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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