The human spine has 24 vertebrae and is usually separated into 3 sections: the Lumbar curve, the Thoracic curve, the Cervical curve. I will be doing a three-part series for the spine, as the spine as a whole is too complicated to summarize effectively in one post. We will move from top to bottom and each post will get longer as we move closer to the base of the spine. For now, we will start with the seven Cervical vertebrae which allow for the greatest rotation and support the neck, skull, and brain. These are the most mobile vertebrae and have extraordinarily complex neural, venous, and muscular connections and passageways.
C1 (C1-C7 are cervical, C1 being on top) is the highest spinal vertebrae and is also known as the Atlas. This is drawn from Greek mythology as a metaphor because the atlas supports the globe of the head. This vertebrae is special as you can see from its shape; the brain stem extends into the vertebrae at the same time as the vertebrae has lots of room to tilt forward, back, and to the sides. The atlas is also fused with the Axis (C2) and has no body as a
result. The Axis is the seat upon which the Atlas rotates and provides support to circularly rotate the head. These first two vertebrae are particularly significant because the brain stem connects the spinal cord at the base of C2 to the brain.
C3 through C6 are somewhat uniform and share many characteristics. In order to move forward, we need some vocab work and general characteristics of vertebrae to be able to compare them.
Vertebral Characteristics : A typical vertebra consists of two essential parts— ananterior segment, the body, and a posterior part, the vertebral or neural arch; these enclose a foramen, the vertebral foramen. The vertebral arch consists of a pair of pedicles and a pair of laminæ, and supports seven processes—four articular, two transverse, and one spinous.
body – The thick connecting structure supporting the bone
vertebral arch – The extensions from the body which connect to each other through ligaments and muscle tissue
pedicles – The two short process which connect the arch to the body of the vertebrae
laminae – two broad plates extending from the pedicles
process – anatomical terms for an extension, or outgrowth of tissue from a larger body
transverse processes – project up and down from where the lamina meets the pedicles. In the cervical spine this is pierced by the transverse foramen, which is discussed below
spinous processes – the fin like posterior tip of the vertebrae that extends back from the lamina
articular processes – these connect the vertebrae at the junction of the lamina and pedicles, form the links of the spine
tubercle – describes a round nodule, small eminence, or warty outgrowth found on bones or skin
Now that we have a decent idea about the characteristics of vertebrae we can look in detail at the cervical vertebrae. The first six vertebrae are wider than they are long and they overlap with the front of the vertebrae below. The Laminae are narrow, but widen on the inferior side, so each vertebrae is wider at the bottom than top make the lower vertebrae wider than the upper. The spinous processes are short and bifid (split), with one end being longer than the other. Articular pillars are formed by the superior and inferior articular processes that have fused and link the vertebrae together. The transverse processes are pierced by the transverse foramen, which gives passage to the vertebral artery, vertebral vein, and a plexus of sympathetic nerves. The seventh foramen lacks the artery, but contains the vein and sympathetic nerves.
The seventh cervical vertebrae is fairly unique. It is called the Vertebra prominens and has a long and palpable spinous process that isn’t split and that you can see in about 70% of people, hence its name. It’s considerably bigger spinous process gives it more support for veins and nerves which start to bundle heavily and for the muscles that extend horizontally in the shoulders and down the arms. See more detail on the nervous connections to the right.
The veins and arteries of the cervical vertebrae run parallel to the left and right of the spinal column. It is a complex wiring that interlace with each vertebrae.
The muscles of the neck are detailed in a prior post here. Stay tuned for the Thoracic spine, the middle 12 vertebral columns and how they function within the body.