2A Bones - Biol 255 Unit 2A B Krumhardt Ph.D GDCB ISU 1...

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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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2A Bones - Biol 255 Unit 2A B Krumhardt Ph.D GDCB ISU 1...

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