Unit 2

• Divisions of the skeletal system


  • Axial skeleton
  • Appendicular skeleton
• Bones in the axial skeleton


  • Skull
  • Vertebrae
  • Thorax
  • Hyoid bone
• Bones in the skull

  • Cranial bones (8)
  • Facial bones (14)
• The adult human skeleton consists of 206 bones (excluding wormian and sesamoid bone)
• Bone is an organ
• Axial skeletal system


  80 bones composing the skull, vertebrae, thorax, and hyoid bone
• Appendicular skeleton


  126 bones that make up the pectoral girdle, upper extremities, pelvic girdle, and lower extremities
• Bones in the pectoral/shoulder girdle


  • Clavicle (2)
  • Scapula (2)
• Bones in the upper extremities

  • Humerus (2)
  • Ulna (2)
  • Radius (2)
  • Carpal (16)
  • Metacarpal (10)
  • Phalanges (28)
• Bones in the pelvic girdle

  • Hip/coxal bones (2)
• Bones in the lower extremities


  • Femur (2)
  • Patella (2)
  • Tibia (2)
  • Fibula (2)
  • Tarsal (14)
  • Metatarsal (10)
  • Phalanges (28)
• Frontal bone


  Singular bone that forms the forehead, anterior portion of the roof of the skull, and part of the eye orbit
• Frontal eminences


  • Two rounded prominences located at the upper part of the forehead
• Glabella


  Small, smooth elevation that lies between the superciliary arches, on the lower part of the forehead just above the medial ends of the eyebrows
• Superciliary arches


  • Two arches that extend laterally from the glabella
• Supraorbital margins


  • Two margins where the frontal bones thicken above the eye sockets, the upper rim of the eye-socket, inferior to the superciliary arches
• Coronal suture


  Immovable joint or articulation between the frontal and two parietal bones

  
• Frontal sinuses


  Paranasal cavities within the frontal bone that drain into the nasal cavities
• Parietal bones


  Two bones that form the greater portion of the sides and roof of the cranial cavity
• Sagittal suture


  Immovable joint or articulation between the two parietal bones
• Temporal bones


  Two bones situated at the sides (lateral aspect) and base of the skull (cranial floor), inferior to the parietal bones
• Squama/squamous portion of the temporal bone


  • Thin, vertical, flat portion that forms the anterior/front and superior part of the temple
• Zygomatic process


  Projects from the inferior portion of the squama of the temporal bone and articulates with the temporal process of the zygomatic bone to form the zygomatic arch
• Squamousal suture


  Immovable joint or articulation between the parietal bone and temporal bone
• Mandibular fossa


  Depression on the inferior, posterior surface of the zygomatic process of the temporal bone that articulates with the condylar process of the mandible to form the temporomandibular joint (TMJ)
• External auditory meatus/ear canal


  Runs from the outer ear to the middle ear, allowing sound to enter
• Mastoid process


  Located posterior and inferior to the external auditory meatus, serves as a point of attachment for the sternocleidomastoid muscle
• Styloid process


  Slender process that projects from the inferior surface of the temporal bone and serves as a point of attachment for muscles and ligaments of the tongue, neck, and hyoid bone
• Petrous portion of the temporal bone

  Triangular-shaped, hardest part of the temporal bone, situated between the sphenoid and occipital bones, contains the ear ossicles, middle ear, and structures involved in hearing and equilibrium, also contains the carotid canal through which the internal carotid artery passes
• SCM muscle


  The bump you feel behind your ear
• Petrous portion of the temporal bone


  Found in the floor of the cranial cavity, triangular in shape, situated between the sphenoid and occipital bones, the hardest part of the temporal bone
• The petrous portion of the temporal bone contains or houses the ear ossicles (3 bones in each ear); the malleus, the incus and the stapes
• The petrous portion of the temporal bone also contains the carotid canal or carotid foramen, through which the internal carotid artery passes
• Occipital bone


  A singular bone situated at the posterior part and most of the base of the cranium
• Foramen magnum


  • A large opening located in the inferior portion of the occipital bone, through which the medulla oblongata and vertebral arteries pass
• Occipital condyles


  • Two oval shaped processes located on either side of the foramen magnum, which articulate with the atlas (first cervical vertebrae)

  
• Lambdoidal suture


  • Found between the 2 parietal bones and the occipital bone
• External occipital protuberance


  • A prominent midline projection on the posterior surface just above the foramen magnum, the bump you feel at the back of the head

  
• Superior nuchal line


  • Two bony ridges that extend laterally from each side of the external occipital protuberance, serving as the origin for the occipitofrontalis muscle
• Sphenoid bone


  A singular bone, described as bat or winged shaped, situated at the middle part of the base of the skull, posterior and slightly superior to the nasal cavities