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Chapter 3

Epithelial tissues

Objectives

1. Name the four major tissue types and their subcategories (a. epithelial)

2. Explain the structure and function of each tissue

3. Give the primary locations of the tissue types in the body

4. Identify slides or pictures of each tissue

Tissues

• Groups of cells that are similar in structure and function

• Four primary types– Epithelium– Connective– Nervous– Muscle

EPITHELIATISSUES

•Location includes linings, coverings & glands• Functions include protection, absorption, filtration & secretion

•http://www.stegen.k12.mo.us/tchrpges/sghs/ksulkowski/TissueSlides.htm

•http://kcfac.kilgore.cc.tx.us/kcap1/practical_1_photos.htm

Characteristics of Epithelia Tissues

• Form continuous sheets bound by cell junctions (p. 57)

• Free surface or apical surface is exposed to body’s exterior or cavity of an organ

• Basement membrane are underlining layers• Avascular – no blood vessels; rely on diffusion of

gases & nutrients from underlying connective tissues

• regenerates

APICAL SURFACE

BASEMENT MEMBRANE

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Classification of Tissue

Given two names:• Cell arrangement (layers)

– Simple: one layer– Stratified: more than one layer

• Cell shape– Squamous: flat– Cuboidal: cube shaped– Columnar: columns

simple squamous

simple cuboidal cellssimple columnar

stratified squamous

SIMPLE EPITHELIA

Functions mainly to absorb, secrete & filtrate substances;

too thin to protect

1. SIMPLE SQUAMOUS

• Single, flat & scale like• Large central nucleus• Forms membranes

where rapid diffusion occurs

• Locations: air sacs of lungs, lining heart, blood vessels &kidneys, serous membranes

2. SIMPLE CUBOIDAL

• Single, cube shaped • Large central nuclei• Locations: tubules of

kidneys, ducts of glands & ovary

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3. SIMPLE COLUMNAR

• Single layer of tall cells with oval nuclei

• May contain goblet cells that secrete mucus

• Locations: lines digestive tract & gall bladder, mucous membranes

4. PSEUDOSTRATIFIED COLUMNAR

• “false layers”• Some cells look shorter

than others making it look stratified

• Nuclei at various levels• Can be ciliated –

respiratory tract• Nonciliated located in

ducts of glands & male urethra

STRATIFIED EPITHELIA

Multiple layers of cells found in areas of protection

1. Stratified Squamous

• Free surface looks squamous while lower layers are either cuboidal or columnar

• Found in areas of friction – mouth, esophagus, skin or birth canal

2. Stratified Cuboidal

• 2 layers; cube shaped• Found in adult sweat

glands, conjunctiva of eye, male urethra, pharynx & epiglottis

3. Stratified Columnar

• Multiple layers of column shaped cells

• Lines tubules of kidneys

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4. Transitional

• Modified stratified squamous but large & more rounded

• Ability to change shape allowing organs to stretch or distend

• Lines urinary bladder, ureters & urethra

GLANDULAR EPITHELIA

• Consists of one or more cells that produce or secrete a product called a hormone

1. Endocrine

• Ductless glands• Hormones diffuse

directly into blood vessels that weave through the gland

• Thyroid, pituitary, adrenal

2. Exocrine

• Contains a duct through which secretions empty

• Sebaceous (oil), sweat, mammary, pancreatic, liver

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