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BONES AND SKELETAL TISSUES

BONES AND SKELETAL TISSUES. SKELETAL CARTILAGES. Skeletal cartilages : Made of some variety of cartilage Consists primarily of water High water content accounts for its resilience Ability to spring back to its original shape after being compressed Contains no nerves or blood vessels

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BONES AND SKELETAL TISSUES

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  1. BONESANDSKELETAL TISSUES

  2. SKELETAL CARTILAGES • Skeletal cartilages: • Made of some variety of cartilage • Consists primarily of water • High water content accounts for its resilience • Ability to spring back to its original shape after being compressed • Contains no nerves or blood vessels • Surrounded by a layer of dense irregular connective tissue called the perichondrium • Acts like a girdle to resist outward expansion when the cartilage is compressed • Contains the blood vessels from which nutrients diffuse through the matrix to reach the cartilage cells • This mode of nutrient delivery limits cartilage thickness

  3. SKELETAL CARTILAGES • Three types: • Hyaline • Elastic • Fibrocartilage • All three types have the same basic components: • Cells called chondrocytes • Encased in small cavities (lacunae) within an extracellular matrix containing a jellylike ground substance and fibers

  4. HYALINE CARTILAGE • Looks like a frosted glass when freshly exposed • Provides support with flexibility and resilience • Most abundant skeletal cartilage • Chondrocytes appear spherical • Only fiber type in the matrix is fine collagen fibers

  5. HYALINE CARTILAGE

  6. HYALINE CARTILAGE • Includes: • Articular cartilages: • Cover the ends of most bones at movable joints • Costal cartilages: • Connect the ribs to the sternum (breastbone) • Respiratory cartilages: • Form the skeleton of the larynx (voicebox) • Reinforces other respiratory passageways • Nasal cartilages: • Support the external nose

  7. BONE CARTILAGE

  8. ELASTIC CARTILAGE • Looks very much like hyaline cartilages, but they contain more stretchy elastic fibers and so are better able to stand up to repeated bending

  9. ELASTIC CARTILAGE

  10. ELASTIC CARTILAGE • More flexible than hyaline • Located only in the: • External ear • Epiglottis of the larynx: • Flap that bends to cover the opening of the larynx each time we swallow

  11. BONE CARTILAGE

  12. FIBROCARTILAGE • Highly compressible and have great tensile strength • Perfect intermediate between hyaline and elastic cartilages • Consist of roughly parallel rows of chondrocytes alternating with thick collagen fibers

  13. FIBROCARTILAGE

  14. FIBROCARTILAGE • Occur in sites that are subjected to both heavy pressure and stretch: • Padlike cartilages (menisci) of the knee • Discs between vertebrae

  15. BONE CARTILAGE

  16. Growth of Cartilage • Growth occurs in two ways: • Appositional growth(growth from the outside) results in outward expansion due to the production of cartilage matrix on the outside of the tissue • Cartilage-forming cells in the surrounding perichondrium secrete new matrix against the external face of the existing cartilage tissue • Interstitial growth(growth from inside) results in expansion from within the cartilage matrix due to division of lacunae-bound chondrocytes and secretion of matrix • Lacunae-bound chondrocytes divide and secrete new matrix, expanding the cartilage from within

  17. Growth of Cartilage • Typically, cartilage growth ends during adolescence when the skeleton stops growing • Under certain conditions—during normal bone growth in youth and during oldage—calcium salts may be deposited in the matrix and cause it to harden, a process called calcification • NOTE: calcified cartilage is NOT bone

  18. CLASSIFICATION OF BONES • 206 named bones of the human skeleton are divided into two groups: • Axial skeleton: • Forms the long axis of the body • Protect, support, or carry other body parts • Includes: • Skull • Vertebral column • Rib cage • Appendicular skeleton: • Bones of the upper and lower limbs, and the girdles (pectoral/shoulder and pelvic/hip) that attach them to the axial skeleton • Help us to get from place to place (location)

  19. BONE CARTILAGE

  20. CLASSIFICATION OF BONES • Classified by shape: • Long • Short • Flat • Irregular

  21. BONE SHAPE

  22. Long Bones • Longer than they are wide: • Have a definite shaft and two ends • Consist of all limb bones except patellas, the carpels (wrist), and tarsals (ankles) • Named for their elongated shape, NOT their overall size • Example: the three bones in your fingers (digits) are long bones, even though they are very small

  23. BONE SHAPE

  24. Short Bones • Somewhat cube-shaped • Include: • Carpals: wrist • Tarsals: ankle • Sesamoid bone: • Shaped like a sesame seed • Special type of bone that forms in a tendon • Example: patella • Vary in size • Some clearly act to alter direction of pull of a tendon • Functions of others is not known

  25. BONE SHAPE

  26. Flat Bone • Thin, flattened and often curved • Include: • Most skull bones • Sternum (breastbone) • Scapulae (shoulder blades) • Ribs

  27. BONE SHAPE

  28. Irregular Bones • Complicated shapes that do not fit in any of the previous classes • Example: • Vertebrae • Coxae (hip bone)

  29. BONE SHAPE

  30. FUNCTIONS OF BONES • Besides contributing to body shape and form, our bones perform several important functions: • 1. Support • 2. Protection • 3. Movement • 4. Mineral storage • 5. Blood cell formation

  31. Support • Bones provide a framework that supports the body and cradles its soft organs • Examples: • Bones of the lower limbs act as pillars to support the body trunk • Rib cage supports the thoracic wall

  32. Protection • Fused bones at the skull protect the brain • Vertebrae surround the spinal cord • Rib cage helps protect the vital organs of the thorax

  33. Movement • Skeletal muscles, which attach to bones by tendons, use bones as levers to move the body and its parts • As a result, we can walk, grasp objects, and breathe

  34. Mineral Storage • Bone is a reservoir for minerals • Most important are calcium and phosphates • Stored minerals are released into the bloodstream as needed for distribution to all parts of the body: • Deposits and withdrawals of minerals to and from the bones go on almost continuously

  35. Blood Cell Formation • Most blood cell formation(hematopoiesis) occurs in the marrow cavities of certain bones

  36. Bone Structure • Because bones contain various types of tissue, bones are organs: • Bone (osseous) tissue • Nervous tissue in their nerves • Cartilage tissue in their articular cartilages • Fibrous connective tissue lining their cavities • Muscle and epithelial tissues in their blood vessels

  37. Gross Anatomy • Bone markings are projections, depressions, and openings found on the surface of bones that function as sites of muscle, ligament, and tendon attachment, as joint surfaces, and as openings for the passage of blood vessels and nerves

  38. Projections (bulges): grow outward from the bone surface Projections that sites of muscle and ligament attachment: Tuberosity: elevated round swelling Large and rounded May be roughened Crest: elongated prominence Narrow ridge Usually prominent Trochanter: to run Very large Blunt Irregularly shaped ONLY in the femur Line: Narrow ridge Less prominent than crest Tubercle: little swelling Small and rounded Epicondyle: above a knuckle (condyle) Raised area on or above a condyle Spine: Sharp, slender, often pointed projection Process: Any bone prominence Names of Bone Markings

  39. Names of Bone Markings • Projections That Help to Form Joints: articulation • Head: • Bony expansion carried on a narrow neck • Facet: small face • Smooth, nearly flat articular surface • Condyle: knuckle • Rounded articular projection • Ramus: branch • Armlike bar of bone

  40. Names of Bone Markings • Depressions and openings: • Allow blood vessels and nerves to pass • Meatus: passage/opening • Canal-like passageway • Sinus: curve, hollow • Cavity within a bone, filled with air and lined with mucous membrane • Fossa: furrow or shallow depression • Shallow, basinlike depression in a bone • Often serves as an articular surface • Groove: ditch • Furrow • Fissure: slender deep furrow • Narrow, slitlike opening • Foramen: passage/opening • Round or oval opening through a bone

  41. Bone Textures • Compact: • All bones have a dense outer layer consisting of compact bone that appears smooth and solid • Spongy Bone: • Internal to compact bone is spongy bone, which consists of honeycomb, needle-like, or flat pieces, called trabeculae (little beam) • In living bones the open spaces between trabeculae are filled with red or yellow bone marrow

  42. Compact/Spongy Bone

  43. Typical Long Bone Structure • All long bones have the same general structure: • Diaphysis: dia (through) / physis (growth) • Tubular shaft • Forms the long axis of the bone • Constructed of a relatively thick collar of compact bone that surrounds a central medullary cavity or marrow cavity • In adults, the medullary cavity contains fat (yellow marrow) and is called the yellow bone marrow • Epiphyses: epi (upon) / epiphyses (singular) • The ends of the bone • Consist of internal spongy bone covered by an outer layer of compact bone • Joint surfaces of each epiphysis is covered with a thin layer of articular (hyaline) cartilage, which cushions the opposing bone ends during joint movement and absorbs stress

  44. LONGBONE

  45. Typical Long Bone Structure • Epiphyseal line: sometimes called the metaphysis • Located between the epiphyses and diaphysis in an adult • Is the remnant of the epiphyseal plate, a disc of hyaline cartilage that grows during childhood to lengthen the bone

  46. LONGBONE

  47. Typical Long Bone Structure • Membranes: Periosteum • The external surface of the entire bone except the joint surfaces is covered by a glistening white, double-layered membrane called the periosteum (peri=around / osteo=bone) • Outer fibrous layer is dense irregular connective tissue • Inner osteogenic layer abutting the bone surface consists primarily of: • Bone-forming cells: osteoblasts • Bone-destroying cells: osteoclasts

  48. LONGBONE

  49. Typical Long Bone Structure • Membranes: Periosteum • Richly supplied with nerve fibers, lymphatic vessels, and blood vessels, which enter the diaphysis via a nutrient foramen • Secured to the underlying bone by perforating (Sharpey’s) fibers • Tufts of collagen fibers that extend from its fibrous layer into the bone matrix • Provides anchoring points for tendons and ligaments • At these points the perforating fibers are exceptionally dense

  50. LONGBONE

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