2 Cartilage Embryo More prevalent than in adult Skeleton initially mostly cartilageBone replaces cartilage in fetal and childhood periods
3 Location of cartilage in adults External earNose“Articular” – covering the ends of most bones and movable joints“Costal” – connecting ribs to sternumLarynx - voice box
4 Epiglottis – flap keeping food out of lungs Cartilaginous rings holding open the air tubes of the respiratory system (trachea and bronchi)Intervertebral discsPubic symphysisArticular discs such as meniscus in knee joint
5 Remember the four basic types of tissue… Epithelium Connective tissue Connective tissue properCartilageBoneBloodMuscle tissueNervous tissue
7 Cartilage is connective tissue Cells called chondrocytesAbundant extracellular matrixFibers: collagen & elastinJellylike ground substance of complex sugar molecules60-80% water (responsible for the resilience)No nerves or vessels(hyaline cartilage)
8 Types of cartilage: 3 Hyaline cartilage: flexible and resilient Chondrocytes appear sphericalLacuna – cavity in matrix holding chondrocyteCollagen the only fiberElastic cartilage: highly bendableMatrix with elastic as well as collagen fibersEpiglottis, larynx and outer earFibrocartilage: resists compression and tensionRows of thick collagen fibers alternating with rows of chondrocytes (in matrix)Knee menisci and annunulus fibrosis of intervertebral discs
13 Before we look at collagen pic… Hyaline cartilage: flexible and resilientChondrocytes appear sphericalLacuna – cavity in matrix holding chondrocyteCollagen the only fiberElastic cartilage: highly bendableMatrix with elastic as well as collagen fibersEpiglottis and larynxFibrocartilage: resists compression and tensionRows of thick collagen fibers alternating with rows of chondrocytes (in matrix)Knee menisci and annulus fibrosis of intervertebral discs
14 Triple helix of collagen molecules form fibril Fibrils aggregate into collagen fibers
15 Growth of cartilage Appositional Interstitial “Growth from outside”Chrondroblasts in perichondrium (external covering of cartilage) secrete matrixInterstitial“Growth from within”Chondrocytes within divide and secrete new matrixCartilage stops growing in late teens (chrondrocytes stop dividing)Regenerates poorly in adults
16 Now about bones…like other connective tissue: cells separated by extracellular matrix with collagen but also mineral crystalsBone
17 Bones Functions Support 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 neededBlood cell formation and energy storageBone marrow: red makes blood, yellow stores fat
18 Classification of bones by shape Long bonesShort bonesFlat bonesIrregular bonesPneumatized bonesSesamoid bones-embedded in tendon(Short bones include sesmoid bones)
20 Gross anatomy of bones Compact bone Spongy (trabecular) bone-red bone marrowBlood vesselsMedullary cavity-yellow bone marrowMembranesPeriosteumEndosteum
21 Flat bones Spongy bone is called diploe when its in flat bones Have bone marrow but no marrow cavity
22 Long bones Tubular diaphysis or shaft Epiphyses at the ends: covered with “articular” (=joint) cartilageEpiphyseal line in adultsKids: epiphyseal growth plate (disc of hyaline cartilage that grows to lengthen the bone)Blood vesselsNutrient arteries and veins through nutrient foramen
24 Periosteum Endosteum Connective tissue membrane Covers entire outer surface of bone except at epiphysesTwo sublayers1. Outer fibrous layer of dense fibrous 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 (Sharpey’s fibers)EndosteumCovers the internal bone surfacesIs also osteogenic
25 The Skeleton Is Divided Into Two Distinct Parts: The axial skeleton consists of bones that form the axis of the body and support and protect the organs of the head, neck, and trunk.Click on these links to read about the axial parts of the body.The skullThe sternumThe ribsThe backbone
26 The Second Part of the Skeleton The appendicular skeleton is composed of bones that anchor the appendages to the axial skeleton.Click on these links to read about the appendicular parts of the body.The lower bodyThe upper bodyThe shouldersThe pelvic area
27 Terms (examples) chondro refers to cartilage osteo refers to bone chondrocyteendochondralperichondriumosteo refers to boneosteogenesisosteocyteperiostiumblast refers to precursor cell or one that produces somethingosteoblastcyte refers to cellOsteocyte
28 Martini p 128, Table 5.1, Common Bone Marking Terminology (for figure see next slide)
31 Isolated osteon: Nutrients diffuse from vessels in central canal Alternating direction of collagen fibers increases resistance to twisting forces
32 Spongy bone- flexibility, lightweight bone Layers of lamellae and osteocytesSeem to align along stress lines
33 Chemical composition of bones Cells, matrix of collagen fibers and ground substance (organic: 35%)Contribute to the flexibility and tensile strengthMineral crystals (inorganic: 65%)Primarily calcium phosphateLie in and around the collagen fibrils in extracellular matrixContribute to bone hardnessSmall amount of water
34 Bone development Osteogenesis: “formation of bone” From osteoblastsBone tissue first appears in week 8 (embryo)Ossification: “to turn into bone”Intramembranous 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
35 Remember the three germ tissues… Ectoderm - epithelialEndoderm - epithelialMesoderm is a mesenchyme tissueMesenchyme cells are star shaped and do not attach to one another, therefore migrate freelyFrom 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)
36 Intramembranous ossification Occurs mainly in the skull (flat bones)
37 Endochondral ossification Modeled in hyaline cartilage, called cartilage modelGradually replaced by bone: begins late in second month of developmentPerichondrium 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
38 Endochondral ossification Stages 1-3 during fetal week 9 through 9th monthStage 5 is process of long bone growth during childhood & adolescenceStage 4 is just before birth
39 Organization of cartilage within the epiphyseal plate of a growing long bone
40 Epiphyseal growth plates in child, left, and lines in adult, right (see arrows)
41 Factors regulating bone growth Vitamin D: hormone that regulates calcium levelsParathyroid 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 epiphyseal growth plate.
42 Bone remodeling Osteoclasts Osteoblasts Triggers Bone resorption, breaks down/destroys old bone cellsOsteoblastsBone deposition, builds bonesTriggersHormonal: parathyroid hormoneMechanical stressOsteocytes are closely related to osteoblasts
43 Types of Body Joints Synarthroses- no movement Amphiarthroses- minimal movementDiarthroses- free movement, most common type in body
44 Synarthrotic JointsFibrous connective tissue grows between articulating bones in the skull.The joints in the skull are called sutures.
45 Amphiarthrotic Joints This joint type uses cartilage to connect articulating bones, allowing for some movement.Found in the pubic symphisis , the vertebrae, and intercostal (between ribs) cartilage.
46 Diarthrotic Joints Free moving Found along with tendons and ligaments between bones of the extremities.Contains two layers of articular cartilage with a synovial membrane in between.Flexion- bending a jointExtension- straightening a joint
47 Types of Diarthrotic Joints Ball and Socket- Shoulder, HipHinge- elbow and kneePivot- neck (allows for head rotation)Saddle- phlangesGliding- vertebraeCondyloid- radius/wrist joint
48 Repair of bone fractures (breaks) Simple- bone doesn’t penetrate skinCompound- bone penetrates skin
49 Disorders of cartilage and bone Defective 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
50 Pagets disease – excessive turnover, abnormal bone (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- osteoclasts outpace the osteoblastsRheumatoid Arthritis- auto-immune disease in which the body will attack its own joints.
52 Difference between male and female skeletons Males are generally largerMales have deeper, narrower pelvis, females are broaderFemale pelvic inlet is wider, to compensate for baby’s head. This also means that the pubic angle is wider in females.