In vertebrate anatomy, ribs are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax. In some animals, especially snakes, ribs may provide support and protection for the entire body.
In anatomy, the atlas (C1) is the most superior (first) cervical vertebra of the spine and is located in the neck.
The rib cage is an endoskeletal enclosure in the thorax of most vertebrate animals that comprises the ribs, vertebral column and sternum, which protects vital organs such as the heart, lungs and great vessels. The circumferential enclosure formed by left and right rib cages, together known as the thoracic cage, is a semi-rigid bony and cartilaginous structure which surrounds the thoracic cavity and supports the shoulder girdles to form the core part of the axial skeleton.
In anatomy, the axis or epistropheus is the second cervical vertebra (C2) of the spine, immediately inferior to the atlas, upon which the head rests.
The levator scapulae is a slender skeletal muscle situated at the back and side of the neck. It originates from the transverse processes of the four uppermost cervical vertebrae; it inserts onto the upper portion of the medial border of the scapula. It is innervated by the cervical nerves C3-C4, and frequently also by the dorsal scapular nerve. As the Latin name suggests, its main function is to lift the scapula.
The omohyoid muscle is a muscle that depresses the hyoid. It is located in the front of the neck, and consists of two bellies separated by an intermediate tendon. The omohyoid muscle is proximally attached to the scapula and distally attached to the hyoid bone, stabilising it. Its superior belly serves as the most lateral member of the infrahyoid muscles, located lateral to both the sternothyroid muscles and the thyrohyoid muscles.
In tetrapods, cervical vertebrae are the vertebrae of the neck, immediately below the skull. Truncal vertebrae lie caudal of cervical vertebrae. In sauropsid species, the cervical vertebrae bear cervical ribs. In lizards and saurischian dinosaurs, the cervical ribs are large; in birds, they are small and completely fused to the vertebrae. The vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have seven cervical vertebrae, with the only three known exceptions being the manatee with six, the two-toed sloth with five or six, and the three-toed sloth with nine.
The anterior longitudinal ligament is a ligament that extends across the anterior/ventral aspect of the vertebral bodies and intervertebral discs the spine.
The thoracolumbar fascia is a complex, multilayer arrangement of fascial and aponeurotic layers forming a separation between the paraspinal muscles on one hand, and the muscles of the posterior abdominal wall on the other. It spans the length of the back, extending between the neck superiorly and the sacrum inferiorly. It entails the fasciae and aponeuroses of the latissimus dorsi muscle, serratus posterior inferior muscle, abdominal internal oblique muscle, and transverse abdominal muscle.
The intervertebral foramen is an opening between two pedicles of adjacent vertebra in the articulated spine. Each intervertebral foramen gives passage to a spinal nerve and spinal blood vessels, and lodges a posterior (dorsal) root ganglion. Cervical, thoracic, and lumbar vertebrae all have intervertebral foramina.
The iliolumbar ligament is a strong ligament which attaches medially to the transverse process of the 5th lumbar vertebra, and laterally to back of the inner lip of the iliac crest.
The posterior longitudinal ligament is a ligament connecting the posterior surfaces of the vertebral bodies of all of the vertebrae of humans. It weakly prevents hyperflexion of the vertebral column. It also prevents posterior spinal disc herniation, although problems with the ligament can cause it.
The anterior sternoclavicular ligament is a broad band of fibers attached to the clavicle above, and to the manubrium below. The ligament overlies the anterior (front) surface of sternoclavicular joint.
The articulations of the heads of the ribs constitute a series of gliding or arthrodial joints, and are formed by the articulation of the heads of the typical ribs with the costal facets on the contiguous margins of the bodies of the thoracic vertebrae and with the intervertebral discs between them; the first, eleventh and twelfth ribs each articulate with a single vertebra.
The posterior atlantooccipital membrane is a broad but thin membrane extending between the to the posterior margin of the foramen magnum above, and posterior arch of atlas below. It forms the floor of the suboccipital triangle.
The costotransverse joint is the joint formed between the facet of the tubercle of the rib and the adjacent transverse process of a thoracic vertebra. The costotransverse joint is a plane type of synovial joint which, under physiological conditions, allows only gliding movement.
The lateral costotransverse ligament is a short, thick, though ligament of the costotransverse joint which strengthens the joint posteriorly. It connects the tubercle of a rib, and the transverse process of the corresponding vertebra.
A superior costotransverse ligament is a ligament of the costotransverse joint that attaches onto the crest of the neck of a rib, and onto the transverse process of the vertebra superior to the rib.
The lumbar fascia is the lumbar portion of the thoracolumbar fascia. It consists of three fascial layers - posterior, middle, and anterior - that enclose two muscular compartments. The anterior and middle layers occur only in the lumbar region, whereas the posterior layer extends superiorly to the inferior part of the neck, and the inferiorly to the dorsal surface of the sacrum. The quadratus lumborum is contained in the anterior muscular compartment, and the erector spinae in the posterior compartment. Psoas major lies anterior to the anterior layer. Various superficial muscles of the posterior thorax and abdomen arise from the posterior layer - namely the latissimus dorsi, and serratus posterior inferior.
The spinal column, a defining synapomorphy shared by nearly all vertebrates, is a moderately flexible series of vertebrae, each constituting a characteristic irregular bone whose complex structure is composed primarily of bone, and secondarily of hyaline cartilage. They show variation in the proportion contributed by these two tissue types; such variations correlate on one hand with the cerebral/caudal rank, and on the other with phylogenetic differences among the vertebrate taxa.
