University of Colorado Boulder



JointsJoints: articulations/points where bones meet and connectDegrees of mobility:Diarthrotic joints: freely moveableEx: shoulder, knee, wrist, etc.Amphiarthrotic joints: slightly moveableEx: intervertebral discsSynarthrotic joints: immovableEx: tooth in socketJoints change with ageSynostosis: 2 bones fused into one by bone tissueFormed at various ages, when bones fuse at jointNo mobilityNot considered a jointEx: coxal bone fuses from 3 parts (by adulthood), skull bones fused together (after middle age)Joint classificationFibrous joints:Bones joined by dense regular CT = ligament (connects bone to bone)Mobility: synarthrotic to diarthroticTypes of fibrous joints:Suture:Ex: between skull bones (synarthrotic)Syndesmosis: length of fibers varies -> determines mobilityEx: distal tibiofibular joint (synarthrotic), interosseous membrane in forearm (diarthrotic)Gomphosis:Ex: between tooth and socket (synarthrotic)Cartilaginous joints:Bones joined by cartilageTypes of cartilaginous joints:Synchondrosis: bones joined by hyaline cartilageEx: epiphyseal plate (synarthrotic), 1st sternocostal joint (synarthrotic)Symphysis: main cartilage is fibrocartilage, may contain hyaline cartilage as wellEx: intervertebral disc (amphiarthrotic), pubic symphysis (amphiarthrotic) Synovial joints:Bones separated by a fluid-containing joint cavityAll are freely moveable -> diarthroticEx: knee, shoulder, knuckle, wrist, between most ribs and sternum, between ear bones, etc.Anatomy of synovial joint:Joint cavity:Contains synovial fluidBlood filtrateLubricatesArticular capsule:Inner layer: synovial membrane (produces synovial fluid by filtrationOuter layer: fibrous capsule with dense irregular CTArticular cartilage:Made of hyaline cartilageFunction: absorbs compression forces -> protects bonesNourished by weight bearing intermittentlyReinforcing ligaments:Dense regular CT that connects bone to boneThree kinds:Capsular: thickened part of the capsuleExtracapsular: outside the capsuleEx: fibular and tibial collateral ligaments of kneeIntracapsular: inside the capsuleEx: anterior and posterior cruciate ligaments of kneeArticular disc (meniscus):In a few synovial jointsFunction:Evens out the distribution of compression forcesHelps stabilize jointAllows additional movementsEx: temporomandibular (jaw) jointEx: kneeTissue type: fibrocrtilageBursae and tendon sheathsClosed sacs of synovial fluidPrevent friction among structuresBursitis: inflammation of a bursaTendon sheath: a bursa that wraps around a tendonMovements of jointsTerms of orientation in anatomyAxes: infinite line that has a specific orientationAnterior-posterior axis: anterior to/from posteriorSuperior-inferior axis: superior to/from inferiorLeft-right axis: left to/from rightDescribing movements using planes and axesMovements:Transitional (linear) = move in straight line (not in planes)Specific directions:Elevation: move superiorlyDepression: move inferiorlyProtraction: move anteriorlyRetraction: move posteriorlyFeature of temporomandibular joint that is useful for these movements is articular discAround an axis:Angular movement: change angle between two bonesFlexion: decrease joint angle (sagittal)Extension: increase joint angle (sagittal)Abduction: move away from midline of body (frontal)Adduction: move toward midline of body (frontal)Circumduction: movement that describes a cone in space (transverse)Special movements of the feet:Dorsiflexion: turn foot upward (sagittal)Plantar flexion: turn foot downward (sagittal)Inversion: turn sole of foot medially (frontal)Eversion: turn sole of foot laterally (frontal)Rotation: bone moves around its own longitudinal axisIn axial region (transverse):Left rotation: turn anterior surface to leftRight rotation: turn anterior surface to rightIn appendicular region (transverse):Medial rotation: turn anterior surface toward midlineLateral rotation: turn anterior surface away from midlineSpecial movements of forearm:Pronation: turn palms posterior (transverse)Supination: turn palms anterior (transverse)These are medial/lateral rotation of the forearmMovement around an axis corresponds to movement within a planeSynovial joints classified by shapeDescribed by:Shape of articulating bone surfacesNumber of axes around which movement can occur:Change angle between bones (angular movement)Move bone around its longitudinal axis (rotation)Plane joint (gliding joint):Only translational (linear) movementNonaxial (no axes)Ex: intercarpal and intertarsal jointsHinge joint:Flexion/extension (typically)Uniaxial (1 axis)Ex: elbowPivot joint:RotationUniaxial (1 axis)Ex: proximal and distal radioulnar jointsCondylar joint:Movements around all axes except axis of rotation (oval so can’t spin)Biaxial (2 axes)Ex: metacarpophalangeal (knuckle) jointsSaddle joint:Movement around all axes except axis of rotation (similar to condylar joint)Biaxial (2 axes)ONLY 2 Ex: 1st carpometacarpal joint (base of thumb) and sternoclavicular jointBall-and-socket joint:Most freely moving jointMovements around all axes including rotation (circular so can spin)Multiaxial/triaxial (3 axes)ONLY 2 Ex: shoulder and hip jointsJoint health and pathologyInjuriesDislocation: bones forced out of normal positionsSprain: ligaments are stretched or tornHas poor blood supply so slow healingStretched ligaments make joint less stableCartilage injury: heals even slowerJoint stability: resistance to dislocationInversely related to range of motion (mobility)Ex: shoulder has large range of motion-> low stability, elbow has small range of motion-> high stabilityFactors affecting stability:Shape of articular surfaceEx: shoulder vs. elbowLigamentsEx: knee, wristMusclesEx: shoulderRotator cuff: 4 tendons (= 4 attached muscles) wrapped closely around joint capsuleDiseasesArthritis: inflammatory or degenerative joint diseasesOsteoarthritis:Wear and tear from normal agingOccurs in most elderly peopleRheumatoid arthritis:An autoimmune diseaseBegins with inflammation of synovial membraneGouty arthritis (gout):Caused by excess uric acid retention -> deposited in synovial membraneMuscleAs a tissue and as an organOrgans are made of tissues, which are made of cells, not other tissues!Examples of tissues that are components of a muscle organMuscle tissueBloodOther connective tissuesNervous tissue, etc.FunctionsExert force: movement, maintain postureStabilize jointsProduce heatSpecial features of muscle tissueContractile: exerts force by contracting (shortening) -> pulls things togetherElectrically excitable: like nervous tissue, allows rapid stimulation of the whole cell at onceTypes of muscle tissueSkeletal: voluntary (typically)Cardiac: heartSmooth: walls of other hollow organsSkeletal muscleFunction: to move bonesAttachments:Origin: the less moveable attachment (proximal)Insertion: the more moveable attachment (distal)Actions:Must cross a joint to act on that jointAction depends on side bone attachment is onMuscles do work by shortening, not by lengtheningAntagonist muscle: different muscle to “undo” another’s actionAgonist (prime mover): muscle that has major responsibility for a particular actionSynergist: a muscle that helps the agonistBasic anatomy:Sheaths of connective tissue organize muscle fibers (cells)Epimysium: surrounds entire musclePerimysium: surrounds each fascicle (bundle of muscle fibers)Endomysium: surrounds muscle fiber (cell)Tendon: extension of the sheaths, connects the muscle to boneFascia surrounds groups of musclesMicroscopic anatomy:Muscle fiber (cell):Typically nearly as long as whole muscleContains many myofibrils = long organelles made of actin (thin) and myosin (thick) filamentsIn muscle cells, both actin and myosin are organized into myofilaments (a type of microfilament)Each section of myofibril is called a sarcomere = the basic functional unit of skeletal muscle contractionMultinucleate (has many nuclei)Striations: indicate repeating groups of protein filaments (actin, myosin, etc.)Cells cannot divide after birthIn strength training, each muscle fiber thickens by adding more protein filamentsStrength is proportional to total cross-sectional area of fibers attached to tendonEx: pennate muscles are stronger than parallel muscle (have more cross-sectional area of fibers)Satellite cells: undifferentiated cells between the muscle fibersContinue dividing through life as neededGrowth, strength training, or muscle damage -> satellite cells merge with muscle fibers (adds nucleus)Nerve cells: direct nervous stimulation is the ONLY cause of contractionMotor unit: motor neuron + all the muscle fibers it innervatesMotor neuron: nerve cell that controls muscle fibersNeuromuscular junction: region where motor neuron contacts muscle fiberMechanism of contraction: the sliding filament mechanismMyosin (thick) and actin (thin) filaments slide past one anotherMyosin heads “crawl” along actin and dragSarcomere shortens by increasing overlap of actinThe filaments do NOT shorten (but everything around the does)Cardiac muscleFound in walls of the heartInvoluntaryMuscle anatomy:Branching chains of short cellsStacked end-to-end1 or 2 nuclei per cellCells cannot divide after birthIntercalated discs: junctions between cellsGap junctions: ions carry signal between cellsFascia adheres: similar to desmosomes b/c hold adjoining cells togetherStriated (orderly structure)SarcomeresActin and myosinCauses of contraction:1. Spontaneously generated (pace-maker cells)Note: the rate of spontaneous contraction is affected by nervous input2. Via gap junctions from other cardiac muscle cellsSmooth muscleMuscle in walls of hollow organs (other than the heart)InvoluntaryMuscle anatomy:Fusiform cells (spindle-shaped)Grouped into sheets of cells having similar orientationUninucleate (1 nucleus per cell)Can divide after birthRegenerates/heals much better than other muscle tissuesActin and myosinNO striations or sarcomeresDense bodies: anchor actin to intermediate filaments to transmit forceGap junctions: to coordinate contractionLoose organization allows smooth muscle cells to generate force even when greatly stretchedOften arranged in circular and longitudinal layers:Contract circular layer -> narrows the tubeContract longitudinal layer -> shortens the tubeCauses of contraction:1. By direct nervous control (but involuntary)Other chemical signals (ex: hormones)StretchVia gap junctions from other smooth muscle cellsSpontaneously generated (like pace-maker cells)What all 3 muscle tissue types have in common!!!Actin and myosinParts of cytoskeleton (intermediate filaments, microtubules)Other organelles (mitochondria)All associated with endomysiumDigestive SystemFunction: process food molecules and move them into the bloodOrgans of digestive systemGastrointestinal (GI) tract (alimentary canal, digestive tract, gut)MouthPharynxEsophagusStomachSmall intestineLarge intestineAccessory organs:Salivary glandsLiverGallbladderPancreasInternal/external lining of GI tract and Structure of GI tract wall:*Membrane: 2 layers (epithelium lines space; connective tissue nourishes epithelium)Mucosa (mucous membrane):Line lumen (interior space) of GI tractSimple columnar epithelium through most of its lengthEndocrine cells: release product into blood (inside body)Exocrine cells: release product into lumen (outside body)Ex: mucusHas other epithelial cells for absorptionRate of cell turnover is rapidLamina propria = CTMALT = mucosa-associated lymphoid tissue (with immune cells)Blood/lymph vessels, nervesGlands (exocrine)Muscularis mucosaeLayer of smooth muscleUnique to digestive systemTwitches to dislodge sharp objectsSubmucosa = CT:Tough but flexibleSubmucosal nerve plexus (network of nerves)Part of enteric nervous systemBlood/lymph vessels, nervesGlands (exocrine)Muscularis externa = muscle layer:Ex: peristalsis = pushing food along the GI tractCircular muscle – contraction narrows tractLongitudinal muscle – contraction shorten tractMyenteric nerve plexus – part of enteric nervous systemSerosa (serous membrane): called the peritoneum in abdominopelvic cavityLines peritoneal cavity (space between organs)Cavity is narrow, crowded by organsVisceral peritoneum (deep inner lining of cavity/outer layer of organ wall): produces serous fluid by filtration (mostly)CTVisceral Mesothelium: simple squamousPeritoneal cavityParietal peritoneum (superficial outer lining of cavity/inner layer of body wall)Parietal Mesothelium: simple squamousCT*Mesentery: double layer of peritoneum connecting parietal and visceral peritoneum (technically an organ)Supports GI tractCarries vessels and nervesStores fatDuring development, some organs in abdominopelvic cavity become buried in body wall and lose mesentery = secondarily retroperitonealStill has peritoneum on one side (side not on body wall)Have adventitia (CT between organs on body wall) on other sideEx: pancreasOrgans that keep mesentery = intraperitonealEx: stomachSteps in food processing1. Ingestion: food taken into the mouth2. Mechanical breakdown and mixing -> more surface area exposed to chemical action (no chemical bonds broken!)3. Secretion (enzymes, mucus, etc.)4. Chemical digestion: breaking down large nutrient molecules (ex: protein) into smaller ones (ex: amino acids)5. Absorption: small molecules actively taken up by epithelium -> moves into blood or lymph6. Propulsion: move food along tract by swallowing and peristalsis7. Defecation: eliminate indigestible material from anusOrgans of the GI tract*Proximal and distal describe relative positions of organs along the tube from mouth to anus (follow the tube)Mouth (oral cavity):Epithelium type: non-keratinized stratified squamousChewing forms bolus of foodAccessory organs:Salivary glands: secrete saliva into the mouthIncludes enzyme to initiate carbohydrate digestion in the mouthPharynx:Sections belonging to GI tract:OropharynxLaryngopharynxEpithelium type: non-keratinized stratified squamousSwallowing: skeletal muscles propel food through pharynx (mostly reflex = involuntary)Esophagus:Function: delivers food from pharynx to stomachLocation: mediastinum (area between the lungs)Characteristics:has both smooth and skeletal muscle (all involuntary) -> peristalsisCardiac sphincter at exit into stomach with thickened smooth muscleCircular muscle layer of muscularis externa is thickPrevents reflux from stomachIf fails to close (ex: due to hiatal hernia) -> GERD (gastroesophageal reflux disease)Epithelium type: non-keratinized stratified squamousStomach:Function:Stores foodChurns food (for mechanical breakdown and mixing) -> chymeBegin chemical digestion of proteinsSecretion:Mucus and bicarbonate (exocrine)Acid (HCl) – sterilizes, separates molecules (exocrine)Digestive enzyme – to break down proteins (exocrine)Gastrin – a hormone (messenger via blood) to stimulate acid secretion (endocrine)Absorption: some water and ions, but no nutrients (molecules that can be broken down for energy)*Stomach is not essential for survivalGross Anatomy:Pyloric sphincter: circular muscle at distal end of stomach that evens out flow of chyme to small intestineRugae: folds of mucosa and submucosa, allow distentionMicroscopic Anatomy:Muscularis externa: has 3rd muscle layer = oblique (deepest)Mucosa:Simple columnar epitheliumSurface epithelium (includes gastric pits) secretes bicarbonate (alkaline-neutralizes acid) and mucusGastric glands:Mucous neck cells: secrete bicarbonate and mucusParietal cells: produce HClChief cells: produce pepsinogen (inactive enzyme)Enteroendocrine cells: produce gastrin (hormone)Stem cells: at pit/gland boundary, maturing cells migrateNo goblet cells in stomach!Small intestine:Function:Chemical digestionPrimary site of digestionAbsorptionPrimary site of nutrient absorptionSecretionMixing by segmentationGross Anatomy:Duodenum:Shortest part of small intestineReceives secretions from pancreas and gallbladderDuodenal glands (submucosa):Secretes bicarbonate (neutralizes stomach acid)and mucusJejunum:Most absorption occurs hereIleum:Has Peyer’s patches (aggregated lymphoid nodules)An example of MALTIn lamina propria and submucosaWall of the small intestineEpithelium type: simple columnarPlicae circulares (“circular folds”): folds of mucosa and submucosaPermanent unlike rugaeSlows down passage of chymeIncreases surface areaVilli: projections of mucosa -> increase surface areaAbsorption of nutrients (from gut lumen to blood/lymph)Sugars and amino acids absorbed by blood capillariesLipids absorbed by lacteals (special lymph vessels)Microvilli: folding of plasma membrane of enterocytes (absorptive cells)Increase surface areaGoblet cells:Function: secrete mucusIntestinal crypts (glands):In mucosa, between villiSecretes intestinal juiceMaintains liquid state of chymeEnteroendocrine cellsStem cellsLarge intestine:Function:Absorb water, ions, some vitamins, but no nutrientsPassageway for materials that cannot be absorbed = fecesGross Anatomy:Cecum:Ileocecal valve: prevents backflow into small intestineVermiform appendix:Has lymphoid tissueAppendicitis: inflamed appendixPeritonitis: inflamed peritoneumOccurs if appendicitis is not treatedColon:Ascending colonTransverse colonDescending colonSigmoid colonRectum:Muscular, specialized for defecationAnal canal:Opening guarded by:Internal anal sphincter (smooth muscle) - involuntaryExternal anal sphincter (skeletal muscle) - voluntaryWalls of large intestine:Teniae coli: three thickened bands of longitudinal muscle layerHaustra: bulges due to contraction of teniae coliEpithelium type: mostly simple columnarColonocytes: absorptive cellsGoblet cellsDistal part of anal canal: non-keratinized stratified squamousPlenty of MALTIntestinal crypts (glands)Goblet cellsStem cells ................
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