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22 Cards in this Set
- Front
- Back
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what is extracellular portion of bones made of?
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calcium phosphate and collagen fibers
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what is hematopoiesis?
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blood cell formation. first in yolk sac, second in liver/spleen, third(mature) bone marrow
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explain red and yellow marrow
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red marrow is rbc's wbc's and platelets. yellow marrow is fat
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Elaborate on the organic and inorganic portion of bones
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bones are 35% organic and 65% inorganic. Organic=osteocytes, fibers and ground substance. Inorganic=mostly hydroxyapatites(mineral salts)
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What is an osteoblast?
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a bone-forming cell(immature). Actively makes osteoid (non-ossified type I collagen). Layers that alternate in direction for tensile strength. Ground substance is chondroitin sulfate. Non-dividing cells. Interconnecting cytoplasmic processes extending through canaliculi that runs through lacunae. Lines surface of growing bone.
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What is an osteocyte
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Smaller than osteoblasts, processes occupying canaliculi. Non-dividing. Each has its own canaliculi.
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What is an osteoclast?
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Large mitotic cell with multiple nuclei. Arise from monocytes or macrophages. Resorbs surplus or inferior bone matrix, as found in depressions called Howship's Lacunae. Ruffled border poking into bone. Secretory cell. Hydrolytic enzymes help digest organic compound.
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Explain two stages of breakdown of bone matrix by osteoclast.
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1.) Focal Decalcification-Organic acids build up under ruffled border. 2.)Extracellular Digestion-Acid hydroxylases liberated at ruffled border
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Explain composition of bone matrix
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1.) Calcification-Deposition of insoluble calcium salts. 2.)Ossification-Bone tissue is formed 3.)Osteoid-bone tissue with uncalcified organic matrix. 4.)Calcification-Concentration of calcium and phosphate ions reach level required for calcium phosphate deposition
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What is the periosteum?
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Highly vascularized/innervated fibrous CT covering of external surface of bone. Layers are outer(fibroblasts, collagen fibers and ground substance) and inner(osteocytes).
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How are osteogenic cells stimulated to osteoblasts?
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In well-vascularized areas. Chondroblasts are in areas with poor vascularization.
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What is bone canaliculi?
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Small canals within ossified matrix. Interconnect osteocyte lacunae and ensure that all surfaces of the osteocyte are bathed in fluid.
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What are the two types of bone?
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Spongy(cancellous) and compact
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What is spongy bone?
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Numerous spaces with each space containing marrow. Contains bone marrow and trabecula(spicules).
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What is compact bone?
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No marrow spaces, composed of tightly packed structural units called osteons(Haverisan Systems). Outer surface of every bone
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Explain compaction.
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Transformation of spongy to compact bone. Osteoblasts deposit new osteoid on trabeculae in layer-like fashion(appositional growth). With each layer that is deposited, spaces between trabecula become narrower and the trabeculae wider. When spaces are gone=compaction.
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What is an example of spongy bone and compact bone?
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Spongy=marrow cavity (central region). Compact=bone collar
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Explain the Haversian Canal System
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Compaction results in filling of marrow spaces by deposition of osteoid in lamellar, concentric fashion. Each osteon(or Haversian System) is built around a blood vessel of old marrow space.
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What is a Haversian Canal?
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Inner space of osteon that houses one or two blood vessels. Vessels nourish osteocytes of osteon via diffusion of nutrients and oxygen through bone fluid that fills each canaliculi.
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What is Volkmann's Canal?
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Passageways that link adjacent Haversian Canals. NOT surrounded by concentric lamellae.
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What are the outer and inner circumferential lamellae?
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Bone nearing full size smooths off inner and outer shaft surfaces.
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What is interstitial lamellae?
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Remnants of pre-existing systems that are replaced during remodeling. Incomplete remnants.
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