L11 Epithelia PDF

L11- EPITHELIA Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES At the end of this session the student would be able to: Define epithelial tissue and list its function Classify and describe epitheli...

L11- EPITHELIA Dr.Pugazhandhi Bakthavatchalam Assistant Professor of Anatomy and Physiology, AUACAS, American University of Antigua LEARNING OUTCOMES At the end of this session the student would be able to: Define epithelial tissue and list its function Classify and describe epithelial tissue and give examples of their distribution with regards to function 2-Sep-24 2  EPITHELIAL TISSUE DEFINITION: The thin protective layer of cells covering the body surfaces or lining the internal surfaces of the body cavities, tubes and hollow organs CHARACTERISTICS OF EPITHELIAL TISSUE: Cells are closely packed together Cells rest on a basement membrane Contains no capillaries, Nutrition is derived from the nearest capillaries Surface cells are destroyed by wear and tear , and are replaced by new cells produced by mitosis-phenomenon- turn over 2-Sep-24 3  education.med.nyu.edu 2-Sep-24 4  FUNCTIONS PROTECTION–mechanical abrasion, chemical injury, bacterial invasion ABSORPTION–nutrients and ions FILTRATION–allows passage of solutes with certain sizes SECRETION-secretion of enzymes, hormones or mucous secretion SENSORY RECEPTION–reception of external stimuli 2-Sep-24 5  BASEMENT MEMBRANE: a thin, delicate membrane of protein fibres and mucopolysaccharides separating an epithelium from underlying tissue education.med.nyu.edu 2-Sep-24 6 CLASSIFICATION OF EPITHELIUM Structurally and functionally divided into : Covering epithelium covers the body surfaces or lines the cavities of the body Glandular epithelium specialized cells that produce secretion 2-Sep-24 7  Covering epithelium Covers the body surfaces or lines the cavities of the body External surface epidermis of the skin Internal surface body cavities (peritoneal, pericardial and pleural cavities) tracts/tubes (digestive tract, respiratory tract, blood vessels) 2-Sep-24 8  CLASSIFICATION OF COVERING EPITHELIA Epithelial tissue Simple Compound Squamous Stratified Transitional Columnar Squamous Columnar Cuboidal Cuboidal Pseudostratified Keratinized Non -keratinized 2-Sep-24 9  CLASSIFICATION OF EPITHELIUM Based on Number of layers of cells Simple- one layer of cells. Each extends from basement membrane to the free surface Stratified- more than one layer. Pseudostratified- tissue appears to be stratified, but all cells contact basement membrane so it is in fact simple Based on Shape of cells Squamous- flat, scale-like Cuboidal- about equal in height and width Columnar- taller than wide 2-Sep-24 10  CLASSIFICATION OF EPITHELIUM 2-Sep-24 11 SIMPLE EPITHELIUM 4 types-  Simple Squamous  Simple Columnar  Simple Cuboidal  Pseudostratified 2-Sep-24 12  SIMPLE SQUAMOUS EPITHELIUM  Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm  Locations: kidney glomeruli, air sacs of lungs, lining of heart, blood vessels, lining of ventral body cavities  Functions: allows passage of materials by diffusion and filtration secretes lubricating substances in body cavities 2-Sep-24 13  SIMPLE CUBOIDAL EPITHELIUM Single layer of cube-like cells with rounded nuclei Locations: kidney tubules, ducts and secretory portions of small glands, ovary surface Functions: absorption Secretion 2-Sep-24 14  SIMPLE COLUMNAR EPITHELIUM Single layer of tall and column-like cells with oval nuclei Locations: intestines, gall bladder, uterine tube Functions: absorption secretion 2-Sep-24 15  PSEUDOSTRATIFIED EPITHELIUM Appear as if it consists of more than one layer but only a single layer is present with all cells resting on the basement membrane. Cells are tall and short with nuclei located at different levels Locations: respiratory tract, epididymis, ductus deferens Functions: absorption secretion 2-Sep-24 16 STRATIFIED EPITHELIUM  Stratified squamous epithelium 2 types : keratinised and non-keratinised Locations: keratinised : skin non-keratinised : all body openings (mouth, anus, vagina, oesophagus) Function: protection –withstand physical abrasion and resist chemical injury  Stratified squamous epithelium 2 types : keratinised and non-keratinised Non- keratinised- vagina Keratinised- skin  Stratified cuboidal epithelium Rare Locations: ducts of sweat glands, mammary glands and salivary glands Function: protection Stratified columnar epithelium Rare Locations: large ducts of exocrine organ, male urethra Functions: protection secretion  Transitional epithelium Special epithelium Number of cell layers is changeable according to the state of the organ Surface cells : large and binucleated Locations: lined most of the urinary tract such as urinary bladder Function: allows distension Prevents absorption of toxic substances of urine Specialization of epithelial cell surfaces Based on the function of the cells : Microvilli: Helps in absorption Cilia: hair-like structures present on cell surfaces, Motile Stereocilia: bundles of actin filaments, Non-motile Flagella: Movement  Specialization of epithelial cell surfaces Microvillus  finger-like projection  to increase the surface area of the cells  absorption  locations : intestine, kidney (PCT)  in LM, appear as striated border/brush border  REFERENCES Drake R.L., Gray’s Anatomy for Students, 2nd Edition, 2009, Churchill Livingstone Moore, Clinically Oriented Anatomy, 6th Edition, 2009, Lippincott Williams & Wilkins Standring, Gray’s Anatomy: The Anatomical Basis of Clinical Practice, 40thEdition, 2008 Ellis H, Human Sectional Anatomy: Atlas of body sections, CT and MRI images, 3rd Edition, 2007, CRC Press Johannes W Rohen, Color Atlas of Anatomy: A photographic study of the human body, 7th Edition, Lippincott Williams & Wilkins Sadler T W, Langman's Medical Embryology, 12th Edition, 2011, Lippincott Williams & Wilkins Kenneth S Saladin, Human Anatomy, 2nd Edition, 2008, McGraw-Hill Companies 02-Dec-22 25 02-Dec-22 26