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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