A&P Chapter 6

Axial skeleton
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Terms in this set (107)
Axial skeleton
bones of the skull, vertebral column and rib cage
appendicular skeleton
bones of the upper and lower limbs, shoulder, and hip
Classification of bones by shape
-long, short, flat, irregular
long bones
longer than they are wide
Image: long bones
Short bones
Cube-shaped bones (in wrist and ankle)
Sesamoid bones (within tendons, e.g., patella)
Image: Short bones
flat bones
thin, flattened, and usually curved
Image: flat bones
irregular bones
complicated shapes
Image: irregular bones
Functions of bones
support, protection, movement, mineral storage, blood cell formation, triglyceride storage
support (of bone)
form the framework that supports the body and cradles soft organs
protection (of bone)
provide a protective case for the brain, spinal cord and vital organs
movement (bone)provide levers for musclesmineral storage (bone)reservoir for minerals, especially calcium and phosphorusblood cell formation (bone)Hematopoiesis occurs in red marrow cavities of certain bonestriglyceride storage is inbones -triglyceride=energyBone texturescompact and spongyCompact bones-dense outer layer -made of osteonsspongy bone (cancellous bone)made of honeycomb of trabeculaetrabeculaesupporting bundles of bony fibers in spongy boneStructure of long bonediaphysis, epiphysis, metaphysisDiaphysisshaft of a long bone -compact bone collar surround medullary (marrow) cavitymedullary cavityin adults contain fat (yellow marrow)epiphysesExpanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfacesepiphyseal lineremnant of growth platearticular cartilage (hyaline)covers surfaces that form joints along with lubricating fluid, allow ease of movementMembranes of bonesperiosteum and endosteumPeriosteum-outer fibrous layer -inner osteogenic layer -nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina -secured to underlying bone by sharpey's fiberstypes of inner osteogenic layerosteoblasts, osteoclasts, osteogenic cellsosteoblastsbone forming cellsosteclastsbreak down boneosteogenic cellsbone stem cellsnutrient foraminanerve fibers, lymphatic vessels, and blood vessels from periosteum enter the diaphysis from this openingsharpey's fiberssecure periosteum to underlying boneEndosteum-Delicate membrane on internal surfaces of bone -Also contains osteoblasts and osteoclastsStructure of short, irregular, and flat bonesPeriosteum-covered compact bone on the outside Endosteum-covered spongy bone within Spongy bone called diploë in flat bones Bone marrow between the trabeculae -no diaphysis or epiphysesDiploespongy bone in flat boneshematopoietic tissuered marrowred marrow cavities of adults-trabecular cavities of the heads of the femur and humerus -trabecular cavities of the diploe of flat bonesred marrow of newborn, infants, children-medullary cavities in long bones -all spaces in spongy boneCells of bonesosteogenic/osteoprogenitor cells, osteoblasts, osteocytes, osteoclastsOsteogenic (osteoprogenitor) cellsstem cells in periosteum and endosteum that give rise to osteoblastsosteoblastbone-forming cellosteocytesmature bone cellsosteoclastslarge cells that resorb or break down bone matrixstructural unit of compact boneosteon or haversian systemparts of the osteonLamellae, osteocytes, lacunaelamellaeweight-bearing, column-like matrix tubesOsteocytes liebetween the lamellaeLacunaesmall cavities in bone that contain osteocytes3 types of canals in compact bone-perforating (Volkmann's)canals -central (haversian) canal -canaliculiPerforating (Volkmann's) canals-At right angles to the central canal -Connects blood vessels and nerves of the periosteum and central canalCentral (Haversian) Canalcontains blood vessels and nervesCanaliculiHairlike canals that connect lacunae to each other and the central canalwhere do the nerves, veins and arteries lie in the bone?central canalTabeculae-align along lines of stress -no osteons -contain irregularly arranged lamellae, osteocytes, and canaliculi -capillaries in endosteum supply nutrientsorganic bone componentsbone cells (osteogenic/blasts/cytes/clasts) and osteoidosteoidorganic bone matrix secreted by osteoblaststwo things found in osteoid-ground substance -collagenground substance containsglycoproteins and proteoglycanscollagen fibers in the boneprovide tensile strength and flexibilityinorganic components of boneHydroxyapatites (mineral salts)Hydroxyapatite-65% of bone by mass -mainly calcium phosphate crystals -responsible for hardness and resistance to compressionOsteogenesis (ossification)bone tissue formationstages of bone development1. bone formation 2. postnatal bone growth 3. bone remodeling and repairwhen does bone formation occur?begins in the 2nd month of developmentwhen does postnatal bone growth occur?until early adulthoodwhen does bone remodeling and repair occur?lifelongTwo types of ossificationintramembranous and endochondralintramembranous ossificationmembrane bone develops from fibrous membrane, forms flat bones (clavicles and cranial bones)endochondral ossification-Cartilage (endochondral) bone forms by replacing hyaline cartilage -Forms most of the rest of the skeleton -requires the breakdown of hyaline cartilage prior to ossificationsteps of intramembranous ossification1) ossification centers appear in the fibrous CT membrane 2)Osteoid is secreted within the fibrous membrane and calcifies, trapped osteoblast become osteocytes 3)Woven bone and periosteum form 4)Lamellar bone replaces woven bone, just deep to the peristeum. Red marrow appearsWoven bonesaccumulating osteoid is laid down between embryonic blood vessels in a random manner and the result of the network of trabeculae is woven boneAt week 9 of an embryo thebone collar forms around the diaphysis of the hyaline cartilage modelBetween week 9 and month 3 of an embryocartilage in the center of the diaphysis calcifies and then develops cavitiesat month three of the embryothe periosteal bud invades the internal cavities and spongy bone formsAt birth thediaphysis elongates and the medullary cavity forms. SECONDARY OSSIFICATION centers appear in the epiphysesIn the childhood to adolescence theepiphyses ossify. When completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilagestypes of Postnatal Bone Growthinterstitial growth and appositional growthinterstitial growthincrease in length of long bones -until pubertyAppositional growthincrease thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfacesGrowth in length of long bonesEpiphyseal plate cartilage organizes into four important functional zonesFour functional zones of epiphyseal plate cartilageProliferation (growth), Hypertrophic, Calcification, Ossification (osteogenic)proliferation zonecartilage cells undergo mitosisHypertrophic zoneolder cartilage cells enlargeCalcification zonematrix calcifies; cartilage cells die; matrix begins deteriorating; blood vessels invade cavityOssification zonenew bone formsHormonal Regulation of Bone Growth-Growth hormone -thyroid hormoneGrowth Hormonestimulates epiphyseal plate activity in infancy and childhoodThyroid hormonemodulates activity of growth hormone until pubertyTestosterone and estrogenpromote adolescent growth spurts, end growth by inducing epiphyseal plate closureBone depositOccurs where bone is injured or added strength is needed; Requires a diet rich in protein; vitamins C, D, and A; calcium; phosphorus; magnesium; and manganesewhat cells create bone depositosteoblastsBone resorptionOsteoclasts secrete Lysosomal enzymes (digest organic matrix) Acids (convert calcium salts into soluble forms)Remodeling bone unitsosteoblast for deposit bone and osteoclasts for resorb bonewhat controls continual remodeling of bone?-Hormonal mechanisms that maintain calcium homeostasis in the blood -Mechanical and gravitational forces -dont start from scratch, you have the frame to work off ofCalcium is necessary for-transmission of nerve impulses -muscle contraction -blood coagulation -secretion by glands and nerve cells -cell divisionWhat primarily controls blood calciumPTHParathyroid hormone negative feedback mechanism-decrease in blood Ca2+ levels -parathyroid glands release PTH -PTH stimulates osteoclasts to degrade bone matrix and release Ca2+ -increases blood Ca2+ levelswhat hormone may also affect blood Ca2+ levels?CalcitoninCalcitonin Feedback Loop-increases in blood Ca2+ levels -parafollicular cells of thyroid release calcitonin -osteoblasts deposit calcium salts -decrease blood Ca2+ levelsWolff's lawa bone grows or remodels in response to forces or demands placed upon itObservations supporting Wolff's law-Handedness (right or left handed) results in bone of one upper limb being thicker and stronger -Curved bones are thickest where they are most likely to buckle -Trabeculae form along lines of stress -Large, bony projections occur where heavy, active muscles attachHomeostatic imbalancesosteomalacia, rickets, osteoporosisosteomalaciaabnormal softening of bones in adults -caused by vitamin D deficiency and insufficient dietary calciumRicketsVitamin D deficiency in children causing bowed legs and other bone deformitiespurpose do vitamin Dbring calcium from gut to bodyOsteoporosis-loss of bone mass (resorption outpaces deposit) -spongy bone of spine and neck of femur become most susceptible to fracturerisk factors of osteoporosisLack of estrogen, calcium or vitamin D; diabetes mellitus