6. The Skeletal System

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  • 6. The Skeletal System

    1. 1. The Skeletal System
    2. 2. Learning Objectives <ul><li>List the cell types that make up bone; describe the function of each cell type. </li></ul><ul><li>List the functions of bone and differentiate between cancellous and compact bone. </li></ul><ul><li>Describe the process of endochondral bone formation and growth. </li></ul><ul><li>Describe the process of intramembranous bone formation. </li></ul><ul><li>List and describe the four shapes of bone. </li></ul><ul><li>Differentiate between yellow and red bone marrow. </li></ul><ul><li>List and define terms used to describe shape and surface features of bone. </li></ul><ul><li>List the components of the axial and appendicular skeletons. </li></ul><ul><li>Name the bones of the thoracic and pelvic limbs; the internal and external bones of the face and cranium. </li></ul><ul><li>List the divisions of the spinal column and describe the structure of the ribs and sternum. </li></ul><ul><li>List and describe the three classification of joints. </li></ul>
    3. 3. Bone <ul><li>Second hardest substance in the body </li></ul><ul><li>Composed of cells embedded in a matrix </li></ul><ul><ul><li>Matrix is made up of collagen fibers embedded in a protein and polysaccharides </li></ul></ul>
    4. 4. Functions of Bone <ul><li>Support </li></ul><ul><li>Protection </li></ul><ul><li>Leverage </li></ul><ul><li>Storage </li></ul><ul><li>Blood cell formation </li></ul>
    5. 5. Bone Structure <ul><li>Two types of bone </li></ul><ul><li>Cancellous bone: light and spongy </li></ul><ul><li>Compact bone: dense and heavy </li></ul>
    6. 6. Cancellous Bone <ul><li>Tiny &quot;spicules&quot; of bone that appear randomly arranged </li></ul><ul><li>Spaces between the spicules contain bone marrow </li></ul>
    7. 7. Compact Bone <ul><li>Shafts of long bones and the outside layer of all bones </li></ul><ul><li>Composed of haversian systems that run lengthwise with the bone </li></ul>
    8. 8. Haversian Systems <ul><li>Concentric layers of ossified bone matrix arranged around a central canal </li></ul><ul><ul><li>Blood and lymph vessels and nerves </li></ul></ul>
    9. 9. Bone Structure <ul><li>Periosteum: membrane that covers outer surfaces of bones </li></ul><ul><ul><li>Outer layer is composed of fibrous tissue </li></ul></ul><ul><ul><li>Inner layer contains osteoblasts </li></ul></ul><ul><ul><li>Not present on articular surfaces </li></ul></ul>
    10. 10. Bone Structure <ul><li>Endosteum: membrane that lines the hollow interior surfaces of bones </li></ul><ul><ul><li>Also contains osteoblasts </li></ul></ul>
    11. 11. Bone Cells <ul><li>Osteoblasts: cells that produce bone </li></ul><ul><ul><li>Harden matrix through ossification </li></ul></ul><ul><li>Once surrounded by bone, osteoblasts are called osteocytes </li></ul><ul><li>Osteoclasts: remodel/remove bone </li></ul>
    12. 12. Blood Supply to Bone <ul><li>Volkmann canals : channels through bone matrix that contain blood vessels </li></ul><ul><li>Blood vessels in the Volkmann canals join with blood vessels in the haversian systems. </li></ul>
    13. 13. Blood Supply to Bone <ul><li>Nutrient foramina: channels in many large bones </li></ul><ul><li>Contain large blood vessels, lymph vessels, and nerves </li></ul>
    14. 14. Bone Formation <ul><li>Two possible mechanisms: </li></ul><ul><li>1. Endochondral bone formation </li></ul><ul><ul><li>Grows into and replaces cartilage </li></ul></ul><ul><li>2. Intramembranous bone formation </li></ul><ul><ul><li>Develops from fibrous tissue membranes </li></ul></ul>
    15. 15. Endochondral Bone Formation <ul><li>Primary growth center: bones develop in the diaphyses </li></ul><ul><ul><li>Cartilage rod </li></ul></ul><ul><li>Cartilage is removed as bone is created </li></ul><ul><li>Secondary growth centers: develop in the epiphyses of the bone </li></ul>
    16. 16. Endochondral Bone Formation <ul><li>Epiphyseal plates: </li></ul><ul><li>cartilage located </li></ul><ul><li>between diaphysis </li></ul><ul><li>and epiphyses of bone </li></ul><ul><ul><li>Sites where new bone </li></ul></ul><ul><ul><li>develops to allow long </li></ul></ul><ul><ul><li>bones to lengthen </li></ul></ul>
    17. 17. Endochondral Bone Formation <ul><li>Osteoblasts replace </li></ul><ul><li>cartilage with bone </li></ul><ul><li>on the diaphyseal </li></ul><ul><li>surface of the plate. </li></ul><ul><li>When the bone has </li></ul><ul><li>reached its full size, </li></ul><ul><li>the epiphyseal plates </li></ul><ul><li>completely ossify. </li></ul>
    18. 18. Intramembranous Bone Formation <ul><li>Occurs in certain skull bones </li></ul><ul><li>Bone forms in the fibrous tissue membranes that cover the brain in the developing fetus. </li></ul>
    19. 19. Bone Shapes <ul><li>Four basic shapes: </li></ul><ul><ul><li>Long </li></ul></ul><ul><ul><li>Short </li></ul></ul><ul><ul><li>Flat </li></ul></ul><ul><ul><li>Irregular </li></ul></ul>
    20. 20. Bone Marrow <ul><li>Fills the spaces within bones </li></ul><ul><li>Two types: </li></ul><ul><ul><li>Red bone marrow </li></ul></ul><ul><ul><li>Yellow bone marrow. </li></ul></ul>
    21. 21. Red Bone Marrow <ul><li>Forms blood cells </li></ul><ul><li>Majority of the bone marrow of young animals </li></ul><ul><li>Only a small portion of the marrow of older animals </li></ul><ul><li>Confined to a few specific locations in older animals </li></ul>
    22. 22. Yellow Bone Marrow <ul><li>Consists primarily of adipose connective tissue </li></ul><ul><li>Most common type of marrow in adult animals </li></ul><ul><li>Can revert to red bone marrow if needed </li></ul>
    23. 23. Bone Features <ul><li>Articular Surfaces : </li></ul><ul><li>Condyle: large, round articular surface </li></ul><ul><li>Head: spherical articular surface on the proximal end of a long bone </li></ul><ul><ul><li>Joins with the shaft of the bone at the neck region </li></ul></ul><ul><li>Facet: flat articular surface </li></ul>
    24. 24. Bone Features <ul><li>Processes </li></ul><ul><li>Projections off a bone surface </li></ul><ul><li>Name depends on location </li></ul><ul><li>Examples: </li></ul><ul><ul><li>Spinous process of a vertebra </li></ul></ul><ul><ul><li>Trochanter on the femur </li></ul></ul><ul><ul><li>Tuberosity on the ischium </li></ul></ul><ul><ul><li>Spine on the scapula </li></ul></ul><ul><ul><li>Wing on the atlas </li></ul></ul>
    25. 25. Bone Features <ul><li>Foramen: hole in a bone; may contain blood vessels, nerves </li></ul><ul><li>Fossa: depressed area on the surface of a bone </li></ul>
    26. 26. Axial Skelton <ul><li>Skull </li></ul><ul><li>Hyoid bone </li></ul><ul><li>Spinal column </li></ul><ul><li>Ribs </li></ul><ul><li>Sternum </li></ul>
    27. 27. Skull <ul><li>Usually consists of 37 or 38 separate bones </li></ul><ul><li>Most of the skull bones are joints called sutures. </li></ul><ul><li>The mandible is connected to the rest of the skull by a synovial joint. </li></ul>
    28. 28. Bones of the Cranium <ul><li>External bones : </li></ul><ul><li>Frontal bones (2) </li></ul><ul><li>Interparietal bones (2) </li></ul><ul><li>Occipital bones (1) </li></ul><ul><li>Parietal bones (2) </li></ul><ul><li>Temporal bones (2) </li></ul><ul><li>Internal Bones : </li></ul><ul><li>Ethmoid bone (1) </li></ul><ul><li>Sphenoid bone (1) </li></ul>
    29. 29. Hyoid Bone <ul><li>Sometimes included with the cranial bones </li></ul><ul><li>Also called the hyoid apparatus </li></ul><ul><li>Composed of several portions of bone united by cartilage </li></ul>
    30. 30. Bones of the Ear <ul><li>Incus (2) </li></ul><ul><li>Malleus (2) </li></ul><ul><li>Stapes (2) </li></ul>
    31. 31. Bones of the Face <ul><li>External : </li></ul><ul><li>Incisive bones (2) </li></ul><ul><li>Lacrimal bones (2) </li></ul><ul><li>Mandible (1 or 2) </li></ul><ul><li>Maxillary bones (2) </li></ul><ul><li>Nasal bones (2) </li></ul><ul><li>Zygomatic bones (2) </li></ul>
    32. 32. Bones of the Face <ul><li>Internal : </li></ul><ul><li>Vomer bone (1) </li></ul><ul><li>Turbinates (4) </li></ul><ul><li>Pterygoid bones (2) </li></ul><ul><li>Palatine bones (2) </li></ul>
    33. 33. Vertebrae <ul><li>Consist of a body, an arch, and processes </li></ul><ul><li>Intervertebral disks: cartilage separating bodies of adjacent vertebrae </li></ul>
    34. 34. Vertebrae <ul><li>Vertebral arches </li></ul><ul><li>line up to form the </li></ul><ul><li>spinal canal </li></ul><ul><li>Vertebrae usually </li></ul><ul><li>contain several </li></ul><ul><li>processes </li></ul><ul><ul><li>Spinous process </li></ul></ul><ul><ul><li>Transverse processes </li></ul></ul><ul><ul><li>Articular processes </li></ul></ul>
    35. 35. Vertebral Regions <ul><li>Cervical </li></ul><ul><ul><li>C1 atlas </li></ul></ul><ul><ul><li>C2 axis </li></ul></ul>
    36. 36. Vertebral Regions <ul><li>Thoracic </li></ul><ul><li>Lumbar </li></ul><ul><li>Sacral </li></ul><ul><li>Coccygeal </li></ul>
    37. 37. Ribs <ul><li>Flat bones that form lateral walls of the </li></ul><ul><li>thorax </li></ul><ul><li>Dorsal heads of the ribs articulate with thoracic vertebrae </li></ul>
    38. 38. Ribs <ul><li>Costal Cartilage: </li></ul><ul><li>ventral ends of the ribs </li></ul><ul><li>Costochondral junction : </li></ul><ul><li>area where costal </li></ul><ul><li>cartilage meets bony rib </li></ul>
    39. 39. Ribs <ul><li>Costal cartilages </li></ul><ul><li>join the sternum or </li></ul><ul><li>the costal cartilage </li></ul><ul><li>ahead of them </li></ul><ul><li>Floating ribs: cartilage does not join anything at all </li></ul><ul><ul><li>Often end in the muscles </li></ul></ul><ul><ul><li>of the thoracic wall </li></ul></ul>
    40. 40. Sternum <ul><li>The breastbone </li></ul><ul><li>Forms the floor of the thorax </li></ul><ul><li>Composed of sternebrae </li></ul><ul><li>Manubrium sterni: most cranial sternebra </li></ul><ul><li>Xiphoid process: most caudal sternebra </li></ul>
    41. 41. Appendicular Skeleton <ul><li>Thoracic Limb </li></ul><ul><li>Scapula </li></ul><ul><li>Humerus </li></ul><ul><li>Radius </li></ul><ul><li>Ulna </li></ul><ul><li>Carpal bones (carpus) </li></ul><ul><li>Metacarpal bones </li></ul><ul><li>Phalanges </li></ul>
    42. 42. Scapula <ul><li>Flat, triangular bone </li></ul><ul><li>Forms portion of the shoulder joint </li></ul><ul><li>Spine of the scapula: longitudinal ridge on lateral surface </li></ul><ul><li>Glenoid cavity : shallow, concave articular surface </li></ul>
    43. 43. Humerus <ul><li>Long bone of the </li></ul><ul><li>brachium </li></ul><ul><li>Forms portion of </li></ul><ul><li>the shoulder joint </li></ul><ul><li>and elbow joint </li></ul><ul><li>Tubercles: processes </li></ul><ul><li>where shoulder </li></ul><ul><li>muscles attach </li></ul>
    44. 44. Humerus <ul><li>Condyles: articular </li></ul><ul><li>surfaces </li></ul><ul><ul><li>Trochlea: articulates </li></ul></ul><ul><ul><li>with ulna </li></ul></ul><ul><ul><li>Capitulum: articulates </li></ul></ul><ul><ul><li>with radius </li></ul></ul><ul><li>Olecranon fossa: </li></ul><ul><li>indentation above </li></ul><ul><li>condyle </li></ul><ul><li>Epicondyles: non-articular </li></ul>
    45. 45. Antebrachium <ul><li>Ulna </li></ul><ul><li>Olecranon process </li></ul><ul><ul><li>Point of the elbow </li></ul></ul><ul><ul><li>Site for tendon attachment of triceps brachii muscle </li></ul></ul><ul><li>Trochlear notch: concave articular surface </li></ul><ul><li>Anconeal and coronoid processes </li></ul>
    46. 46. Antebrachium <ul><li>Radius </li></ul><ul><li>Main weight-bearing bone of the antebrachium </li></ul><ul><li>Articulates with humerus and ulna </li></ul><ul><li>Styloid process articulates with carpus </li></ul>
    47. 47. Carpus <ul><li>Two rows of carpal bones </li></ul><ul><li>Proximal row bones are named (“radial carpal bone,” “ulnar carpal bone,” etc.) </li></ul><ul><li>Distal row bones are numbered medial to lateral </li></ul>
    48. 48. Metacarpal Bones <ul><li>Extend distally from distal carpal bones to proximal phalanges </li></ul><ul><li>Dogs & cats - 5 digits </li></ul><ul><ul><li>Numbered medial to </li></ul></ul><ul><ul><li>lateral </li></ul></ul><ul><ul><li>Metacarpal I: dewclaw </li></ul></ul>
    49. 49. Metacarpal Bones <ul><li>Horses </li></ul><ul><ul><li>One large metacarpal bone (cannon bone) </li></ul></ul><ul><ul><li>Two smaller vestigial metacarpal bones (splint bones) </li></ul></ul><ul><ul><ul><li>Non weight-bearing </li></ul></ul></ul>
    50. 50. Metacarpal Bones <ul><li>Cattle </li></ul><ul><ul><li>Two fused metacarpal bones (bones III and IV) </li></ul></ul>
    51. 51. Thoracic Limb Phalanges - Equine <ul><li>1 digit with 3 phalanges </li></ul><ul><ul><li>Proximal phalanx (long pastern bone) </li></ul></ul><ul><ul><li>Middle phalanx (short pastern bone) </li></ul></ul><ul><ul><li>Distal phalanx (coffin bone) </li></ul></ul><ul><li>Also have sesamoid bones </li></ul>
    52. 52. Thoracic Limb Phalanges - Bovine <ul><li>Four digits on each limb </li></ul><ul><li>Two support weight, two are vestigial (dewclaws) </li></ul><ul><li>Each digit has a proximal, middle, and distal phalanx </li></ul><ul><li>Also proximal distal sesamoid bones </li></ul>
    53. 53. Thoracic Limb Phalanges - Canine and Feline <ul><li>Digit I (dewclaw): one proximal and one distal phalanx </li></ul><ul><li>Digits II to V: a proximal, a middle, and a distal phalanx </li></ul><ul><ul><li>Ungual process –surrounds the claw on distal phalanx </li></ul></ul>
    54. 54. Appendicular Skeleton <ul><li>Connected to the axial skeleton at the sacroiliac joint </li></ul><ul><li>Pelvic Limb: </li></ul><ul><li>Pelvis </li></ul><ul><ul><li>Ilium </li></ul></ul><ul><ul><li>Ischium </li></ul></ul><ul><ul><li>Pubis </li></ul></ul><ul><li>Femur </li></ul><ul><li>Tibia </li></ul><ul><li>Fibula </li></ul><ul><li>Tarsal bones (tarsus) </li></ul><ul><li>Metatarsal bones </li></ul><ul><li>Phalanges </li></ul>
    55. 55. Pelvis <ul><li>3 fused bones </li></ul><ul><ul><li>Ilium </li></ul></ul><ul><ul><li>Ischium </li></ul></ul><ul><ul><li>pubis </li></ul></ul><ul><li>Pelvic symphysis: cartilaginous joint between the two halves of the pelvis </li></ul>
    56. 56. Pelvis <ul><li>Ilium </li></ul><ul><ul><li>Projects in dorsocranial direction </li></ul></ul><ul><ul><li>Forms sacroiliac joint with the sacrum </li></ul></ul><ul><li>Ischium </li></ul><ul><ul><li>Caudalmost pelvic bone </li></ul></ul><ul><ul><li>Forms caudal portion of the pelvic floor </li></ul></ul><ul><li>Pubis </li></ul><ul><ul><li>Forms cranial portion of the pelvic floor </li></ul></ul>
    57. 57. Femur <ul><li>Proximal end forms </li></ul><ul><li>part of hip joint </li></ul><ul><li>Femoral head fits </li></ul><ul><li>deeply into acetabulum </li></ul><ul><li>of pelvis </li></ul><ul><li>Trochanters: processes </li></ul><ul><li>where hip and thigh </li></ul><ul><li>muscles attach </li></ul>
    58. 58. Femur <ul><li>Shaft extends downward </li></ul><ul><li>to form the stifle joint </li></ul><ul><li>with patella & tibia </li></ul><ul><li>Articular surfaces: </li></ul><ul><ul><li>2 condyles </li></ul></ul><ul><ul><li>trochlea </li></ul></ul><ul><li>Trochlea: articular </li></ul><ul><li>groove containing </li></ul><ul><li>the patella </li></ul>
    59. 59. Patella and Fabellae <ul><li>Patella </li></ul><ul><li>Large sesamoid bone </li></ul><ul><li>Formed in the distal tendon of the quadriceps femoris muscle </li></ul><ul><li>Protects the tendon </li></ul><ul><li>Fabellae </li></ul><ul><li>Two small sesamoid bones in proximal gastrocnemius muscle tendons of dogs and cats </li></ul><ul><li>Not present in cattle or horses </li></ul>
    60. 60. Tibia <ul><li>Main weight-bearing bone of lower limb </li></ul><ul><li>Forms the stifle joint with the femur, the hock with the tarsus </li></ul><ul><li>Tibial tuberosity </li></ul><ul><li>Tibial crest </li></ul>
    61. 61. Fibula <ul><li>Parallel to tibia </li></ul><ul><li>Not weight-bearing </li></ul><ul><li>Serves as a muscle attachment site </li></ul><ul><li>Lateral malleolus: knob-like process </li></ul>
    62. 62. Tarsus <ul><li>Hock </li></ul><ul><li>2 rows of tarsal bones </li></ul><ul><ul><li>Proximal row is named; distal row is numbered medial to lateral </li></ul></ul><ul><li>Calcaneal tuberosity: point of attachment for the tendon of the gastrocnemius muscle </li></ul>
    63. 63. Metatarsal Bones <ul><li>Dogs & cats: four metatarsal bones (II to V) </li></ul><ul><li>Horses: one large metatarsal bone (cannon bone) and two small metatarsal bones (the splint bones) </li></ul>
    64. 64. Pelvic Limb Phalanges <ul><li>Similar to thoracic limb phalanges </li></ul><ul><li>Exceptions: dogs and cats </li></ul><ul><ul><li>Usually only 4 digits (II to V) </li></ul></ul>
    65. 65. Visceral Skeleton <ul><li>Bones that form in organs </li></ul><ul><li>Examples </li></ul><ul><ul><li>os cordis: in heart of cattle and sheep </li></ul></ul><ul><ul><li>os penis : in penis of dogs, beaver, raccoons, and walruses </li></ul></ul><ul><ul><li>os rostri : in nose of swine </li></ul></ul>
    66. 66. Joints <ul><li>Three general classifications : </li></ul><ul><li>Fibrous joints: immovable </li></ul><ul><li>Cartilaginous joints: slightly movable </li></ul><ul><li>Synovial joints: freely movable </li></ul>
    67. 67. Fibrous Joints <ul><li>Synarthroses </li></ul><ul><li>United by fibrous </li></ul><ul><li>tissue </li></ul><ul><li>Examples: sutures </li></ul><ul><li>of skull, splint bones </li></ul><ul><li>of horses </li></ul>
    68. 68. Cartilaginous Joints <ul><li>Amphiarthroses </li></ul><ul><li>Capable of slight rocking movement </li></ul><ul><li>Examples: mandibular symphysis, pubic symphysis, intervertebral disks </li></ul>
    69. 69. Synovial Joints <ul><li>Diarthroses </li></ul><ul><li>Components </li></ul><ul><ul><li>Articular surfaces on bones </li></ul></ul><ul><ul><li>Articular cartilage (hyaline) covering articular surfaces </li></ul></ul><ul><ul><li>Fluid-filled joint cavity enclosed by a joint capsule </li></ul></ul><ul><ul><ul><li>Synovial membrane </li></ul></ul></ul><ul><ul><ul><li>Synovial fluid </li></ul></ul></ul><ul><ul><li>Ligaments - fibrous connective tissue </li></ul></ul>
    70. 70. Synovial Joint Movements <ul><li>Flexion </li></ul><ul><li>Extension </li></ul><ul><li>Adduction </li></ul><ul><li>Abduction </li></ul><ul><li>Rotation </li></ul><ul><li>Circumduction </li></ul>
    71. 71. Synovial Joint Movements <ul><li>Flexion and Extension </li></ul><ul><li>Opposite movements </li></ul><ul><li>Increase or decrease the angle between two bones </li></ul>
    72. 72. Synovial Joint Movements <ul><li>Adduction and Abduction </li></ul><ul><li>Opposite movements </li></ul><ul><li>Move an extremity toward or away from medial plane </li></ul>
    73. 73. Synovial Joint Movements <ul><li>Rotation </li></ul><ul><li>Twisting movement of a part on its own axis </li></ul><ul><li>Circumduction </li></ul><ul><li>Movement of an extremity so that the distal end moves in a circle </li></ul>
    74. 74. Types of Synovial Joints <ul><li>Hinge joints </li></ul><ul><li>Gliding joints </li></ul><ul><li>Pivot joints </li></ul><ul><li>Ball-and-socket joints </li></ul>
    75. 75. Hinge Joints <ul><li>Ginglymus joints </li></ul><ul><li>One joint surface swivels around another </li></ul><ul><li>Only capable of flexion and extension </li></ul><ul><li>Example: elbow joint </li></ul>
    76. 76. Gliding Joints <ul><li>Arthrodial joints </li></ul><ul><li>Rocking motion of one joint surface on the other </li></ul><ul><li>Primarily capable of flexion and extension </li></ul><ul><li>Abduction and adduction possible </li></ul><ul><li>Example: carpus </li></ul>
    77. 77. Pivot Joints <ul><li>Trochoid joints </li></ul><ul><li>One bone pivots </li></ul><ul><li>(rotates) on another </li></ul><ul><li>Only capable of </li></ul><ul><li>rotation </li></ul><ul><li>Example: the </li></ul><ul><li>atlantoaxial joint </li></ul>
    78. 78. Ball-and-Socket Joints <ul><li>Spheroidal joints </li></ul><ul><li>Allow for all joint movements </li></ul><ul><li>Examples: shoulder and hip joints </li></ul>

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