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Varolium bridge: structures, characteristics and functions

Varolium bridge: structures, characteristics and functions

October 1, 2022

The Varolium bridge, also known as annular protrusion or brainstem bridge, is one of the most important parts of the brain. In fact, a small lesion in this structure could lead to sudden death or entry into a coma.

The reason for the importance of the Varolium bridge is that it is one of the largest portions of a structure known as brainstem, responsible among other things for maintaining automatic mechanisms that keep us alive.

Next we will see the anatomy, the parts and the functions of the ring protuberance, as well as the health problems that can be triggered if there are alterations in their behavior due to injuries or illnesses.


  • Related article: "Parts of the human brain (and functions)"

What is the Varolio bridge?

The trunk-fetal bridge it is the most bulky part of the brainstem , reason why also it receives the name of annular protuberance. It is located between the other two main anatomical structures of this portion of the brain; on the upper part, it borders the mesencephalon, while its lower edge is in contact with the medulla oblongata.

The limit that separates the annular protuberance of the medulla oblongata is the protuberant groove, while its border with the mesencephalon is the pontone-encephalic sulcus.

Anatomy of the annular protrusion

Like any other region of the central nervous system, the lump is composed mainly of neurons and glial cells. However, in this region of the brain The bundles of axons are of special importance that go vertically from the brain to the spinal cord to the brain and vice versa. That is to say, that the annular protuberance acts in part as a means of communication between two large portions of the central nervous system.


However, the Varolium bridge also contains bundles of neurons that are distributed projecting to the sides, forming the beginnings of the middle cerebellar peduncles, which are two of the areas through which the brainstem connects to the cerebellum.

Another of the most remarkable anatomical features of the Varolium bridge is that its front face, the closest to our face, It is convex, bulging outward , which makes it stand out a lot about the other two main structures of the brainstem.

Inside the Varolio bridge the basilar groove is found , a small space through which crosses the basilar artery, one of the main responsible for keeping the cells of large areas of the brain alive.

In addition, the protuberance forms the beginning of the trigeminal nerve, one of the most important cranial nerves.


Parts of the trunk bridge

The ring protuberance is formed by a set of cores , consisting of groups of associated neurons that are responsible for similar functions. They are the following.

Abductor motor somatic nucleus

A nucleus of neurons linked to the cranial nerve known as the abducens nerve, responsible for the movement of the abduction of the eye.

Trigeminal special motor core

The functions of this nucleus have to do with the trigeminal nerve, and consist basically of visceral movements.

Special motor core of the facial

Like the previous one, it takes care of certain visceral movements.

Superior salivatory nucleus

The functions of this nucleus are vegetative, and therefore automatic.

Its functions

The functions of the Varolio bridge are diverse, although almost all are of great importance for survival.

1. Communication link

The ring protrusion acts as a bridge between groups of neurons that, if they do not go through this structure, they would be cut off from each other. It allows information to flow from inside the skull outwards and vice versa.

2. Motor coordination

The Varolium bridge works in conjunction with the cerebellum and other structures , as the basal ganglia, to allow the automatic and unconscious coordination of muscle groups. This makes it possible for us to maintain the balance in an upright position, for example.

  • Maybe you are interested: "Human cerebellum: its parts and functions"

3. Homeostatic regulation

The ring protrusion plays an essential role in functions such as regulation of temperature and other basic physiological processes , like the heartbeat.

Regulation of consciousness

This region of the brainstem is traversed by the reticular formation, and for that reason it plays a role in the regulation of states of consciousness. It intervenes in the circadian cycles of sleep and wakefulness, and also makes consciousness, in itself, something possible.

Injuries and associated diseases

The destruction or alteration of the normal functioning of the Varolium bridge It has very serious consequences , since it affects very basic and necessary processes to stay alive.

This is because a failure in this region of the brain may cause insufficient blood or oxygen to reach the brain , producing death by hypoxia.

The diseases that can affect this structure are several, but include Alzheimer's disease and Parkinson's , since both damage large regions of the central nervous system and impede the normal functioning of networks of neurons.


Valorium Guide | DC Unchained (October 2022).


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