TISSUESTISSUES

STRUCTURAL ORGANIZATIONSTRUCTURAL ORGANIZATION► Life is characterized by hierarchical orders of Life is characterized by hierarchical orders of

organizationorganization AtomsAtoms MoleculesMolecules OrganellesOrganelles CellsCells TissuesTissues OrgansOrgans Organ systemsOrgan systems OrganismOrganism (Population)(Population) (Community)(Community) (Ecosystem)(Ecosystem)

STRUCTURAL ORGANIZATIONSTRUCTURAL ORGANIZATION► The cell is the lowest level of organization that can live The cell is the lowest level of organization that can live

independently as an organismindependently as an organism

STRUCTURAL ORGANIZATIONSTRUCTURAL ORGANIZATION► In multicellular organisms, specialized cells are In multicellular organisms, specialized cells are

grouped into grouped into tissues A A tissuetissue is a group of cells similar in structure and is a group of cells similar in structure and

performing a common functionperforming a common function

► Organs are comprised of Organs are comprised of combinations of various combinations of various tissuestissues

► Organ systems include Organ systems include multiple organs working multiple organs working togethertogether

TISSUE TYPESTISSUE TYPESFour major tissue typesFour major tissue types►Epithelial tissueEpithelial tissue►Connective tissueConnective tissue►Muscle tissueMuscle tissue►Nervous tissueNervous tissue

EPITHELIAL TISSUEEPITHELIAL TISSUE►Sheets of cells covering body surfaces or lining Sheets of cells covering body surfaces or lining

body cavitiesbody cavities►Form boundaries between different Form boundaries between different

environmentsenvironments e.g., Epidermis of skin separates inside and outside e.g., Epidermis of skin separates inside and outside

of bodyof body e.g., Epithelium lining urinary bladder separates e.g., Epithelium lining urinary bladder separates

underlying cells from urineunderlying cells from urine

EPITHELIAL TISSUEEPITHELIAL TISSUE►Many diverse functionsMany diverse functions

ProtectionProtection AbsorptionAbsorption FiltrationFiltration ExcretionExcretion SecretionSecretion Sensory receptionSensory reception

EPITHELIUM CHARACTERISTICSEPITHELIUM CHARACTERISTICS► CellularityCellularity

Little extracellular materialLittle extracellular material

► Specialized contactsSpecialized contacts Tight junctions & desmosomesTight junctions & desmosomes

► PolarityPolarity Basal and apical surfacesBasal and apical surfaces

► Supported by connective tissueSupported by connective tissue► AvascularAvascular

Nourished from belowNourished from below

► InnervatedInnervated► RegenerationRegeneration

Rapid cell division at basal surfaceRapid cell division at basal surface

CLASSIFICATION OF EPITHELIACLASSIFICATION OF EPITHELIA

Cell layersCell layers►Simple epitheliaSimple epithelia

Single cell layerSingle cell layer►Facilitates absorption and Facilitates absorption and

filtrationfiltration

►Stratified epitheliaStratified epithelia Two or more cell layersTwo or more cell layers

►Common in high-abrasion Common in high-abrasion areasareas

e.g., Skin surface, mouthe.g., Skin surface, mouth

CLASSIFICATION OF EPITHELIACLASSIFICATION OF EPITHELIA

Cell shapeCell shape►All epithelia have six sidesAll epithelia have six sides►Cells vary in heightCells vary in height►Three common shapesThree common shapes

Squamous cellsSquamous cells Cuboidal cellsCuboidal cells Columnar cellsColumnar cells

Shape of nucleus conforms to Shape of nucleus conforms to shape of cellshape of cell

CLASSIFICATION OF EPITHELIACLASSIFICATION OF EPITHELIA

Cell layers & cell shapeCell layers & cell shape►Two namesTwo names

First name indicates cell layersFirst name indicates cell layers Second name indicates cell shapeSecond name indicates cell shape

e.g., Simple squamous epitheliume.g., Simple squamous epithelium e.g., Stratified cuboidal epitheliume.g., Stratified cuboidal epithelium

ENDOCRINE GLANDSENDOCRINE GLANDS►““Ductless glandsDuctless glands””

(Ducts are eventually lost)(Ducts are eventually lost)

►Produce hormonesProduce hormones Secreted directly into extracellular space via Secreted directly into extracellular space via

exocytosisexocytosis

►Many (but not all) are epithelial derivativesMany (but not all) are epithelial derivatives►More information in their own chapterMore information in their own chapter

EXOCRINE GLANDSEXOCRINE GLANDS►More numerous than endocrine glandsMore numerous than endocrine glands►Secrete into body cavities or onto body surfacesSecrete into body cavities or onto body surfaces

(i.e., Not into extracellular space)(i.e., Not into extracellular space) Unicellular glands via exocytosisUnicellular glands via exocytosis Multicellular glands via ductsMulticellular glands via ducts

►DiverseDiverse e.g., Mucous, sweat, oil, and salivary glands, etc.e.g., Mucous, sweat, oil, and salivary glands, etc.

EXOCRINE GLANDSEXOCRINE GLANDSUnicellular Gland: Goblet cellUnicellular Gland: Goblet cell►Shaped like a gobletShaped like a goblet►Present in columnar epithelia of intestinal and Present in columnar epithelia of intestinal and

respiratory tractsrespiratory tracts►Produce Produce mucinmucin

Mucin + water Mucin + water mucus mucus Protects and lubricatesProtects and lubricates

EXOCRINE GLANDSEXOCRINE GLANDSMulticellular Glands: Structural ClassificationMulticellular Glands: Structural Classification►SimpleSimple►CompoundCompound

►TubularTubular►Alveolar (acinar)Alveolar (acinar)►TubuloalveolarTubuloalveolar

CONNECTIVE TISSUECONNECTIVE TISSUE►Found everywhere in the bodyFound everywhere in the body

Most widely distributed primary tissueMost widely distributed primary tissue

►Four main classesFour main classes Connective tissue properConnective tissue proper CartilageCartilage Bone tissueBone tissue BloodBlood

CONNECTIVE TISSUECONNECTIVE TISSUE►Major functionsMajor functions

Binding and supportBinding and support ProtectionProtection InsulationInsulation TransportationTransportation

►Which of these functions are accomplished by Which of these functions are accomplished by bone and cartilage? Fat? Bloodbone and cartilage? Fat? Blood??

CONNECTIVE TISSUECONNECTIVE TISSUECommon CharacteristicsCommon Characteristics► Common originCommon origin

All connective tissues All connective tissues arise from mesenchyme arise from mesenchyme (an embryonic tissue) (an embryonic tissue)

► Degrees of vascularityDegrees of vascularity AvascularAvascular poorly vascularpoorly vascular highly vascularhighly vascular

► Extracellular matrixExtracellular matrix Largely composed of non-living extracellular matrixLargely composed of non-living extracellular matrix

CONNECTIVE TISSUECONNECTIVE TISSUE►Three main structural elementsThree main structural elements

Ground substanceGround substance FibersFibers CellsCells

Ground substance + fibers = matrixGround substance + fibers = matrix

FIBERSFIBERS► Three types of fibers provide supportThree types of fibers provide support

Collagen fibersCollagen fibers► ““WhiteWhite”” fibers fibers ►Strongest and most abundantStrongest and most abundant

Tensile strength > steelTensile strength > steel

Elastic fibersElastic fibers► ““Yellow fibersYellow fibers””►Long, thin, branching fibersLong, thin, branching fibers►Contain the protein elastinContain the protein elastin

Can stretch and recoilCan stretch and recoil

Reticular fibersReticular fibers►Fine collagenous fibersFine collagenous fibers►Networks surround and support soft tissue of organsNetworks surround and support soft tissue of organs

CELLSCELLS►Connective tissue is a home for many other cell Connective tissue is a home for many other cell

typestypes Fat cellsFat cells LeukocytesLeukocytes MacrophagesMacrophages Mast cellsMast cells

These last three types of cells will be dealt with in These last three types of cells will be dealt with in great detail in the blood chaptergreat detail in the blood chapter

Macrophages and mast cells will be dealt with in Macrophages and mast cells will be dealt with in some detail nowsome detail now

NERVOUS TISSUENERVOUS TISSUE► Main component of the nervous systemMain component of the nervous system

Brain, spinal cord, and nervesBrain, spinal cord, and nerves Regulates and controls body functionsRegulates and controls body functions

► Two main cell typesTwo main cell types NeuronsNeurons

►Generate and conduct Generate and conduct nerve impulsesnerve impulses

Supporting cellsSupporting cells►Non-conducting cells Non-conducting cells

that support, insulate, that support, insulate, and protect neuronsand protect neurons

MUSCLE TISSUEMUSCLE TISSUE►Highly cellularHighly cellular►Well vascularizedWell vascularized►Responsible for most types of body movementResponsible for most types of body movement►Possess myofilamentsPossess myofilaments

Actin and myosinActin and myosin

►Three typesThree types Skeletal muscleSkeletal muscle Cardiac muscleCardiac muscle Smooth muscleSmooth muscle

SKELETAL MUSCLESKELETAL MUSCLE

►Skeletal muscle cellsSkeletal muscle cells a.k.a., a.k.a., ““Muscle fibersMuscle fibers”” Long, cylindrical cellsLong, cylindrical cells MultinucleateMultinucleate StriatedStriated VoluntaryVoluntary

SKELETAL MUSCLESKELETAL MUSCLE► Forms organs called skeletal musclesForms organs called skeletal muscles

Packaged by sheets of connective tissuePackaged by sheets of connective tissue Attached to bones of skeletonAttached to bones of skeleton

► Contract to pull on bones or skinContract to pull on bones or skin Movement resultsMovement results

CARDIAC MUSCLECARDIAC MUSCLE► Found only in the wall of the heartFound only in the wall of the heart► Contractions propel blood through blood vesselsContractions propel blood through blood vessels► Cardiac muscle cellsCardiac muscle cells

““MyocytesMyocytes”” StriatedStriated UninucleateUninucleate BranchingBranching InvoluntaryInvoluntary

SMOOTH MUSCLESMOOTH MUSCLE► Found mainly in walls of hollow organsFound mainly in walls of hollow organs

e.g., Intestines, esophagus, blood vessels, etc.e.g., Intestines, esophagus, blood vessels, etc. Contractions squeeze substances through these organsContractions squeeze substances through these organs

► No visible striationsNo visible striations► Smooth muscle cellsSmooth muscle cells

Spindle shapedSpindle shaped UninucleateUninucleate InvoluntaryInvoluntary

BODY DEFENSESBODY DEFENSES►Mechanical barriers are the bodyMechanical barriers are the body’’s first line of s first line of

defense against injury and infectiondefense against injury and infection Skin and mucous membranesSkin and mucous membranes Respiratory ciliaRespiratory cilia Acids secreted into stomach and from skinAcids secreted into stomach and from skin

►Tissue injury breaches this first line of defenseTissue injury breaches this first line of defense Stimulates inflammatory and immune responsesStimulates inflammatory and immune responses

►Second and third lines of defense, respectivelySecond and third lines of defense, respectively

Tissue is ultimately repairedTissue is ultimately repaired