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Chapter 4: Organization at the Tissue Level

Tissues are collections of cells that serve a collective purpose

Collections of tissues form organs

Socrative app – course 701439

?1. What is your name

? 2. Name 4 types of tissue.

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An Introduction to Tissues

TissuesStructures with discrete structural and

functional properties

Tissues in combination form organs, such as

the heart or liver

Organs can be grouped into 11 organ systems

? 3. List the 11 organ systems

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4-1 Four Types of Tissue

Tissue Are collections of cells and cell products that

perform specific, limited functions

Four types of tissue

1. Epithelial tissue

2. Connective tissue

3. Muscle tissue

4. Neural tissue

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4-1 Four Types of TissueEpithelial Tissue

Covers exposed surfaces

Lines internal passageways

Forms glands

Connective Tissue Fills internal spaces Supports other tissues Transports materials Stores energy

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4-1 Four Types of TissueMuscle Tissue

Specialized for contraction Skeletal muscle, heart muscle, and walls of

hollow organs

Neural Tissue Carries electrical signals from one part of the

body to another

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4-2 Epithelial Tissue

Epithelia Layers of cells covering internal or external

surfaces

Glands Structures that produce secretions

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4-2 Epithelial Tissue

Characteristics of Epithelia

Cellularity (cell junctions)

** Cell membrane features

Polarity (apical and basal surfaces)

** think apex (top; peak) and basement (below)

Attachment (basement membrane or basal lamina)

Avascularity

Without blood vessels

Regeneration

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Figure 4-1 The Polarity of Epithelial Cells

Cilia

Microvilli

Apicalsurface

Golgiapparatus

Nucleus

Mitochondria

Basement membrane

Basolateralsurfaces

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4-2 Epithelial Tissue

Functions of Epithelial Tissue

1. Provide Physical Protection

2. Control Permeability

3. Provide Sensation

4. Produce Specialized Secretions (glandular

epithelium)

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4-2 Epithelial TissueSpecializations of Epithelial Cells

1. Move fluids over the epithelium (protection)

2. Move fluids through the epithelium (permeability)

3. Produce secretions (protection and messengers)

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? 4. What are 4 functions of

epithelial cell?

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4-2 Epithelial Tissue

Intercellular Connections

Support and communication

CAMs (cell adhesion molecules) Transmembrane proteins

Intercellular cement Proteoglycans

Hyaluronan (hyaluronic acid) Glycosaminoglycans

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4-2 Epithelial Tissue

Intercellular Connections

Cell junctions

Form bonds with other cells or extracellular

material

1. Tight junctions

2. Gap junctions

3. Desmosomes

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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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4-2 Epithelial Tissue

Tight Junctions Between two plasma membranes

Adhesion belt attaches to terminal web

Prevents passage of water and solutes

Isolates wastes in the lumen (open space

down the center of a tube)

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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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4-2 Epithelial Tissue

Gap Junctions Allow rapid communication

Are held together by channel proteins

(junctional proteins, connexons)

Allow ions to pass

Coordinate contractions in heart muscle

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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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4-2 Epithelial Tissue

Desmosomes

CAMs, dense areas, and intercellular cement

Spot desmosomes (“spot weld”)Tie cells together Allow bending and twisting

HemidesmosomesAttach cells to the basal lamina

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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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? 5. What types of intercellular connections are used to ‘glue’

epithelial cells together?

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4-2 Epithelial Tissue

Attachment to the Basement Membrane Clear layer (lamina lucida)

Thin layer Secreted by epitheliaBarrier to proteins

Dense layer (lamina densa)Thick fibersProduced by connective tissueStrength and filtration

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4-2 Epithelial Tissue

Epithelial Maintenance and Repair

Epithelia are replaced by division of

germinative cells (stem cells)

Near basement membrane

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4-3 Classification of Epithelia Singular = Epithelium; Plural = Epithelia

Classes of Epithelia

1. Based on shape Squamous epithelia — thin and flat

Cuboidal epithelia — square shaped

Columnar epithelia — tall, slender rectangles

2. Based on layers Simple epithelium — single layer of cells

Stratified epithelium — several layers of cells

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Table 4-1 Classifying Epithelia

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Table 4-1 Classifying Epithelia

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4-3 Classification of EpitheliaSquamous Epithelia

Simple squamous epitheliumAbsorption and diffusion

MesotheliumLines body cavities

EndotheliumLines heart and blood vessels

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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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4-3 Classification of EpitheliaSquamous Epithelia

Stratified squamous epitheliumProtects against attacks

Keratin protein adds strength and water resistance

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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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4-3 Classification of EpitheliaCuboidal Epithelia

Simple cuboidal epitheliumSecretion and absorption

Stratified cuboidal epitheliaSweat ducts and mammary ducts

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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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? 6. What are the major classifications

of epithelial cells?

*** pg 116, 117***

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4-3 Classification of EpitheliaTransitional Epithelium

Tolerates repeated cycles of stretching and

recoiling and returns to its previous shape

without damage

Appearance changes as stretching occurs

Situated in regions of the urinary system (e.g.,

urinary bladder)

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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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4-3 Classification of Epithelia

Columnar Epithelia

Simple columnar epithelium

Absorption and secretion

Pseudostratified columnar epithelium

Cilia movement

Stratified columnar epithelium

Protection

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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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4-3 Classification of Epithelia

Glandular EpitheliaEndocrine glands

Release hormones Into interstitial fluid

No ducts (adrenal glands, ovaries, testes)

Exocrine glandsProduce secretions

Onto epithelial surfaces

Through ducts (sweat, salivary, mammary)

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4-3 Classification of Epithelia

Glandular Epithelia

Modes of Secretion

1. Merocrine secretion

2. Apocrine secretion

3. Holocrine secretion

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4-3 Classification of Epithelia Merocrine Secretion

Produced in Golgi apparatus Released by vesicles (exocytosis) For example, sweat glands

Apocrine Secretion Produced in Golgi apparatus Released by shedding cytoplasm For example, mammary glands

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4-3 Classification of Epithelia

Holocrine Secretion Released by cells bursting, killing gland cells

Gland cells replaced by stem cells

For example, sebaceous glands

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Figure 4-6a Modes of Glandular Secretion

Salivary gland

Mammary gland

Hair

Sebaceousgland

Hair follicle

Merocrine. In merocrine secretion, secretory vesicles are discharged at the apical surface of the gland cell by exocytosis.

Secretoryvesicle

Golgiapparatus

Nucleus

TEM 3039

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Figure 4-6c Modes of Glandular Secretion

Salivary gland

Mammary gland

Hair

Sebaceousgland

Hair follicle

Stem cell

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

Cell division replaceslost cells

Cells produce secretion,increasing in size

Cells burst, releasingcytoplasmic contents

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4-3 Classification of EpitheliaGlandular Epithelia

Types of SecretionsSerous glands

Watery secretions

Mucous glands Secrete mucins

Mixed exocrine glands Both serous and mucous

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4-3 Classification of EpitheliaGlandular Epithelia

Gland StructureUnicellular glands

Mucous (goblet) cells are the only unicellular exocrine glands

Scattered among epithelia

For example, in intestinal lining

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4-3 Classification of Epithelia

Gland Structure Multicellular glands

1. Structure of the duct Simple (undivided) Compound (divided)

2. Shape of secretory portion of the gland Tubular (tube shaped) Alveolar or acinar (blind pockets)

3. Relationship between ducts and glandular areas Branched (several secretory areas sharing one duct)

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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