052 EPITHELIUM AND GLANDS Dr Larry Johnson Objectives

052 EPITHELIUM AND GLANDS Dr. Larry Johnson

Objectives • Identify every epithelium present in any tissue section. • Differentiate between mucus and serous secreting epithelia. • Identify single-celled glands, endocrine glands and the various types of exocrine glands. • Detail the structure of the sebaceous gland. • Identify the different types of sweat glands and distinguish the duct from the secretory region. • Identify myoepithelial cells and know their function. From: Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual

ORIGIN AND DISTRIBUTION OF EPITHELIUM ECTODERM - EPIDERMIS OF SKIN AND EPITHELIUM OF CORNEA TOGETHER COVERS THE ENTIRE SURFACE OF THE BODY; SEBACEOUS AND MAMMARY GLANDS ECTODERM ENDODERM - ALIMENTARY TRACT, LIVER, PANCREAS, GASTRIC GLANDS, INTESTINAL GLANDS • ENDOCRINE GLANDS - LOSE CONNECTION WITH SURFACE MESODERM • ENDOTHELIUM - LINING OF BLOOD VESSELS • MESOTHELIUM - LINING SEROUS CAVITIES ENDODERM

Characteristics of epithelium • Classification by # of layers • Simple = single layer • Stratified = multiple, stacked layers • Pseudostratified = appears to be multiple layers, but all cells touch basement membrane (all cells do not necessarily reach lumen) • Classification by shape • Squamous = flat • Cuboidal = square • Columnar = column

Laboratory Experience • Identify and characterize various types of epithelia • Recognize various glands and modes of secretion • Recognize gland associated structures/cells and differentiate glands from their ducts • Understand significance of cytological expression of epithelial cells with regard to function 053 Slide 93 Slide 35

Slide 33: Kidney (PAS/hematoxylin) Periodic acid – Schiff • Used to visualize: glycogen, glycoproteins, and glycosaminoglycans • Steps in PAS staining 1. 2. Periodic acid oxidizes 1, 2 -glycols to aldehydes Schiff’s reagent colors the aldehyde groups (pink to magenta) Brush border Basement membrane The brush border is composed of numerous microvilli which function to increase surface area for absorption of nutrient material and fluid. The structure on the brush border that stains with periodic-acid Schiff (PAS) stain is the glycocalyx.

EM 1 & 7 Slide 33 glycocalyx PAS staining Lipid in SER Observe various brush border - microvilli The brush border is composed of numerous microvilli of a uniform size projecting into a lumen. Each microvillus is composed of microfilaments (actin) surrounded by the cell membrane.

EM 2 Stereocilia of the epididymis - long thin microvilli Stereocilia are very long, branched, non-motile microvilli of differing lengths that function in absorption from the lumen.

EM 5 & 6 Observe cell junctions characteristic of epithelium

SPECIALIZATION OF EPITHELIA MAINTAIN EXTENSIVE CONTACTS AMONG CELLS STRUCTURALLY AND FUNCTIONALLY POLARIZED JUNCTIONS ZONULA OCCLUDENS - TIGHT JUNCTION (BELT) ZONULA ADHERENS – ADHERING BELT DESMOSOME (MACULA ADHERENS) - SPOT ATTACHMENT GAP JUNCTIONS - COMMUNICATION

Terminal bars 32409

Slide 32: Kidney (H&E) Simple squamous Simple cuboidal

Slide 75: Thyroid gland (endocrine) Simple cuboidal epithelium Basement membrane

SUMMARY OF TISSUE FEATURES OF EPITHELIUM • AVASCULAR • EXTRANEOUS CELLS • REGENERATION • MIGRATION 32409

SUMMARY OF TISSUE FEATURES OF EPITHELIUM Slide 258 • AVASCULAR • EXTRANEOUS CELLS • REGENERATION • MIGRATION • METAPLASIA • BASEMENT MEMBRANE

SECRETION – ACTIVE PROCESS CONSUMING ENERGY EXOCRINE GLANDS - DELIVER THEIR SECRETION INTO DUCTS OPENING INTO EXTERNAL OR INTERNAL SURFACE ENDOCRINE GLANDS DUCTLESS, DELIVER THEIR SECRETIONS INTO THE LYMPH OR BLOOD STREAM PANCREAS has exocrine has endocrine

EXOCRINE GLANDS DUCT • SIMPLE - UNBRANCHED DUCT • COMPOUND - BRANCHED DUCT SECRETORY PORTION • TUBULAR • COILED TUBULAR • BRANCHED TUBULAR • ALVEOLAR • BRANCHED ACINAR • TUBULOALVEOLAR MUCUS VS SEROUS

TUBULAR COILED TUBULAR BRANCHED TUBULAR ALVEOLAR BRANCHED ACINAR TUBULOALVEOLAR

ACINUS = FUNCTIONAL UNIT SEROUS 072 MUCOUS Mucous - Light staining Cytoplasm and dark, flattened nucleus at base of cell 072 Serous – dark red staining cytoplasm and lighter, spherical nucleus

Slide 072: Submandibular gland Simple columnar epithelia Stratified columnar epithelia

Slide 072: Submandibular gland Serous cells Mucous cells Serous demilune The submandibular gland is a mixed (seromucous) gland whose mode of secretion is merocrine secretion = exocytosis without loss of cellular components

MECHANISM FOR RELEASE OF SECRETORY PRODUCTS MEROCRINE SECRETION – EXOCYTOSIS W/O LOSS OF SURFACE MEMBRANE APOCRINE SECRETION – LOSS OF PART OF APICAL CYTOPLASM AND SOME PLASMA MEMBRANE HOLOCRINE SECRETION – RELEASE OF WHOLE cell CYTOCRINE SECRETION – MELANIN GRANULES TRANSFERRED FROM MELANOCYTE TO KERATINOCYTES

MEROCRINE APOCRINE

CYTOCRINE SECRETION - PASS MELANIN GRANULES FROM MELANOCYTES TO KERATINOCYTES

Alternative slide 250 Slide 61: Terminal Ileum Brush border composed of microvilli Microvilli are fingerlike projections that greatly increase the surface area of certain cells to help increase absorption. Microvilli are non-motile and are composed of a core of thin microfilaments called actin. Goblet cell releasing contents Simple columnar epithelium

Alterative slide 242 Slide 40: Trachea Goblet cell releasing contents Ciliated pseudostratified columnar epithelium with goblet cells Note thick basement membrane of the respiratory pseudostratified columnar epithelium. The main function of cilia is to sweep or move fluids, cells, or particulate matter across cell surface in the lumen as to remove dust in the lungs. Microtubules of the axoneme are at the core of cilia and make them motile.

Slide 93: Epididymis Pseudostratified columnar epithelium with stereocilia Microvilli: small, non-motile projections composed of thin microfilaments Stereocilia: long, non-motile projections (branched microvilli) composed of thin microfilaments Cilia: larger, long, motile projections composed of thick microtubules

Slide 35: Urinary bladder Transitional epithelium Specialized “dome-shaped” cells Basal cells

Slide 34: Ureter Transitional epithelium

Stratified squamous epithelium: the protection epithelium • Keratinized stratified squamous Slide 029 (thick or thin) • Prevent dessication • Protect against abrasion • Prevent foreign invasion • Ex. Slide 29: Thick skin (ventral surface of finger) Slide 52 • Non-keratinized stratified squamous • Moist lubricated surface • Ex. Slide 52: Tongue

Slide 52 : Tongue Non-keratinized stratified squamous epithelium Mucous acini Serous acini Mucous cells stain light and serous cells stain dark.

Slide 53: Esophagus Non-keratinized stratified squamous epithelium

Slide 29: Thick skin (ventral surface of finger) Epidermis with keratinized stratified squamous epithelium Dermis Hypodermis The major function of this type of epithelium (thick skin) is for protection from mechanical stress, but it also prevents dehydration.

Slide 29 : Thick skin (ventral surface of finger) Keratinized stratified squamous epithelium Polyhedral cells Cuboidal cells of the stratum basale The cells in the stratum basale serve as stem cells for the epidermis, and their progeny differentiate as they move away from the base.

Slide 29 : Thick skin (ventral surface of finger) Duct of eccrine sweat gland with stratified cuboidal epithelium Eccrine sweat gland Myoepithelial cells are eosinophilic because of the presence of a high density of contractile protein. These cells surround the gland like a net and expel glandular secretions upon contraction.

Slide 31: Thin skin (scalp) Sebaceous glands The mode of secretion used by sebaceous glands is holocrine secretion Keratinized, stratified squamous epithelium

Slide 66: Recto-anal junction Anus – stratified squamous Rectum - simple columnar epithelium

Slide 66 : Recto-anal junction Sebaceous glands Apocrine sweat gland Eccrine sweat gland

GLANDS OF EPIDERMAL ORIGIN SWEAT GLANDS • ECCRINE - COMMON SWEAT GLAND LOCAL COOLING • APOCRINE AXILLARY REGION - FUNCTION IN ANIMALS, discharge in hair follicle

Epithelial tissues of the body • Use table as guide • Generalizations • Entire GI system from gastroesophageal junction to rectoanal junction is lined by simple columnar epithelium • Cilia is present in most respiratory passages

EPITHELIA ARE SPECIALIZED FOR FUNCTIONS ABSORPTION - INTESTINE SECRETION - PANCREAS TRANSPORT - EYE, ENDOTHELIUM IN VESSELS EXCRETION - KIDNEY PROTECTION – AGAINST MECHANICAL DAMAGE AND DEHYDRATION SENSORY RECEPTION – PAIN TO AVOID INJURY, TASTE BUDS, OLFACTORY, ETC. CONTRACTION – MYOEPITHELIUM

SURFACE SPECIALIZATIONS OF EPITHELIA MICROVILLI - INTESTINE ABSORPTIVE CELL CILIA - RESPIRATORY EPITHELIUM BASAL LAMINA – ALL EPITHELIUM 038 b 33 INTERCELLULAR CANALICULUS – HEPATOCYTE SECRETORY CANALICULUS – GASTRIC PARIETAL CELL FLAGELLA 32409

SURFACE SPECIALIZATIONS OF EPITHELIA INTERCELLULAR CANALICULUS – HEPATOCYTE

SURFACE SPECIALIZATIONS OF EPITHELIA SECRETORY CANALICULUS – GASTRIC PARIETAL CELL

Clinical Correlation Slide 38 Edward C. Klatt, M. D. Mercer University School of Medicine Normal larynx with ciliated pseudostratified columnar epithelium Abnormal larynx with stratified squamous epithelium

Many illustrations in these VIBS Histology You. Tube videos were modified from the following books and sources: Many thanks to original sources! • Bruce Alberts, et al. 1983. Molecular Biology of the Cell. Garland Publishing, Inc. , New York, NY. • Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc. , New York, NY. • William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA. • Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY. • Don W. Fawcett. 1986. Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA. • Don W. Fawcett. 1994. Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY. • Arthur W. Ham and David H. Cormack. 1979. Histology. J. S. Lippincott Company, Philadelphia, PA. • Luis C. Junqueira, et al. 1983. Basic Histology. Lange Medical Publications, Los Altos, CA. • L. Carlos Junqueira, et al. 1995. Basic Histology. Appleton and Lange, Norwalk, CT. • L. L. Langley, et al. 1974. Dynamic Anatomy and Physiology. Mc. Graw-Hill Book Company, New York, NY. • W. W. Tuttle and Byron A. Schottelius. 1969. Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO. • Leon Weiss. 1977. Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY. • Leon Weiss and Roy O. Greep. 1977. Histology. Mc. Graw-Hill Book Company, New York, NY. • Nature (http: //www. nature. com), Vol. 414: 88, 2001. • A. L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13 th ed. Mc. Graw • Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual - Slide selections were largely based on this manual for first year medical students at TAMHSC

The End!