What is the axis of a bone?
In anatomy, the axis (from Latin axis, “axle”) or epistropheus, is the second cervical vertebra (C2) of the spine, immediately inferior to the atlas, upon which the head rests. The axis’ defining feature is its strong odontoid process (bony protrusion) known as the dens, which rises dorsally from the rest of the bone.
What two bones does the axis articulate with?
Introduction to Axis Bone Anatomy:
articulates with the anterior arch of the atlas bone, where they form a pivot joint. rotates side-to-side, the atlas bone rotates around the peg-like odontoid process. This is the reason why the second cervical vertebra is also called the axis bone.
What movement does the axis allow?
The axis is the second cervical vertebra; it has what is called the odontoid process about which the atlas rotates. The joint between the atlas and axis is a pivot type of joint. It allows the head turn from side to side.
What does the axis lack?
Thus, this joint is called the atlanta-axial joint, and its main function is to allow the head to rotate around the neck. Also, same as the atlas, axis does not contain a vertebral body. Significantly, the absence of the vertebral body also supports the wide range of motions achievable by the head.
What muscles attach C2?
Attachments:
- attached to the anterior surface of the vertebral body. longus colli.
- attached to transverse processes. levator scapulae. scalenus medius. splenius cervicis.
- attached to spinous processes. semispinalis cervicis. rectus capitis posterior major. …
- attached to posterior surface of lamina. multifidus and longissimus.
What does the dens attach to?
The dens (odontoid process) of the axis exists as a superior projection from the C2 vertebral body and is conical in shape and serves as an attachment site for the transverse, apical, and alar ligaments [1-2].
Does axis have a Centrum?
The axis has an elongated centrum, the dens, which extends into the large neural canal of the atlas. The shape of the dens restricts motions between the first two vertebrae to rotations parallel to the long axis of the body.
How is the axis different from other vertebrae?
The axis is somewhat analogous to the other cervical vertebrae in shape, but it differs slightly for two reasons: its spinous process isn’t as obviously bifid, and the presence of the dens.
Why is the axis bone called the axis?
It is called the “axis” because the uppermost cervical vertebra (called the atlas) rotates about the odontoid process of C2. The joint between the axis and atlas is a pivot type of joint. … The Latin word “axis” means axle or pole. The axis bone serves as the axle about which the atlas (and the head) turn.
Does the axis have a transverse foramen?
The axis. The second cervical vertebra is the axis (Fig. … Both transverse processes have a transverse foramen for the vertebral arteries. The superior articular facets of the axis articulate with the inferior articular facets of the atlas.
Is the axis an irregular bone?
An irregular bone is one of the types of bones classified by shape. … Axis bone and other vertebrae. Hyoid bone. Sphenoid bone.
What is the main axis of the body?
Explanation: In anatomy, the second cervical vertebra (C2) of the spine is named the axis (from Latin axis, “axle”) or epistropheus. By the atlanto-axial joint, it forms the pivot upon which the first cervical vertebra (the atlas), which carries the head, rotates.
What are alar ligaments?
In anatomy, the alar ligaments are ligaments which connect the dens (a bony protrusion on the second cervical vertebra) to tubercles on the medial side of the occipital condyle.
Is the dens anterior or posterior?
The dens or odontoid process exhibits a slight constriction or neck, where it joins the body. On its anterior surface is an oval or nearly circular facet for articulation with that on the anterior arch of the atlas.
Does C7 have a transverse foramen?
C7 possesses the standard cervical vertebral features but has some distinct features: … C7 transverse foramina are small, and do not transmit the vertebral artery.
Where does alar ligaments attach?
occipital condyles
The alar ligaments join the lateral margins of the sloping upper posterior margin of the dens of C2 to the lateral margins of the foramen magnum (adjacent to the occipital condyles) and lie on either side of the apical ligament. They may be oblique or vertical and are thickest at the occipital attachment.
What is Flavum?
One of a series of bands of elastic tissue that runs between the lamina from the axis to the sacrum, the ligamentum flavum connects the laminae and fuses with the facet joint capsules. … As we age, the ligament loses elastin, and this allows the ligament to encroach on the canal.
Where does the transverse ligament attach?
Attachments. It is attached on either side to a small tubercle on the medial surface of the lateral mass of the Atlas. As it crosses the odontoid process, a small fasciculus (crus superius) is prolonged upward and another (crus inferius) downward, from the superficial or posterior fibers of the ligament.
What ligament attaches to neck of rib?
Costotransverse ligament – Connects the neck of the rib and the transverse process.
Where does the posterior longitudinal ligament attach?
The posterior longitudinal ligament runs in the spinal canal attaching to the vertebral bodies and vertebral discs and tightens with cervical flexion.
What is Odontoid Peg?
The odontoid process (also dens or odontoid peg) is a protuberance (process or projection) of the Axis (second cervical vertebra). It exhibits a slight constriction or neck, where it joins the main body of the vertebra.
What muscles attach to ribs?
The intercostals are muscles between the ribs that form the chest cavity wall. Lying below the pectoral muscles, the intercostal muscles form the chest wall and play a key role in respiration. All intercostal muscles originate on the lower border of a rib and attach to the upper border of the rib below.
What back muscles attach to ribs?
The intercostal muscles, commonly referred to simply as the intercostals, connect the ribs and help make up the chest wall. When these muscles overstretch or tear, they can cause significant pain in the mid- and upper back. Intercostal muscle strain is a common injury in athletics and hard labor.