Connective Tissues of the Skeleton JACKI HOUGHTON, DC Cartilages Bones

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Transcript of Connective Tissues of the Skeleton JACKI HOUGHTON, DC Cartilages Bones

  • Connective Tissues of the SkeletonJACKI HOUGHTON, DCCartilagesBones

  • Functions of the Skeletal SystemA. SupportB. ProtectionC. MovementD. Mineral Storage (Calcium + Phosphorus)E. Hematopoiesis (blood cell formation in red marrow)F. Energy Storage (lipids/fat stored in yellow marrow)

  • Define Cartilage remember your connective tissues?The skeletal System includes all of the cartilages.What should I know about cartilage?What are the types of cartilages?Where would I find each of these types of cartilages?What are the functional properties of cartilage as a tissue?

  • CartilageEmbryoMore prevalent in the embryo than in adultSkeleton is initially mostly cartilageBone replaces cartilage in fetal and childhood periods3 types: hyaline, elastic and fibrocartilageSo what is cartilage? It is a connective tissue which has differing properties, depending on its function. Hyaline cartilage lines the ends of bones and cushions them. The hyaline wears better than bone.Elastic cartilage is still but will bend and return to its original shape.Fibrocartilage has great tensile strength and can absorb shock.

  • Location of cartilage in adultsExternal ear - elasticNose - hyalineArticular covering the ends of most bones and movable joints - hyalineCostal connecting ribs to sternum - hyaline Larynx - voice box -elastic

  • Epiglottis flap keeping food out of lungs - elasticCartilaginous rings holding open the air tubes of the respiratory system (trachea and bronchi) hyalineIntervertebral discs - fibrocartilagePubic symphysis - fibrocartilageArticular discs such as meniscus in knee joint - fibrocartilage

  • BonesFunctionsSupport (give body its shape)Movement: muscles attach by tendons and use bones as levers to move bodyProtectionSkull brainVertebrae spinal cordRib cage thoracic organsMineral storageCalcium and phosphorusReleased as ions into blood as needed Blood cell formation and energy storageBone marrow: red makes blood, yellow stores fat

  • Chemical composition of bonesCells, matrix of collagen fibers and ground substance (organic: 35%)Contribute to the flexibility and tensile strengthMineral crystals (inorganic: 65%)Primarily calcium phosphate Lie in and around the collagen fibrils in extracellular matrixContribute to bone hardnessSmall amount of water

  • Bone developmentOsteogenesis: formation of bone From osteoblastsBone tissue first appears in week 8 (embryo)Ossification: to turn into boneIntramembranous ossification (also called dermal since occurs deep in dermis): forms directly from mesenchyme (not modeled first in cartilage)Most skull bones except a few at baseClavicles (collar bones)Sesamoid bones (like the patella)Endochondral ossification: modeled in hyaline cartilage then replaced by bone tissueAll the rest of the bones

  • Endochondral ossificationStages 1-3 during fetal week 9 through 9th month Stage 4 is just before birthStage 5 is process of long bone growth during childhood & adolescence

  • Remember the three germ tissuesEctoderm - epithelial Endoderm - epithelial Mesoderm is a mesenchyme tissueMesenchyme cells are star shaped and do not attach to one another, therefore migrate freely

    From the last slide:Intramembranous ossification: forms directly from mesenchyme (not modeled first in cartilage)Most skull bones except a few at baseClavicles (collar bones)Sesmoid bones (like the patella)

  • Intramembranous ossification

    (osteoid is the organic part)

  • Endochondral ossificationModeled in hyaline cartilage, called cartilage modelPerichondrium is invaded by vessels and becomes periosteumOsteoblasts in periosteum lay down collar of bone around diaphysisCalcification in center of diaphysisPrimary ossification centersSecondary ossification in epiphysesEpiphyseal growth plates close at end of adolescenceDiaphysis and epiphysis fuseNo more bone lengtheningSee next slide

  • Epiphyseal growth plates in child, left, and lines in adult, right (see arrows)

  • Factors Regulating Bone GrowthVitamin D, parathyroid hormone, calcitonin, GH, TH, Sex Hormones

  • Nutrients diffuse from vessels in central canalAlternating direction of collagen fibers increases resistance to twisting forces osteon:

  • Compact boneOsteons: pillarsLamellae: concentric tubesHaversian canalsOsteocytes

  • Spongy boneLayers of lamellae and osteocytesSeem to align along stress lines

  • Factors regulating bone growthVitamin D: increases calcium from gut Parathyroid hormone (PTH): increases blood calcium (some of this comes out of bone) Calcitonin: decreases blood calcium (opposes PTH)Growth hormone & thyroid hormone: modulate bone growthSex hormones: growth spurt at adolescense and closure of epiphyses

  • Bone remodelingOsteoclastsBone resorptionOsteoblastsBone depositionTriggersHormonal: parathyroid hormoneMechanical stressOsteocytes are transformed osteoblasts

  • Terms (examples)chondro refers to cartilagechondrocyteendochondralperichondriumosteo refers to boneosteogenesisosteocyteperiostiumblast refers to precursor cell or one that produces somethingosteoblastcyte refers to cellosteocyte

  • Repair of bone fractures (breaks)Simple and compound fracturesClosed and open reduction

  • Disorders of cartilage and boneDefective collagenNumerous genetic disorderseg. Osteogenesis imperfecta (brittle bones) AD (autosomal dominant)eg. Ehlers-Danlos (rubber man)Defective endochondral ossificationeg. Achondroplasia (short limb dwarfism) - ADInadequate calcification (requires calcium and vitamin D)Osteomalacia (soft bones) in adultsRickets in childrenNote: AD here means autosomal dominant inheritance

  • (continued)Pagets disease excessive turnover, abnormal boneOsteosarcoma bone cancer, affecting children primarilyOsteoporosis usually age related, esp. femalesLow bone mass and increased fracturesResorption outpaces bone deposition

  • Normal boneOsteoporotic bone

  • Classification of bones by shapeLong bonesShort bonesFlat bones Irregular bonesPneumatized bonesSesamoid bones(Short bones include sesmoid bones)

  • Know these!

  • Gross anatomy of bonesCompact boneSpongy (trabecular) boneBlood vesselsMedullary cavityMembranesPeriosteumEndosteum

  • Flat bonesSpongy bone is called diploe when its in flat bonesHave bone marrow but no marrow cavity

  • Long bonesTubular diaphysis or shaftEpiphyses at the ends: covered with articular (=joint) cartilageEpiphyseal line in adults the epiphyseal plate usually closes at 20 years oldKids: epiphyseal growth plate (disc of hyaline cartilage that grows to lengthen the bone)Blood vesselsNutrient arteries and veins through nutrient foramen

  • Periosteum Periosteal Bud - A vascular connective tissue bud from theperichondriumthat enters thecartilageof a developing long bone and contributes to the formation of a center forossification. Connective tissue membraneCovers entire outer surface of bone except at epiphysesTwo sublayers1. Outer fibrous layer of dense irregular connective tissue2. Inner (deep) cellular osteogenic layer on the compact bone containing osteoprogenitor cells (stem cells that give rise to osteoblasts) Osteoblasts: bone depositing cellsAlso osteoclasts: bone destroying cells (from the white blood cell line)Secured to bone by perforating fibers (Sharpeys fibers)

    EndosteumCovers the internal bone surfacesIs also osteogenic

  • Bone markings reflect the stresses

  • Bone markings*Bone pain is called ostealgia*Projections that are the attachments sites for muscles and ligamentsSurfaces that form jointsDepressions and openings

    Learn them using:Marieb lab book p 101, Table 8.1, Bone MarkingsorMartini p 128, Table 5.1, Common Bone Marking Terminology (next slide)

  • Martini p 128, Table 5.1, Common Bone Marking Terminology(for figure see next slide)