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Unformatted text preview: Biol 255 Unit 2A B. Krumhardt, Ph.D., GDCB, ISU 1 Biology 255 Unit 2A Bones B. Krumhardt, Ph.D. GDCB, Iowa State University Functions Support Protection Movement Mineral storage Blood cell production - (red bone marrow)-"hematopoiesis" Storage of Energy (yellow bone marrow) Bone Cells Less than 1% of weight Osteoprogenitor cells - unspecialized CT cells, become osteoblasts Osteoblasts - form bone (secrete matrix), divide by mitosis Osteocytes - (from osteoblasts) maintain bone, not mitotic Osteoclasts -(from monocytes) resorb bone for development, growth (remodeling), maintenance, repair of bone AND keeping blood calcium up if diet calcium is low Bone Matrix Cartilage - 35% of weight (in adults) provides flexibility Hyaline cartilage and fibrocartilage Mineral - hydroxyapatites - 65% of weight (in adults) provides strength Calcium phosphate & calcium carbonate Small amounts of other minerals Biol 255 Unit 2A B. Krumhardt, Ph.D., GDCB, ISU 2 Bone types Spongy bone Trabeculae composed of parallel lamelae Thin plates of bone with large spaces (usually filled with red marrow - hematopoiesis) More spongy bone in short flat irregular shaped bones than in long bones Diploe - spongy layer in flat bones Compact bone Few spaces - layer over spongy bone Thicker in diaphysis than epiphysis Protection & support Compact Bone Structure Osteon - structural unit of compact bone Central (Haversian) canals run longitudinally with blood vessels and nerves within Around these - circular rings of concentric lamellae - hard, calcified; oriented at angles to withstand stress Spaces between rings- lacunae - osteocytes within (support function) Radiating out every way - canaliculi with osteocyte processes extending into extracellular fluid network for nutrient delivery and waste removal Perforating canals - allow blood vessels & nerves to enter Between osteons - interstitial lamellae - lamellae not connected to other osteons via perforating canals (fragments of older osteons) Circumferential lamellae enclose entire bone within periosteum Biol 255 Unit 2A...
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