Chapter 6 Bones & Skeletal Tissue PDF

CHAPTER 6: BONES AND SKELETAL TISSUE Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Skeletal Cartilages Three Types: 1) Hyaline cartilages Provide support, flexibility, and resilience Most abundant type Is present in these cartilages: ● ● ● ● Articular – covers the ends of lo...

CHAPTER 6: BONES AND SKELETAL TISSUE Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Skeletal Cartilages Three Types: 1) Hyaline cartilages Provide support, flexibility, and resilience Most abundant type Is present in these cartilages: ● ● ● ● Articular – covers the ends of long bones Costal – connects the ribs to the sternum Respiratory – makes up larynx, reinforces air passages Nasal – supports the nose Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Cartilages 2) Elastic cartilages Similar to hyaline cartilages, but contain elastic fibers Is present in these cartilages: The external ear Epiglottis Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Cartilages 3) Fibrocartilages Collagen fibers—have great tensile strength Is present in these cartilages: Menisci of the knee Intervertebral discs Pubic symphysis Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Growth of Cartilage ● ● ● ● ● ● ● 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 © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of Bones ● ● Axial skeleton – bones of the skull, vertebral column, and rib cage Appendicular skeleton – bones of the upper and lower limbs, shoulder (including clavicles), and hip Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of Bones by Shape ● ● ● ● Flat bones Thin, flat, slightly curved Irregular bones Complicated shapes Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Bones ● ● ● ● ● ● Support For the body and soft organs Protection For brain, spinal cord, and vital organs Movement Levers for muscle action Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Functions of Bones ● ● ● ● Storage Minerals (calcium and phosphorus) and growth factors Blood cell formation (hematopoiesis) in marrow cavities Triglyceride (energy) storage in bone cavities Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Markings ● ● ● ● Bulges, depressions, and holes that serve as: Sites of attachment for muscles, ligaments, and tendons Joint surfaces Conduits for blood vessels and nerves Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Markings: Projections ● ● ● ● ● ● ● ● ● Sites of muscle and ligament attachment Tuberosity—rounded projection Crest—narrow, prominent ridge Trochanter—large, blunt, irregular surface Line—narrow ridge of bone Tubercle—small rounded projection Epicondyle—raised area above a condyle Spine—sharp, slender projection Process—any bony prominence Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Markings: Projections ● ● ● ● ● ● ● ● ● Projections that help to form joints Head Bony expansion carried on a narrow neck Facet Smooth, nearly flat articular surface Condyle Rounded articular projection Ramus Armlike bar Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Markings: Depressions and Openings ● ● ● ● ● ● Meatus Canal-like passageway Sinus Cavity within a bone Fossa Shallow, basinlike depression Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings ● ● ● ● ● ● Groove Furrow Fissure Narrow, slitlike opening Foramen Round or oval opening through a bone Gross Anatomy of Bones: Bone Textures ● ● Compact bone – dense outer layer Spongy (cancellous) bone – honeycomb of trabeculae Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of a Long Bone ● ● ● Diaphysis (shaft) Compact bone collar surrounds medullary (marrow) cavity Medullary cavity in adults contains fat (yellow marrow) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of a Long Bone ● ● ● ● ● Epiphyses Expanded ends Spongy bone interior Epiphyseal line (remnant of growth plate) Articular (hyaline) cartilage on joint surfaces Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membranes of Bone ● ● ● ● ● ● ● ● Periosteum Outer fibrous layer Inner osteogenic layer Osteoblasts (bone-forming cells) Osteoclasts (bone-destroying cells) Osteogenic cells (stem cells) Nerve fibers, nutrient blood vessels, and lymphatic vessels enter the bone via nutrient foramina Secured to underlying bone by Sharpey’s fibers Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Membranes of Bone ● ● ● Endosteum Delicate membrane on internal surfaces of bone Also contains osteoblasts and osteoclasts Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 ● Have no diaphysis or epiphyses Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Location of Hematopoietic Tissue (Red Marrow) ● ● ● ● In infants Found in the medullary cavity and all areas of spongy bone In adults Found in the diploë of flat bones, and the head of the femur and humerus Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Bone ● ● ● ● ● ● ● ● ● Cells of bones: Osteogenic (osteoprogenitor) cells Stem cells in periosteum and endosteum that give rise to osteoblasts Osteoblasts Bone-forming cells Osteocytes Mature bone cells Osteoclasts Cells that break down (resorb) bone matrix Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Bone: Compact Bone ● ● ● ● Haversian system, or osteon—structural unit Lamellae Weight-bearing Column-like matrix tubes ● Central (Haversian) canal ● Contains blood vessels and nerves Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 Osteoid—organic bone matrix secreted by osteoblasts Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Development ● ● ● ● ● Osteogenesis (ossification)—bone tissue formation Stages Bone formation—begins in the 2nd month of development Postnatal bone growth—until early adulthood Bone remodeling and repair—lifelong Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Two Types of Ossification Intramembranous ossification Membrane bone develops from fibrous membrane Forms flat bones, e.g. clavicles and cranial bones Endochondral ossification Cartilage (endochondral) bone forms by replacing hyaline cartilage Forms most of the rest of the skeleton Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Postnatal Bone Growth ● ● ● ● Interstitial growth: length of long bones Appositional growth: thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Growth in Length of Long Bones ● ● ● ● ● Epiphyseal plate cartilage organizes into four important functional zones: Proliferation (growth) Hypertrophic Calcification Ossification (osteogenic) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Bone Growth ● ● ● ● ● ● ● ● Growth hormone Stimulates epiphyseal plate activity Insulin-like Growth Factors (IGFs), produced by liver Stimulate osteoblasts, promote cell division at the epiphyseal plate, and enhance protein synthesis Thyroid hormone Promote bone growth by stimulating osteoblasts Modulates activity of Growth hormone Insulin Promotes bone growth by increasing the synthesis of bone proteins Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Regulation of Bone Growth ● ● ● Testosterone and estrogens (at puberty) Promote adolescent growth spurts End growth by inducing epiphyseal plate closure Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Bone Remodeling ● Remodeling units – adjacent osteoblasts and osteoclasts deposit and resorb bone at periosteal and endosteal surfaces Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Factors Affecting Bone Growth and Bone Remodeling ● Normal bone metabolism depends on several factor ● Minerals ● ● ● ● ● ● Large amounts of calcium and phosphorus and smaller amounts of magnesium, fluoride, and manganese are required for bone growth and remodeling Vitamins Vitamin A stimulates activity of osteoblasts Vitamin C is needed for synthesis of collagen Vitamin D helps build bone by increasing the absorption of calcium from foods in the gastrointestinal tract into the blood Vitamins K and B12 are also needed for synthesis of bone proteins Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Importance of Ionic Calcium in the Body ● ● ● ● ● ● Calcium is necessary for: Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Control of Blood Ca2+ ● Primarily controlled by parathyroid hormone (PTH) Blood Ca2+ levels Parathyroid glands release PTH PTH stimulates osteoclasts to degrade bone matrix and release Ca2+ Blood Ca2+ levels Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Hormonal Control of Blood Ca2+ ● May be affected to a lesser extent by calcitonin Blood Ca2+ levels Parafollicular cells of thyroid release calcitonin Osteoblasts deposit calcium salts Blood Ca2+ levels Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Response to Mechanical Stress ● ● ● ● ● ● Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it Observations supporting Wolff’s law: Handedness (right or left handed) results in bone of one upper limb being thicker and stronger Curved bones are thickest where they are most likely to buckle Trabeculae form along lines of stress Large, bony projections occur where heavy, active muscles attach Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classification of Bone Fractures 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 © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Common Types of Fractures ● ● ● ● All fractures can be described in terms of Location External appearance Nature of the break Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fracture Types ● ● ● ● Comminuted fracture The bone is splintered, crushed, or broken into pieces Compression fracture The bone is crushed Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fracture Types ● ● ● ● Spiral fracture Ragged break when excessive twisting forces are applied Epiphyseal fracture Epiphysis separates from the diaphysis along the epiphyseal plate Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Fracture Types ● ● ● ● Depressed fracture Broken bone portion is pressed inward Greenstick fracture A partial fracture in which one side of the bone is broken and the other side bends Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Other Fractures ● ● ● ● ● ● ● ● Impacted fracture One end of the fractured bone is forcefully driven into another Pott’s fracture Fracture of the fibula, with injury of the tibial articulation Colles’ fracture A fracture of the radius in which the distal fragment is displaced Stress fracture A series of microscopic fissures in bone Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Hematoma forms Torn blood vessels hemorrhage Clot (hematoma) forms Site becomes swollen, painful, and inflamed Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture 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 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Bony callus formation New trabeculae form a bony (hard) callus Bony callus formation continues until firm union is formed in ~2 months Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stages in the Healing of a Bone Fracture Bone remodeling In response to mechanical stressors over several months Final structure resembles original Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances ● ● ● ● ● 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 Example: Infants of breastfeeding mothers deficient in Vitamin D will also be Vitamin D deficient and develop rickets Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Homeostatic Imbalances ● ● ● ● ● 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 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Osteoporosis: Treatment and Prevention ● ● ● ● ● Calcium (preferrably in a multi-mineral supplement), vitamin D, and fluoride supplements Weight-bearing exercise throughout life Hormone (estrogen) replacement therapy (HRT) slows bone loss Natural progesterone cream prompts new bone growth Some drugs (Fosamax, SERMs, statins) increase bone mineral density Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings 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 (drug that prevents loss of bone mass) Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of Bones ● ● ● 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 Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings