Unit 1

• Five general functions of the skeletal system


  • Supports and stabilizes surrounding tissues
  • Protects vital organs
  • Assists in body movement
  • Storage area for mineral salts
  • Manufactures blood cells
• Intramembranous ossification


  Simple and more direct method.

  Occurs within fibrous membrane.

  Occurs only in the formation of the cranium or skull.

  Complete ossification does not occur until a few months after birth.
• Endochondral ossification


  Bone formation in cartilage
• Anterior fontanel


  Also known as frontal. Largest fontanel, located at angles of parietal and frontal bones, closes in 18-24 months
• Posterior fontanel


  Also known as occipital. Smaller fontanel, located between parietal and occipital bones, closes 2 months after birth
• Compact bone


  Dense and strong, deposited in a layer over spongy bone, thicker in diaphysis
• Classifications of bone


  • Long
  • Short
  • Flat
  • Irregular
  • Sesamoid
  • Wormian
• Long bones


  • Greater length than width, have diaphysis, epiphysis, and are slightly curved for strength
• Short bones


  • Cube-shaped, nearly equal length and width, spongy texture with thin compact bone layer
• Flat bones


  • Thin, curved, provide muscle attachment and protection
• Irregular bones


  • Complex shape, do not fit into other categories
• Sesamoid bones


  • Small, nodular, found where tendons pass over joints, protect tendons and increase mechanical effect
• Wormian bones


  • Small, isolated bones found in cranial sutures, result of intramembranous ossification
  • Mostly found in the lambdoidal suture
• Anatomy of a long bone


  • Diaphysis or shaft
  • Epiphysis
  • Metaphysis
  • Articular cartilage
  • Periosteum
  • Medullary canal or cavity
  • Endosteum
• Bone markings


  • Depressions and openings: allow for the passage of soft tissue, such as nerves, blood vessels, ligaments, etc. Examples: foramen, canal or meatus, fissure, sinus, fossa.
  • Processes: projections or outgrowths on bone that forms joints or attachment for connective tissue. Examples: condyle, epicondyle, facet, head, crest, line/linea, spine, tubercle, tuberosity, trochlea, trochanter.
• Ossification

  • Begins around the 6th or 7th week of embryonic life and continues throughout adulthood
• Diaphysis or shaft is the long, cylindrical, main portion of the bone
• Epiphyses are the distal and proximal ends of the bone
• Metaphysis are the regions of immature bone where the diaphysis and epiphyses meet
• Articular cartilage is a thin layer of hyaline cartilage covering the epiphysis of the bone. It reduces friction and absorbs shock at freely movable joints.
• Periosteum is dense connective tissue that surrounds the bone surface not covered by articular cartilage. It contains bone forming cells that enable bone to grow in diameter or thickness, but not in length. It protects the bone, assists in fracture repair, helps nourish the bone tissue, and contains blood vessels and nerves.
• Medullary canal or cavity is a hollow chamber within the diaphysis that contains yellow bone marrow, which consists of fat cells (lipids).
• Endosteum is a thin membrane that lines the medullary cavity. It also contains bone forming cells.
• Spongy bone

  Also known as cancellous bone, contains many large spaces where you will find red bone marrow. Makes up most of the bone tissue of short, flat, and irregular bones, and most of epiphysis of long bones.
• Foramen: an opening, hole, or passage, especially in a bone. Blood vessels, nerves, or ligaments pass.
• Canal: A tube-like opening or tunnel coursing through a bone. Also known as meatus.
• Fissure: A narrow slit between adjacent parts of bone, which blood vessels or nerves pass.
• Sinus: A cavity in the bone that is filled with air or blood.
• Fossa: A depression or hollow in the body of a bone.
• Condyle: A large, rounded projection of a bone that articulates with another bone.
• Epicondyle: A projection above a condyle.
• Facet: A smooth, flat articular surface.
• Head of a bone: The rounded articular projection supported on the neck.
• Crest: A narrow ridge of bone.
• Line/Linea: A less prominent ridge of bone than a crest.
• Spine: Any sharp, slender process.
• Tubercle: A small rounded projection on a bone, usually at the end of a long bone.
• Tuberosity: A large, rounded, usually roughened projection larger than a tubercle.
• Trochlea: Shaped like a pulley or spool of thread.
• Trochanter: A very large projection found only on the femur.