Chapter 4

Klennex isn’t the Only TissueTissues are groups of cells with similar

structures and functionsHistology is the study of them

4 primary typesEpithelial – covering an boundary formationConnective – support, protect, and bindMuscle – contractions cause movementNervous - control and communication

Organs often composed of all 4

Zygote blastocystCells organize into 3

primary germ layers (gastrulation) 2nd- 3rd week

Germ layersEctoderm

Epidermis and nervous systemEndoderm

Linings of digestive and respiratory tracts

Mesoderm Skeletal, muscular, and

circulatory systems

Embryonic Development

Epithelial TissueCovers or lines; glands tooFunctions reflect structure

Protection, absorption, filtration, excretion, secretion, sensory reception, and gas exchange

CharacteristicsCellularity: cells packed tight together, bound by tight

junctions and desmosomesPolarity

Apical and basal surfacesConnective tissue attachment

Basal lamina (noncellular) to reticular lamina (ECM) Resists stretching and tearing

Avascular, but innervatedRegeneration

Friction and external substance exposure

Classifying EpitheliaLayer ShapeSimple: 1

Absorbtion, secretion, and filtration

Stratified: 2+Protection

Pseudostatified: looks 2+, but not

Squamous: flattened, scale-like

Cuboidal: sides equal, box-like

Columnar: taller than wide

Transitional: variesNuclei shape and apical

layer

Simple … EpitheliaColumnar

Round/oval nuclei; possibly goblet cells

Digestive tract, and gland ducts; small bronchi, uterine tubes, and uterus

Absorption, secretion of mucus, cilia propels substances

CuboidalLarge spherical central nucleiKidney tubules, ducts of glands, and

ovary surfaceSecretion and absorption

SquamousDisc-shaped central nucleiKidney glomeruli, air sacs of lungs,

capillaries, linings of heart & lymphatic system

Diffusion and filtration; secretes lubricant

Additional EpitheliaPseudostratified columnar

Nuclei at different levels; possible goblet cells, cilia

Male repo. tracts; respiratory tract Secretion and propulsion via cilia

Stratified squamous Apically, basally cuboidal; living

cells are basal Surfaces that are exposed

externally and into all openings Protect abrasive surfaces

Transitional epithelium Stratified and cuboidal basally,

squamous apically as urine volume increases

Ureters, bladder, and urethra Change as urinary organs collect

and excrete

Glandular EpitheliaEndocrine

Ductless Release hormones by exocytosis into blood

Acts on target organ(s)Exocrine

Possess ducts Secretions onto body surface or within cavities

1 or 2 secretion modes Merocrine: exocytosis, pancreas and sweat Apocrine: accumulate at apex and pinches off, mammary maybe Holocrine: accumulate and rupture, sebaceous

Cellularity Unicelluar: goblet cells Multicellular

Simple (unbranched): gastric and sebaceous Compound (branched): duodenal, mammary, and salivary

Connective TissueNever exposed to environment outside the

bodyFunctions

Protect, insulate, transport, support, and bind other tissues together

CharacteristicsComposed of multiple cell types

Mesenchyme originRange of vascularityPrimarily extracellular matrix (ECM)

Non-living; responsible for CT strength and abrasion

CT StructureGround substance

Unstructured space filler Liquid, gel-like, or solid

FibersCollagen: tough with lots of collagen protein; white

fibersElastic: flexible and stretchable with lots of elastin

protein; yellow fibersReticular: add extra support with collagen and

glycoproteinCells (-blast or –cyte)

FibroblastChondroblastOsteoblastHematopoietic stem cell

Connective Tissue Classification

Supporting CT

Cartilage: solid,rubbery matrix

Bone: solid,crystalline matrix

Connective tissues

CT Proper Fluid CT

Loose: Fibersloose, open;i.e. adipose

Dense: Fibers densly packed;

i.e. tendons

Blood: in circulatory

system

Lymph: inlymphatic

system

Bold = 4 main types

Loose CTAreolar

Matrix with all 3 fibers and multiple cellsWidely distributed throughout the bodyLubricates and nourishes epithelia;

strength; elasticity; support; immune protection Edema: inflammatory swelling of liquids

AdiposeSimilar to areolar, but stores more

nutrientsSubcutaneous layer; around organs

Brown vs white fatStores triglycerides; insulates; energy

reserve; protectsReticular

Similar to areolar, but only reticular fibersLiver; spleen; lymph nodesSupport and slow body fluids

Dense CTDense regular

Mostly parallel collagen fibers, some elastic Wavy for stretch

Attaches muscle to bone (tendon), muscle to muscle (aponeuroses), bone to bone (ligament)

Resists tension (1 direction), support, and stabilization

Irregular denseCollagen is thicker and not parallelDermis; joint and organ capsulesResists tension (multiple directions)

CartilageAvascular and w/o innervationsHyaline (gristle)

Most abundant; chondrocytes in lacunaeEnds of long bones (growth plates); ribs to

sternum; septum; respiratory systemSupport with pliability; compressive stress

ElasticMore elastic fibers than hyalineExternal ear and epiglottisShape and flexibility

Fibrocartilage Less firm than hyaline; thick collagen

fibersIntervertebral discs; knee joint; pubic

symphysisResist compression; absorb shock; prevent

bone rubbing

Osseous TissueCollagen fibers and

calcium saltsOsteon

Concentric lamellaeLacunae

Osteocytes produce bone Osteoclasts breakdown

bone

CanaliculiCompact boneSpongy bone

Blood55% plasma

90% water45% cellular

componentsErthrocytesLeukocytesThrombocytes

Nervous TissueCentral nervous systemPeripheral nervous systemMost incapable of dividingNeurons

Cell bodyProcesses

Axon Dendrites

Neuroglia

Muscle TissueCellular and vascularized

Myofilaments Responsible for movementsFound through the bodySkeletal

Striated in appearance, multinucleate, voluntary Moves body parts Can’t divide, but partial regeneration

Smooth No striations, uninucleate, involuntary Moves substance (object) along Can divide

Cardiac Striated, uninucleate, involuntary Heart, has intercalated discs Can’t divide or regenerate

MembranesCutaneous

Exterior exposure; dryStratified squamous

and dense irregular CTMucous

Exterior opening cavities; ‘moist membranes

Str. squ or si. cub. and loose CT

SerousSi. squ. And loose CTLine ventral body

cavity; moist membranes