Pineal gland (or epiphysis): functions and anatomy

March 29, 2024

Within the encephalon there are numerous structures with very diverse functions, which are connected with a large number of body systems. Although we can generally consider that the nervous system has an effect on other body systems, some of the structures that are part of it are also considered part of other body systems.

It is the case of the pineal gland or epiphysis , which besides part of the nervous system is an important part of the endocrine system.

Pineal gland or epiphysis

Considered by René Descartes as the place where the animal spirits that governed processes such as sensitivity, imagination, impulsivity or emotion lived, the nerve center where the human soul lived, the pineal gland has been studied for many centuries .

The first records on the study of this structure date from the third century BC, in which it was proposed that it regulated the flow of thoughts. Later it would be analyzed by Galeno, Descartes and other multiple thinkers and professionals from various fields. The study of the pineal gland advanced and deepened especially since the 20th century, in which began to study their functions scientifically from the study of cases of patients with tumors in this area.

To this day, we know that the pineal gland or epiphysis is a structure located in the dorsomedial part of the diencephalon, between the superior colliculi and over the third cerebral ventricle . Is about an endocrine regulatory center that participates in a multitude of different processes fundamental for the development of the organism, sending to the sanguineous circuit different hormones.

With a shape similar to that of a cone of a pine (resemblance from which it derives its name), the pineal gland has interesting properties, since It has been shown to be photosensitive, reacting to the level of ambient lighting . In the same way, it seems to be affected by external chemicals and even electromagnetic waves.

Irrigation and innervation

The pineal gland is strongly irrigated at the blood level, at a level similar to that of the kidneys. It is a structure that participates actively in the secretion of various hormones , the main one being melatonin but also influencing the emission of the follicle-stimulating and luteinizing hormones. Later these hormones reach the blood, which carries them to their target organs.

As regards the nerve connections of the pineal gland, it is innervated by the autonomic nervous system, both by the sympathetic and parasympathetic branches. At the sympathetic level, its main nervous connection is the superior cervical ganglion. With regard to the lymph nodes that innervate it at the parasympathetic level, we can find the otic and pterygopalatine ganglion.

Main functions: what does it participate in?

The pineal gland is a relevant structure and linked to different situations. Being part of both the nervous system and the endocrine system, its basic functioning is the emission of various hormones that will alter different brain and other body systems. Specifically we can establish that some of The main functions of this structure are the following .

1. Regulation of biorhythms

The pineal gland is the part of the brain that, in reaction to the amount of light present in the environment, is responsible for secreting melatonin. Synthesized from serotonin, this hormone is involved in the regulation of circadian and infradian rhythms, so being the main secretor of melatonin, the epiphysis has a primordial function in regulating the sleep-wake cycle.

When the visual information coming from the optic nerve reaches the epiphysis (having passed through the suprachiasmatic nucleus) superior cervical ganglion, indicates that the ambient illumination is low or non-existent, the pineal gland proceeds to secrete the hormone known as melatonin , which will subsequently be sent to different brain regions. In the presence of illumination, however, the production of melatonin is inhibited.

2. Development and maturation

Some of the medical cases that in modern times have stimulated the investigation of the pineal gland or epiphysis reflected a fact that has subsequently been confirmed experimentally: the epiphysis has a great relevance when it comes to establishing the onset of puberty . In these cases adolescents with tumors in this gland manifested precocious puberty. Subsequent investigations have put this fact in relation to the melatonin production of this structure .

During the first years of life the pineal gland is strongly activated, with melatonin production declining towards eight to twelve years, when the first physiological changes that will culminate with the passage from child to adult begin to take shape. Thus, through various investigations It has been shown that the activity of the pineal gland delays puberty , beginning this stage of life when it is less active. In other words, another of the main functions of the pineal gland is to regulate the entrance to sexual maturity.

3. Sexual behavior

The pineal gland participates actively in the secretion of various hormones, among which are some of those that govern the menstrual cycle in women, specifically luteinizing and follicle-stimulating hormones.

In addition to this, by regulating the biological rhythms through melatonin, the epiphysis also influences seasonal sexual behavior in other animal species. The pineal gland interacts with other structures linked to sexuality , like for example the septal nuclei, to guarantee the correct functioning in this activity so important from the point of view of the evolution.

4. Emotion and happiness

The participation of the pineal epiphysis or gland in the emotional sphere has a great relevance. In addition to other hormones with an effect on mood, the pineal gland participates in the generation of endorphins, the hormones that cause states of happiness and allow pain to be regulated . In fact, its involvement in the limbic system makes it a fundamental component of emotional processes, which depend on the interaction between the brain and organs distributed by the body that secrete hormones.

5. Pigmentation

While it may not seem as relevant as the previous ones, the melanin secreted by the pineal gland It participates in the pigmentation of the skin, giving a slightly dark tone in multiple species. This function is secondary, and in fact there are genetic variants of the human being in which melanin has little effect on the way in which the skin tone changes. On the other hand, in cases of albinism this function disappears, with all the biological and social problems that this entails.

6. Participation in other aspects

Regardless of their participation in the previously mentioned, the pineal gland participates in other processes. For example, it has been shown that it has to do with the regulation of body temperature . Likewise, the hormones that it generates also have an effect in aspects such as attention, concentration, memory and other higher mental functions . Keep in mind that virtually any brain structure linked to the secretion of hormones has an effect on cognition, and the pineal gland is no exception.