Vertebre Lombari: What are they? Anatomy, Function and Pathologies of A.Griguolo

Generality

The lumbar vertebrae are the 5 vertebrae that make up the lumbar segment of the spine, interposing between the 12 thoracic vertebrae and the 5 sacral vertebrae.

The lumbar vertebrae are the widest and strongest vertebrae in the spine, this because they have the important task of supporting most of the body weight on the back.

Identified by the capital letter L and a number from 1 to 5 depending on the cranio-caudal positioning, the lumbar vertebrae represent the spinal tract at the level of which ends the spinal cord (between the first and second lumbar vertebrae) and begins the cauda equina.

The lumbar vertebrae may be subject to various medical conditions, including sciatica due to L4 or L5 radiculopathy, lumbar spondylolysis and lumbar spondylolisthesis.

What are lumbar vertebrae?

The lumbar vertebrae are the 5 vertebrae that follow the 12 thoracic vertebrae and precede the 5 sacral vertebrae .

The lumbar vertebrae are the components of the so-called lumbar tract (or segment ) of the spine.

The lumbar vertebrae are identified with the capital letter L (which stands for "lumbar"), plus a number between 1 and 5, which indicates its cranio-caudal positioning (clearly, the number 1 identifies the first lumbar vertebra, the number 2 the second lumbar vertebra, the number 3 the third lumbar vertebra etc.).

To understand: revision of the Vertebral Column and Vertebrae

The spine, or spine, is the bone structure that:
- It runs vertically along the center of the back;
- It is the backbone of the human body;
- It houses and protects the spinal cord (which, along with the brain, makes up the central nervous system ).
Starting from the apex, the vertebral column can be divided into 5 segments (or sections): the cervical segment, the s. thoracic, the s. lumbar, the s. sacral and the s. coccygeal;
The vertebral column is composed of 33-34 overlapping irregular bones, called vertebrae, which are separated from each other by a thin fibrocartilage structure called the intervertebral disk;
Of the 33-34 vertebrae forming the spine, 7 belong to the cervical tract, 12 to the thoracic tract, 5 to the lumbar tract, 5 to the sacral tract and 4/5 to the coccygeal tract;
Although their specific anatomy varies in relation to the tract of spine considered, all the vertebrae present:
- A cuboid-shaped element in a ventral position, called a vertebral body ;
- An arched formation in dorsal position, called vertebral arch ;
- A hole between the arch and the body, whose name is a vertebral hole ;
- A prominence in the center of the outer edge of the arch, called the spinous process ;
- A prominence for each external side of the vertebral arch, called the transverse process .

Anatomy

The lumbar vertebrae are the widest and heaviest vertebrae in the spine; as will be seen later, this allows them to perform the function to which they are assigned in the best possible way.

The lumbar vertebrae belong to the particular category of vertebrae, which, in addition to the classic transverse and thorny processes, also presents the 2 upper articular processes and the 2 lower articular processes.

The lumbar vertebrae constitute the segment of the vertebral column in which the spinal cord terminates (between L1 and L2) and where the cauda equina begins, ie the nerve structure similar to a bundle, which groups the last 10 pairs of spinal nerves, before their spill from the spine.

What are spinal nerves?

Spinal nerves are the even nerves of the peripheral nerve system that originate from the spinal cord.

Localization of the lumbar vertebrae

The lumbar vertebrae run from where the posterior part of the rib cage ends to where the posterior part of the pelvis begins. Remember that the thoracic cage includes the 12 thoracic vertebrae, the sternum and the 12 pairs of ribs (which emerge from the 12 thoracic vertebrae), while the pelvis includes the sacrum (ie the sacral vertebrae) the two iliac bones and the coccyx (ie the coccygeal vertebrae);
The first lumbar vertebra (L1) is on the same level as the anterior end of the IX pair of ribs; this level of height is called the transpyloric plane, because it is the plane in which the pylorus of the stomach resides.

Did you know that ...

In addition to the pylorus of the stomach, the transpylorinic plane includes the bottom of the gallbladder, the celiac trunk, the superior mesenteric artery, the terminal tract of the spinal cord, the initial tract of the filum terminalis (or terminal strand), the renal vessels, the arteries medium adrenals and the hilum of the kidneys.

Characteristics of the components of lumbar vertebrae

VERTEBRAL BODY

The vertebral body of the lumbar vertebrae (or lumbar vertebral body) is a very voluminous formation (the most voluminous when compared with the vertebral bodies of the other vertebrae).

If viewed from above, the vertebral body of the lumbar vertebrae is morphologically similar to a human kidney, so it looks like a bean.

Analyzing the vertebral body of the lumbar vertebrae from L1 to L5 (therefore in the cranio-caudal direction), it emerges that:

The posterior aspect of the lumbar vertebral bodies changes from slightly concave to slightly convex;
The diameter of the vertebral bodies increases from vertebra to vertebra; in practical terms, this means that L1 is the lumbar vertebra from the smallest vertebral body, while L5 is the lumbar vertebra from the largest vertebral body.

Did you know that ...

The L5 lumbar vertebra is by far the largest vertebra in the spine.

VERTEBRAL ARCH

Vertebral arch of a generic vertebra.

As a rule, the vertebral arch of a generic vertebra consists of:

The two peduncles, which constitute the point of connection between the arch and the vertebral body,
The two intervertebral holes, which are the channels used for the passage of the spinal nerves exiting the spinal cord, and
The lamina, which is the curved bony segment that runs from a peduncle to a peduncle and from which the transverse processes originate, just after the aforementioned peduncles, and, halfway, the spinous process.

In the vertebral arch of the lumbar vertebrae, the two peduncles and the lamina appear as large bony formations (it is possible to note their strengthening as it descends along the lumbar tract), which gives considerable resistance to the entire vertebral structure.

It should be noted that the vertebral arch of the lumbar vertebrae is the emergency point also for the two upper joint processes and the two lower joint processes: these 4 bone projections come to life from the lamina, after the transverse processes, but before the spinous process.

What is the intervertebral hole? Some more details

The intervertebral hole is an even lateral opening of the vertebral column, which originates from the superposition of two vertebrae.

The very first segment (the so-called root ) of the spinal nerves passes through the intervertebral holes.

SPINY PROCESS

The spinous process of the lumbar vertebrae is a bony projection with an irregular edge, of short length but very large.

The spinous process of the lumbar vertebrae serves, as in all vertebrae, to anchor the muscles and / or ligaments of the back .

TRANSVERSE PROCESSES

Ligament architecture of lumbar vertebrae.

The transverse processes of the lumbar vertebrae are long and slender.

In the first 3 lumbar vertebrae, they are horizontal; in the last 2 lumbar vertebrae, instead, they are slightly oriented upwards.

It should be noted that, while in the 3 upper lumbar vertebrae the transverse processes emerge clearly on the lamina, in the 2 lower lumbar vertebrae arise from the peduncles.

Deputed as in all other vertebrae at the anchorage of muscles and / or ligaments of the back, the transverse processes of the lumbar vertebrae occupy a more ventral position than the upper and lower articular processes.

Did you know that ...

In the thoracic vertebrae, the transverse processes are found behind the upper and lower articular processes, ie in a more dorsal position.

UPPER JOINT PROCESSES

The upper joint processes of the lumbar vertebrae are well-defined bone formations, which project upwards with respect to the lamina of the vertebral arch, from which they originate.

At the free end, the superior articular processes of the lumbar vertebrae are provided with a smooth region, covered with hyaline cartilage, which takes the generic name of facet ( of the superior articular processes ) and which serves to anchor a lumbar vertebra to the vertebra immediately higher. they serve to guarantee on the posterior surface, moreover, the superior articular processes present some growths, called mammillary processes, whose job is to hook some deep muscles of the back.

LOWER JOINT PROCESSES

The lower joint processes of the lumbar vertebrae are well-defined bony projections, which develop downwards with respect to the lamina of the vertebral arch, from which they originate.

At the free end, the lower joint processes have a smooth region, covered with hyaline cartilage and called facet ( lower joint processes ).

As happens in all the vertebrae that are provided with these components, the lower articular processes of each lumbar vertebra are used, through the region called facet, to anchorage to the underlying vertebrae.

VERTEBRAL HOLE

La cauda equina.

The lumbar vertebrae have a vertebral hole of triangular shape, larger than the vertebral hole resulting from the thoracic vertebrae, but smaller than the vertebral hole present at the cervical level.

In the vertebral hole formed by the lumbar vertebrae, the spinal cord is concluded (at the level of the lumbar vertebra L2) and cauda equina begins.

Articulation with the Sacred Bone

The L5 lumbar vertebra is the protagonist of the important joint that joins the lumbar tract to the sacral tract of the spine; the sacral tract of the vertebral column is composed of vertebrae (the sacral vertebrae) which are fused together, forming a unique structure known as sacrum .

variants

In some people, the lumbar vertebrae are 6 instead of 5.

Function

The lumbar vertebrae have the task of supporting most of the weight of the body that weighs on the spine; this explains why they are more voluminous than the other vertebrae: the size guarantees them a greater capacity to support the load.

The lumbar vertebrae also provide protection for the final portion of the spinal cord and the subsequent cauda equina.

Curiosity

Of the 5 lumbar vertebrae and all vertebrae in general, the L5 lumbar vertebra is the one most involved in supporting the body weight. This is why evolution has meant that it was the largest vertebra in the spine.

diseases

The lumbar vertebrae may be subject to various medical conditions, including:

Sciatica (or sciatica ) resulting from a radiculopathy at the level of L4 or L5;
Lumbar spondylolysis ;
Lumbar spondylolisthesis .

Sciatica due to L4 or L5 radiculopathy

Sciatica and sciatica are the two medical terms that indicate the inflammation of the sciatic nerve (or ischial nerve), due to a compression or an irritation of the root or the first part of the nerve in question. It is important to remind readers that the sciatic nerve is a derivation of the last 2 lumbar spinal nerves, which emerge from the lumbar vertebrae L4 and L5, and the first 3 sacral spinal nerves, which instead emerge from the sacral vertebrae S1, S2 and S3.
Radiculopathy is the medical term that describes the suffering of one or more spinal nerves, resulting from the compression or irritation of the root or nerve tract adjacent to the root of the nerves mentioned above.

The sciatica deriving from a radiculopathy L4 or L5, therefore, is the inflammation of the sciatic nerve, which arises from the compression or irritation of the root (or of the nerve tracts immediately following the root) of the spinal nerves that emerge from the lumbar vertebrae L4 or L5.

In a sciatica deriving from an L4 or L5 radiculopathy, the compression / irritation of the sciatic nerve may depend on various conditions, such as:

A hernia of the intervertebral disc that separates the lumbar vertebrae L4 and L5 or the lumbar vertebra L5 from the sacral vertebra S1;
A spinal stenosis, ie a narrowing of the spinal canal;
A stenosis of the intervertebral hole ;
A spinal tumor .

Sciatica with L4 or L5 radiculopathy causes pain, often associated with tingling, a feeling of weakness and soreness, along the lower limb, where the sciatic nerve passes.

What are intervertebral discs?

The intervertebral discs are the circular structures of the vertebral column, composed externally of fibrocartilage and internally of a gelatinous substance ( pulpy nucleus ), which separate the individual vertebrae between them.

Lumbar Spondylolysis

Lumbar spondylolysis is the medical expression that defines a defect or stress fracture of the vertebral arch of a lumbar vertebra.

In most cases, lumbar spondylolysis is the consequence of a repeated microtrauma against the lumbar vertebra involved.

Anyone can develop lumbar spondylolysis; statistics, however, say that this condition is more common among children and adolescents who practice contact sports.

Lumbar Spondylolisthesis

Lumbar spondylolisthesis is a disease of the spine, in which there is an abnormal sliding of a lumbar vertebra on the underlying lumbar vertebra.

Lumbar spondylolisthesis can be a congenital condition or a condition that originates from a trauma to the lumbar vertebrae or from a continuous anomalous stress of the latter.