Figure 4-1 The Polarity of Epithelial Cells

Cilia

Microvilli

Apicalsurface

Golgiapparatus

Nucleus

Mitochondria

Basement membrane

Basolateralsurfaces

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Figure 4-2 Cell Junctions

Gapjunctions

Hemidesmosome

Spotdesmosome

ClearlayerDenselayer

Intermediatefilaments

Basementmembrane

Dense area

Embedded proteins(connexons)

Proteoglycans

Cell adhesionmolecules (CAMs)

Terminal web

Adhesion belt

Tight junction

Interlockingjunctional

proteins

Tight junction

Adhesion belt

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Figure 4-2a Cell Junctions

This is a diagrammatic view of an epithelial cell,showing the major types of intercellularconnections.

Gapjunctions

Hemidesmosome

Spotdesmosome

Terminal web

Adhesion belt

Tight junction

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Figure 4-2b Cell Junctions

Tight junction

Adhesion belt

A tight junction is formed by the fusion of the outer layers of two plasma membranes. Tight junctions prevent the diffusion of fluids and solutes betweenthe cells. A continuous adhesion belt lies deep to the tight junction. This belt is tied to the microfilaments of the terminal web.

Terminal web

Interlockingjunctional

proteins

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Figure 4-2c Cell Junctions

Embedded proteins(connexons)

Gap junctions permit the free diffusion of ions and small molecules between two cells.

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Figure 4-2d Cell Junctions

Intermediatefilaments

Dense area

Cell adhesionmolecules (CAMs)

Proteoglycans

A spot desmosome tiesadjacent cells together.

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Figure 4-2e Cell Junctions

ClearlayerDenselayer

Hemidesmosomes attach a cell to extracellular structures, such as the protein fibers in the basement membrane.

Basementmembrane

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Table 4-1 Classifying Epithelia

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Table 4-1 Classifying Epithelia

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Figure 4-4c Cuboidal and Transitional Epithelia

Transitional Epithelium

FUNCTIONS: Permitsexpansion and recoilafter stretching

LOCATIONS: Urinarybladder; renal pelvis;ureters

LM 400

Urinary bladder

LM 400

Empty bladder

Epithelium(relaxed)

Connective tissue andsmooth muscle layers

Epithelium(stretched)

Connective tissue andsmooth muscle layers

Basement membrane

Full bladder

Basement membrane

LM 400

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Figure 4-3a Squamous Epithelia

Simple Squamous Epithelium

Lining of peritoneal cavityConnective tissue

Nucleus

Cytoplasm

LOCATIONS: Mesothelia lining ventral body cavities; endothelia lining heartand blood vessels; portions of kidney tubules (thin sections of nephron loops); inner lining of cornea; alveoli of lungs

FUNCTIONS: Reduces friction; controls vessel permeability; performsabsorption and secretion

LM 238

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Figure 4-3b Squamous Epithelia

LOCATIONS: Surface of skin; lining of mouth, throat, esophagus, rectum, anus, and vagina

FUNCTIONS: Provides physical protection against abrasion, pathogens, and chemical attack

Surface of tongue

Squamoussuperficial cells

Stem cells

Basementmembrane

Connectivetissue

LM 310

Stratified Squamous Epithelium

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Figure 4-4a Cuboidal and Transitional Epithelia

Simple Cuboidal Epithelium

LOCATIONS: Glands; ducts;portions of kidney tubules; thyroidgland

FUNCTIONS: Limited protection,secretion, absorption

Kidney tubule

Connectivetissue

Nucleus

Cuboidalcells

Basementmembrane

LM 650

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Figure 4-4b Cuboidal and Transitional Epithelia

LOCATIONS: Lining of some ducts(rare)

FUNCTIONS: Protection, secretion,absorption

LM 500

Lumenof duct

Sweat gland duct

Stratifiedcuboidal

cellsBasementmembrane

Nuclei

Connectivetissue

Stratified Cuboidal Epithelium

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Figure 4-4c Cuboidal and Transitional Epithelia

Transitional Epithelium

FUNCTIONS: Permitsexpansion and recoilafter stretching

LOCATIONS: Urinarybladder; renal pelvis;ureters

LM 400

Urinary bladder

LM 400

Empty bladder

Epithelium(relaxed)

Connective tissue andsmooth muscle layers

Epithelium(stretched)

Connective tissue andsmooth muscle layers

Basement membrane

Full bladder

Basement membrane

LM 400

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Figure 4-5a Columnar Epithelia

LOCATIONS: Lining ofstomach, intestine, gallbladder,uterine tubes, and collectingducts of kidneys

FUNCTIONS: Protection,secretion, absorption

Simple Columnar Epithelium

Microvilli

Cytoplasm

Intestinal lining

Basementmembrane

Looseconnective tissue LM 350

Nucleus

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Figure 4-5b Columnar Epithelia

LOCATIONS: Lining ofnasal cavity, trachea, andbronchi; portions of malereproductive tract

FUNCTIONS: Protection,secretion, move mucuswith cilia

Pseudostratified Ciliated Columnar Epithelium

Cilia

Trachea

Cytoplasm

Nuclei

Basementmembrane

Looseconnective tissue

LM 350

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Figure 4-5c Columnar Epithelia

LOCATIONS: Small areas ofthe pharynx, epiglottis, anus,mammary glands, salivarygland ducts, and urethra

FUNCTION: Protection

Stratified Columnar Epithelium

Salivary gland duct

Deeper basalcells

Looseconnective tissue

Superficialcolumnar cells

Cytoplasm

Nuclei

Basementmembrane

LumenLumen

LM 175

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Figure 4-6 Modes of Glandular Secretion.

Secretoryvesicle

Golgiapparatus

Nucleus

TEM × 3039

In merocrine secretion, the product is released from secretoryvesicles at the apical surface of the gland cell by exocytosis.

(a) Merocrine secretion

(b) Apocrine secretion

Apocrine secretion involves the loss of apical cytoplasm.Inclusions, secretory vesicles, and other cytoplasmic componentsare shed in the process. The gland cell then grows and repairs itselfbefore it releases additional secretions.

Breaksdown

Regrowth

(c) Holocrine secretion

Holocrine secretion occurs as superficial gland cells burst.Continued secretion involves the replacement of these cellsthrough the mitotic divisions of underlying stem cells.

Golgi apparatus

1 2 3 4

3

2

1

Cells burst, releasingcytoplasmic contents

Cells form secretoryproducts and increasein size

Cell division replaceslost cells

Stem cell

Salivary gland

Mammary gland

Hair

Sebaceous gland

Hair follicle

Secretion

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Figure 4-6a Modes of Glandular Secretion.

Secretoryvesicle

Golgiapparatus

Nucleus

TEM × 3039

In merocrine secretion, the product is released from secretoryvesicles at the apical surface of the gland cell by exocytosis.

(a) Merocrine secretion

Salivary gland

Mammary gland

Hair

Sebaceous gland

Hair follicle

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Figure 4-6b Modes of Glandular Secretion.

(b) Apocrine secretion

Apocrine secretion involves the loss of apical cytoplasm. Inclu-sions, secretory vesicles, and other cytoplasmic components are shed in the process. The gland cell then grows and repairs itselfbefore it releases additional secretions.

Breaksdown

Regrowth

Golgi apparatus

1

Salivary gland

Mammary gland

Hair

Sebaceous gland

Hair follicle

Secretion

2 3 4

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Figure 4-6c Modes of Glandular Secretion.

Salivary gland

Mammary gland

Hair

Sebaceous gland

Hair follicle

(c) Holocrine secretion

Holocrine secretion occurs as superficial gland cells burst. Contin-ued secretion involves the replacement of these cells through the mitotic divisions of underlying stem cells.

1

Cells burst, releasingcytoplasmic contents

Cells form secretoryproducts and increasein size

Cell division replaceslost cells

Stem cell

2

3

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Figure 4-7 A Structural Classification of Exocrine Glands

SIMPLE GLANDS

Glandcells

SIMPLETUBULAR

SIMPLE COILEDTUBULAR

Examples:

Examples:

Examples:• Intestinal glands • Merocrine sweat

stage in developmentof simple branchedglands

SIMPLE BRANCHEDTUBULAR

Examples:• Gastric glands• Mucous glands

• Not found in adult; a

SIMPLE ALVEOLAR(ACINAR)

SIMPLE BRANCHEDALVEOLAR

Examples:• Sebaceous (oil)

glandsof esophagus,tongue, duodenum

glands

Duct

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Figure 4-7 A Structural Classification of Exocrine Glands

COMPOUND GLANDS

COMPOUNDTUBULAR

COMPOUND ALVEOLAR(ACINAR)

COMPOUND TUBULOALVEOLAR

Examples:• Mucous glands (in mouth)

Examples:

• Bulbo-urethral glands (inmale reproductive system)

tubules)

• Mammary glandsExamples:

• Salivary glands• Glands of respiratory

passages• Testes (seminiferous• Pancreas

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Figure 4-8 The Cells and Fibers of Connective Tissue Proper

Reticularfibers

Melanocyte

Fixedmacrophage

Plasma cell

Bloodin vessel

Adipocytes(fat cells)

Groundsubstance

Mast cell

Elasticfibers

Freemacrophage

Collagenfibers

Fibroblast

Mesenchymalcell

Lymphocyte

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Figure 4-10a Loose Connective Tissues.

Areolar Tissue

Fibrocytes

Macrophage

Collagenfibers

Mast cell

Elastic fibers

Areolar tissueLM × 380

a

LOCATIONS: Within and deep to thedermis of skin, and covered by theepithelial lining of the digestive,respiratory, and urinary tracts;between muscles; around joints,blood vessels, and nerves

FUNCTIONS: Cushions organs; providessupport but permits independentmovement; phagocytic cellsprovide defense againstpathogens

Areolar tissuefrom pleura

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Figure 4-10a Adipose and Reticular Tissues

Adipose Tissue

LOCATIONS: Deep to the skin,especially at sides, buttocks,breasts; padding around eyesand kidneys

FUNCTIONS: Providespadding and cushionsshocks; insulates(reduces heat loss);stores energy

Adipose tissue

Adipocytes(white adipose

cells)

LM 300

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Figure 4-10b Adipose and Reticular Tissues

Reticular Tissue

FUNCTIONS: Provides supportingframework

LOCATIONS: Liver, kidney, spleen,lymph nodes, and bone marrow

Reticular tissuefrom liver

Reticular Tissue

Reticular fibers

LM 375

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Figure 4-11a Dense Connective Tissues

Dense Regular Connective Tissue

Collagenfibers

Fibroblastnuclei

Tendon LM 440

LOCATIONS: Between skeletalmuscles and skeleton (tendonsand aponeuroses); betweenbones or stabilizing positionsof internal organs (ligaments);covering skeletal muscles;deep fasciae

FUNCTIONS: Providesfirm attachment; conductspull of muscles; reducesfriction between muscles;stabilizes relative positionsof bones

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Figure 4-11b Dense Connective Tissues

Collagenfiber

bundles

Deep dermis LM 111

Dense Irregular Connective Tissue

LOCATIONS: Capsules ofvisceral organs; periosteaand perichondria; nerveand muscle sheaths; dermis

FUNCTIONS: Providesstrength to resist forcesapplied from manydirections; helpsprevent overexpansionof organs such asthe urinary bladder

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Figure 4-11c Dense Connective Tissues

Elasticfibers

Fibroblastnuclei

Elastic ligament

Elastic Tissue

LOCATIONS: Between vertebraeof the spinal column (ligamentumflavum and ligamentum nuchae);ligaments supporting penis;ligaments supporting transitionalepithelia; in blood vessel walls

FUNCTIONS: Stabilizespositions of vertebrae andpenis; cushions shocks;permits expansion andcontraction of organs

LM 887

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Connective Tissues

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Figure 4-13a The Growth of Cartilage

Interstitial growth

Chondrocyte undergoes divisionwithin a lacuna surrounded bycartilage matrix.

As daughter cells secrete additional matrix, theymove apart, expanding the cartilage from within.

LacunaChondrocyte

MatrixNew matrix

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Figure 4-13b The Growth of Cartilage

Appositional growth

As the matrix enlarges, morechondroblasts are incorporated;they are replaced by divisions ofstem cells in the perichondrium.

These immaturechondroblasts secretenew matrix.

New matrix

ImmaturechondrocyteOlder matrix

Maturechondrocyte

FibroblastDividing stem cell

Perichondrium

Cells in the cellular layerof the perichondriumdifferentiate intochondroblasts.

Chondroblasts

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Figure 4-14a Types of Cartilage

Hyaline Cartilage

LOCATIONS: Between tips of ribs and bones of sternum; covering bone surfaces at synovial joints; supporting larynx (voice box), trachea, and bronchi; forming part of nasal septum

FUNCTIONS: Provides stiff butsomewhat flexible support;reduces frictionbetween bonysurfaces

Hyaline cartilage

LM 500

Matrix

Chondrocytesin lacunae

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Figure 4-14b Types of Cartilage

Elastic Cartilage

LOCATIONS: Auricle of externalear; epiglottis; auditory canal;cuneiform cartilages of larynx

FUNCTIONS: Provides support,but tolerates distortion withoutdamage andreturns tooriginal shape

Elastic cartilage

Elastic fibersin matrix

Chondrocytein lacuna

LM 358

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Figure 4-14c Types of Cartilage

Fibrocartilage

LOCATIONS: Pads within kneejoint; between pubic bones ofpelvis; intervertebral discs

FUNCTIONS: Resistscompression;prevents bone-to-bonecontact; limitsmovement

Fibrocartilage

Fibrousmatrix

Chondrocytesin lacunae

LM 400

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Figure 4-15 Bone

Canaliculi

Osteocytesin lacunae

Matrix

Central canal

Blood vessels

LM 375

Osteon

Osteon

Fibrouslayer

Cellularlayer

Periosteum

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Table 4-2 A Comparison of Cartilage and Bone

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Figure 4-16a Membranes

Mucous secretion

Mucous membranes are coated with thesecretions of mucous glands. These membranes line the digestive, respiratory, urinary, and reproductive tracts.

Epithelium

Lamina propria(areolar tissue)

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Figure 4-16b Membranes

Serous membranes line the ventral body cavities (the peritoneal, pleural, and pericardial cavities).

Transudate

Mesothelium

Areolar tissue

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Figure 4-16d Membranes

Synovial membranes line joint cavities and produce the fluid within the joint.

Articular (hyaline) tissue

Synovial fluid

Capsule

Capillary

Adipocytes

Areolartissue

EpitheliumSynovialmembrane

Bone

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Figure 4-16c Membranes

The cutaneous membrane, or skin, covers the outer surface of the body.

Epithelium

Areolar tissue

Dense irregularconnective tissue

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Figure 4-17 The Fasciae

Body wall

Body cavity

Skin

Connective Tissue Framework of Body

Superficial Fascia

Deep Fascia

Subserous Fascia

Rib

Serous membrane

Cutaneous membrane

• Forms a strong, fibrous

• Dense connective tissue• Bound to capsules,

• Between serous

• Areolar tissue

internal framework

tendons, and ligaments

membranes anddeep fascia

• Between skin and

adipose tissue• Also known as

underlying organs• Areolar tissue and

subcutaneous layeror hypodermis

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