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BIO 210 LabInstructor Dr. Rebecca Clarke
Chapter 4 The Tissue Level of Organization
Tissue
Histology = study of tissuesTissue = group of cells that perform
specific, limited functions
Composition of TissuesBasic components
CellsMatrix
Surrounds cellsConsists of
Ground substanceProtein fibers or proteins
4 Major Groups of TissuesEpithelial tissueConnective tissueMuscle tissueNeural tissue
Epithelial Tissue Covers exposed surfacesLines internal passagewaysForms glands
Connective Tissue Fills internal spacesSupports other tissuesTransports materialsStores energy
Muscle Tissue Specialized for contraction movement
Neural Tissue Carries electrical signals (nerve impulses)
from one part of the body to another
Epithelial Tissue Includes
Epithelia = layers of cells that coverExternal/exposed surfaces (skin)Internal surfaces that line internal passageways and
cavitiesGlands = cellular structures that produce
secretions; are attached to or derived from epithelia
Classes of EpitheliaBased on cell shape and layers
Table 4–1
Figure 4–3a
Simple Squamous Epithelium
Figure 4–3b
Stratified Squamous Epithelium
Simple Cuboidal Epithelium
Figure 4–4a
Stratified Cuboidal Epithelium
Figure 4–4b
Transitional Epithelium
Figure 4–4c
Simple Columnar Epithelium
Figure 4–5a
Stratified Columnar Epithelium
Figure 4–5c
Pseudostratified Columnar Epithelium
Figure 4–5b
Glandular Epithelia
Endocrine and exocrine glands
Range from scattered cells to complex organs (glands)
Figure 4–6
Endocrine GlandsDuctless glandsRelease secretions (hormones) into
interstitial fluid or bloodRegulate/coordinate activities of many
tissues, organs, organ systems
Exocrine GlandsRelease secretions
onto epithelial surfaces, e.g., simplest = one-cell goblet cell (in respiratory and digestive tracts)
through ducts, e.g., sweat, digestive, lacrimal, mammary glands
What are the structures and functions of different types of connective tissues?
Characteristics of Connective Tissues
Fills internal spacesMany diverse functionsMany highly-specialized cellsMuch more matrix than cells
Components of ConnectiveTissueCells – highly varied, specialized
populationsMatrix
Consists ofGround substance Fills spaces between cells and surrounds connective
tissue fibers Clear, colorless, amorphous substance; changes
according to tissue Viscous (“syrupy”) due to proteoglycans and
glycoproteinsProtein fibers/proteins
Can be fluid, gel or solid, e.g., gelatin dessertDetermines specialized function
Classification of Connective TissuesConnective tissue proper
Connects and protectsLoose and dense connective tissues
Fluid connective tissuesTransport systemsBlood and lymph
Supporting connective tissuesStructural strengthCartilage and bone
Connective Tissue Proper
Figure 4–8
8 Cell Types of Connective Tissue ProperMesenchymal
cellsFibroblastsPhagocytes
MacrophagesMicrophages
Mast cellsAdipocytesMelanocytes Lymphocytes
Mesenchymal CellsMesenchyme = first connective tissue in
developing embryo (see text Fig 4-9)Are connective tissue stem cells; give
rise to all other connective tissue cellse.g., Respond to local injury/infection by
dividing daughter cells that differentiate into other connective tissue cells, e.g., fibroblasts, macrophages, etc.
Fibroblasts“Fiber builder”Most abundant cell typeFound in all connective tissue properSecrete
polysaccharide (+ protein proteoglycans viscous ground substance)
protein subunits large fibers
PhagocytesPhagocytes (“cell eaters”)
Macrophages (“big eaters”)Microphages (“little eaters”)
MacrophagesLarge, amoeba-like cells of the immune
systemEat pathogens and damaged cells;
“garbage disposal” cellsRelease chemicals that activate immune
system mobilizes body defenses2 classes
fixed macrophages stay in tissue; frontline defense
free macrophages migrate through tissues; reinforcements
Microphages(NOT in Fig 4-8)
Phagocytic white blood cells (WBCs), i.e., neutrophils and eosinophils
Attracted to site of infection/injury by chemicals released by macrophages
Mast CellsSmall mobile cellsStimulate inflammation after injury or
infectionCytoplasm filled with granules that
contain/release histamine and heparinBasophils are mast cells carried by blood
AdipocytesAdipose or fat cellsStore fatContain single, large lipid droplet; nucleus,
other organelles, cytoplasm squeezed to side class ring appearance
Number of cells varies with tissue, body region, individual
Melanocytes Synthesize, store melanin (brown pigment)
dark colorCommon in skin epitheliumDetermine skin, eye, hair color
LymphocytesSpecialized immune cells in lymphatic
systeme.g., plasma cells that produce antibodies;
one of body’s defense mechanismsWBCs that leave bloodstream and migrate
throughout bodyNumbers increase with tissue damage
Protein FibersProvide structural strength to connective
tissues3 types
CollagenReticularElastic
Collagen FibersMost common fibersLarge, long, straight, unbranchedStrong, flexible (like rope); very little
stretchPredominate in ligaments (connect bone to
bone) and tendons (connect muscle to bone)
Reticular FibersSame protein subunits as collagen but
Thinner, shorterArranged differently branched network of
interwoven fibers (stroma)Strong, flexibleStabilizes functional cells of organs
(parenchyma), e.g., hepatic cells of liverStabilizes position of blood vessels,
nerves, etc.Connects epithelium to body
Elastic FibersContain protein elastinBranched and wavyReturn to original length after stretchinge.g., elastic ligaments of vertebrae
Categories of Connective Tissue ProperLoose connective tissue
more ground substance, less fibers e.g., fat (adipose tissue)
Dense connective tissuemore fibers, less ground substancee.g., tendons
Loose Connective TissueFew soft fibers loose, open framework;
“packing materials” of bodyFills spaces between organsCushions, stabilizes cellsSupports epithelia, blood vessels, nerves
Loose Connective Tissue (cont.)3 types
Areolar tissueAdipose tissueReticular tissue
Areolar TissueLeast specializedOpen framework of cells/fibersCan distort, return to original shape
because of elastic fibers Most of volume is viscous ground
substanceHighly vascular, e.g., subcutaneous
layer under skin, common injection siteFig 4-8
Adipose Tissue
Primarily adipocytes (adipose cells)
Figure 4–10a
Adipose CellsAdipocytes in adults do not divide
expand to store fatshrink as fats are released
Mesenchymal cells divide and differentiateto produce more fat cellswhen more storage is needed
Reticular TissuePrimarily reticular fibers
Figure 4–10b
Reticular TissueComplex, 3-dimensional networkSupportive fibers (stroma)
support functional cells (parenchyma)Reticular organs
spleen, liver, lymph nodes, and bone marrow
Dense Connective TissuesTightly packed with high numbers of
collagen or elastic fibersMany fibroblastsVery strong tissuesTypes of dense connective tissues
dense regular connective tissuedense irregular connective tissueelastic tissue
Dense Regular Connective TissueTightly packed, parallel collagen fibersMake up tendons, ligaments, aponeuroses
Figure 4–11a
Dense Regular Connective TissuesTendons - attach skeletal muscles to bonesLigaments - connect bone to bone and
stabilize organsAponeuroses - attach in sheets on large,
flat muscles
Dense Irregular Connective TissueStrength in many directions
Figure 4–11b
Dense Irregular Connective Tissues
Interwoven meshwork of collagen fibers layered in skinaround cartilages (perichondrium)around bones (periosteum)form capsules around some organs (e.g.,
liver, kidneys, spleen)
Elastic TissueMade of elastic fibers
e.g., elastic ligaments of spinal vertebrae
Figure 4–11c
Fluid Connective TissuesBlood and lymphCells suspended in fluid matrix = watery
ground substance with dissolved proteins
Blood Formed Elements
RBCs (erythrocytes)WBCs (leukocytes)Platelets
Figure 4–12
LymphCells – 99% lymphocytes, rest are
macrophages or microphages Matrix = fluid from CVS exits at capillaries
interstitial fluid enters lymphatic vessels (= lymph) that return it to CVS (recirculatory system)
Along way, cells of immune system monitor composition of lymph and respond to signs of injury or infection
Essential to homeostasis – eliminates local differences in nutrients, wastes, toxins, maintains blood volume, alerts immune system
Fluid Tissue Transport SystemsCardiovascular system (blood)
arteriescapillariesveins
Lymphatic system (lymph)lymphatic vessels
Supporting Connective TissuesSupport soft tissues and body weight
Cartilage for shock absorption and protection
Bone for weight support
Supporting Connective TissuesCharacteristics
Provide strong framework that supports bodyCells – less diverse than CTMatrix
Dense ground substanceCartilage – rubbery, gel-likeBone - calcified, crystalline, solid matrix
Many fibers
Cartilage ComponentsCells
Chondrocytes = only cells presentOccupy lacunae (small chambers)
Matrix Ground substance = firm gel with…Chondroitin sulfates (polysaccharide
derivatives); form complexes with proteins proteoglycans
Protein fibersType and number + proteoglycans determine
physical properties
Cartilage StructureAvascular = no blood vessels
chondrocytes produce antiangiogenesis factor
Perichondriumsurrounds cartilage and separates it from
tissue
Types of CartilageHyaline cartilage
translucent matrixno prominent fibers
Elastic cartilagetightly packed elastic fibers
Fibrocartilagevery dense collagen fibers
Hyaline Cartilage
Figure 4–14a
Hyaline CartilageMost commonMatrix - contains closely packed
collagen fibers tough, flexible supportReduces friction between bonesExamples
Connects ribs and sternumNasal cartilagesCartilages that support respiratory
passageways, e.g., tracheaArticular cartilages – cover bone surfaces
within synovial joints, e.g., elbow, knee; reduce friction
Elastic Cartilage
Figure 4–14b
Elastic CartilageMany elastic fibers resilient, flexible
structures; supports but bends easilyExamples
auricle/pinna of outer earepiglottis (in larynx) auditory tube (airway to middle ear)small cartilages in larynx
Fibrocartilage
Figure 4–14c
FibrocartilageVery little ground substanceMatrix dominated by densely
interwoven collagen fibers extremely durable, toughResists compressionActs as shock absorberPrevents bone-to-bone contact
Examples:Intervertebral discs = pads between
vertebraeBetween pubic bonesPads knee joints
BoneAlso called osseous tissueOsteocyte = bone cell
Arranged around central canalSmall channels through matrix (canaliculi)
access blood supplyPeriosteum
covers bone surfaceHelps attach bone to surrounding tissues,
tendons, ligaments
Bone
Figure 4–15
Bone Ground Substance Very small amount of ground substance 2/3 of matrix is calcium salts (minerals) =
hydroxyapatiteCalcium phosphateCalcium carbonate
1/3 of matrix dominated by collagen fibers Minerals organized around collagen fibers Remarkable properties of bone
Strong (calcified salts) + somewhat flexible structure (collagen fibers)
Highly resistant to shattering (like steel-reinforced concrete mineralized matrix like concrete collagen fibers equiv to steel reinforcing rods
Comparing Cartilage and Bone
Table 4–2
What are the structures and functions of the three types of muscle tissue?
Muscle TissueSpecialized for contraction; produces all
body movementDistinct organelles and processesMultinuclearHas many fibers; orderly appearanceunder voluntary or involuntary controlOne of two kinds of cells/tissues in body
that stop replicating past stage of growth and development; (other is neural tissues/neurons)
3 Types of Muscle TissueSkeletal muscle - large body muscles
responsible for movementCardiac muscle - found only in the heartSmooth muscle - found in walls of hollow,
contracting organs (blood vessels; urinary bladder; respiratory, digestive and reproductive tracts)
Classification of Muscle CellsStriated (muscle cells with a banded
appearance) or nonstriated (not banded)
Single nucleus or multinucleate
Controlled voluntarily (consciously)or involuntarily (automatically)
Skeletal Muscle Striated, voluntary, multinucleated
Figure 4–18a
Skeletal Muscle CellsVery long (some > 1 ft) and thin; called muscle
fibersMultinucleate; 100s of nuclei/cellCytoskeleton contains actin and myosin filaments
Filaments organized into repeating groups striated/banded appearance
Contract when stimulated by nerves; provide voluntary control over muscle activities
Adjacent muscle fibers connected by collagen and elastic fibers that blend into attached tendon or aponeurosis; when contract, pull on attached bone, producing movement
Can’t divide; new muscle fibers produced through divisions of satellite (stem) cells; can partially repair after injury
Cardiac Muscle TissueStriated, involuntary, single nucleus
Figure 4–18b
Cardiac Muscle Cells Cardiac muscle cell = cardiocyte
Smaller than skeletal muscle cellUsually one centrally positioned nucleusActin and myosin filaments arranged in same way as in
skeletal muscle; striations Cells form branching networks; connected at specialized
regions = intercalated discs (like dovetail joints) Ion movement through gap junctions helps coordinate
contractions throughout heart Rely on pacemaker cells to establish regular rate of
contraction; neural stimulation not required Involuntary muscle contractions Very limited ability to repair
Smooth Muscle TissueNonstriated, involuntary, single nucleus
Figure 4–18c
Smooth Muscle Cells Smooth muscle cell
small, spindle-shaped cell, tapered endssingle oval nucleusactin and myosin filaments organized differently from those
of skeletal and cardiac muscles, no striations “smooth” appearance
Nervous system does not provide voluntary control over contractions; hence, smooth muscle = involuntary muscle
Cells can divide and regenerate after injury Location:
Walls of blood vesselsAround hollow organs, e.g., urinary bladder In layers around respiratory, circulatory, digestive,
reproductive tracts
What is the basic structure and role of neural tissue?
Neural (Nervous) TissueSpecialized for conducting electrical
impulsesRapidly senses internal or external
environmentProcesses information and controls
responses
Neural Tissue98% concentrated in central nervous
system (CNS)brainspinal cord
Remaining 2% in peripheral nervous system (PNS)
2 Types of Neural Cells1. Neurons
nerve cells perform electrical communication
2. Neuroglia support cells repair and supply nutrients to neurons
Neuron
Figure 4–19
Cell Parts of a NeuronCell body
contains the nucleus and nucleolusDendrites
short branches extending from the cell bodyreceive incoming signals
Cell Parts of a NeuronAxon (nerve fiber)
long, thin extension of the cell bodycarries outgoing electrical signals to their
destination
Characteristics of NeuronsLongest cells in body – some > 1 meterCannot divide under normal circumstances
so very limited ability to repair selvesOne of only two kinds of cells/tissues in
body that stop replicating after stage of growth and development (other is muscle tissue)
Neuroglia
Figure 4–19