EPITHELIUM AND GLANDSDr. Larry Johnson

052

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

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

ECTODERM

ENDODERM

MESODERM

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 93Slide 35Slide 53

Slide 33: Kidney (PAS/hematoxylin)

Basement membrane

Brush border

Periodic acid – Schiff • Used to visualize: glycogen, glycoproteins, and glycosaminoglycans• Steps in PAS staining

1. Periodic acid oxidizes 1,2-glycols to aldehydes2. Schiff’s reagent colors the aldehyde groups (pink to magenta)

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

Observe various brush border - microvilliThe 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.

glycocalyx

PASstaining

Slide 33

Lipid in SER

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 EPITHELIAMAINTAIN EXTENSIVE

CONTACTS AMONG CELLSSTRUCTURALLY AND FUNCTIONALLY POLARIZED

JUNCTIONSZONULA OCCLUDENS - TIGHT JUNCTION (BELT)ZONULA ADHERENS –

ADHERING BELTDESMOSOME (MACULA

ADHERENS) - SPOT ATTACHMENTGAP JUNCTIONS - COMMUNICATION

Terminal bars

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Slide 32: Kidney (H&E)

Simple squamous Simple squamous

Simple cuboidal Simple cuboidal

Slide 75: Thyroid gland (endocrine)

Simple cuboidal epithelium Basement membrane

SUMMARY OF TISSUE FEATURES OF EPITHELIUM

• AVASCULAR• EXTRANEOUS CELLS

• REGENERATION• MIGRATION

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SUMMARY OF TISSUE FEATURES OF EPITHELIUM

• AVASCULAR• EXTRANEOUS CELLS

• REGENERATION• MIGRATION

• METAPLASIA• BASEMENT MEMBRANE

Slide 258

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 endocrine

PANCREAS has exocrine

EXOCRINE GLANDSDUCT

• SIMPLE - UNBRANCHED DUCT• COMPOUND - BRANCHED DUCT

SECRETORY PORTION• TUBULAR• COILED TUBULAR• BRANCHED TUBULAR• ALVEOLAR• BRANCHED ACINAR• TUBULOACINAR• TUBULOALVEOLAR

MUCUS VS SEROUS

TUBULARCOILED TUBULARBRANCHED TUBULARALVEOLAR

BRANCHED ACINARTUBULOACINARTUBULOALVEOLAR

ACINUS = FUNCTIONAL UNIT

SEROUS MUCOUS

Mucous - Light staining Cytoplasm and dark, flattened nucleus at base of cell

Serous – dark red staining cytoplasm and lighter, spherical nucleus

072

072

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

Slide 61: Terminal Ileum

Goblet cell releasing contents

Simple columnar epithelium

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.

Alternative slide 250

Slide 40: Trachea

Ciliated pseudostratified columnar epithelium with

goblet cells

Goblet cell releasing contents

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..

Note the thick basement membrane of the respiratorypseudostratified columnar epithelium.

Alterative slide 242

Slide 93: Epididymis

Pseudostratified columnar epithelium with stereociliaMicrovilli: small, non-motile projections composed of thin microfilamentsStereocilia: long, non-motile projections (branched microvilli) composed of thin microfilamentsCilia: larger, long, motile projections composed of thick microtubules

Slide 35: Urinary bladder

Specialized “dome-shaped” cells

Basal cells

Transitional epithelium

Slide 34: Ureter

Transitional epithelium

Stratified squamous epithelium: the protection epithelium

• Keratinized stratified squamous (thick or thin)• Prevent dessication• Protect against abrasion• Prevent foreign invasion• Ex. Slide 29: Thick skin (ventral

surface of finger)

• Non-keratinized stratified squamous• Moist lubricated surface• Ex. Slide 52: Tongue

Slide 029

Slide 52

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 withkeratinized stratifiedsquamous 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 sweatgland with stratifiedcuboidal epithelium

Eccrine sweat gland

Myoepithelial cells

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)

Keratinized, stratifiedsquamous epithelium

Sebaceous glands

The mode of secretion used by sebaceous glands is holocrine secretion

Slide 66: Recto-anal junction

Rectum - simple columnar epitheliumAnus – stratified squamous

Slide 66 : Recto-anal junction

Eccrine sweat glandSebaceous glands Apocrine 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

gastro-esophageal junction to recto-anal junction is lined by simple columnar epithelium

• Cilia is present in most respiratory passages

EPITHELIA ARE SPECIALIZED FOR FUNCTIONS

ABSORPTION - INTESTINESECRETION - PANCREASTRANSPORT - EYE, ENDOTHELIUM IN VESSELSEXCRETION - KIDNEYPROTECTION – AGAINST

MECHANICAL DAMAGE AND DEHYDRATION

SENSORY RECEPTION – PAIN TO AVOID

INJURY, TASTE BUDS, OLFACTORY, ETC.

CONTRACTION – MYOEPITHELIUM

SURFACE SPECIALIZATIONS OF EPITHELIA

MICROVILLI - INTESTINE ABSORPTIVE CELLCILIA - RESPIRATORY EPITHELIUM

BASAL LAMINA – ALL EPITHELIUM

INTERCELLULAR CANALICULUS – HEPATOCYTE

SECRETORY CANALICULUS – GASTRIC PARIETAL CELL

FLAGELLA

038b

33

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SURFACE SPECIALIZATIONS OF EPITHELIA

INTERCELLULAR CANALICULUS – HEPATOCYTE

SURFACE SPECIALIZATIONS OF EPITHELIA

SECRETORY CANALICULUS – GASTRIC PARIETAL CELL

Clinical Correlation

Normal larynx with ciliated pseudostratified columnar epithelium

Abnormal larynx with stratified squamous epithelium

Edward C. Klatt, M.D.Mercer University School of Medicine

Slide 38

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• Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY.

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• 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. McGraw-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. McGraw-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, 13th ed. McGraw

• 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

Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!

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