A Chemical Analysis of Bone Bones provide: • Support and movement (limbs, axial skeleton) • Protection (skull bones) • Mineral storage • Blood cell development (long bone marrow) Bone is made up of: • 35% collagen, ground substance and cells • 65% calcium Bone is alive! Bone cell types: • Osteoblasts: Make and deposit components of bone extracellular matrix • Osteoclasts: Degrade and resorb bone for remodeling • Osteocytes: “watcher cells” Sit in bone and monitor its current status Cartilage and Bone • • • • Cartilage--function, types, location Bone Tissue--structure, types Long Bone Structure and Development Most common bone problems – Fractures – Osteoporosis What is cartilage? • Skeletal tissue--maintains certain shape and form • Very resilient (bouncy or rubbery), mostly water • Grows fast--forms embryonic skeleton Kinds of cartilage • Hyaline cartilage--most common in the body, found in joints • Elastic cartilage--epiglottis, ear • Fibrocartilage--intervertebral disk, menisci of knee Types of bony tissue Compact Bone • Osteon - basic function unit of compact bone – Central canal - run parallel to surface of bone • contains blood vessels – Concentric lamellae - cylinders of bone – Lacunae - house osteocytes – Canaliculi - minute passageways that lacunae • Processes of osteocytes extend into canaliculi – Perforating or Volkmann’s canal • run perpendicular to long axis. • contain blood vessels that then branch to enter central canal STRUCTURE OF COMPACT BONE Types of bony tissue • Compact Bone – Dense tissue at surface of bones – Haversian canals – Osteocytes in lacunae – Highly vascularized Types of bony tissue • Trabecular (“spongy”) bone – Trabeculae (oriented to give mechanical strength) – Interior of long bones, skull bones – Epiphyses of long bones – Intramembranous ossification (osteoblasts lay down bone around blood vessels in connective tissues of dermis (after 8 weeks of development) View of Spongy Bone Osteoporosis - Affects elderly, especially women Bone resorption proceeds faster than deposition Low estrogen levels implicated but estrogen replacement now considered risky Flat, Short, Irregular Bones • Flat Bones – No diaphyses or epiphyses – A sandwich of cancellous (spongy) bone between compact bone • Cancellous bone (Spongy bone) – Composed of bony plates known as trabeculae Bone Shapes • Long – Ex. Upper and lower limbs • Short – Ex. Carpals and tarsals • Flat – Ex. Ribs, sternum, skull, scapulae • Irregular – Ex. Vertebrae, facial Bone Matrix If mineral removed, bone is too bendable If collagen removed, bone is too brittle Bone Fractures • Treatment is reduction – Closed--set in place by physical manipulation from outside body – Open--surgical placement of pins or screws • Healing – Hematoma – Fibrocartilaginous callus – Bony calllus – Remodeling by osteoclasts/osteoblasts Types of Fractures Types of Fractures Comminuted Compression Spiral fracture Epiphyseal fx Depressed fx Greenstick fx Fracture repair in stages Calcium regulation is negative feedback mechanism Calcium Homeostasis Correction for Hypercalcemia Factors Affecting Bone Growth • Size and shape of a bone determined genetically but can be modified and influenced by nutrition and hormones • Nutrition – Lack of calcium, protein and other nutrients during growth and development can cause bones to be small – Vitamin D • Necessary for absorption of calcium from intestines • Can be eaten or manufactured in the body • Rickets: lack of vitamin D during childhood • Osteomalacia: lack of vitamin D during adulthood leading to softening of bones – Vitamin C • Necessary for collagen synthesis by osteoblasts • Scurvy: due to deficiency of vitamin C • Lack of vitamin C also causes wounds not to heal, teeth to fall out Why do bones need to “remodel?” Bone Growth at an Epiphyseal Cartilage Effects of Aging on Skeletal System • Bone matrix decreases. – More brittle due to lack of collagen; but also less hydroxyapetite. • Bone mass decreases. – Highest around 30. – Male bone mass denser due to testosterone and greater weight. – African Americans and Hispanics have higher bone masses than Caucasians and Asians. – Rate of bone loss increases 10 fold after menopause. • Cancellous bone lost first, then compact. • Increased bone fractures • Bone loss causes deformity, loss of height, pain, stiffness – Stooped posture – Loss of teeth