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53 Cards in this Set
- Front
- Back
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What does the skeletal system include??
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bones, ligament, cartilage, and other tissues that conect bone
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How many bones in the body |
206
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Axial Skeleton
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skull,thorax, and vertebral column longitudinal axis of the body 80 bones |
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Appendicular Axis
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limbs and pectoral and pelvic girdle which attach the limbs to the axial skeleton 126 bones |
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Functions of the skeletal system
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1. Support 2.Storage of minerals: Ca++ salt & PO4 ions in blood fluids 3.Blood cell production: RBC's &WBCs and platlets made in red bone marrow 4.Protection: of soft organs and tissues 5.Leverage: function as levers that can change the magnitude and forces generated by skeletal muscle |
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Why are bones hollow
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Because they'd be to heavy if not.
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Compact bone
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-dense -thin layer surrounds spongy bone in epiphysis and the medullary cavity in diaphysis - lamellae made up of osteons - contains capillaries and venules |
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Spongy Bone
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-cancellous/ trabecular bone - located where bone is not heavily stressed or where stresses occur in many directions (heads) -struts and plates called trabeculae -no capillaries or venules - Nutrients reach by diffusion along canaliculi |
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What is the structural unit of compact bone?
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Osteon
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Osteoprogenitor Cells
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- mesenchymal cells- multipotent (can become many different cells) stromal cells -in the periosteum & Endosteum - divide to produce osteoblasts - important in repairing fractures - goes through alot of mitosis |
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Osteocytes
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-mature bone cells -live in lacunae -secrete osteoid; control mineral deposition -Build bone when stressed -secrete acid phosphatase -can't divide Functions: 1) Bone Turnover: maintain protein and mineral content 2) Bone Repair: release chemicals to stimulate bode formation |
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Osteoblasts
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-immature bone cells -in periosteum - secrete organic component of matrix= osteoid |
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Osteoclasts
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-Found throughout bone -Breaks down bone -bone reabsorption & homeostasis of minerals in bodily fluids |
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Bone cell lineage
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Osteogenic cell---Osteoblast-----Osteocytes
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Where do osteoclasts come from
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WBCs
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Medullary Cavity
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marrow cavity within hollow shaft of the bone -contais red and yellow bone marrow |
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Red bone marrow function
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produces blood cells - highly vascularized |
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Yellow bone marrow
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-is adipose tissue -storage of energy reserves |
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Articular Cartilage
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covers portions of epiphysis
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metaphyseal artery and vein
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carry blood to and from the metaphysis and to the epiphysis
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Periosteum
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connective tissue which wraps around the diaphysis -rich nervous and blood supply -means for tendon and ligament attachment |
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Haversian System
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how the compact bone receive blood from the periosteum i.e osteons |
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Layers of the Periosteum
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1. Fibrous outer layer: collagen fibers (sharpey's fibers) 2. Inner cellular layer: filled with fibroblasts, osteoprogentitors, and osteo blasts |
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Functions of the periosteum
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1. Isolation of bone from surrounding tissue 2.a route for circulatory and nervous supply 3. participates in bone growth and repair |
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Endosteum location
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Lines the medullary cavity
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Cells in Endosteum
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1. Osteoprogenitors 2. Osteoblasts 3.Osteoclasts |
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Endosteum function
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1. bone growth 2. Repair 3. Remodeling |
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Osteogenisis
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Bone formation
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what type of bone formation occurs in the embryo
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1) endochondral ossification 2) intramembranous ossification |
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what type of bone formation occurs in children
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1) interstitial growth (length) 2)appositional growth (width) |
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what type of bone formation occurs in adults
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bone remodeling
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When is hyaline cartilage replaced by bone in an embryo?
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by week 8
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Endochondrial Ossification
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- osteoblasts replace the chondrocytes
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Steps of Endochondrial Ossification
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1)-hyaline cartilage expands and grows -chondrocytes die and cavities are formed in the cartilage 2)-Blood vessels grow around cartilage -cells of perichondrium convert to osteoblasts -periosteum forms 3)-Blood vessels penetrate cartilage - fibroblasts traveling in blood differentiate into osteoblasts - begin producing spongy bone at Primary ossification center - bone formation then spreads along the shaft 3) - creates a medullary cavity - shaft becomes thicker and longer 4)-capillaries and osteoblasts migrate into the epiphysis -creates secondary ossification centers 5)- epiphysis is filled with spongy bone -articular cartilage remains around joint cavity -epiphyseal cartilage separates the epiphysis and diaphysis |
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Steps of Intramembranous Ossification
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1)-Mesenchyme cells cluster and differentiate into osteogenic cells and then into osteoblast -Osteoblasts osteoids which mineralize -forms ossification center 2)-Bony matrix (bony spicule) secreted intofibrous membrane -Calcification occurs, osteoid is mineralized 3) -Trabeculae Form 4)Periosteum is formed: mesenchyme at the periphery of the bone develop into periosteum |
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Postnatal growth in length
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-Chondrocytes in epiphyseal plate continue to divide and grow -osteoblasts migrate towards epiphysis replacing cartilage with bone |
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Which cells are responsible for lateral bone growth?
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osteoblasts and osteoclasts
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How are osteons and central canals formed during appositional growth
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1) Ridges in periosteum create grooves for periosteal blood vessel 2)Periosteal ridge fuses forming endosteum lined tunnel 3)Osteoblasts build new concentric lamellae, forming an osteon 4)Bone continues to grow outwards as osteoblasts build lamallae |
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What is Appositional growth??
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enlargement of the diameter of the bone
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How is appositional growth attained??
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Osteoblasts under the periosteum lay down bone (adds circumferential lamallae - osteoblasts trapped within the lamellae become osteocytes while osteoclasts break down bone on the inside of the cavity = bone increases in diameter and cavity enlarges |
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Growth at puberty
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rising levels of sex,growth, and thyroid hormones stimulate bone growth dramatically -cartilage in epiphyseal plate is replaced with bone - |
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Bone Remodeling
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-occurs throughout life -involves resorption of old bone and deposition of new bone |
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Why does bone remodeling occur?
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In response to... -bone growth -blood Ca++ levels -mecanincal stress!! |
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Where are nerve endings in the bone located?
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in the periosteum and endosteum
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Hormonal requirements for bone growth.
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1) growth hormone: from the pituitary gland. Promotes osteoblast activity 2)Thyroxin: stimulates cell metabolism and osteoblast activity 3) Calcitriol: from kidneys and derived from Vit D3. Allows absorption of Ca++ and PO4 from digestive tract 4)Estrogen and Testosterone: causes osteoblasts to build bone faster |
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Nutrional Requirements for bone growth
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1) Calcium and Phosphate 2)Vitamin C: collagen synthesis and osteoblast differentation 3)Vitamin A: Osteoblast activity 4) synthesis of proteins in bone |
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What organs monitor Ca levels
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Parathyroid and thyroid glands
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What happens when Ca levels are low
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Parathyroid gland releases parathyroid Hormone -stimulate osteoclast activity -increases absorbtion of Ca from intestine -decrease rat of excretion |
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What happens when Ca is to high
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Thyroid gland releases calcitronin -inhibits activity of osteoclasts -increases rate of excretion |
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Wolff's law
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bones are remodelled in response to forces placed on them -stress generates electrical current in bone -Osteocytes release chemicals to stimulate osteoblasts and osteoclasts |
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Osteopenia
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reduction in bone mass -starts between age 30-40 -mostly effects epiphysis, vertebrae , jaws |
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What causes Osteopenia
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-decreased osteoblast activity |
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Osteoperosis
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loss of bone mass sufficient to compromise function
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