Biomedical Engineering Reference
In-Depth Information
and the pectoral and pelvic girdles. The vertebral column consists of separate
bones, the vertebrae. The vertebrae are arranged above each other. Because
the separate vertebrae are attached to each other by means of fibrous carti-
laginous discs, they form a flexible column. Each vertebra has articular sur-
faces above and below, which allow articulation movement between them.
The vertebral column of 26 vertebrae is divided into five regions according to
their position and structure. There are seven cervical (neck) vertebrae, twelve
thoracic (chest) vertebrae, five lumbar vertebrae, one fused sacral vertebra,
and one coccyx.
• Cervical vertebrae. The neck region consists of seven cervical verte-
brae. These are the smallest vertebrae in the vertebral column. The
first two cervical vertebrae are known as the atlas and axis. They are
specially adapted to support the skull and to enable it to move. They
differ from the structure of the typical vertebra in certain respects.
• Thoracic vertebrae. There are 12 thoracic vertebrae. The centrum is
large and sturdy and the neural spines are long and directed down-
ward. The long neural spines form an anchorage for the muscles and
ligaments that support the head and neck. The head (or capitulum)
of each of the first 10 pairs of ribs fits into and articulates with the
semicircular facet, which is situated between two successive centra
(i.e., between the inferior surface of one and the superior surface of
the next centrum). These facets occur on both sides of the centrum.
The tubercle of the rib articulates with the facet at the tip of the
transverse process.
• Lumbar vertebrae. These 5 vertebrae are the largest and strongest in
the vertebral column. The transverse processes are very long for the
attachment of the powerful back muscle that maintains the posture
and flexes the spine in movement.
• The sacrum (1) forms the posterior wall of the pelvis. The sacrum
is a large, triangular bone at the base of the spine and at the upper
and back part of the pelvic cavity, where it is inserted like a wedge
between the two hip bones. Its upper part connects with the last
lumbar vertebra and the bottom part with the coccyx (tailbone).
• The coccyx (1) is one mass of four to five small coccygeal vertebrae
that have fused into one, commonly called the tailbone.
A.2.1.4 Thoracic Cage (25)
The human rib cage, also known as the thoracic cage, is a bony and
cartilaginous structure that surrounds the thoracic (chest) cavity and sup-
ports the pectoral (shoulder) girdle, forming a core portion of the human
skeleton. A typical human ribcage consists of 14 true ribs, 10 false ribs, and
one sternum.
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