Anatomy PHL 212 Dr. Dina A. A. Hassan Associate Professor College of Pharmacy (Female Section) Sattam Bin Abdulaziz University Al kharj / Kingdom of Saudi Arabia Email :- da.hassan@psau.edu.sa 1
Anatomy PHL 212 2
OBJECTIVES Upon completion of this lecture, students should be able to: Gain knowledge regarding different types of epithelium and their functions. Have a basic understanding of the microscopic structure of various types of epithelial tissue. Gain knowledge regarding the normal locations of various epithelial tissue types. Explain the relations between the different types of epithelial tissue of the human body.
TISSUE
Tissue Groups of closely associated cells that are similar in structure and function are called tissues Four primary tissues types: Epithelial (covering) tissue Connective(support) tissue Musclular (movement)tissue Nervous (control) tissue
Chapter Outline Epithelial Tissue Connective Tissue Nervous Tissue Muscle Tissue
SECTION I EPITHELIAL TISSUE
Epithelial Tissue Epithelial tissue is a sheet of cells with little extracellular material lying in the space between them. Epithelial tissue covers all the inner and outer surfaces of the body including; Skin Viscera of the digestive and respiratory system The lining of body cavities Linings of blood vessels Most glandular tissue
Special Characteristics of Epithelium
Special Characteristics of Epithelium 1) Cellularity : formed of sheets of cells 2) Polarity: All epithelia exhibit polarity where the cells near the apical surface differ from those at the basal surface Apical surfaces can be smooth, most have microvilli, and some have cilia The basal surface of epithelium is called the basal lamina, which acts as a selective filter that determines which molecules are allowed to enter the epithelium Deep to the basal lamina is a layer of reticular fibers belonging to the underlying connective tissue Together the reticular fibers and the basal lamina form the basement membrane
Special Characteristics of Epithelium 3) Supported by connective tissue All epithelial tissue sheets rest upon and are supported by connective tissue 4) Specialized connection (cell junctions) between epithelial cells. 5) Innervated but avascular Epithelial tissues are supplied with nerve cells Epithelial tissues contain no blood vessels Epithelial tissue receive nutrients by substances diffusing from blood vessels in the underlying connective tissue layers 6)Regeneration Epithelial cells have a high regenerative capacity
Types of Epithelial Tissue (epithelium) Simple epithelium: formed of one layer Stratified epithelium: formed of more than one layer
Simple Epithelia cells are arranged in one layer that have the same shape There are four major classes of simple epithelia 1- Simple squamous epithelium has flat epithelium. eg: line blood vessels (endothelium) or serous membrane ( mesothelium) Function: Thin and permeable for easy filtration or diffusion. 2- Simple cuboidal epithelium has cubical epithelium eg: thyroid gland. Important functions are secretion and absorption 3-Simple columnar epithelium has tall shaped epithelium e.g. Unciliated in the digestive tract Ciliated in the respiratory passages functions are secretion and absorption 4- Pseudostratified columnar epithelium : Single layer of cells of differing heights BUT all of them rest on the basement membrane. eg. trachea.
Simple Squamous Epithelium Simple Cuboidal Epithelium
Types of Simple Columnar Epithelium Ciliated simple columnar epithelium in the respiratory passages Non ciliated simple columnar epithelium in the stomach mucosa
Pseudostratified Epithelium Pseudostratified columnar ciliated epithelium lining the human trachea
Stratified Epithelia cells are arranged in more than one layer According to the shape of the top epithelial layer, there are also four major classes of stratified epithelia Stratified squamous epithelium Stratified cuboidal epithelium Stratified columnar epithelium Transitional epithelium (a modified stratified squamous epithelium)
Stratified Squamous Epithelium composed of several cell layers Surface cells are flattened (squamous) Types: keratinized epithelium has surface layer of dead cells (keratin ) e.g.: skin Non keratinized epithelium lacks the layer of dead cells.e.g. esophagus
Stratified Squamous Epithelium Stratified squamous epithelium lining the esophagus Keratinized stratified squamous epithelium lining the skin
Stratified Cuboidal Epithelium Stratified cuboidal forming a duct of parotid gland Stratified Columnar Epithelium Stratified columnar epithelium lining the male urethra
Transitional Epithelium The cells vary in shape depending on the degree of distension of the organ eg. Urinary bladder
Epithelial Surface Features The apical, lateral and basal cell surfaces of epithelia have special features Apical surfaces either smooth, have microvilli or have cilia Lateral surfaces have cell junctions Basal surface has a basal lamina
Microvilli Microvilli are fingerlike extension of the plasma membrane of apical epithelial cells Microvilli maximize the surface area across which small molecules enter or leave cells. Site & function: In the epithelial cells of the small intestine to increase surface area for absorption.
Cilia & Flagellum a. Cilia are hair-like, highly motile extensions of the apical surface of epithelia cells Function: The cilia on an epithelium bend and move in coordinated waves. The waves push mucus or ovum over its surface. Site : Respiratory tract, digestive tract and ovary. Mucus Mucous is a viscid secretion that can trap and remove foreign particles and bacteria from internal body surfaces through movement of cilia. b. Flagellum Long isolated cilium Only found as sperm in human (site)
Cells junctions Cells junctions are characteristic of epithelia cells. Types of cell junction: 1 ) Tight junctions 2) Adherens junctions 3) Desmosomes 4) Gap junctions
Cell Junctions PHL 212 Tight junctions: So close It prevents molecules from passing through epithelial cells Adherens junctions: Transmembrane linker proteins Desmosomes: Filaments anchor to the opposite side Gap junctions: It is a spot-like junction Allow small molecules to move between cells 26
Glandular Epithelia A glandular epithelium is a type of epithelium that make a secretion Secretion are aqueous (water-based) products The protein product is made in rough ER, packed into secretory granules by Golgi apparatus, released from the cell by exocytosis Glands are classified on where they release their secretion: Endocrine (internal secretion through blood vessels) Exocrine (external secretion through ducts) Mixed gland do both. As ; liver, gonads, pancreas Exocrine glands are classified by number of cells: unicellular exocrine glands multicellular exocrine glands
Endocrine & Exocrine Glands 1- Endocrine glands a. They deliver secretion directly (through blood vessels) into the extracellular space. b. They secrete only hormones c. Pituitary, Thyroid, Parathyroid, Adrenal, Thymus are e.g. of endocrine gland 2-Exocrine glands a. They deliver secretion through a duct into a body surface or into a body cavity b. They secrete mucous, sweat, oil, saliva, bile, digestive enzymes, and many other substances c. mucus glands Sweet, sebaceous and salivary gland are e.g. of exocrine glands
Goblet cells It is the only unicellular exocrine gland found in columnar epithelium cells lining the intestinal and respiratory tract
Types of Exocrine Glands Simple glands un-branched duct Compound glands - branched duct Shape of gland Acinar - secretory cells form dilated sac Tubular secretory cells form tubes Tubuloacinar - both tube and sacs PHL 212 30
classification of exocrine glands according to their modes of secretion Merocrine glands (salivary, sweat, pancreas) Secret their products by exocytosis and gland is not altered (fig. a) Holocrine glands (sebaceous oil glands) The entire cell ruptures releasing the secretions (fig. b) Apocrine glands (mammary glands) The apex of the secretory cell pinches off and release its secretion (fig. c) (c)
Conclusion & summary
references Books: Gray's Anatomy for Students: With STUDENT CONSULT Online Access by Richard L. Drake, A. Wayne Vogl and Adam W. M. Mitchell The Complete Human Body + DVD By; Elaine Marieb & Katja Hoehn ISBN-10: 075666733X ISBN-13: 978-0756667337 Publication Date: August 16, 2010 Websites: www.pubmed.com www.biomednetspacebmn.com
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