipid bilayer such as ion & gas  Facilitated diffusion: Large molecules, that do not dissolve in lipid bilayer of the cell membrane such as amino acids, glucose, transport via large integral protein as a carrier. 2- Active transport: The movement of molecules across a cell membrane from a region of their lower concentration to a region of their higher concentration (against the concentration gradient). This process require energy such as Na+ K+ pumps.  3.Bulk transport Active process to transport large particles, it includes: – Endocytosis: Phagocytosis (cell eating): Cell membrane extends pseudopodia to fuse around solid particle. This part of membrane separate with particle forming (phagosome) & passes to cytoplasm. Pinocytosis (cell drinking): Fluid droplets enter the cell to form pinocytic vesicles.  – Exocytosis: Type of bulk transport by which the cell extrudes its waste products. The secretary vesicles inside the cell fuse with the cell membrane & its content is discharged out of the cell.. 4- Functions of cell coat: -Selective permeability by their receptors -Cell protection, adhesion & recognition 5- Cell membrane modifications: Microvilli (increase surface area), cilia (move particles in one direction) 6- Conduction of excitation wave: For sensation in nerve & contraction in muscle In Alzheimer's disease, altercations in the phospholipid component of cell membranes disrupting the function of brain cells.