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The coracoacromial arch, formed by the acromion and coracoid process of the scapula with the strong coracoacromial ligament stretching between them, prevents upward dislocation; when the head of the humerus dislocates, it usually does so in a downward direction. The elbow joint is formed by the articulation of the humerus with the forearm bones: the trochlea articulates with the ulna, and the capitulum with the head of the radius. The elbow is a hinge joint, stabilized by collateral ligaments on each side.

When taking a breath, the anterior (front) ends of the upper ribs, along with the sternum, lift up and forward to increase the chest’s front-to-back diameter, while the lower ribs move up and out, increasing the side-to-side diameter. Most ribs have a costal groove marking the lower border, on the inner surface, where nerves and vessels of the thoracic wall lie. THORAX Transverse process of T1 Cervical spine (Seven vertebrae make up the spine in the neck) Thoracic spine (Twelve vertebrae, providing attachment for twelve pairs of ribs) T10 T9 T8 T7 T6 T5 T4 Thoracic curvature This dorsally convex type of curvature is technically known as a kyphosis, from the Greek for crooked Intervertebral disc Weight-bearing cartilaginous joint composed of an outer annulus fibrosus (fibrous ring) and an inner nucleus pulposus (pulpy nucleus) Demifacet for rib joint Vertebral foramen Large compared with the size of the body; contains the spinal cord Transverse foramen The vertebral artery passes through here Vertebral foramen Body Superior articular facet Vertebral foramen Lateral mass Superior articular facet Articulates with the condyle of the occipital bone, on the base of the skull CERVICAL Lamina AXIS (C2) ATLAS (C1) Spinous process Tends to be small and forked; for the attachment of back muscles Superior articular facet Transverse process For neck muscle attachment Body Made of cancellous bone containing blood-making bone marrow Spinous process Transverse foramen Transverse process Dens (odontoid peg) This projection sticks up to articulate with the atlas Posterior arch Transverse foramen Anterior arch The atlas has no body, but it has an anterior arch that forms a joint with the dens of the axis The spine, or vertebral column, occupies a central position in the skeleton, and plays several extremely important roles: it supports the trunk, encloses and protects the spinal cord, provides sites for muscle attachment, and contains blood-forming bone marrow.

TOOTH Capsular layer Middle layer Cambial layer Bone Occipital bone Uniting layer SKULL Suture These joints exist between flat bones of the skull. They are flexible in the skull of a newborn baby, and allow growth of the skull throughout childhood. The sutures in the adult skull are interlocking, practically immovable joints, and eventually fuse completely in later adulthood. Parietal bone Forms the roof and side of the skull SKELETAL SYSTEM Parietal bone HEAD AND NECK 034 Zygomatic bone Occipital bone Forms the lower part of the back of the skull Frontal bone Zygomatic bone This roughly triangular bone connects the frontal bone, maxilla, and temporal bone Temporal bone Articulates with the parietal, sphenoid, and occipital bones and contains the ear apparatus, including the ossicles Mastoid process ARTICULATED VIEW Maxilla Nasal bones Two bones, attaching to the frontal bone above and the maxillae to the side, form the bridge of the nose Angle of mandible The masseter muscle attaches down to this angle, which tends to be slightly flared outward in men Ramus of mandible Orbital surface of maxilla Body of mandible The mandible develops as two separate bones, which fuse in infancy DISARTICULATED VIEW MALLEUS STAPES INCUS OSSICLES OF THE EAR Alveolar process of mandible Projects up from the mandible and forms the sockets for the lower teeth Alveolar process of maxilla Projects down from the maxilla and forms the sockets for the upper teeth Maxilla Articulates with the opposite maxilla in the midline, with the nasal, frontal, and lacrimal bones above, and the sphenoid, ethmoid, and palatine bones Vomer Zygomatic bone Zygomatic process Lacrimal bone Nasal bone Orbital plate of ethmoid bone Petrous part of temporal bone HEAD AND NECK Sphenoid bone 035 036 SKELETAL SYSTEM T1 (first thoracic) vertebra Clavicle First rib Smaller and more curved than all the other ribs; the thoracic inlet is formed by the first rib on each side, together with the manubrium sterni and the body of the T1 vertebra Scapula Second costal cartilage The upper seven ribs are true ribs, and all attach directly to the sternum via costal cartilages Third rib Fourth rib Fifth rib Sixth rib Seventh rib Eighth to tenth ribs The costal cartilages of these ribs each attach to the costal cartilage above Eleventh and twelfth ribs These are also called floating ribs because they do not attach to any others 037 THORAX Transverse process of T1 Each rib articulates with the transverse processes of the corresponding thoracic vertebra Head of first rib The heads of the ribs articulate with the bodies of vertebrae Manubrium sterni The sternum is shaped like a dagger or short sword; manubrium means handle or hilt in Latin Manubriosternal joint Body of sternum Sternum comes from the Greek for breastbone Xiphisternal joint Xiphoid process The tip of the sternum takes its name from the Greek word for sword THORAX ANTERIOR (FRONT) The skeleton of the thorax plays several extremely important roles.