Cytology PDF Introduction

CYTOLOGY 1 Chapter CYTOLOGY INTRODUCTION  Histology: (histo = tissue, ology = science) It is the science that deals with the MICROSCOPIC study of the normal tissues. Cells Tissue...

CYTOLOGY 1 Chapter CYTOLOGY INTRODUCTION  Histology: (histo = tissue, ology = science) It is the science that deals with the MICROSCOPIC study of the normal tissues. Cells Tissues Organs Systems Body Cytology Epithelial tissue Spleen Circulatory System Connective tissue Liver Lymphatic System Muscular tissue Kidney Respiratory system Nervous tissue Digestive system  Differences between LM & EM L.M. E.M. Source of illumination Day light/ electric light Beam of electrons Stains used Many stains so many 1 stain only (Osmic acid): colors shades of grey Magnification Power 1500 ↑ 100,000 Field Examined Many cells (tissue) 1 or 2 cells The most commonly used stain for L.M. examination is Hematoxylin and Eosin Stain (H&E)  Hematoxylin (H): basic stain « stains the acidic components with a blue color. “Basophilic”.  Eosin (E): acidic stain. « stains the basic components with a red color. “Acidophilic”. 2 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY CYTOLOGY  Definition of the cell:  The smallest part of the body that can exist independently  The basic structural and functional unit of the body. CELL CYTOPLASM NUCLEUS Matrix Organelles Inclusions Fluid component of: Lipids, Living Non-living proteins, carbohydrates, permanent Temporary minerals, ions and Essential Not essential water. Metabolically active Metabolically inert Have vital functions Membranous Non Membranous 1. Cell membrane 1. Ribosomes 2. Mitochondria 2. Centrioles 3. Endoplasmic Reticulum 4. Golgi Apparatus 5. Lysosomes HISTOLOGY with ZAHRA Stain 3 1 Chapter CYTOLOGY General scheme of the organelles:  Definition: Membranous or non-membranous organelle + general function.  Light microscope picture (LM): Seen or not seen + Stains.  Electronic microscope picture (EM): more details Electron dense  Electron lucent  Structure: EM ‫ مــع التركيــز ع ـلـى ال ـ‬LM + EM ‫هتكتــب‬Structure ‫لــو مفيــش عنــوان ـفـى الــدرس اســمه‬  Function: ‫الزم تكــون مرتــب الوظايــف ـفـي دماغــك كو يــس األهــم ثــم األهم‬  Clinical note (if present): ‫ ا كتــب الــدرس كامــا ور يــح دماغــك‬correlate the structure to the function : ‫لــو الســؤال بيقــول‬ The key to SUCCESS is to START before you are ready 4 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY (A) MEMBRANOUS ORGANELLES: 1 CELL MEMBRANE (PLASMA MEMBRANE - PLASMALEMMA - UNIT MEMBRANE - TRI-laminar MEMBRANE)  Definition: The outer limiting membrane of the cell and considered with cell protection and transport.  LM: « Difficult to be seen as it is very thin (7.5:10 nm) « seen when stained with silver (Ag) or PAS  EM: « Tow dark lines (electron-dense) Separated by light (electron lucent) one, (tri-laminar membrane). Molecular structure of the cell membrane: Lipid CHO Oligosaccharides On the outer surface only Phospholipids Cholesterol Each phospholipid Between molecule has: the tails and Glycoproteins Glycolipids ; Head (polar maintain - charged - the stability hydrophilic - of cell Protein 50:60% directed towards membrane aqueous solution) ; Tail (non-polar – not charged Peripheral proteins Integral proteins – hydrophobic - Loosely attached Contains trans-membrane directed away from Supporting function proteins which help transport aqueous solution). (Channels - Pumps - Receptors) HISTOLOGY with ZAHRA Stain 5 1 Chapter CYTOLOGY  Molecular structure of the cell membrane:- 1. lipid component: 1. Phospholipid molecules: 2 layers (lipid bilayer) and each molecule has: « hydrophilic polar head: charged and directed towards aqueous solution. « hydrophobic non-polar tail: non-charged and directed inwards away from the aqueous. 2. Cholesterol: « present among the hydrophobic tails. « restrict the movement of phospholipid molecules to stabilize the cell membrane 2. Protein component: 1. Peripheral proteins: (Extrinsic) « loosely attached to both surfaces of the cell membrane 2. Integral proteins: (Intrinsic) are present in the lipid bilayer in the form of: « Small molecules « Large molecules (Trans-membrane protein): extend across the membrane and act as pathways for ions and molecules (Trans-membrane transport). 3. Carbohydrate component: At the external surface, conjugated either with proteins or lipids (glycoproteins and glycolipids), forming the cell coat (Glycocalyx). 6 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY Transport across the cell membrane: Passive transport Active Vesicular Without energy (no ATP) Needs energy With concentration (ATP) gradient Against Endocytosis Exocytosis concentration gradient Facilitated Simple Cell products diffusion diffusion Na+/K+ pump Needs help Water & Residual bodies (carrier or dissolved channel) gases Glucose Phagocytosis Pinocytosis Receptor mediated endocytosis The cell engulfs Binding of the hormone to its receptor the cell engulfs solid particles as (present in pits) to form coated vesicles fluids forming bacteria forming The cytoplasmic surface of the pit is pinocytic vesicles. phagosomes coated by clathrin protein HISTOLOGY with ZAHRA Stain 7 1 Chapter CYTOLOGY 1) Passive transport: 1. Passive diffusion: movement of solute from a high concentration to a lower concentration. 2. Facilitated diffusion: They need carrier and pass through integral protein (with concentration gradient) e.g. glucose. 2) Active transport: « against concentration gradient, « needs energy e.g. Na+/K+ pump 3) Vesicular transport: 1. Endocytosis: the uptake of materials across the cell membrane into the cytoplasm of the cell. Receptor-mediated Phagocytosis Pinocytosis endocytosis (cell eating): (cell drinking): (selective transport): the process of engulfing the process of 1. Specific molecules bind solid particles by the cell engulfing fluid to their receptors that membrane to form an droplets by the cell accumulate at the plasma internal phagosome membrane to form membrane (phagocytic vesicle) pinocytotic vesicles. 2. Gradual Invagination of the plasma membrane forms coated pits that become surrounded on the cytoplasmic side by protein molecules called clathrin. 3. The coated pit invaginates and pinches off, forming a coated vesicle containing the specific molecules and their receptors 8 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY 2. Exocytosis: a process for moving substances from the cytoplasm of the cell to the outside. Functions of the cell coat (Glycocalyx): it includes receptors that participate in important interactions such as:- 1. Cell adhesion: The glycocalyx helps in attachment of some cells to each other & to extracellular matrix components, 2. Cell recognition. 3. Cell immunity: It binds antigens to the cell surface Cell membrane modification: 1. Microvilli (increase the surface area for absorption) 2. Cilia (push particles at one direction) 3. Flagella (allow sperm movement) 4. Stereocilia (long microvilli) HISTOLOGY with ZAHRA Stain 9 1 Chapter CYTOLOGY 2 MITOCHONDRIA (Mitos = thread, chondros = granule)  Definition: Membranous organelles, responsible for respiration and energy production. They are the power-house of the cell.  Number : « More numerous in cells that have a high energy requirement. e.g. muscle cells, liver, heart and sperm cells  LM: « acidophilic structures. « Appear as rods, granules or filamentous, when stained with: ) Iron HX (dark blue) ) Janus green (green)  EM: oval or rounded vesicles surrounded by 2 membranes. - The outer membrane: is smooth. - The inner membrane: forms incomplete shelves called cristae which increase its surface area enhancing its ability to produce ATP. - The space in-between is called inter-membranous space - Mitochondrial Matrix: composed of: 9 enzymes that synthesize ATP via (Krebs’s cycle) 9 DNA & RNA. 9 Matrix granules rich in Ca+2 (regulate the activity of some mitochondrial enzymes.  Functions: 1. Cell respiration & production of ATP: ATP is the primary source of cell energy. That’s why they are called the power house of the cell. 2) They can form proteins for themselves and can divide (self-replication): as they have their own DNA and RNA. 10 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY 3 ENDOPLASMIC RETICULUM a system of interconnected membranous tubules and vesicles forming a reticulum in the cytoplasm Rough Smooth Membranous organelle considered with Membranous organelle considered Def. protein synth with lipid & steroid synth. protein forming cells e.g. plasma cell & steroid forming cells, Site fibroblast & chondroblast e.g. Endocrine glands. « In H&E stained sections, rER « when abundant causes LM appears basophilic due to the cytoplasmic acidophilia presence of ribosomes (rRNA). « Parallel, flattened cisternae studded « branching and anastomosing with ribosomes on its outer surface. tubules or vesicles « No ribosomes on outer surface EM 1. Protein synthesis by attached 1. Lipid synthesis (e.g. ribosomes. Phospholipid & cholesterol 2. Initial Segregation of formed 2. Steroid hormones synth. as proteins. cortisone & testosterone. 3. Initial Glycosylation. 3. Breakdown of glycogen to Function 4. Packing of formed proteins in glucose in liver cells. membranous vesicles (transfer 4. Detoxification of drugs, vesicles) to be delivered to Golgi hormones and alcohol in apparatus. liver cells. 5. Protection of cytoplasm from 5. Calcium ions (Ca++) hydrolytic enzymes formed inside release (pump) in muscle it. contraction. 6. intracellular transport 6. intracellular Transport HISTOLOGY with ZAHRA Stain 11 1 Chapter CYTOLOGY 4 GOLGI APPARATUS  Definition: Membranous organelles, that is well developed in secretory cells. It is considered the secretory apparatus of the cell.  LM: 1. in H & E stained sections:  it does not appear.  It can be seen as an unstained area (negative Golgi image) in protein secreting cells which have deeply basophilic cytoplasm 2. In Silver (Ag) stained sections: as brown network of fibrils either:  Apical: between nucleus and secretory pole in secretory cells.  Perinuclear: surrounds the nucleus in nerve cells.  EM: 1. Saccules: Several membrane-bound flattened. Slightly curved, with flat centers and dilated ends. Interconnected and arranged above each other forming stacks. Each stack has 2 faces ; Entry (convex , Cis) Face: It receives transfer vesicles from rER. ; Exit (Trans) Face: (concave) from which secretory vesicles arise.. 12 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY Fate of Secretory vesicles: Remain inside the cell in the form of lysosomes. Release their content outside the cell by exocytosis.  Functions: 1. Modification of proteins delivered from rER by addition of carbohydrates and sulfates 2. Concentration and packaging of these large molecules for cell secretion (by exocytosis) or use within the cell. 3. Synthesis of lysosomes. 4. Renewal and maintenance of cell membrane HISTOLOGY with ZAHRA Stain 13 1 Chapter CYTOLOGY 5 LYSOSOMES  Definition: « Membrane-bound organelles (vesicles) that function to digest nutrients, foreign and dead materials  Origin: « Lysosomes contain hydrolytic enzymes (e.g acid phosphatase) which are synthesized in the rER and then transferred to the Golgi apparatus for further concentration and packing. « Newly released Lysosomes from Golgi that are not involved in any of the digestive processes are called primary lysosomos. « Primary lysosomes when involved in digestive processes (2ry lysosomes).  Number: Abundant in phagocytic cells (macrophages).  LM: by Histochemical stains that detect acid phosphatase enzyme..  EM: They are classified into: lysosomes Primary lysosomes Secondary lysosomes Membranous vesicles Membranous vesicles Doesn’t enter into digestive events enter into digestive events homogeneous heterogeneous Hetero Lysosome Multivesicular Bodies Auto Lysosome Residual Bodies 1ry lysosome fuses 1ry lysosome fuses with 1ry lysosome fuses (Undigested with a phagosome a pinocytic vesicle with old organelles material) exocytosis Remain in the cell as lipofuscin lipofuscin ↑ with age specially in non-dividing cells pigment 14 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY  Functions of Lysosomes: 1. Digestion of materials ingested by endocytosis (nutrients, bacteria and viruses). 2. Breakdown of old cellular organelles. 3. Release thyroid hormone from thyroglobulin stored in thyroid follicles. 4. Fertilization by helping the sperm to penetrate the ovum. 5. Post-mortem autolysis by digestion of the whole cell after death. HISTOLOGY with ZAHRA Stain 15 1 Chapter CYTOLOGY (B) NON-MEMBRANOUS ORGANELLES: 1 RIBOSOMES  Definition: Non-membranous electron dense particles concerned with protein synthesis.  Number: Abundant in protein synthesizing cells.  LM: « When abundant they cause cytoplasmic basophilia.  EM: « Small electron-dense granules. « each is formed of 2 subunits, small & large. « The large subunit contains a groove in its center which contains the polypeptide chain. « They may be: 9 Free: in the cytoplasm. 9 Attached: to rER by the large subunits.  Functions: Protein synthesis. « Free ribosomes form proteins used by the cell. « Attached ribosomes form proteins secreted by the cells. 16 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY 2 CENTRIOLES  Definition: « non membranous Cylindrical structures composed of highly organized MT. [MTs are fine tubules formed of tubulin protein and they determine the shape of the cells]  LM: « Demonstrated with iron hematoxylin stain as two dark bodies near the nucleus.  EM: « 2 cylindrical structures, perpendicular to each other « The wall of each cylinder is formed of: « 9 bundles of MT, each bundle is formed of 3 MTs (triplets), So the wall of the centriole is formed of 9 x 3 = 27 MTs.  Functions: 1. During cell division, the centrioles duplicate. Each pair moves to one pole of the cell and become organizing centers for MTs of the mitotic spindle. 2. Share in the formation of cilia and flagella. HISTOLOGY with ZAHRA Stain 17 1 Chapter CYTOLOGY NUCLEUS:  Definition: « The largest and most distinct component of all cells « not present in RBCs and platelets (not true cells) « Nuclei may have different numbers, shapes, sizes and locations  LM: large, basophilic structure that usually occupies the widest part of the cell..  Structure (components) of the nucleus: 1. Nuclear membrane (Envelope). 2. Chromatin material. 3. Nucleolus. 4. Nuclear sap. 1- Nuclear Membrane (Nuclear Envelope)  L.M: a single basophilic line  E.M: « It consists of two parallel membranes separated by a perinuclear space. « The 2 membranes fuse at intervals forming nuclear pores. Outer nuclear membrane: Faces the cytoplasm and is continuous with the rER at certain sites, this membrane is studded with ribosomes. Inner nuclear membrane: chromatin threads (peripheral chromatin). Nuclear pore complex : permit the passage of certain materials in both directions between the nucleus and cytoplasm 18 HISTOLOGY with ZAHRA Stain  1 Chapter CYTOLOGY 2- Chromatin  Definition: « It is the substance of genetic materials composed of DNA and proteins, it « condenses to form chromosomes during cell division  Chromatin Is found in two forms: Euchromatin Heterochromatin nature « Extended (uncoiled) active « Condensed (coiled) inactive « Present in open face nuclei « Present in closed face nuclei « Predominates in « Predominates in metabolically metabolically active inactive cells cells involved in protein synthesis. LM « Pale basophilic « Dark basophilic EM « Electron lucent « Electron dense Sites of heterochromatin: a) Peripheral Chromatin: attached to the inner nuclear membrane. b) Chromatin islands: scattered throughout the nuclear sap. c) Nucleolus-associated chromatin: around the nucleolus. HISTOLOGY with ZAHRA Stain 19 1 Chapter CYTOLOGY 3- Nucleolus  L.M: « it is a spherical, deeply basophilic mass in the nuclei of cells. « It is active in protein synthesis. « It is basophilic due to the presence of RNA and DNA.  E.M: « It has dark and light areas. DARK AREAS LIGHT AREAS formed of formed of « pars amorpha (Nucleolar organizer): DNA which the nucleolar sap carries the genes encoding rRNA. « Pars fibrosa (fibrillar component): Small fibrils of newly formed rRNA. « Pars granulosa (granular component): Large granules of mature rRNA 4- Nuclear Sap  It is the colloidal solution found between the chromatin and the nucleolus and contains enzymes and lipoproteins.  Functions: 1. Carries the genetic information. 2. Controls the cell functions. 3. Forms RNA for protein synthesis. 4. Important for cell division. 20 HISTOLOGY with ZAHRA Stain