Anatomy of the Spine (part 2: Thoracic)

The twelve vertebrae in the middle of your back comprise the thoracic spine, below the 7 cervical and above the 5 lumbar vertebrae. Each vertebrae connects ribs in the front of the body to form the rib cage which connects to the spine between the thoracic vertebrae. The thoracic spine could be considered the most versatile, though the cervical is capable of greater rotation and the lumbar provides more support for the skeletal structure. It also protects and provides nerve supplies for the essential organs including the heart, liver, kidneys, stomach, lungs, and intestines inside of the rib cage. This area of the spine is one of the most important and is also one of the most unusual skeletal structures seen in nature (due to being the middle of the unique, three curve spine).

The thoracic discs are particular, allow for certain movements spineand more flexibility and rotation at the superior portion.You can see the differences between the cervical discs and lumbar discs on the right. The curvature of the spine is very apparent and is what allows for human biped movement (apes use their hands on the ground because of the singular curve in their spine; this hints towards the progression of the human spine. You can also see the significant rotation that the thoracic vertebrae allow for, giving the skeletal structure mobility above the lumbar spine.

The Thoracic spine is one of the most important nervous gateways in the body, creating the gateway between the peripheral nerves spinal nerve mapof the upper body and the central nervous system. The peripheral nerves begin to leave the spinal nerves at the ganglion nerves, or connective nerve clusters, for the arms where the thoracic spine begins; the nerves then cascade down to connect all of the ribs, until the lumbar spine connects to the lower body and lowest abdominal organs. Essentially, the nervous system controls the entire upper body through the thoracic nerve connections and the biggest vital organs sit right in the middle of these nerves. nervesThe thoracic spine connects directly to the rib cage, making it one of the most important protective structures of the human

autonomic nervous systemskeleton. The heart has nerves that extend up into the neck (think about the thyroid’s control over the heart) and is largely connected to the middle vertebrae of the spine. The lungs also share these thoracic nerves and nestle the heart; they are meant to provide the heart with support and surround it. The stomach, liver, pancreas, small intestine, and adrenals share the lower portions of the thoracic nerves, while the large intestine has connections to both the lumbar spine and the thoracic spine. thoracic muscles

There are many different muscles of the thoracic spine and middle back because the thoracic spine is the gateway to control center of the upper body, which is where the majority of movement takes place (the hands and fingers are finely tuned and the shoulder is a durable and versatile joint). The vertical muscles that extend up the spine and interconnect vertebrae are the deepest layer of muscle and the diaphragm (the breathing muscle) is also included in this musculature.

deep thoracic musclesThe deepest muscles of the spine interconnect the vertebrae to ensure structural stability. There are also fascia that extend up and down the length of the spine, known as the vertical erectors (they help humans to stand up straight). vertical spinal erectors You can see them detailed on the left. There is also significantly denser ligamentation towards the inferior portion of the spine, leaving the upper portion more mobile and connected with muscular tissue. The spinal cord itself is completely protected and supported by these muscles, allowing for the extensive movements that humans are capable of.

This concludes the second part of three about the human spine and its anatomical functionality. If you have any questions, feel free to comment, but stay tuned for part 3 where we will dive into the lumbar portion of the human spine.

Anatomy of the Spine (Part1: Cervical)

Cervical Spine

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.

Cervical Vertebrae 1

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

Posterior ligaments of C2
Posterior ligaments of C2

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 Vertebral arch labelledessential 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 arteryvertebral 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 Cervical Nervesthat 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.

Cervical Veins

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.