THORACIC VERTEBRAE: CHARACTERISTICS, FUNCTIONS, EMBRYOLOGY, ANATOMY - ANATOMY AND PHYSIOLOGY - 2024

The thoracic vertebrae, also known as the dorsal vertebrae, are twelve bones that make up together with the intervertebral discs, the second portion of the spinal column.

The thoracic vertebrae are shaped like a heart. The main characteristic of these bone bodies is that they have articular facets for the insertion of the ribs. The main function of the thoracic vertebrae is to protect its content, body support and balance. They also serve as an articular surface for the ribs, forming firm but mobile joints that allow respiratory movements.

Thoracic vertebrae. By Anatomography - en: Anatomography (setting page of this image), CC BY-SA 2.1 jp, The spine or spine is an anatomical structure that extends from the skull to the coccyx. It is made up of a cervical portion, a thoracic portion, a lumbar portion, a sacral portion, and a coccygeal portion.

The first dorsal vertebra (T1) is located after the seventh cervical (C7). After the twelfth dorsal vertebra (T12), the lower back begins which is the lumbar region.

The thoracic spine is the joint of each thoracic vertebra with the next, separated by a cushion of cartilage called the intervertebral disc that provides cushioning and lubrication to avoid friction of the bones.

The intervertebral discs, in the case of the thoracic spine, are thinner than those of other portions of the spine, supporting better cushioning.

Embryology

The development of the bones begins from the fourth week of gestation. At that time, primitive cells can be seen that are arranged around the structure, which will give shape to the spinal cord.

These cells are the ones that, between the fifth and eighth weeks, will form the vertebrae and the spinal column.

The thoracic vertebrae form around the ninth week of gestation. At this time they begin a process of rotation, finally forming the definitive vertebral bodies with their posterior orifice that opens the way to the spinal cord.

Along with these elements the ribs originate around the heart and primitive lungs, so the thoracic vertebrae gradually acquire their characteristic articular facets.

By the sixteenth week the spine is fully formed, as well as the rest of the anatomical features of the thoracic spine. Finally, the physiological curvature that balances the body develops after birth.

Anatomy and Features

Anatomy

The thoracic vertebrae, also called the dorsal vertebrae, are 12 bones that are located in the middle portion of the spine.

Each spinal segment has different characteristics and functions. Thus, each of the 12 thoracic vertebrae acquires a shape and structure depending on the specific site where it is located.

characteristics

The thoracic or dorsal vertebrae share general characteristics to the rest. However, they differ greatly due to their function and location. The vertebral bodies are strong and thick. They are made up of a type of bone called trabecular bone that contains bone marrow, which is a substance that forms blood cells.

The irrigation of the thoracic vertebrae is ensured by the intercostal branches, which come directly from the aorta. As for the vertebral bodies, their size increases, the lower vertebrae being more voluminous than the upper ones.

In their back, they have a hole through which the spinal cord passes, which is the most important neurological structure after the brain.

The most obvious feature that differentiates the thoracic vertebrae from the rest is the presence of two articular facets (or semi-facets) for the ribs. These veneers are additional to those that normally have all the vertebrae to articulate with each other.

The facet that forms the joint for the ribs is formed by the union of the semi-facets of two vertebrae. For example, the fourth and fifth dorsal vertebrae articulate and form a single facet, in which the fifth rib articulates.

Each vertebra has a posterior portion that projects outward, called the spinous process. In the case of the dorsal vertebrae, this segment is longer than that of other portions of the spine, but they decrease in size drastically from the ninth to the twelfth vertebra (T9-T12).

With respect to the intervertebral discs, in the thoracic spine these are thinner and smoother than in the rest of the spinal segments.

Atypical dorsal vertebrae

Within the vertebrae that make up the dorsal column, there are three that present special and unique characteristics.

The first dorsal vertebra (T1) has a complete costal articular facet, not a semi-facet, since the seventh cervical vertebra does not articulate with the first rib. Thus, T1 articulates itself with the first costal arch.

In addition to this, it has some characteristics of the cervical vertebrae. Its spinous process is almost horizontal, unlike the rest of the ridges whose spinous processes are long and directed downwards.

The graph shows the peculiar thoracic vertebra (T1) OpenStax College

The eleventh and twelfth vertebrae (T11 and T12) also have an articular facet for a rib. Like T1, they do not have semi-veneers.

Furthermore, T12 is a transitional vertebra between the dorsal and lumbar. Although it has characteristics of its own segment, it is not as mobile as the other vertebrae, limiting itself to flexion and extension movements, as the lumbar segment does.

Features

The dorsal vertebrae have a strong enough structure to support the weight of the body and maintain the upright position of most of the trunk.

It is rare that they are injured as they adapt to cushioning rebounds well, especially when jumping or stomping.

When articulated in the thoracic spine, they assist the mechanical process of respiration, forming tight joints but mobile enough to allow the necessary respiratory movements of the ribs.

On the thoracic spine

The spinal column is an articulated bony and cartilaginous structure that extends from the skull to the coccyx. It is divided into five segments according to their location and characteristics: the cervical, the dorsal or thoracic, the lumbar, the sacral or sacrococcygeal and the coccyx.

Spine. User: Mikael Häggström

The thoracic vertebrae are individual bones that articulate with each other, separated by cartilage with a very pulpy center called the intervertebral disc.

The adult spine has 33 vertebrae, of which 12 are thoracic or dorsal. In the literature they are often described with the letter D or T and the number of the vertebra to be named. For example, T7 to describe the seventh thoracic vertebra.

The spine has four normal or physiological curvatures that develop after birth, completing its final structure by puberty.

Evolution of the spine from child to adult. Laboratoires Servier

These curvatures are called kyphosis and lordosis depending on their direction. Kyphosis are curves that project outward from the body, and lordoses are those that project inward.

Due to the weight they must bear and the position of the body to maintain balance in the standing position, kyphosis is recognized in the thoracic vertebrae, articulated in the spine.

Any curvature in the lateral axis is considered a pathology that must be treated. This disease is called scoliosis.

References

1. Waxenbaum, J. A; Futterman, B. (2018). Anatomy, Back, Thoracic Vertebrae. StatPearls, Treasure Island (FL) Taken from: ncbi.nlm.nih.gov
2. DeSai, C; Agarwal, A. (2018). Anatomy, Back, Vertebral Column. StatPearls, Treasure Island (FL) Taken from: ncbi.nlm.nih.gov
3. Panjabi, M. M; O'Holleran, J. D; Crisco, J. J; Kothe, R. (1997). Complexity of the thoracic spine pedicle anatomy. European spine journal: official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. Taken from: ncbi.nlm.nih.gov
4. Vargas Sanabria, M. (2012). Anatomy and physical examination of the cervical and thoracic spine. Legal Medicine of Costa Rica. Taken from: scielo.sa.cr
5. Well Sanchez, AM. (2014). Spine and hip scan: how to manage scoliosis. Pediatrics Primary Care. Taken from: scielo.isciii.es