BIO 201

Tissues 1

HistologyHistology

Study of TissuesStudy of Tissues

Epithelial TissueEpithelial Tissue Intercellular Junctions and Intercellular Junctions and

GlandsGlands

Connective TissueConnective Tissue

MembranesMembranes

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Muscular Tissue Muscular Tissue

Nervous TissueNervous Tissue

The Study of TissuesThe Study of Tissues

Histology (microscopic anatomy)Histology (microscopic anatomy) study of tissues and how they form organsstudy of tissues and how they form organs

TissueTissue Tissue Tissue group of similar cells and cell products (i.e., ECM)group of similar cells and cell products (i.e., ECM)

Organ Organ composed of 2 or more tissue types (almost always connective composed of 2 or more tissue types (almost always connective

and epithelial; usually includes muscle and nervous)and epithelial; usually includes muscle and nervous)

Four primary tissue classesFour primary tissue classesith li l tiith li l ti

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epithelial tissueepithelial tissue

connective tissueconnective tissue

muscular tissuemuscular tissue

nervous tissuenervous tissue

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Tissues 2

Features of TissuesFeatures of Tissues

Differences between tissuesDifferences between tissues type and function of cellstype and function of cells characteristics of the characteristics of the

surrounding matrix (surrounding matrix (extracellular extracellular matrix; ECMmatrix; ECM)) ground substance made from ground substance made from

proteins, sugars, and sometimes proteins, sugars, and sometimes mineralsminerals called many different names (ECF, called many different names (ECF,

ECM, tissue fluid, interstitial fluid, ECM, tissue fluid, interstitial fluid, basement membrane)basement membrane)

amount of space occupied by amount of space occupied by

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cells versus matrixcells versus matrix very little ECM exists between very little ECM exists between

epithelial and muscle cellsepithelial and muscle cells connective tissue cells are widely connective tissue cells are widely

separated by ECMseparated by ECM

Epithelial TissueEpithelial Tissue

One or more layers of closely adhering cellsOne or more layers of closely adhering cells

Forms a flat sheet with the upper surface exposed to the Forms a flat sheet with the upper surface exposed to the environment or an internal body cavityenvironment or an internal body cavity one side of tissue exposed to “outside”one side of tissue exposed to “outside”

Sits on Sits on basement membranebasement membrane (at the (at the basalbasal surface of cells)surface of cells) thin layer of thin layer of collagencollagen and adhesive proteinsand adhesive proteins

anchors epithelium to underlying connective tissue; provides anchors epithelium to underlying connective tissue; provides supportsupport

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Tissues 3

LayersLayers

Simple epitheliumSimple epithelium contains one layer of cellscontains one layer of cells

named by shape of cellsnamed by shape of cells

Stratified epitheliumStratified epithelium contains more than one layercontains more than one layer

named by shape of named by shape of apicalapical (surface) (surface) cellscells

d t ll (d t ll (b l llb l ll ) it) it

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deepest cells (deepest cells (basal cellsbasal cells) sit on ) sit on basement membranebasement membrane

ShapeShape

•• Squamous (squashed)Squamous (squashed)•• Allows rapid diffusion of Allows rapid diffusion of

substances; secretes serous substances; secretes serous fluidfluidfluidfluid

•• Cuboidal (square)Cuboidal (square)•• Absorption & secretion; Absorption & secretion;

produces mucusproduces mucus

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•• Columnar (rectangular)Columnar (rectangular)•• Absorption & secretion; Absorption & secretion;

produces mucusproduces mucus•• Often ciliatedOften ciliated

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Tissues 4

Epithelial FunctionsEpithelial Functions

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Intercellular JunctionsIntercellular Junctions

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All cells except blood cells are anchored to each other (or to the All cells except blood cells are anchored to each other (or to the matrix surrounding them) by matrix surrounding them) by intercellular junctions intercellular junctions formed by formed by adhesion proteinsadhesion proteins

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Tissues 5

DesmosomesDesmosomes

Patch between 2 cells Patch between 2 cells holding them together holding them together g gg gagainst mechanical stressagainst mechanical stress CONNECTINGCONNECTING gap between cells is spanned gap between cells is spanned

by mesh of filamentsby mesh of filaments often called often called adhesion junctionadhesion junction

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Tight JunctionsTight Junctions

Encircle the cell joining itEncircle the cell joining it Encircle the cell, joining it Encircle the cell, joining it to surrounding cellsto surrounding cells BARRIERBARRIER prevents substances and prevents substances and

bacteria from passing bacteria from passing between cellsbetween cells

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Tissues 6

Gap JunctionsGap Junctions

Transmembrane proteins form Transmembrane proteins form a watera water--filled channelfilled channel

Small solutes (metabolites and Small solutes (metabolites and ions) pass directly from cell to ions) pass directly from cell to cell cell COMMUNICATINGCOMMUNICATING

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aka electrical synapseaka electrical synapse

Cell to Cell JunctionsCell to Cell Junctions

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Tissues 7

Endocrine and Exocrine GlandsEndocrine and Exocrine Glands Glands secrete substances Glands secrete substances ExocrineExocrine glands connect to surface with a glands connect to surface with a ductduct (tube)(tube) EndocrineEndocrine glands secrete their products (glands secrete their products (hormoneshormones) )

directly into directly into bloodstreambloodstream Some glands are mixed Some glands are mixed

gonads release gametes and secrete hormones into bloodgonads release gametes and secrete hormones into blood pancreas secretes digestive enzymes and hormonespancreas secretes digestive enzymes and hormones

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Types of Exocrine SecretionsTypes of Exocrine Secretions

Serous glandsSerous glands produce thin, watery produce thin, watery

secretionssecretions sweat milk tears andsweat milk tears and sweat, milk, tears and sweat, milk, tears and

digestive juicesdigestive juices

Mucous glandsMucous glands produce a glycoprotein, produce a glycoprotein, mucinmucin, ,

that helps form a sticky that helps form a sticky secretion called secretion called mucusmucus nasal, reproductive, nasal, reproductive,

respiratory secretions respiratory secretions

Cytogenic glands release Cytogenic glands release

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y g gy g gwhole cells whole cells produce gametesproduce gametes

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Tissues 8

Endocrine GlandsEndocrine Glands

Produce chemical Produce chemical signals that cause asignals that cause asignals that cause a signals that cause a responseresponse hormonehormone

Released into Released into blood!!blood!!

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Connective TissueConnective Tissue

Consists of widely spaced cells separated by fibers and Consists of widely spaced cells separated by fibers and ground substanceground substance

Most abundant and variable tissue typeMost abundant and variable tissue type Most abundant and variable tissue typeMost abundant and variable tissue type

FunctionsFunctions connectsconnects structures to each otherstructures to each other

gives gives supportsupport and and protectionprotection (physical & immune)(physical & immune)

stores energystores energy

movementmovement and and transporttransport of materialsof materials

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Tissues 9

Ground Ground SubstanceSubstance of Connective Tissueof Connective Tissue

Gelatinous or rubbery material found in between cellsGelatinous or rubbery material found in between cells Consists of large moleculesConsists of large molecules

proteoglycansproteoglycans embedded in plasma membranesembedded in plasma membranes embedded in plasma membranes embedded in plasma membranes create a strong bond to other cells or extracellular matrixcreate a strong bond to other cells or extracellular matrix

glycoproteinsglycoproteins proteinprotein--carbohydrate complexes that bind plasma membrane to carbohydrate complexes that bind plasma membrane to

collagen or proteoglycans outside the cellscollagen or proteoglycans outside the cells

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Cells of Connective TissueCells of Connective Tissue

FibroblastsFibroblasts produce protein fibers and ground substanceproduce protein fibers and ground substance

White blood cellsWhite blood cells MacrophagesMacrophages phagocytose foreign materialphagocytose foreign materialMacrophagesMacrophages phagocytose foreign material phagocytose foreign material

NeutrophilsNeutrophils phagocytose bacteria phagocytose bacteria

Plasma cellsPlasma cells synthesize antibodiessynthesize antibodies

Mast cellsMast cells in skin secrete heparin that inhibits clotting and in skin secrete heparin that inhibits clotting and histamine that dilates blood vesselshistamine that dilates blood vessels

AdipocytesAdipocytes or fat cells store triglyceridesor fat cells store triglycerides

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Tissues 10

Fibers of Connective TissueFibers of Connective Tissue

Collagen fibersCollagen fibers tough tough

resistant to stretch, yet flexibleresistant to stretch, yet flexible

tendons, ligaments and deep layer of the skin (dermis)tendons, ligaments and deep layer of the skin (dermis)

Elastic fibersElastic fibers thin branching fibers made of thin branching fibers made of elastinelastin

stretch & recoil like rubberband (elasticity)stretch & recoil like rubberband (elasticity)

give skin, lungs and arteries ability to stretch and recoilgive skin, lungs and arteries ability to stretch and recoil

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Reticular fibersReticular fibers thin thin collagen fiberscollagen fibers coated with coated with glycoproteinglycoprotein

form framework for spleen and lymph nodesform framework for spleen and lymph nodes

Types of Fibrous Connective TissueTypes of Fibrous Connective Tissue

Loose connective tissueLoose connective tissue contains gelcontains gel--like groundlike ground contains gelcontains gel like ground like ground

substance between cellssubstance between cells

Dense connective tissueDense connective tissuefib fill th b tfib fill th b t

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fibers fill the spaces between fibers fill the spaces between cellscells

2 types varying in fiber 2 types varying in fiber orientationorientation dense regular connective dense regular connective

tissuetissue

dense irregular connective dense irregular connective tissuetissue

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Tissues 11

Adipose TissueAdipose Tissue

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Large, emptyLarge, empty--looking cells with thin marginslooking cells with thin margins Nucleus pressed against cell membraneNucleus pressed against cell membrane

Energy storage, insulation, cushioningEnergy storage, insulation, cushioning Subcutaneous fat beneath skin and surrounding organsSubcutaneous fat beneath skin and surrounding organs

CartilageCartilage

Supportive connective tissue with rubbery matrixSupportive connective tissue with rubbery matrix

ChondroblastsChondroblasts produce cartilage matrix, once surrounded produce cartilage matrix, once surrounded by cartilage by cartilage chondrocyteschondrocytesy gy g yy

No blood vessels so diffusion must bring in nutrients and No blood vessels so diffusion must bring in nutrients and remove wastesremove wastes injured cartilage heals slowlyinjured cartilage heals slowly

Major types of cartilage depend upon fiber typesMajor types of cartilage depend upon fiber types hyaline, fibrocartilage and elastic cartilagehyaline, fibrocartilage and elastic cartilage

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Tissues 12

CartilageCartilage

FibrocartilageFibrocartilage Cartilage containing extensive Cartilage containing extensive

parallel collagen fibersparallel collagen fibers Resists compression andResists compression and Resists compression and Resists compression and

absorbs shock in some jointsabsorbs shock in some joints Pubic symphysis and Pubic symphysis and

intervertebral discsintervertebral discs

HyalineHyaline

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Clear, glassy matrix; fine Clear, glassy matrix; fine dispersed collagen fibers; dispersed collagen fibers; chondrocytes in small clusters chondrocytes in small clusters enclosed in lacunaeenclosed in lacunae

Joints; supportive material in Joints; supportive material in larynx, trachea, bronchi larynx, trachea, bronchi

BoneBone

Spongy bone looks Spongy bone looks spongy in appearancespongy in appearance delicate struts of bonedelicate struts of bone always covered by compact always covered by compact

bonebone

Compact bone looks solid Compact bone looks solid in appearancein appearance more complex arrangementmore complex arrangement cells and matrix vertically cells and matrix vertically

orientedoriented

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Tissues 13

BloodBlood

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Variety of cells and cell fragmentsVariety of cells and cell fragments white blood cells, red blood cells, and plateletswhite blood cells, red blood cells, and platelets

Found in heart and blood vesselsFound in heart and blood vessels

Mucous MembranesMucous Membranes

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Consists of epithelium, connective (basal lamina or lamina Consists of epithelium, connective (basal lamina or lamina propria) and underlying muscular tissuespropria) and underlying muscular tissues

Lines passageways that open to the exterior: digestive, Lines passageways that open to the exterior: digestive, respiratory, urinary and reproductiverespiratory, urinary and reproductive

Mucous coating and movement of cilia trap and remove Mucous coating and movement of cilia trap and remove foreign particles and bacteria from internal surfaces of bodyforeign particles and bacteria from internal surfaces of body

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Tissues 14

Cutaneous, Synovial and Serous Cutaneous, Synovial and Serous MembranesMembranes

Cutaneous membrane (skin)Cutaneous membrane (skin) stratified squamous epithelium resting on layer of connective tissuestratified squamous epithelium resting on layer of connective tissue relatively dry layer serves protective functionrelatively dry layer serves protective function

S i l b li j i tS i l b li j i t Synovial membrane lines joints Synovial membrane lines joints secretes secretes synovialsynovial fluid rich in hyaluronic acid into the joint fluid rich in hyaluronic acid into the joint

Serous membrane (serosa) Serous membrane (serosa) –– internal membraneinternal membrane covers organs and walls of body cavities, produces covers organs and walls of body cavities, produces serousserous fluidfluid

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Muscular TissueMuscular Tissue

Elongated cells that respond to stimuli by Elongated cells that respond to stimuli by contractingcontracting Function is to exert physical force on other tissuesFunction is to exert physical force on other tissues

h dh d move handmove hand push blood through a vesselpush blood through a vessel expel urineexpel urine

Important source of body heatImportant source of body heat Three types of muscleThree types of muscle

skeletal, cardiac and smoothskeletal, cardiac and smooth

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Tissues 15

Skeletal MuscleSkeletal Muscle

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Long, cylindrical, unbranched cells with Long, cylindrical, unbranched cells with striationsstriations Movement, facial expression, posture, breathing, speech, Movement, facial expression, posture, breathing, speech,

swallowing and excretionswallowing and excretion

Cardiac MuscleCardiac Muscle

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Short branched cells with striations and Short branched cells with striations and intercalated discsintercalated discs Pumps bloodPumps blood

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Tissues 16

Smooth MuscleSmooth Muscle

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Short cells; nonstriatedShort cells; nonstriated Sheets of muscle in viscera; iris; hair follicles and sphincters Sheets of muscle in viscera; iris; hair follicles and sphincters

Swallowing, GI tract functions, labor contractions, control of airflow, Swallowing, GI tract functions, labor contractions, control of airflow, erection of hairs and control of pupilerection of hairs and control of pupil

Nervous TissueNervous Tissue

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Large Large neuronsneurons with long cell processes surrounded by with long cell processes surrounded by much smaller much smaller glialglial cells lacking cells lacking dendritesdendrites and and axonsaxons

Found in brain, spinal cord, nerves & gangliaFound in brain, spinal cord, nerves & ganglia CommunicationCommunication and and controlcontrol of bodily functionsof bodily functions