Tissues IntroductionTissues Introduction

Epithelial Tissue Epithelial Tissue ClassificationClassification

GlandsGlands

Cell SpecializationCell Specialization

Multicellularity requires a Multicellularity requires a division of labordivision of labor

Cells look and function Cells look and function differently (specialize) in differently (specialize) in different parts of the body different parts of the body (ex. bone cell vs. nerve cell)(ex. bone cell vs. nerve cell)

Cells specialize into types Cells specialize into types of tissues, then form of tissues, then form organs. organs.

HistologyHistology

Study of tissues (groups of Study of tissues (groups of cells that are similar in cells that are similar in structure and function)structure and function)

4 Tissue Types4 Tissue Types

1. Connective Tissue1. Connective Tissue

Support Support Connect layers of tissue to Connect layers of tissue to each othereach other

Bone, ligaments, fatBone, ligaments, fat

(we will study these in great detail in class (we will study these in great detail in class later…)later…)

2. Nervous Tissue2. Nervous Tissue

ControlControl Brain, nerves, Brain, nerves, spinal cordspinal cord

Highly Highly specialized specialized cells that cells that generate and generate and conduct nerve conduct nerve impulsesimpulses

3. Muscular Tissue3. Muscular Tissue

MovementMovement Highly vascularHighly vascular Contraction involves myosin Contraction involves myosin protein filament and cytoskeleton protein filament and cytoskeleton microfilament, actinmicrofilament, actin

2 categories:2 categories: Striated muscle tissue (voluntary or Striated muscle tissue (voluntary or partly voluntary control)partly voluntary control)

Smooth muscle tissue (involuntary)Smooth muscle tissue (involuntary)

3. Muscular Tissue3. Muscular Tissue Striated MuscleStriated Muscle

Ex. SkeletalEx. Skeletal Attached to skeletal bonesAttached to skeletal bones Long, cylindrical multi-nucleated Long, cylindrical multi-nucleated cellscells

Visible striationsVisible striations Voluntary controlVoluntary control

Ex. CardiacEx. Cardiac Also striated, but uni-nucleatedAlso striated, but uni-nucleated Branching cells fit tightly with Branching cells fit tightly with special junctions called intercalated special junctions called intercalated discsdiscs

3. Muscular Tissue3. Muscular Tissue

Smooth muscleSmooth muscle No striationsNo striations Spindle shapedSpindle shaped One central nucleusOne central nucleus Involuntary muscleInvoluntary muscle

Ex. digestive systemEx. digestive system

4. Epithelial Tissue4. Epithelial Tissue

InterfaceInterface tissue that forms tissue that forms boundaries boundaries between environments between environments and lines surfacesand lines surfaces

““epithe-” means “laid on”epithe-” means “laid on”

Coverings and Protection Coverings and Protection (ex. skin)(ex. skin)

Excretion & Secretion Excretion & Secretion (ex. glands)(ex. glands)

Filtration Filtration ((ex. kidneys)ex. kidneys)

Absorption Absorption (ex. digestive system)(ex. digestive system)

Identifying Identifying Characteristics of Characteristics of Epithelial TisuesEpithelial Tisues

1. Tight 1. Tight fitting fitting sheetssheets

Regardless of cell Regardless of cell shape or number shape or number of layersof layers

Identifying Identifying CharacteristicsCharacteristics

2. Apical-Basal Polarity2. Apical-Basal Polarity Apical Surface = top Apical Surface = top

surface that borders surface that borders an “open” space called an “open” space called LUMENLUMEN

Basal Surface = bottom Basal Surface = bottom surface that borders surface that borders underlying supportive underlying supportive connective tissueconnective tissue

LUMEN

Connective Tissue

Identifying Identifying CharacteristicsCharacteristics

Apical Surface Apical Surface Often w/ Often w/

microvilli (brush microvilli (brush border)border)

Increases SA in Increases SA in areas that need to areas that need to absorb or secreteabsorb or secrete

Some with cilia to Some with cilia to move substances move substances along lumenalong lumen

LUMEN

Connective Tissue

Identifying Identifying CharacteristicsCharacteristics

Basal Surface Basal Surface Has adhesive sheet of Has adhesive sheet of

glyco-proteins secreted glyco-proteins secreted by epithelial cells by epithelial cells called the basal laminacalled the basal lamina

Connective Tissue Connective Tissue beneath secretes beneath secretes collagen, creating the collagen, creating the Reticular Lamina.Reticular Lamina.

Basal Lamina + Basal Lamina + Reticular Lamina = Reticular Lamina = Basement MembraneBasement Membrane (defines the epithelial (defines the epithelial boundary)boundary)

LUMEN

Connective Tissue

LUMEN

Identifying Identifying CharacteristicsCharacteristics

3. Avascular (a = 3. Avascular (a = without)without) Lacks blood vesselsLacks blood vessels Nourished by Nourished by connective tissueconnective tissue

But InnervatedBut Innervated w/ nerve fibersw/ nerve fibers

4. Regeneration and 4. Regeneration and repair quicklyrepair quickly

Classification Classification of Epithelial of Epithelial

Tissue:Tissue:Cell ShapeCell Shape

Cross-sectionCross-section SquamousSquamous – flat, like a – flat, like a fried egg, or scale-likefried egg, or scale-like

CuboidalCuboidal – cubes, large – cubes, large spherical central nucleispherical central nuclei

Columnar – columns, long Columnar – columns, long oval nuclei, usually oval nuclei, usually near basal surfacenear basal surface

Classification of Classification of Epithelial Tissue Cell Epithelial Tissue Cell

LayersLayers SimpleSimple (one layer) (one layer) Thin: limited, no Thin: limited, no protectionprotection

Sparse cytoplasmSparse cytoplasm Found where rapid Found where rapid diffusion is a diffusion is a priority priority (ex. kidneys, (ex. kidneys, lungs)lungs)

StratifiedStratified (many (many layers)layers)

ThickThick Protective role, Protective role, subject to wear and subject to wear and teartear

Regenerate from basal Regenerate from basal surface to replace surface to replace apical surface cells apical surface cells that rub off or diethat rub off or die

Cells differ in shape Cells differ in shape at apical and basal at apical and basal surface. (named for surface. (named for apical surface)apical surface)

Pseudo-stratifiedPseudo-stratified

Shapes vary in height Shapes vary in height Nuclei at different levels – Nuclei at different levels – appear stratified, but aren’t.appear stratified, but aren’t.

All cells reach basement All cells reach basement membrane; only a few reach the membrane; only a few reach the surfacesurface

false

Simple Squamous Simple Squamous EpitheliumEpithelium

Function and LocationFunction and Location Areas of high diffusion rates:Areas of high diffusion rates:

gasses gasses (ex lungs)(ex lungs)nutrients and waste exchange nutrients and waste exchange (blood vessels and surrounding cells)(blood vessels and surrounding cells)

filtrates filtrates (kidneys)(kidneys) Makes lubricating fluid in Makes lubricating fluid in lining of body cavities lining of body cavities (ex. (ex. serous membranes)serous membranes)

One layer Flat

Simple Squamous EpitheliumSimple Squamous Epithelium(Top View) – cells fit (Top View) – cells fit

like tiled floorlike tiled floor

Figure 4.2

LUMEN

Simple Squamous Simple Squamous EpitheliumEpithelium(side view/cross (side view/cross section) section) – – cells look like cells look like fried eggfried egg

LUMEN

Nucleus of squamous cell

Kidney

Simple Cuboidal Simple Cuboidal EpitheliumEpithelium

Function and LocationFunction and Location Secretion and AbsorptionSecretion and Absorption Covers walls of SMALL ducts, Covers walls of SMALL ducts, glands, kidney tubules, ovariesglands, kidney tubules, ovaries

One layer Cubed

LUMEN

Spherical, large nuclei

Basement membrane

Cuboidal Cell

Apical surface

LUMENSpherical, large nuclei Apical surface

Basal surface

Simple Columnar Simple Columnar EpitheliumEpithelium

Function and LocationFunction and Location Absorption & Secretion Absorption & Secretion (ex. digestive (ex. digestive tract)tract)

When in open to body cavities – When in open to body cavities – called mucous membranescalled mucous membranes

Special FeaturesSpecial Features Often w/ Often w/ microvillmicrovilli on apical surface i on apical surface (brush border)(brush border)

Goblet cellsGoblet cells, single cell glands, , single cell glands, produce protective mucus.produce protective mucus.

One layer columns

LUMEN

Apical surface

Basal surface

Pseudostratified Pseudostratified EpitheliumEpithelium

FunctionFunction AbsorptionAbsorption Secretion of mucus by goblet cellsSecretion of mucus by goblet cells Cilia (larger than microvilli) Cilia (larger than microvilli) sweep mucus sweep mucus

LocationLocation Respiratory Linings & Reproductive Respiratory Linings & Reproductive tracttract

LUMEN

CiliaBasement Membrane

Multilevel nuclei

LUMEN

Stratified Squamous Stratified Squamous EpitheliumEpithelium

StructureStructure Cells often cuboidal or columnar Cells often cuboidal or columnar below apical squamous layerbelow apical squamous layer

Function and LocationFunction and Location ProtectionProtection Keratin (protein) is accumulated in Keratin (protein) is accumulated in older cells near the surface – older cells near the surface – waterproofs and toughens skinwaterproofs and toughens skin

LocationLocation Skin (keratinized), mouth & throatSkin (keratinized), mouth & throat

Multi-layer (thick!)

Flat (only cells on apical surface)

keratin

Dense-Irregular Connective Tissue

Basement Membrane

Squamous

Cuboidal

Columnar

TransitionaTransitional l

EpitheliumEpithelium

StructureStructure Multi-layerMulti-layer Basal surface cells are cuboidal Basal surface cells are cuboidal or columnaror columnar

Apical surface cells vary: changes Apical surface cells vary: changes shape to accommodate for change in shape to accommodate for change in volume due to stretchingvolume due to stretching

FunctionFunction Allows stretchingAllows stretching

LocationLocation Urinary bladder, ureters & urethraUrinary bladder, ureters & urethra

Figure 4.10

Nervous TissueNervous Tissue

Muscular TissueMuscular Tissue

GlandsGlands

Cells that secrete or export a product.Cells that secrete or export a product. Secretion = protein, lipids, hormones, Secretion = protein, lipids, hormones, steroids, acidssteroids, acids

Endocrine glands (internally secreting)Endocrine glands (internally secreting) No duct, release secretion into blood No duct, release secretion into blood vessels vessels

Often hormonesOften hormones Thyroid, adrenal and pituitary glandsThyroid, adrenal and pituitary glands

Exocrine glands (externally secreting)Exocrine glands (externally secreting) Contain ducts, empty onto epithelial surfaceContain ducts, empty onto epithelial surface Sweat, Oil glands, Salivary glands, Mammary Sweat, Oil glands, Salivary glands, Mammary glands.glands.

Shapes of Exocrine Shapes of Exocrine glandsglands

Branching

Simple – single, unbranched duct

Compound – branched.

Shape: tubular or alveolar

Tubular – shaped like a tube

Alveolar – shaped like flasks or sacs

Tubuloalveolar – has both tubes and sacs in gland

Modes of SecretionModes of Secretion

MerocrineMerocrine Released by exocytosis Released by exocytosis Gland is not altered Gland is not altered (Ex: Sweat glands (Ex: Sweat glands

and salivary glands)and salivary glands)

HolocrineHolocrine Gland ruptures and releases Gland ruptures and releases secretion and dead cells as well.secretion and dead cells as well.

Sebaceous Sebaceous (ex. oil glands on the face)(ex. oil glands on the face)

Merocrine

Holocrine