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50 Cards in this Set
- Front
- Back
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Are bones organs? |
Yes, bc they are made of diff types of tissues, primarily Osseous Connective Tissue |
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Compact Bone |
The dense outer layer of bone that is smooth and solid Holds red bone marrow and is full of red blood cells |
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Spongy Bone |
Consists of honeycomb, needle like pieces called Trabeculae Holds yellow bone marrow and is full of adipose cells *trabeculae strengthens *no osteons, but capillaries in endosteum supply nutrients
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Diaphysis |
A long tubular shaft of bone. Made of an outer layer of compact bone around a central medullary cavity filled with yellow bone marrow in adults |
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Epiphyses |
The ends of long bones Consist of compact bone around spongy bone |
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Metaphysis |
The transition bw the diaphysis and epiphysis Contains epiphyseal line and epiphyseal plate |
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Epiphyseal line |
Remnant of epiphyseal plate where bone growth once occurred |
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Periosteum Membrane |
Covers the outside of the bone Contains layer of dense irregular CT to secure the membrane to the bone matrix
Contains nerve fibres & blood vessels that pass into shaft of bone through nutrient foramen openings. Also the anchoring point for tendons |
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Endosteum Membrane |
CT that lines the internal surface of bone Covers the trabecular and lines canals passing through compact bone |
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Osteogenic Layer |
The inner layer in contact with bone that contains osteoprogenitor stem cells that gives rise to almost all bone cells |
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Bone cell lineage |
Osteoprogenitor cell, turns into osteoblast (builds bone), turns into osteocyte (stress/strain sensors) |
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Osteoclast |
Functions in reabsorption, breakdown of bones extra cellular matrix *Carves bone, located in depressed areas called resorption bays |
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Bone Lining Cells |
Flat cells that work with osteocytes to help maintain bone matrix Periosteal cells (external) and endosteal cells (internal) |
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BONE STRUCTURE AND REMODELLING |
Lecture |
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Osteon (Haversian System) |
The structural unit of compact bone Consists of elongated cylinder running parallel to bone. Acts as weight bearer Consists of rings of bone matrix - Lamellae. That contain collagen fibres that withstand stress & resist twisting. Bone salts found bw fibres |
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Central (Haversian) Canal |
Runs through core of osteon. Contains blood vessels and fibres |
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Perforating (Volkmanns) Canal |
Lined with endosteum, occur at right angles to central canal - in case other pathway is blocked. Connect blood vessels and nerves to central canal |
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Lacunae |
Small cavities that contain osteocytes |
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Canaliculi |
Hairlike canals that connect the lacunae to each-other and to central canal *Form when the matrix hardens and cells are trapped. Allow for communication bw osteocytes & permit nutrients & wastes to flow to & from central canal |
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Interstitial Lamellae |
Not part of osteon. Fill gaps bw forming osteons, or remnants of osteons cut by bone remodelling |
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Circumferential Lamellae |
Layers of Lamellae that extend around entire surface of diaphysis. Prevent long bones from twisting |
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Organic components of Bone |
5 kinds of cells and osteoid Osteoid - 1/3 of organic bone matrix, secreted by osteoblasts. Consists of ground substance & collagen fibres (tensile strength and flexibility) Sacrificial bonds (bones resilience) in/bw collagen molecules |
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Inorganic Components of Bone |
Hydroxyapatites (mineral salts) 65% of bones mass. Gives hardness and resistance to compression Bone is half as strong as steel in resisting compression & strong as steel in resisting tension. Lasts long after death bc of minerals |
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Bone Remodelling |
5-7% of bone is recycled each week Spongy bone replaced every 3-4 years & compact bone every 10 years |
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Bone remodelling |
Consists of both bone deposit and resorption Occurs at surfaces of both periosteum & endosteum |
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Bone remodelling |
Consists of both bone deposit and resorption Occurs at surfaces of both periosteum & endosteum |
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Remodelling Units |
Packets of adjacent osteoblasts and osteoclasts coordinate the remodelling process |
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Bone deposit |
New bone matrix is deposited by osteoblasts Osteoid Seam: band of unmineralized bone matrix that marks areas of new deposition Calcification Front: a transition zone bw the osteoid seam & older mineralized bone |
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Bone resorption |
A function of the osteoclasts that dig grooves as they break down bone matrix by secreting lysosomes and H protons. The acidity converts calcium salts to soluble forms Once resorption is complete osteoclasts undergo apoptosis |
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Control of remodelling |
Mostly used to maintain blood calcium homeostasis & balances activity of parathyroid hormones & calcitonin |
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Parathyroid Hormone |
Stimulates osteoclasts to resorb bone, releasing calcium into blood |
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Parathyroid Hormone |
Stimulates osteoclasts to resorb bone, releasing calcium into blood |
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Calcitonin |
Produced by parafollicular cells of thyroid in response to high blood calcium levels. Effects aren’t as strong as PTH but lowers blood calcium levels temporarily |
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Wolff’s Law |
States that bones grow or remodel in response to demands placed on them Stress is off centre so bones bend, compressing one side & stretching the other Diaphysis is thickest where bending stresses are greatest. Bone can be hollow bc stress and tension cancel eachother out in middle of bone |
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Mechanical Stress |
Causes remodelling by producing electrical signals when none is deformed. Compression/tension changes fluid flow w/in canaliculi, which can also stimulate remodeling |
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Hormonal Controls |
Determine whether & when remodelling occurs in response to changing blood calcium levels - but mechanical stress determines where it occurs |
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Bone Growth & Repair |
Lecture |
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Bone Growth & Repair |
Lecture |
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Bone Development / Ossification (osteogenesis) |
The process of bone tissue formation Formation of bony skeleton begins in month 2 of development Bone growth occurs until early adulthood |
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Intramembranous Ossification |
Is when none develops from fibrous membrane These bones are membrane bones *no cartilage & forms the skull & clavicle |
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Steps of Intramembranous Ossification |
1) Development of ossification centre (osteoblasts secrete matrix) 2) Calcification (calcium & other mineral salts are deposited & matrix calcifies/hardens) 3) Formation of trabeculae: matrix develops into trebeculae that fuse to form spongy bone 4) Development of periosteum: Mesenchyme at the periphery of bone develops into periosteum |
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Endochondral Ossification |
When bone forms by replacing hyaline cartilage. Forms most of the skeleton (all bones except skull & clavicle) Called cartilage (endochondral) bones Starts at primary ossification centre (centre of shaft). Blood vessels infiltrate perichondrium, converting it to periosteum, and mesenchymal cells |
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Hormone regulation of bone growth |
Growth hormone - stimulates epiphyseal plate in infancy & childhood Thyroid hormone - modulates activity of growth hormone, ensuring proper proportions Testosterone/Estrogens - at puberty promote growth spurts & end growth by inducing epiphyseal plate closure |
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Postnatal Bone Growth |
• Growth in length occurs at the ossification zone through the rapid division of chondrocytes, calcification and deterioration of cartilage and replacement by bone tissue. • Near end of adolescence, chondroblasts divid often. The epiphyseal plate thins, then is replaced by bone. • Epiphystal Plate Closure occurs when epiphysis and diaphysis fuse. |
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Postnatal Bone Growth, width |
occurs through appositional growth due to deposition of bone matrix by osteoblasts beneath the periosteum. • Osteoclasts remove bone from the endosteal surface, so the bones do not get too heavy. Bones thicken in response to increased stress from muscle activity or added weight. involves more building up than breaking down, which leads to thicker, stronger bone while ensuring that the bone is not too heavy. |
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Bone Fractures |
Position of the bone ends after the fracture. • Nondisplaced: ends retain normal position. • Displaced: ends are out of normal alignment. Completeness of the break. Complete: broken all the way through. • Incomplete: not broken all the way through. Whether the skin is penetrated. • Open (compound): skin is penetrated. • Closed (simple): skin is not penetrated. |
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Hematoma Formation |
Immediately after the bone breaks, torn blood vessels hemorrhage, forming a mass of clotted blood called a hematoma. The site is swollen, painful, and inflamed. |
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Fibrocartilaginous Callus Formation |
Capillaries grow into the hematoma. Phagocytic cells clear debris. Fibroblasts secrete collagen fibres to connect the broken ends. Fibroblasts, cartilage, osteogenic cells begin the reconstruction of bone This mass of repair tissue is called a fibrocartilaginous callus. |
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Bony Callus Formation |
Within one week, new trabeculae appear in the fibrocartilaginous callus. Callus is converted to a bony (hard)) callus of spongy bone. continues for about 2 months until a firm union forms. |
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Bone Remodelling |
Bone remodeling begins during bony callus formation and continues for several months. Excess material on the diaphysis exterior and within medullary cavity is removed. Compact bone is laid down to reconstruct the shaft walls. The final structure resembles the original structure and responds to the same mechanical stressors. |
