Anatomy & Organs

Atlas – structure, function & diseases

Atlas

The atlas is the first cervical vertebra that supports the skull . It forms an articulated connection with the parietal bone. Ruptures in the area of ​​the atlas ring can destroy the medulla oblongata and lead to death.

What is the atlas?

The cervical spine of humans and most other mammals consists of a total of seven vertebrae. Compared to the cervical spine, the lumbar and thoracic spine are significantly less mobile. The cervical spine owes its mobility primarily to the so-called atlas.

This is the first cervical vertebra, which carries the entire head and a particularly rotatable vertebral joint. The Atlas got its name from the Greek titan Atlas, who, according to legend, had to shoulder the burden of the sky.

The atlas is the part of the cervical spine closest to the skull and meets the second cervical vertebra, the axis, in a functional unit known as the nick. The nod allows the head to bend in an anterior direction, enabling the human to nod. In clinical practice, the abbreviation C1 stands for the atlas. The anatomy of the atlas and axis is quite different from the rest of the vertebrae in the spine .

Anatomy & Structure

The atlas appears as a ring-like shape. The cervical vertebra has lost its vertebral body in the course of evolution . Laterally and ventrally, the atlas bears bony thickenings, which are called massae laterales and end in semicircular bony arches. The bony arches are called atlas arches and correspond to the arcus anterior and posterior atlantis.The spinous process of the atlas is not pronounced, but is replaced by an elevation of the dorsal side at the arcus posterior, which is also called the tuberculum posterius. A tuberculum anterius also carries the ventral side of the arcus anterior. On the sides of the lateral masses are transverse processes, which are considered to be remnants of the costal process and carry the transverse foramina. On the massae laterales are articular surfaces which, together with the occipital bone, correspond to the atlanto-occipital joint. The atlas joint surfaces together with the axis form the atlantoaxial joint.

The transverse foramen of the atlas is traversed by the so-called vertebral artery, which then passes through the foramen magnum and into the skull. The vertebral foramen is divided into two by the transverse atlantic ligament. Ventral to the transverse atlantic ligament is the dens axis and dorsal to it is the spinal cord .

Function & Tasks

The Atlas takes its name from the Greek titan Atlas. That alone already indicates the main function of the first cervical vertebra. As with the Greek titans, Atlas requires strength above all else. The atlas is the cervical vertebra in close proximity to the skull. It is intended to stabilize the transition between the cervical spine and the head and must also carry the full weight of the skull.

However, the first cervical vertebra is only relevant for stabilizing the head and spine. The head must be movable. From an evolutionary point of view, the human ability to rotate the head has contributed to the survival of the human species. As soon as a human individual has heard a sound and suspected danger behind it, he has turned his head in the direction of the perceived danger. This process could take place within milliseconds due to the articulated connection between the spine and cranial bone and enabled the direct fixation and identification of dangers through the eyes .

The atlas is essentially involved in the articulated connection between the cervical spine and the cranial bone. It therefore gives the head mobility and the ability to rotate in the cervical spine. Without this articulated connection, everyday movements such as nodding would be entirely unfeasible.

The joint of the atlas differs significantly from other intervertebral joints of the spine. Basically, the human spine is most flexible in the area of ​​the cervical spine. On the other hand, the atlas as a whole also prevents dislocations and twists, as it is stabilized by strong ligaments .

Diseases

Some pathological changes in the atlas are particularly well known. These include various developmental disorders and the resulting deformation of the first cervical vertebra. In the development of the atlas, disturbances can occur during embryonic development , which cause partial fusion at the sclerotomes of the upper four somites. In this way, the occipital bone can fuse completely or incompletely with the atlas. This disorder is also referred to as atlas assimilation.Apart from congenital malformations of the first cervical vertebra, the atlas, like all other vertebrae, can be affected by malpositions. The spinal cord runs directly through the atlas, so misalignment of the vertebra can be associated with disorders of the central nervous system and often causes a rigid spine. In addition, the circulation of blood and liquor cerebrospinalis is often impeded in the case of misalignments of the atlas, so that further failures occur.

Apart from these phenomena, the most serious symptomatology associated with the atlas is a broken neck . This is a fracture of the dens axis, which lies with the spinal cord in the atlas ring. When the neck is broken, the ligamentum transversum atlantis and apicis dentis (ligaments) usually tear off. The dens axis thus has considerable freedom of movement and thus often injures the medulla oblongata. This injures the respiratory center of the body and death occurs in a matter of seconds. This injury occurs when people hang themselves. Less well known is the Jefferson fracture, which corresponds to a special form of the atlas fracture and causes the ring of the atlas to burst completely.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.