COLLEGE PHYSICS Chapter 6 Chapter Chapter Title PowerPoint Image Slideshow BONE TISSUE AND THE SKELETAL SYSTEM https www verywellhealth com thmb UL7k28OGmrE2XrDZz7nokhPizfg 2000x1312 filters no upscale max bytes 150000 strip icc GettyImages 139541971 1f2cdfcfae93447bacabe425dec3d65a jpg Bone is a living tissue A child s bones continue to grow and develop while contributing to the support and function of other body systems Bone Functions Support Movement Protect Internal Organs https www wkc lawyers com wp content uploads 2019 01 b2ap3 thumbnail child brain injury head trauma 300x200 jpg https www humankinetics com AcuCustom Sitename DAM 086 19art Main png Store Calcium Phosphate https static toiimg com thumb 79443613 cms width 804 height 603 resizemode 4 imgsize 334388 Bone Composition Organic Component cells and protein fibers gives bone tensile strength and contribute to flexibility Cells secrete osteoid collagen fibers and proteoglycans Inorganic Component Ground Substance gives bone hardness and rigidity It is composed primarily of calcium phosphate Ca3 PO4 2 that interacts with calcium hydroxide Ca OH 2 to form crystals of hydroxyapatite Ca10 PO4 6 OH 2 Other ions and salts are also incorporated into hydroxyapatite Na Mg2 etc The correct proportion of cells ground substance and fibers allows for optimal functioning i e the structure needs to match the function Here is a little analogy where rebars act as fibers and concrete acts as a mineral containing ground substance Many Bones Contain Yellow and or Red Marrow Yellow marrow stores fat Red marrow is responsible for hematopoiesis Hematopoiesis or hemopoiesis is a combination of erythropoiesis leukopoiesis and thrombopoiesis https en wikipedia org wiki Haematopoiesis Classifications of Bones Bones are classified according to their shape The surface features of bones depend on their function location attachment of ligaments and tendons or the penetration of blood vessels and nerves Diagram of Blood and Nerve Supply to Bone Blood vessels and nerves enter the bone through the nutrient foramen pl foramina Bone Anatomy Compact bone cortical bone is dense and contributes 80 of bone mass Spongy bone cancellous bone appears more porous and contributes 20 of bone mass https www visiblebody com blog 3d skeletal system compact bone spongy bone and osteons This cross section of a flat bone shows the spongy bone diplo lined on either side by a layer of compact bone The periosteum forms the outer surface of bone and the endosteum lines the medullary cavity The periosteum attaches to the compact bone via proteinaceous perforating fibers Four types of cells are found within bone tissue Osteogenic cells are undifferentiated and develop into osteoblasts osteoblasts build When osteoblasts get trapped within the calcified matrix their structure and function changes and they become osteocytes trapped in lacunae Osteoclasts develop from monocytes and macrophages and differ in appearance from other bone cells by being multinucleated Bone resorption in osteoclasts Villous projections from an osteoclast form a ruffled border on the surface of bone which increases the membrane surface area Podosomes and their associated linking proteins e g osteopontin meaning bone bridge create an adhesive ring around the ruffled border This creates a resorptive pit that is sealed off from the adjacent bone and from the ECF wherein reactions that facilitate resorption occur Several acids e g citric acid lactic acid are released from the mitochondria and secretory vesicles Hydrogen ions are also released through the actions of carbonic anhydrase and vacuolar ATPase proton pumps This creates an acidic environment in the resorptive pit which results in bone salt dissolution Proteolytic enzymes e g cathepsin K are released from lysosomes in the osteoclast These enzymes break down the collagen bone matrix and are most active in an acidic environment Materials within the resorptive pit are phagocytosed and moved across the cell and released into the ECF this results in an increase in ion concentration in the blood CaK cathepsin K CA carbonic anhydrase Modified from http www pathophys org osteoporosis Compact Bone https en wikipedia org wiki Bone canaliculus media File Transverse section of bone en svg Spongy Bone Spongy bone is composed of trabeculae that contain the osteocytes Red marrow fills the spaces in some bones