Veterinary Medicine Histology Lecture Notes PDF

# Welcome To Faculty of Veterinary Medicine, Mansoura University ## Faculty of Veterinary Medicine, Department of Cytology and Histology, General Program-1st Level Students ## Welcome To Department of Cytology and Histology # HISTOLOGY * Histology means the science of the tissues. + What then...

# Welcome To Faculty of Veterinary Medicine, Mansoura University ## Faculty of Veterinary Medicine, Department of Cytology and Histology, General Program-1st Level Students ## Welcome To Department of Cytology and Histology # HISTOLOGY * Histology means the science of the tissues. + What then is a tissue? * Microscopic observations confirmed that the body is made up of different tissues. + Tissues are made of cells # HISTOLOGY * General Histology (First semester) * Special Histology (Second semester) # GENERAL HISTOLOGY * Cytology * Body tissues # Body Tissues * Epithelial * Connective tissue * Muscular * Nervous # CYTOLOGY * Cytology is the science which deals with the study of the cells. # THE CELL * The cell is the smallest structural and functional units of the living organism (human, animals or plants). # THE CELL The cell consists of: * A mass of protoplasm * Nucleus * Cytoplasm # Cytoplasm * The cytoplasm is the part of protoplasm. * Located around the nucleus. * Designed to perform synthetic and metabolic activities. # Cytoplasm * The cytoplasm consists of structure's matrix (cytosol) * Suspended into it several different kinds of * Cytoplasmic organelles * Inclusions * Cytoskeleton # Cytoplasmic matrix * Non-organelle component * Occupying the intracellular spaces between organelles and inclusions * It contains many soluble proteins, lipids, carbohydrates and small ions. # Cytoplasmic organelles * Permanent * Living * Cytoplasmic structures * Perform specific or vital functions # Cytoplasmic organelles * Two types of cytoplasmic organelles are recognized: * Membranous Organelles * Non-membranous Organelles # Membranous organelles * The membranous organelles are: * Cytoplasmic organelles * Possess a bounding membrane of their own # Membranous organelles * They include: * Cell membrane * Mitochondria * Endoplasmic reticulum * Golgi apparatus * Lysosomes * Peroxisomes # Non Membranous organelles * They are cytoplasmic organelles that possess no bounding membrane of their own. * They include: * Ribosomes * Centrioles # Organelles * Definition * Light Microscope (L.M.) * Electron Microscope (E.M.) * Functions # Cell membrane * Definition: * The cell membrane (plasmalemma or plasmamembrane) * Outer membrane of the cell * Acts as a barrier between its internal and external environment. # Cell membrane * With light microscope (LM): * It is too thin (8-10 nm) to be seen # The Cell Boundary * Condensation of cytoplasm on the inner aspect of the cell membrane * Condensation of the stain (such as silver or PAS) on the carbohydrate-rich coat. * Obliquity of the sections # Cell membrane * With electron microscope (EM): * It appears as a trilaminar structure. * Consisting of outer and inner electron-dense layers separated by an intermediate electron-lucent layer. # Unit Membrane The image shows a diagram of a cell membrane. The unit membrane is labelled with an arrow. # The Molecular Structure of the Cell Membrane * = Fluid mosaic model * Phospholipids * Proteins * Carbohydrates # Phospholipids * The Phospholipids molecules form a central bimolecular layer. * Each molecule is formed of two ends. * polar or hydrophilic (has affinity with water) end. * non-polar or hydrophobic (has no affinity with water) tail. # Phospholipids * Hydrophilic ends are directed outward. * Hydrophobic tails are directed inward toward the center of the membrane. # Proteins * Second major constituent of the cell membrane. * Arranged as globules moving freely within the lipid layer. * Two types of protein globules are recognized; intrinsic or integral protein and extrinsic or peripheral proteins # Proteins * Intrinsic protein Firmly attached to the lipid bilayer. * Some of them extend throughout the entire thickness of the membrane and constitute transmembrane channels. * Extrinsic protein Only partially embedded to either aspects of the membrane. # Carbohydrates * Conjugated with the protein (glycoprotein) and lipid (glycolipid) molecules of the cell membrane. * Project from the outer surface of the cell membrane as cell coat or glycocalyx. # Functions of the cell membrane * Passive Diffusion * Facilitated Diffusion * Active Transport * Selective transport * Endocytosis and exocytosis # Passive. diffusion * Entrance of small molecules. * Depends on a concentration gradient across the plasmalemma. * Diffusion of lipid-soluble substances, oxygen, CO2, water and small ions. # Facilitated diffusion * Depends on a concentration gradient across the plasma lemma. * Transport of large water-soluble molecules such as glucose and amino acids. * Requires carriers # Active transport * Requires the utilization of energy (ATP). * Sodium-potassium pump (sodium out and potassium in). # Selective transport * Depends on the presence of receptors to pick up specific molecule. * Example, hormones. # Endocytosis * Phagocytosis = engulfment of solid particles. * Pinocytosis = minute droplets of fluid. * The engulfed material e.g., bacteria are surrounded by pseudopodia. * After completely surrounded, the plasma membrane fuses forming a vesicle (phagosome or endocytotic vesicle). * Phagosome detaches and float freely. # Endocytosis The image shows a diagram of an endocytosis process. The left side of the diagram shows phagocytosis where a cell consumes a solid particle. The right side of the diagram shows pinocytosis where a cell consumes drops of fluid. # Exocytosis * Some membranous vesicles fuse with the cell membrane. * Release their contents outside the cells. * Occurs in many secretory processes # Exocytosis The image shows a diagram of exocytosis. A vesicle containing proteins fuses with the cell membrane, releasing the proteins into the extracellular environment. # Other Functions of the cell membrane * Transmission of nerve impulses in muscle and nerve cells. * Myelin sheath formation (Schwan cell around peripheral nerves). * Share in the formation of microvilli, cilia, flagella and cell junctions. # Functions of the cell Coat * A. Mechanical and chemical protection. * B. Induction of immunological (antigen-antibody) response. * C. Site for binding of hormones. * D. Formation of intercellular adhesions. * E. Formation of the basement membrane. * F.Cell recognition. # Mitochondria * Mitochondria are membranous organelles. * Involved primarily in cell respiration and energy production * With LM: * Granules * Rod-like * Thread-like # Mitochondria Number * Highly variable * According to the energy requirements of the cells. * Liver cells (active cells) contain as many as 1000 mitochondria. * Small lymphocytes (inactive cells) contain very few. # Mitochondria Location * They are motile organelles. * Localize at intracellular sites of high-energy requirements such as basal regions of ion-transporting cells. # Mitochondria with EM * Ovoid or elongated structures bounded by two membranes # Mitochondria with EM * The inner membrane is covered with tiny spherical projections about 9 µm in diameter supported at narrow stalks. * These are called inner membrane spheres or elementary particles The image shows a diagram of a mitochondrion viewed with an electron microscope. It clearly shows an outer membrane and an inner membrane. The inner membrane has several invaginations called cristae. In the center, a matrix is shown which is bounded by the inner membrane. # Mitochondria Matrix * Many electron-dense granules called matrix granules that are the sites for Ca++ ions storage. * DNA and RNA * Mitochondrial ability to grow, divide and synthesis some of their proteins. # Mitochondria are semiautonomous * Motile * Divide by binary fission * Contain DNA and RNA * Synthesis protein # Binary Fission The image shows a series of diagrams of binary fission. The first diagram shows a mitochondrion with two copies of its DNA molecule. The second diagram shows the mitochondrion getting elongated. The third diagram shows a complete separation of the mitochondrion. # Mitochondria Functions * They house the chains of enzymes * that catalyze reactions * that provide the cells with most of its ATP (adenosine triphosphate). # Mitochondria Functions * On demands, the ATP yields its high-energy phosphate bond to another molecule and become transformed into ADP. * Within the mitochondrial matrix, ADP is transformed again into ATP. # Mitochondria Functions * These processes take place within: * a. Mitochondrial matrix * b. Inner mitochondrial membranes. * The matrix contains enzymes of Krebs cycle and fatty acid oxidation. # Mitochondria Functions * The inner membrane contains the cytochromes and the enzymes involved in ATP production * Participate in regulation of calcium level within the cytosol. # References * Netter's Essential Histology, Ovalle, 2013 * Functional Histology, Kerr, 2009 * Wheater's Review of Histology & Basic Pathology, Baldwin, 2009 * Color Textbook of Histology 3rd Ed, Hiaat, 2014. * Internet source