Skeletal anatomy

• Periosteum

  Lines the outer surface of bone.
• Endosteum

  Lines the inner medullary cavity.
• Spongy bone

  a.k.a cancellous bone or trabecular bone. Contains red bone marrow. At the ends of long bones, inside the vertebrae, ribs, skull, and in joints. Softer and weaker compared to compound bones, but more flexible.
• Red marrow

  Found in the medullary cavities of flat and short bines, articular ends of long bones, bodies of vertebrae, etc.
• Yellow marrow

  Central cavities of long bones, and consist mostly of fat.
• Exoskeleton 


  Found on body surface. Like shell on crabs and tortoise. Nails, horns, hooves, etc.
• Endoskeleton

  Embedded in soft tissues within the body.

  Axial (skull, vertebral column, rib cage)

  Appendicular (pectoral pelvic girdle/limb [forelimb] and pelvic girdle/limb [hindlimb])

  Splanchnic/Visceral (baculum or os penis)
• Flat bones

  Protect internal organs.

  Skull( occipital, parietal, frontal, nasal, lacrimal, vomer)

  Thoracic (sternum, ribs)

  Pelvis (ilium, ischium, pubis)
• Flat bone layers

  Periosteum: thin, outer layer

  Compact bone: hard, dense tissue

  Spongy bone: innermost layer
• Long bone


  Long shaft with rounded head at each end. Lesser amount of spongy bone and marrow.

  Appendicular skeleton

  Forelimb: radius, ulna, digits

  Hindlimb: femur, tibia, digits
• Long bone parts

  Diaphysis: tubular shaft between the proximal and distal ends of bone.

  Epiphysis: wider section at each end of bone. Filled with spongy bone & red marrow fills the spaces in spongy bone.

  Metaphysis: area where epiphysis & diaphysis meets.

  Epiphyseal plate: composed of hyaline cartilage. Turns into epiphyseal line in adulthood.
• Short bone

  Found in carpals and tarsals
• Irregular Bone

  Vertebrae, sacrum, coccyx, temporal, sphenoid, ethmoid, zygomatic, maxilla, mandible, palatine, hyoid
• Sesamoid bone 


  Small, rounded bones embedded in tendons of hands, knees, & feet. E.g. patella ( knee cap)