Spongy trabecular bone a honeycomb of trabeculae

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Spongy (trabecular) bone- a honeycomb of trabeculae Structure the same for all bone shapes:LONG BONES: much longer than wide; a shaft + 2 ends mostly compact bone with marrow cavity; spongy bone near joint ends 1.SHORT BONES: roughly cube-shaped; eg. Wrist, ankle, primarily spongy bone + thin outer layer of compact bone 2.FLAT BONES: thin, flattened & sometimes curved--include skull bones, ribs & breastbone 3.IRREGULAR BONES: leftovers, eg. Vertebrae & hip bones- complicated shapes, primarily spongy bone + thin covering layer of compact bone4.Tubular shaft of a long bone = long axis of the bone Collar of compact bone surrounding marrow cavity (medullary cavity) In adults, medullary cavity contains fat (yellow marrow or yellow bone marrow cavity) Diaphysis:1.Extremities of a long bone, expanded for articulation with other bones Compact bone forms thin outer layer; interior filled with spongy bone Thin layer of hyaline (articular) cartilage Epiphyses: (singular = epiphysis)2.Between diaphysis & each epiphysis, remnant of epiphyseal plateEpiphyseal Line:3.Cover outer (periosteum) & inner (endosteum) surfaces of long bones Both contain osteoblasts & osteocytes Membranes:4.The Microscopic Structure of Long Bones:All 3 other types have similar structure Compact bone outside; spongy bone insideCompact covered with periosteum & spongy lined with endosteum Not cylindrical so no shaft, marrow cavity or epiphyses - but do contain bone marrow between trabeculae Structure of other bone types:This is the structural unit of compact boneOsteon: an elongated cylinder orientated parallel to the long axis of bone -Think of an osteon as a tiny, weight-bearing pillar A single osteon is a group of hollow tubes of bone matrix- think of the rings of a tree; each of the matrix tubes is called lamellar bone Osteon (Haversian) System:Microscopic Structure of Compact Bone:Central (Haversian) Canal: are a series of microscopic tubes in the outermost region of bone called cortical bone that allow blood vessels and nerves to travel through them. Each harversian canal generally contains one or two capillaries and nerve fibers. The channels are formed by concentric layers called lamellae. The harversian canals surround blood vessels and nerve cells throughout bones and communicate with bone cells (contained in spaces within the dense bone matrix called lacunae) through connections called canaliculiPerforating (Volkmann's) Canal: perpendicular to long axis of bone (& to Haversian canals); are any of the small channels in the bone that transmit blood vessels from the periosteum into the bone and that communicate with the harversian canals. The perforating canals provide energy and nourishing elements for osteonsOsteocytes: mature bone cells; sit within small cavities (lacunae) within bony matrix in areas where adjacent lamellae meet Canaliculi: small canals that connect the lacunae with each other; also connected to central anal of Haversian system ANP1106 Page 9

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