Histology I: Microscopic Structure of Cells, Tissues & Organs - PDF

DVM. MVSc. Marwan Taher Abofila  General (Basic) Histology Introduction Cytology Cytogenetics Tissues (Epithelial Tissue) Lectures...

DVM. MVSc. Marwan Taher Abofila  General (Basic) Histology Introduction Cytology Cytogenetics Tissues (Epithelial Tissue) Lectures Connective Tissue Cartilage Bone Blood Muscular Tissue Nervous Tissue Special (Systematic) Histology Cardiovascular System Immune Lymphatic System Integumentary System DVM. MVSc. Marwan Taher Abofila  Histology is Latin term (Histo = Tissue + Ology = Science).  Histology: is the science that deals with microscopic study of the components of (human & animals) which are formed by organization of cells & extracellular material into tissues, organs & different body systems.  Histology involve all aspects of tissue biology, with the focus on how the structure and arrangement of cells perform the specific functions of each organ in an optimal manner.  The main Purposes for study histology: The main objective of a histology course: is to understand the microanatomy of cells, tissues and organs and to correlate morphology (structure & Shape) with function. 1. For learning purposes: to identify the tissue & able to recognize different tissue types. 2. For diagnosis purposes: to differentiate between normal and abnormal tissue. 3. For research purposes: to increase knowledge of body structure lead to give rises to scientific discoveries.. 4. For Technical purposes: to make advances & improve in technology related to biology and medicine.  Q: Why Histology is Important?  A: it is important because it is one of the tools in the medical toolbox for diagnosis of diseases. A great many diseases reveal themselves at the cellular & tissues level; many cancer, bone & other connective tissue diseases, vascular diseases, liver diseases, kidney disease & others can be definitively diagnosed using cytological & histological techniques.  Principles of Histology Theory:-  All living organisms consist of one or more cells.  The cell is the smallest living structural & Functional unit of organism.  All cells arise from preexisting cells by division except Fertilized ovum (Zygote) arise by union of male & female gametes.  The cells are bound together to form tissue. The tissue are combined to form organ. Several organs having interrelated function constitute the different systems of the body.  Cells: is the main structural & functional unit in the body. It’s the smallest unit of living tissues that can exist independently. The minute size of cells (4-150 µm) make their study needs magnifications by the microscope.  Cell types: 1) 1st Based on their differentiation:  Undifferentiated (Stem) Cells  Embryonic stem cells Zygote (Fertilized ova) Totipotential stem cells  Non Embryonic stem cells Germline Stem Cells. Somatic Stem Cells Fetal Stem Cells  Progenitor Cells  Differentiated Cells  Germ Cells (sperm & ova)  Somatic Cells (functional cells such as hepatocyte, RBC & etc.) Cell types: 2) Based on their structures: I. Prokaryotes: such as Bacteria  Usually small & have no true nucleus.  No nuclear membrane & internal membrane.  No organelles in the cytoplasm except ribosomes.  genetic material in the form of single continuous strands forming coils or loops. II. Eukaryotes: such as animal cells  Usually large & have true nucleus.  Has internal & nuclear membranes.  Contains specialized organelles in the cytoplasm.  Genetic material organized into multiple chromosomes.  Cells Produces Extracellular matrix (ECM) that consists of many kinds of molecules, which usually highly organized to form complex structures, such as collagen fibrils and basement membranes.  Tissues:  It is a group of cells with similar structure that specialized to perform related functions which usually has a common embryonic origin. The tissue components includes: cells & extracellular matrix.  Tissue classification into four basic tissue types based on: 1. The cell types, structures & functions. 2. The composition & characteristic of extracellular matrix. 3. space occupied by cells versus matrix.  Types of Tissues:- 1) Epithelial Tissue: Covers body surfaces, lines cavities & formed the most body glands. 2) Connective Tissue: Binds, protects, support body parts, fill spaces & store fat. 3) Nervous Tissue: Excitability, conductivity, transmit information, detect internal & external changes and aid in the maintain homeostatic function. 4) Muscular Tissue: Movement by contractile & generates physical force needed for body or part of body to motion.  Organs: two or more tissues are combined to give larger functional units, which are called organs such as Kidney, liver, spleen & etc.  Systems: several organs having interrelated functions collect to form systems such as digestive system, urinary system & etc.  Types of Microscopes: The basic types of microscope is the light microscope. Other types of microscopes are modification of the light microscope.  The light microscope (LM) In this microscope, we use the day light or electrical light as source of illumination. The light is focused on the lens of the condenser by a mirror or electric light.  The light microscope is composed of: 1) Frame (mechanical) part. 2) Magnification (optical) system. 3) Illumination system. 1) The frame part of LM: Support the different part of the microscope; it consists of base, arm, stage with a central hole for the light to pass through & a body tube carrying the optical system. 2) Illumination system consist of: light source (day light or electric light), condenser & iris diaphragm to regular the amount of light. 3) The Magnification system of LM it consists of: The ocular lens (eye pieces): which are near the eyes. The magnifying power may be 5, 10, & 15. The objective lenses: which are near the object, there are 4 objectives power as the follow: 3 or 5 (low power), 10 (medium power), 20 or 40 (high power),100 (oil immersion objective). Condenser lens: under the stage, used to concentrate & project the light beam on the object.  The light microscope (LM)  Used for examination of histological specimens.  Their usefulness depends on their magnification power & resolution power.  Magnification power = the degree of enlargement.  Resolution power=the least distance between 2 points that can be seen as 2 and not as one point (ability to see details). 1. Resolution power of naked eyes = 0.2mm 2. Resolution power of light microscope = 0.2μm. 3. Resolution power of electron microscope = 0.2nm  Notes Book:  The histology section magnification = magnification power for ocular lens X magnification power of objective lens.  Image is received directly on retina or by camera.  So the maximum magnification power of the light microscope = 100(objective) × 15(eye)= 1500 times.  Units of measurements: 1 centimeter (cm) = 10 millimeters (mm). 1 millimeters (mm) = 1000 micrometers (μm). 1 micrometers (μm) = 1000 nanometer (nm). 1 nanometer (nm) = 10 angstrom (Å).  The electron Microscope (EM)  The detail morphology revealed by EM may be called fine submicroscopic structures (ultrastructure).  There are two types of EM: transmission electron microscope & scanning electron microscope.  Thank you dear students for paying attention