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The Skeletal System (Bones and Joints) Anatomy & Physiology I Chapter 7 Bone as a Tissue osteology – the study of bone skeletal system - composed of bones, joints, cartilages, and ligaments ◦ form strong flexible framework of the body ◦ cartilage – forerunner of most bones covers many joint surfaces of mature bone ligaments – hold bones together at the joints tendons – attach muscle to bone Functions of the Skeleton support – hold the body up, supports muscles, mandible and maxilla support teeth protection – brain, spinal cord, heart, lungs movement – limb movements, breathing, action of muscle on bone electrolyte balance – calcium and phosphate ions acid-base balance – buffers blood against excessive pH changes blood formation – red bone marrow is the chief producer of blood cells 7-3 Bones and Osseous Tissue bone (osseous tissue) - connective tissue with the matrix hardened by calcium phosphate and other minerals mineralization or calcification – the hardening process of bone individual bones consist of bone tissue, bone marrow, cartilage, adipose tissue, nervous tissue, and fibrous connective tissue continually remodels itself and interacts physiologically with all of the other organ systems of the body permeated with nerves and blood vessels, which attests to its sensitivity and metabolic activity 7-4 The Matrix of Bone matrix of osseous tissue is, by dry weight, about one-third organic and two-thirds inorganic matter organic matter – synthesized by osteoblasts ◦ collagen, carbohydrate – protein complexes, such as proteoglycans and glycoproteins inorganic matter ◦ 85% calcium phosphate (hydroxyapatite) ◦ 10% calcium carbonate ◦ other minerals (fluoride, sodium, potassium, magnesium) bone is a composite – combination of two basic structural materials, a ceramic and a polymer ◦ combines optimal mechanical properties of each component ◦ bone combines the polymer, collagen, with the ceramic, hydroxyapatite and other minerals ◦ ceramic portion allows the bone to support the body weight, and protein portion gives bone some degree of flexibility rickets – soft bones due to deficiency of calcium salts osteogenesis imperfecta or brittle bone disease – excessively brittle bones due to lack of protein, collagen Bone Structure Types of osseous (bone) tissue Compact bone - Dense outer layer Spongy (cancellous) bone - Honeycomb of trabeculae Bone marrow ◦ Red marrow ◦ Yellow marrow Bone membranes ◦ Periosteum ◦ Endosteum Spongy bone (diploë) Compact bone Trabeculae Structure of a Long Bone 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 Articular cartilage Epiphysis Red bone marrow Epiphyseal line Marrow cavity Yellow bone marrow Periosteum Nutrient foramen Diaphysis Compact bone Spongy bone Epiphyseal line Epiphysis Articular cartilage Living Dried Structure of a Long Bone Articular cartilage Proximal epiphysis Compact bone Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) Diaphysis Distal epiphysis 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 Membranes of Bone Endosteum ◦ Delicate membrane on internal surfaces of bone ◦ Also contains osteoblasts and osteoclasts Endosteum Yellow bone marrow Compact bone Periosteum Perforating (Sharpey’s) fibers Nutrient arteries 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 Spongy bone (diploë) Compact bone Trabeculae Bone Marrow bone marrow – general term for soft tissue that occupies the marrow cavity of a long bone and small spaces amid the trabeculae of spongy bone red marrow (myeloid tissue) ◦ in nearly every bone in a child ◦ hemopoietic tissue - produces blood cells and is composed of multiple tissues in a delicate, but intricate arrangement that is an organ to itself ◦ in adults, found in skull, vertebrae, ribs, sternum, part of pelvic girdle, and proximal heads of humerus and femur yellow marrow found in adults ◦ most red marrow turns into fatty yellow marrow ◦ no longer produces blood 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 Microscopic Anatomy of Bone Cells of bones ◦ Osteogenic (osteoprogenitor) cells – give rise to osteoblasts Stem cells in periosteum, endosteum and central canals ◦ Osteoblasts – manufacture bone matrix Bone-forming cells ◦ Osteocytes – maintain and repair existing bone matrix Mature bone cells ◦ Osteoclasts – breakdown (resorb) bone matrix Cells that break down and release minerals from bone matrix 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 Compact bone tissue 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 Compact Bone Compact bone Central (Haversian) canal Spongy bone Perforating (Volkmann’s) canal Endosteum lining bony canals and covering trabeculae Osteon (Haversian system) Circumferential lamellae Perforating (Sharpey’s) fibers Lamellae Nerve Vein Artery Canaliculi Osteocyte in a lacuna Periosteal blood vessel Periosteum Lamellae Central canal Lacunae Lacuna (with osteocyte) Interstitial lamellae Compact Bone Nerve Vein Artery Canaliculus Osteocyte in a lacuna Lamellae Central canal Lacunae 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 Bone Deposit Occurs where bone is injured or added strength is needed Requires a diet rich in protein; vitamins C, D, and A; calcium; phosphorus; magnesium; and manganese Bone Resorption Osteoclasts secrete ◦ Lysosomal enzymes (digest organic matrix) ◦ Acids (convert calcium salts into soluble forms) Dissolved matrix is transcytosed across osteoclast, enters interstitial fluid and then blood Control of Remodeling What controls continual remodeling of bone? ◦ Hormonal mechanisms that maintain calcium homeostasis in the blood ◦ Mechanical and gravitational forces Hormonal Control of Blood Ca2+ The level of blood calcium (Ca2+) must be maintained (homeostasis) Calcium is necessary for ◦ ◦ ◦ ◦ ◦ Transmission of nerve impulses Muscle contraction Blood coagulation Secretion by glands and nerve cells Cell division Which hormones are responsible for maintaining blood calcium? 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 When blood calcium levels fall, PTH is released causing blood calcium levels to increase. 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 When blood calcium levels rise, calcitonin is released causing blood calcium levels to decrease. 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 Bone Markings Bulges, depressions, and holes serve as ◦ Sites of attachment for muscles, ligaments, and tendons ◦ Joint surfaces ◦ Conduits for blood vessels and nerves 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 ◦ Condyle – rounded projection ◦ Epicondyle—raised area above a condyle ◦ Spine—sharp, slender projection ◦ Process—any bony prominence 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 Bone Markings: Depressions and Openings Meatus ◦ Canal-like passageway Sinus ◦ Furrow ◦ Cavity within a bone Fissure ◦ Narrow, slitlike opening Fossa ◦ Shallow, basinlike depression Groove Foramen ◦ Round or oval opening through a bone The skeleton Bones of the Axial Skeleton Two main groups of bones Axial skeleton—80 bones of the head and trunk Appendicular skeleton—126 bones of the extremities Framework of the Skull Cranial bones Facial bones Infant skull Framework of the Skull, cont’d Cranial bones ◦ ◦ ◦ ◦ ◦ ◦ Frontal Parietal Temporal Ethmoid Sphenoid Occipital Framework of the Skull, cont’d Facial bones ◦ Mandible ◦ Maxillae ◦ Zygomatic ◦ Nasal ◦ Lacrimal ◦ Vomer ◦ Palatine ◦ Inferior nasal conchae ◦ Ossicle ◦ Hyoid Framework of the Skull, cont’d Infant skull ◦ Anterior fontanel The skull ZOOMING IN • What type of joint is between bones of the skull? The skull, inferior view. ZOOMING IN • What two bones make up each side of the hard palate? Floor of cranium, superior view. ZOOMING IN • What is a foramen? The skull, sagittal section. Infant skull, showing fontanels ZOOMING IN • Which is the largest fontanel? Framework of the Trunk Vertebral column ◦ Cervical vertebrae ◦ Thoracic vertebrae ◦ Lumbar vertebrae ◦ Sacral vertebrae (sacrum) ◦ Coccygeal vertebrae (coccyx) Thorax ◦ Sternum ◦ Ribs True ribs False ribs ◦ Manubrium ◦ Clavicular notch ◦ Sternal angle ◦ Xiphoid process The Vertebral Column (Spine) Anterior view five vertebral groups ◦ ◦ ◦ ◦ 7 cervical in the neck 12 thoracic in the chest 5 lumbar in lower back 5 fused sacral at base of spine ◦ 4 fused coccygeal Posterior view Atlas (C1) Axis (C2) Cervical vertebrae C7 T1 Thoracic vertebrae T12 L1 Lumbar vertebrae L5 S1 Sacrum S5 Coccyx Coccyx Newborn Spinal Curvature spine exhibits one continuous C-shaped curve at birth known as primary curvature Adult Spinal Curvatures C1 ◦ ◦ ◦ ◦ Cervical curvature C7 T1 Thoracic curvature s-shaped vertebral column with four normal curvatures cervical thoracic lumbar pelvic primary curvatures – present at birth ◦ thoracic and pelvic T12 L1 Lumbar curvature L5 S1 Pelvic curvature secondary curvatures – develop later ◦ cervical and lumbar ◦ lifting head as it begins to crawl develops cervical curvature ◦ walking upright develops lumbar curvature Abnormal Spinal Curvatures from disease, paralysis of trunk muscles, poor posture, pregnancy, or congenital defect scoliosis – abnormal lateral curvature ◦ ◦ ◦ ◦ (a) Scoliosis Key Normal Pathological (b) Kyphosis (“hunchback”) most common usually in thoracic region particularly of adolescent girls developmental abnormality in which the body and arch fail to develop on one side of the vertebrae kyphosis (hunchback) – exaggerated thoracic curvature ◦ usually from osteoporosis, also osteomalacia or spinal tuberculosis, or wrestling or weightlifting in young boys (c) Lordosis (“hunchback”) lordosis (swayback) – exaggerated lumbar curvature ◦ is from pregnancy or obesity General Structure of Vertebra body (centrum) ◦ mass of spongy bone that contains red bone marrow ◦ covered with thin shell of compact bone ◦ weight bearing portion ◦ rough superior and inferior surfaces provide firm attachment for intervertebral discs vertebral foramina Posterior Spinous process Lamina Superior articular facet Vertebral arch Transverse process Pedicle Vertebral foramen ◦ collectively form vertebral canal for spinal cord vertebral arch Body ◦ composed of two parts on each side ◦ pedicle – pillarlike and lamina - platelike Anterior spinous process 2nd lumbar vertebra (L2) ◦ projection extending from the apex of arch ◦ extends posteriorly and downward transverse process ◦ extends laterally from point where pedicel and lamina meet superior articular processes ◦ project upward from one vertebra and meets inferior articular processes from the vertebra above facets ◦ flat articular surfaces covered with hyaline cartilage Nucleus pulposus Anulus fibrosus Intervertebral disc Intervertebral Foramen and Discs Superior articular process of L1 L1 Inferior vertebral notch of L1 Intervertebral foramen Superior vertebral notch of L2 intervertebral foramen ◦ when two vertebrae are joined they exhibit and opening; ◦ intervertebral foramen - passageway for spinal nerves ◦ inferior vertebral notch in the pedicle of the upper vertebra ◦ superior vertebral notch in the pedicle of the lower vertebra L2 Spinous process Intervertebral disc L3 Inferior articular process of L3 intervertebral discs (23) ◦ pad consisting of: nucleus pulposus - inner gelatinous mass anulus fibrosus – outer ring of fibrocartilage ◦ bind vertebrae together ◦ support weight of the body ◦ absorb shock ◦ herniated disc (‘ruptured’ or ‘slipped’ disc) puts painful pressure on spinal nerve or spinal cord The first two cervical vertebrae: Atlas and Axis Atlas and Axis Articulation Axis of rotation Dens Atlas Transverse ligament Axis Atlantoaxial joint Bones of the thorax ZOOMING IN • To what bones do the costal cartilages attach? Bones of the Appendicular Skeleton Two divisions Upper Lower The Upper Division of the Appendicular Skeleton The shoulder girdle ◦ ◦ ◦ ◦ ◦ ◦ Clavicle (collarbone) Scapula (shoulder blade) Supraspinous fossa and infraspinous fossa Acromion Glenoid cavity Coracoid process The Upper Division of the Appendicular Skeleton, cont’d The upper extremity ◦ Humerus (arm bone) ◦ Medial and lateral epicondyles ◦ Trochlea ◦ Ulna and radius (forearm bones) ◦ Distal projection (styloid process) ◦ Olecranon ◦ Trochlear notch (semilunar notch) ◦ Carpal bones ◦ Metacarpal bones ◦ Phalanges (finger bones) The shoulder girdle and scapula ZOOMING IN • What does the prefix supra mean? • What does the prefix infra mean? Appendicular Skeleton: Lower Division The pelvic bones ◦ Ilium Iliac crest Anterior superior iliac spine ◦ Ischium Ischial spine Ischial tuberosity ◦ Pubis Pubic symphysis Acetabulum Obturator foramen Ossa coxae The Pelvic Bones ZOOMING IN • What bone is nicknamed the “sit bone”? Comparison of male and female pelvis Appendicular Skeleton: Lower Division, cont’d The lower extremity ◦ Femur Greater trochanter Lesser trochanter Linea aspera ◦ Patella ◦ Tibia (shin bone) Medial malleolus ◦ Fibula Lateral malleolus ◦ Tarsal bones Calcaneus (heel bone) ◦ Metatarsal bones ◦ Phalanges The right femur (thigh bone) Tibia and fibula of the right leg ZOOMING IN • What is the medial bone of the leg? Disorders of Bone Metabolic diseases Tumors Infections Structural problems Metabolic Disorders Characterized by a lack of normal bone formation or excess loss of bone tissue Osteoporosis ◦ Osteopenia Paget’s disease (osteitis deformans) Osteomalacia (in children, rickets) Tumors Two types found in bone tissue Benign Malignant ◦ Osteosarcomas ◦ Chondrosarcomas Infection Two types found in bone tissue Osteomyelitis ◦ Inflammation of the bone caused by pyogenic bacteria Tuberculosis ◦ Pott disease (tuberculosis of the spine) Structural Disorders Curvatures of the spine ◦ Kyphosis (hunchback) ◦ Lordosis (swayback) ◦ Scoliosis Cleft palate Flatfoot Fractures Types of fractures Closed Open Greenstick Impacted Comminuted Spiral Transverse Oblique Skeletal Changes in the Aging Bones undergo significant changes Loss of calcium salts Decrease in protein Reduction in collagen Loss of height Decrease in chest diameter The Joints Classified by material between adjoining bones and by degree of movement permitted Fibrous ◦ Synarthrosis (immovable) Cartilaginous ◦ Amphiarthrosis (slightly movable) Synovial ◦ Diarthrosis (freely movable) More About Synovial Joints Bones are joined by other structures in synovial joints Ligaments Joint capsule Hyaline (articular) cartilage Medial meniscus and lateral meniscus Fat Bursae Structure of a synovial joint. Types of Synovial Joints Classified by types of movement they allow Gliding Hinge Pivot Condyloid Saddle Ball-and-socket Movement at Synovial Joints Flexion Extension Abduction Adduction Circumduction Rotation Movement at Synovial Joints, cont’d Movements characteristic of forearm and ankle ◦ ◦ ◦ ◦ ◦ ◦ Supination Pronation Inversion Eversion Dorsiflexion Plantar flexion Disorders of Joints Mechanical disorders ◦ Dislocation ◦ Sprain Arthritis ◦ Osteoarthritis (degenerative joint disease [DJD]) ◦ Rheumatoid arthritis ◦ Septic (infectious) arthritis ◦ Gout Disorders of Joints, cont’d Herniated disk Backache ◦ Vertebrae diseases ◦ Intervertebral disk disorders ◦ Supporting structure abnormalities ◦ Abdominopelvic disorders ◦ Lumbosacral joint strains Arthroscopic examination of the knee End of Presentation
