Copyright © 2010 Pearson Education, Inc. Skeletal Cartilages Contain no blood vessels or nerves Dense connective tissue girdle of perichondrium contains blood vessels for nutrient delivery to cartilage 1.Hyaline cartilages Provide support, flexibility, and resilience Most abundant type 2.Elastic cartilages Similar to hyaline cartilages, but contain elastic fibers 3.Fibrocartilages Collagen fibers—have great tensile strength Growth Appositional Cells secrete matrix against the external face of existing cartilage Interstitial Chondrocytes divide and secrete new matrix, expanding cartilage from within Calcification of cartilage occurs during Normal bone growth Old age

Copyright © 2010 Pearson Education, Inc. Figure 6.1 Axial skeleton Appendicular skeleton Hyaline cartilages Elastic cartilages Fibrocartilages Cartilages Epiglottis Larynx Trachea Cricoid cartilage Lung Respiratory tube cartilages in neck and thorax Thyroid cartilage Cartilage in external ear Cartilages in nose Articular Cartilage of a joint Costal cartilage Cartilage in Intervertebral disc Pubic symphysis Articular cartilage of a joint Meniscus (padlike cartilage in knee joint) Cartilages

Copyright © 2010 Pearson Education, Inc. Bones of Skeleton Two main groups, by location

Copyright © 2010 Pearson Education, Inc. Classification of Bones by Shape Long bones Longer than they are wide Short bones Cube-shaped bones (in wrist and ankle) Sesamoid bones (within tendons, e.g., patella) Flat bones Thin, flat, slightly curved Irregular bones Complicated shapes

Copyright © 2010 Pearson Education, Inc. Functions of Bones Support For the body and soft organs Protection For brain, spinal cord, and vital organs Movement Levers for muscle action Storage Minerals (calcium and phosphorus) and growth factors Blood cell formation (hematopoiesis) in marrow cavities Triglyceride (energy) storage in bone cavities

Copyright © 2010 Pearson Education, Inc. Table 6.1

Copyright © 2010 Pearson Education, Inc. Table 6.1

Copyright © 2010 Pearson Education, Inc. Figure 6.3a-b Proximal epiphysis (b) (a) Epiphyseal line Articular cartilage Periosteum Spongy bone Compact bone Medullary cavity (lined by endosteum) Compact bone Diaphysis Distal epiphysis Compact bone Dense outer layer Spongy (cancellous) bone Honeycomb of trabeculae Diaphysis (shaft) Compact bone collar surrounds medullary (marrow) cavity Medullary cavity in adults contains fat (yellow marrow) Epiphyses Expanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces Structure of a Long Bone

Copyright © 2010 Pearson Education, Inc. Figure 6.3c Yellow bone marrow Endosteum Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries Membranes of Bone Periosteum Outer fibrous layer Inner osteogenic layer Osteoblasts (bone-forming cells) Osteoclasts (bone-destroying cells) Osteogenic cells (stem cells) Osteocytes (Mature bone cells) Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina Secured to underlying bone by Sharpey’s fibers Endosteum Delicate membrane on internal surfaces of bone Also contains osteoblasts and osteoclasts

Copyright © 2010 Pearson Education, Inc. Figure 6.5 Compact bone Trabeculae Spongy bone (diploë) Structure of Short, Irregular, and Flat Bones Periosteum-covered compact bone on the outside Endosteum-covered spongy bone within Spongy bone called diploë in flat bones Bone marrow between the trabeculae

Copyright © 2010 Pearson Education, Inc. Location of Hematopoietic Tissue (Red Marrow) Red marrow cavities of adults Trabecular cavities of the heads of the femur and humerus Trabecular cavities of the diploë of flat bones Red marrow of newborn infants Medullary cavities and all spaces in spongy bone

Copyright © 2010 Pearson Education, Inc. Microscopic Anatomy of Bone: Compact Bone Perforating (Volkmann’s) canals At right angles to the central canal Connects blood vessels and nerves of the periosteum and central canal Lacunae—small cavities that contain osteocytes Canaliculi—hairlike canals that connect lacunae to each other and the central canal Haversian system, or osteon—structural unit Lamellae Weight-bearing Column-like matrix tubes Central (Haversian) canal Contains blood vessels and nerves Microscopic Anatomy of Bone: Spongy Bone Trabeculae Align along lines of stress No osteons Contain irregularly arranged lamellae, osteocytes, and canaliculi Capillaries in endosteum supply nutrients

Copyright © 2010 Pearson Education, Inc. Figure 6.7a-c Endosteum lining bony canals and covering trabeculae Perforating (Volkmann’s) canal Perforating (Sharpey’s) fibers Periosteal blood vessel Periosteum Lacuna (with osteocyte) (a) (b)(c) Lacunae Lamellae Nerve Vein Artery Canaliculi Osteocyte in a lacuna Circumferential lamellae Osteon (Haversian system) Central (Haversian) canal Central canal Interstitial lamellae Lamellae Compact bone Spongy bone

Copyright © 2010 Pearson Education, Inc. Bone Development: Two Types of Ossification 1.Intramembranous ossification Membrane bone develops from fibrous membrane Forms flat bones, e.g. clavicles and cranial bones 2.Endochondral ossification Cartilage (endochondral) bone forms by replacing hyaline cartilage Forms most of the rest of the skeleton

Copyright © 2010 Pearson Education, Inc. Figure 6.10 Calcified cartilage spicule Osseous tissue (bone) covering cartilage spicules Resting zone Osteoblast depositing bone matrix Proliferation zone Cartilage cells undergo mitosis. Hypertrophic zone Older cartilage cells enlarge. Ossification zone New bone formation is occurring. Calcification zone Matrix becomes calcified; cartilage cells die; matrix begins deteriorating Growth in Length of Long Bones Epiphyseal plate cartilage organizes into four important functional zones: Proliferation (growth) Hypertrophic Calcification Ossification (osteogenic)

Copyright © 2010 Pearson Education, Inc. Hormonal Regulation of Bone Growth Growth hormone stimulates epiphyseal plate activity Thyroid hormone modulates activity of growth hormone Testosterone and estrogens (at puberty) Promote adolescent growth spurts End growth by inducing epiphyseal plate closure

Copyright © 2010 Pearson Education, Inc. Hormonal Control of Blood Ca 2+ Calcium is necessary for Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division

Copyright © 2010 Pearson Education, Inc. Figure 6.12 Osteoclasts degrade bone matrix and release Ca 2+ into blood. Parathyroid glands Thyroid gland Parathyroid glands release parathyroid hormone (PTH). Stimulus Falling blood Ca 2+ levels PTH Calcium homeostasis of blood: 9–11 mg/100 ml BALANCE

Copyright © 2010 Pearson Education, Inc. Hormonal Control of Blood Ca 2+ May be affected to a lesser extent by calcitonin  Blood Ca 2+ levels  Parafollicular cells of thyroid release calcitonin  Osteoblasts deposit calcium salts   Blood Ca 2+ levels

Copyright © 2010 Pearson Education, Inc. Leptin has also been shown to influence bone density by inhibiting osteoblasts

Copyright © 2010 Pearson Education, Inc. Classification of Bone Fractures Bone fractures may be classified by four “either/or” classifications: 1.Position of bone ends after fracture: Nondisplaced—ends retain normal position Displaced—ends out of normal alignment 2.Completeness of the break Complete—broken all the way through Incomplete—not broken all the way through 3.Orientation of the break to the long axis of the bone: Linear—parallel to long axis of the bone Transverse—perpendicular to long axis of the bone 4.Whether or not the bone ends penetrate the skin: Compound (open)—bone ends penetrate the skin Simple (closed)—bone ends do not penetrate the skin

Copyright © 2010 Pearson Education, Inc. Table 6.2 All fractures can be described in terms of Location External appearance Nature of the break

Copyright © 2010 Pearson Education, Inc. Table 6.2

Copyright © 2010 Pearson Education, Inc. Table 6.2

Copyright © 2010 Pearson Education, Inc. Figure 6.15 Hematoma External callus Bony callus of spongy bone Healed fracture New blood vessels Spongy bone trabecula Internal callus (fibrous tissue and cartilage) A hematoma forms. Fibrocartilaginous callus forms. Bony callus forms. Bone remodeling occurs Stages in the Healing of a Bone Fracture 1.Hematoma forms Torn blood vessels hemorrhage Clot (hematoma) forms Site becomes swollen, painful, and inflamed 2.Fibrocartilaginous callus forms Phagocytic cells clear debris Osteoblasts begin forming spongy bone within 1 week Fibroblasts secrete collagen fibers to connect bone ends Mass of repair tissue now called fibrocartilaginous callus 3.Bony callus formation New trabeculae form a bony (hard) callus Bony callus formation continues until firm union is formed in ~2 months 4.Bone remodeling In response to mechanical stressors over several months Final structure resembles original

Copyright © 2010 Pearson Education, Inc. Osteomalacia and rickets Calcium salts not deposited Rickets (childhood disease) causes bowed legs and other bone deformities Cause: vitamin D deficiency or insufficient dietary calcium Osteoporosis Loss of bone mass—bone resorption outpaces deposit Spongy bone of spine and neck of femur become most susceptible to fracture Risk factors Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus Treatment and Prevention Calcium, vitamin D, and fluoride supplements  Weight-bearing exercise throughout life Hormone (estrogen) replacement therapy (HRT) slows bone loss Some drugs (Fosamax, SERMs, statins) increase bone mineral density Homeostatic Imbalances

Copyright © 2010 Pearson Education, Inc. Paget’s Disease Excessive and haphazard bone formation and breakdown, usually in spine, pelvis, femur, or skull Pagetic bone has very high ratio of spongy to compact bone and reduced mineralization Unknown cause (possibly viral) Treatment includes calcitonin and biphosphonates

Copyright © 2010 Pearson Education, Inc. Parietal bone Radius Ulna Humerus Femur Occipital bone Clavicle Scapula Ribs Vertebra Hip bone Tibia Frontal bone of skull Mandible Embryonic skeleton ossifies predictably so fetal age easily determined from X rays or sonograms At birth, most long bones are well ossified (except epiphyses) Nearly all bones completely ossified by age 25 Bone mass decreases with age beginning in 4th decade Rate of loss determined by genetics and environmental factors In old age, bone resorption predominates Developmental Aspects of Bones