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SKELETAL SYSTEM

SKELETAL SYSTEM. TYPES OF BONES. LONG: humerus SHORT: carpals FLAT: frontal bone IRREGULAR: vertebrae. Categorizing bones developmentally…. Endochondral develop from pieces of cartilage deposited as sheets of tissue in embryo Face, appendages Dermal

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SKELETAL SYSTEM

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  1. SKELETAL SYSTEM

  2. TYPES OF BONES • LONG: humerus • SHORT: carpals • FLAT: frontal bone • IRREGULAR: vertebrae

  3. Categorizing bones developmentally… • Endochondral • develop from pieces of cartilage deposited as sheets of tissue in embryo • Face, appendages • Dermal • Formed from sheets of fibrous connective tissue • Clavicle, scapula, flat cranial bones

  4. Alveolar • Teeth • Specialized groupings of bone cells • Sesamoid • Form within tendons due to stress on tendon • Patella, pisiform, various metacarpal, metatarsal bones

  5. Wormian • Small, irregular, isolated; develop within sutures

  6. Bone Structure

  7. Periosteum • “To surround the bone” • Fibrous membrane, covers surface of the bone EXCEPT at the joint surfaces. • Contains nerves and blood vessels • Nutrition, sensation • This is where the tendons & ligaments attach to the bone.

  8. Red marrow spaces (surrounded by trabeculae) YellowMarrow

  9. Epiphysis • At the end of each bone • Made of cancellous or spongy bone • Network of bone called trabeculae • Spaces contain red marrow • Site of hematopoiesis (blood cell production) • Outer surface is compact bone • Within joints, surfaces covered with hyaline articular cartilage

  10. Epiphysial Plate • Also called the “growth plate”; • indicates that additional bone growth is possible • Site of bone elongation • Ossifies over time • then callledepiphysial line

  11. Epiphyseal Plate

  12. Diaphysis • “to grow apart” • Hollow Tube • Made of compact bone: organized into osteons • Rigid but light

  13. Medullary Cavity • Hollow area inside diaphysis • Bordered by spongy bone • Lined by a thin membrane called the endosteum • Capable of generating new bone cells • Adults: contains soft, yellow bone marrow • Mostly adipose tissue • Food reserve for bone cells • Children: more red marrow

  14. Two kinds of bone Cancellous/Trabecular (Spongy) • 80% of bone • many spaces filled with marrow Compact (cortical) • 20% of skeleton structure • 80% of skeletal weight • Structural unit = osteon

  15. The Osteon The structural unit of bone

  16. The OSTEON: Found in compact bone • Matrix is organized into numerous structural units called osteons or Haversian systems. • Consists of calcified matrix arranged in concentric rings called concentric lamellae

  17. The Osteon • The rings surround an opening called the Central (Haversian) Canal • Canal contains blood, lymph vessels and nerves

  18. The Osteon • Mature bone cells = osteocytes • Secrete bone matrix • Composed of collagen fibers and protein (osteocalcin) • The cell resides in a space called a lacuna • Canals, called canaliculi, connect the osteocytes to one another

  19. More on the Osteon • Nutrients pass • from the blood vessel in the central canal • through the canaliculi • to the osteocytes

  20. What can you identify?

  21. The Osteon • Central canals are connected by a horizontal blood vessel housed within the Volkmann’s Canals

  22. joints

  23. Classification: • Structural • Tissue composition, structural complexity • Cartilaginous, fibrous, synovial • Functional • Type of movement allowed • Synarthrotic, amphiarthrotic, diarthrotic

  24. Bursa – Accessory Structure • Sac-like space made of fibrous tissue • Synovial fluid • thick, lubricating fluid • Nourishes, protects joints and surface • Secreted by epithelial cells • Found in articular areas where rubbing between skin, muscle, ligaments, or bones could occur • Can become inflamed/damaged = bursitis

  25. Synarthrotic Joint (Immovable Joints) Fibrous Joint • Produce NO movement • Bone connected to bone by fibrous tissue • Purpose: to securely hold two bones together • Include • Sutures of the skull (synostoses/sutures) • Skull to teeth (gomphosis) • Tibia and fibula (syndemosis)

  26. Amphiarthrotic Joint (Semi-movable) Cartilaginous • Bone connects to bone via cartilage • Allows slight movement • Includes • Pubic symphisis • Vertebrae

  27. Diarthrotic/Synovial Joint • Allows much movement; joint cavity lined by synovial membranes • Some types • Ball & Socket: Shoulder, Hip • Hinge: Knee, Shoulder • Pivot: Atlas/Axis • Gliding: Between carpal bones, between tarsal bones • Saddle: thumb • Ellipsoid/Condyloid: wrist

  28. BONE development and healing

  29. Osteowhat? The first crystals of bone that form are pointed and needle-like: called spicules. • Osteoblasts secrete a mineralized matrix • Once the osteoblast is surrounded by its matrix, it’s called an osteocyte, a bone cell. • Osteoclasts break down bone.

  30. Ossification • Conversion of embryonic tissues into recognizable bone • 2 ways: • Endochondral • Long bones • Intramembranous • Flat bones • Combination – irregular bones

  31. Ossification

  32. Ossification • Mesodermal cells form cartilage centers • Cartilage pegs form • Restructured, filled with hydroxylapatite (calcification) • Pegs formed by fibroblasts • Osteoblasts and osteoclasts sculpt growing bones

  33. An osteoclast in action. Here an osteoclasts is eroding bone. The capsule formed by such action is called a Howship's capsule (H). Similar to the cell of the gut, osteoclasts have a ruffled border which increases the surface area for bone resorption.

  34. Direction of Long Bone Growth • Epiphyseal plate made of hyaline cartilage is responsible for long bone growth. • The direction of growth is toward the diaphysis • The newly forming spongy bone (below the growth plate) is not clearly organized as the older spongy bone in the epiphysis above the growth plate.

  35. Fontanelles – soft spots • Regions of flat bone not fully ossified • Completed during teenage years

  36. healing

  37. Fractures • Bone is cracked/splintered due to physical injury • Categorized by severity of break/angle at which break occurs

  38. Simple: • Crack in bone structure • May not be readily noticeable • Some large; may involve bleeding, pain, swelling • Greenstick fractures • One side frayed from fracture; other twisted, but not broken

  39. Compound/comminuted • Large fracture • One (more) area is displaced, shattered • Bleeding, swelling • Open • Tearing of skin occurs; easily infected

  40. Angle of break • Transverse (horizontal) • Oblique (angle) • Spiral (twisted) • Angulation – bone changes overall shape • For healing to occur, blood accumulation must occur

  41. Healing stages • Fracture • Granulation • Callus • Lamellar bone • Normal contour

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