Bones - Anatomy

The top two cervical vertebrae (C1 and C2) are responsible for allowing the head to move in a nodding motion, as well as side to side. The atlas is the first cervical vertebra (C1), and attaches to the occipital condyles in order to allow a nodding motion. The axis is the second cervical vertebra (C2) and allows for twisting motion from side to side.

The thoracic vertebrae are located in the trunk and allow for twisting motion, and some bending (though this is mostly allowed by the lumbar region). The sacrum is located inferior to the lumbar vertebrae and does not substantially contribute to movement.

There are 33 vertebrae in the human body: 7 cervical vertebrae, 12 thoracic vertebrae, 5 lumbar vertebrae, 5 (fused) sacral vertebrae, 3-4 (fused) coccygeal vertebrae.

Primary curvatures of the spine reflect the original shape of the embryo, and are concave to the anterior. The thoracic and sacral curvatures are examples of primary spinal curvatures. Exaggeration of these curvatures is considered kyphosis.

The cervical and lumbar curvatures are examples of secondary curvatures and are concave to the posterior. Exaggeration of these curvatures is considered lordosis.

The spinous processes of the vertebrae largely dictate their range of motion and ability to interlock with adjacent vertebrae. Cervical vertebrae have short, bifid (split) spinous processes to facilitate a wide range of movement. The neck is capable of twisting, nodding, and lateral deviation. Thoracic vertebrae have long spinous processes that point to the inferior and align with the vertebra immediately inferior. This promotes anterior concavity, allowing the motion of bending forward. Lumbar vertebrae have shorter posterior spinous processes that do not interact with adjacent vertebrae. This allows for twisting motions, as well as anterior and posterior concavity. Next to the cervical vertebrae, the lumbar vertebrae have the largest range of articulation.

The sternum is a bone that is a part of the skeleton of the thorax. It is made of three components: the manubrium, the body, and the xiphoid process. The manubrium is the portion closest to the neck area and has articulations with the clavicle on both sides. It also has three additional articulations: the first rib cartilage, the second rib, and the body of the sternum. The last of these is called the manubriosternal joint, or the angle of Louis. The body of the sternum further articulates with the xiphoid process to form the xiphisternal joint. These angles are important landmarks in locating structures in the thoracic cavity. The xiphoid process can be felt in the epigastric quadrant of the abdomen.

The zygomatic process is a region of the skull. Technically, the zygomatic process is made of three components: the zygomatic process of the frontal bone, the zygomatic process of the maxilla, and the zygomatic process of the temporal bone.

In a human skeleton, there are twelve pairs of ribs found in the thoracic cavity. They extend from the vertebrae and some have attachments to the sternum in the anterior. The ribs provide protection for the organs in the thorax and aid in changing the anterior to posterior and transverse diameter of the chest.

There are three classifications of ribs: true, false, and floating. True ribs are ribs 1 to 7 and attach to the sternum directly. False ribs are ribs 8 to 10 and attach to the cartilage of the ribs above. Ribs 11 and 12 are floating ribs in that they have no anterior attachments.

The pelvic girdle is the combination of pelvis and the sacrum, which form a closed transverse ring. The ilium, the ischium, and the pubis form the pelvis. These three bones fuse together at the acetabulum. The femur articulates with the acetabulum, but is not considered part of the pelvic girdle.

The lower part of the pelvis is formed by the ileum, ishium, and pubic bones. These bones join to create a cavity. This cavity is larger in females to allow the passage of an infant during childbirth.

The pectoral girdle is made up of the scapulae (shoulder blades) and clavicles (collar bones). The coccyx, also referred to as the tailbone, is located at the inferior of the spinal column. The sacrum is a curved set of fused bones that forms part of the posterior pelvis. The tarsus is the collection of seven bones in the foot that form the ankle and instep.

There are twelve thoracic vertebrae, labeled T1 to T12. They have articulations (joints) that connect them with the rib cage. The cervical vertebrae, labeled C1-C7, are located in the neck. The lumbar vertebrae, labeled L1-L5, are located in the lower back. The sacrum is a segment of the vertebral column that forms part of the posterior pelvis. The coccyx, or tailbone, is the most inferior part of the vertebral column.

The xiphoid process is the inferior most portion of the sternum. It begins as a thin strip of cartilage, but slowly ossifies during adulthood. It serves a vital role in respiration as one of the origins of the diaphragm. It is relatively fragile and its position makes it a prime candidate to be damaged by the compression during CPR.

The atlas is the first cervical vertebra, because it holds up the "globe" (the head.) The second cervical vertebra is know as the axis. The other vertebrae are named based on their location within the vertebral column.

The human vertebral column consists of 33 vertebrae. The lumbar vertebrae at the base of the spine are thickest and bear most of the weight of the trunk. The bottom 5 sacral vertebrae and 4 coccygeal vertebrae are fused. Both sets of fused vertebrae comprise two different bones, the sacrum and the coccyx respectively. The 12 thoracic vertebrae contain facets on the bodies and on the transverse processes (except T11 and T12) for articulation with the ribs.

Both the coccyx and the sacrum are comprised of fused vertebrae, but only the sacrum articulates with the hip bones and it does so at the sacroiliac joints. The sacrum is comprised of 5 fused vertebrae.

The spinous process on cervical vertebra number 7 can be felt under the skin and even seen. C7 is the largest and most inferior vertebra of the cervical vertebrae and the spinous process serves as an attachment point for muscles. The transverse foramen is a hole in the direction the vertebral column runs and allows nerves and blood vessels to run the length of the vertebral column. The transverse process is also a point of attachment, but cannot be felt as they extends laterally from the spine. The pedicle allows for the passage of spinal nerves and cannot be palpated. The body is positioned anteriorly, and thus cannot be palpated.

The correct answer is spine. The spine is another word for the vertebral column but is not a region within it.

The vertebral column consists of 33 vertebrae that are divided into 5 regions:

• cervical (neck) = 7 vertebrae
• thoracic (chest) = 12 vertebrae
• lumbar (lower back) = 5 vertebrae
• sacrum = 5 fused vertebrae
• coccyx (tailbone) = 4 (3-5) fused vertebrae

The regions of the vertebral (or spinal) column are divided by the curves of the spine. The vertebrae are named based on each region and within each region the vertebrae are mostly alike, with small variations. The vertebrae in cervical, thoracic and lumbar regions are independent bones and are named by region: cervical (C1-C7), thoracic (T1-T12), lumbar (L1-L5). The sacrum (S1-S5) and coccyx are fused and their vertebrae cannot independently move.

The function of the vertebral column is to surround and protect the spinal cord, which travels along the spinal canal. The spinal cord supplies nerves and receives information from the peripheral nervous system.

The ribs consist of 12 pairs of bones that form the majority of the thoracic cage. False ribs are ribs numbered 8-12. Ribs 8-10 form the anterior costal margin by connecting to the costal cartilage above them.

True ribs are the first seven ribs (ribs 1-7). True ribs are attached to the sternum by costal cartilages. Typical ribs are ribs 3-9. They are called typical because they all have a head, neck, tubercle, and body/shaft. The tenth rib attaches directly to the tenth vertebra, instead of in between vertebrae like ribs 2-9. Lastly we have ribs 11 and 12, which are the “floating” ribs. They are only connected to the vertebrae, and do not articulate with the sternum.

The sacral vertebrae, generally 4-6 in number, are fused in the adult to form the sacrum. Additionally, the coccygeal vertebrae are fused in many individuals to form the coccyx. These are the two types of vertebra that are typically fused in the adult skeleton.

The cervical, thoracic, and lumbar vertebrae do not fuse under normal circumstances.

The cervical vertebrae are the smallest weight-supporting vertebra. The coccygeal and terminal sacral vertebrae are smaller, but they support no weight. The thoracic and lumbar vertebrae are larger in size.

The cervical vertebrae have a foramen in the transverse process. These foramina transmit the vertebral arteries that help supply the brain. There are no foramina in the thoracic, lumbar, or coccygeal vertebrae; the sacral vertebrae have only sacral foramina.

The thoracic vertebrae have facets called costal pits, with which the ribs articulate. No other types of vertebrae have this feature, nor do other types of vertebrae articulate with the ribs.