PG
Pineal Gland
Small endocrine gland regulating circadian rhythm
RegionNeuroanatomy
SystemEndocrine System
What is the Pineal gland?
The pineal gland is an endocrine gland located in the epithalamus, near the center of the human brain. As it is one of the endocrine glands it secretes its product, the hormone called melatonin, directly into the blood. Sleep patterns are considered to be modulated by this hormone as its production is stimulated by the absence of light. The pineal gland has also other functions in the central nervous system but these will be discussed more about later in this text. Its name, the pineal gland owes to the shape it has. It is the shape which resembles a pine cone and some other names that are used to refer to this part of the human anatomy are the pineal body, conarium and the epiphysis cerebri. The pineal gland is a shared feature between most vertebrates with the exception of few and it has been a subject of both scientific and pseudoscientific research for a long time. As a subject of the scientific research, the pineal gland, remains not completely understood even in the twenty first century. In pseudoscience it has been a subject of great interest for many centuries. Supernatural characteristics have been attributed to the pineal gland in many cultures. It has been considered to be a type of a “third eye” or a sort of a connection between the physical and the spiritual domain. The central position it takes inside the brain has, before its physical functions have been discovered, always been a cause for the pineal gland to be considered a mystical part of the body connected with psychic and supernatural powers.
Picture 1: Pineal gland diagram
Where is Pineal gland located?
The pineal gland is located in the thalamus, at the central part of the brain, between the two hemispheres. More specifically, the pineal gland is located behind the third ventricle and the habenular commissure (Nerve fiber bands which connect the diencephalon sides with the habenular nuclei. The principal regulator of the neurotransmitter of the central nervous system). It is inserted deep into the brain and inside a trench located between the two halves of the thalamus.Structure of Pineal gland
The characteristic shape of the pineal gland has already been mentioned previously in this text and it was said that it resembles a pine cone in appearance. This pine cone-like structure is approximately five to eight millimeters in diameter which, size wise, makes it a small endocrine gland. This glandular tissue structure is coated with cerebrospinal fluid which is provided by the third ventricle through the pineal recess.[2]
Picture 2: Structure and Location of Pineal gland
The structure of the pineal gland is very similar to the structure of the rest of the nervous system. Its body is mostly formed by a type of soft tissue called parenchyma containing pinealocytes, the pineal gland cells, embedded in its structure. On all sides, it is covered by the connective tissue and the pia mater layer which is encapsulating the body of the pineal gland5. The pinocyte or the pineal parenchymal cell is categorized as a specialized neuron and it is surrounded by four other different cells in this small structure:- Peptidergic neuron-like cells
- Perivascular phagocyte
- Interstitial cells
- Pinealocytes
Function
The pineal gland's main function is the production of its hormone called melatonin. The production of this hormone is stimulated by changes in the illumination levels, more specifically, it is inhibited by low light levels or darkness. [5]This role of the pineal gland is very important for establishing the so called day-night cycle which is one of the most important cycles when it comes to the functioning of the human brain and body as a whole. This function of melatonin production is by far the most significant function of the pineal gland although the complete influence of this hormone, on the processes developing inside the human body, has not yet been fully understood. Some studies performed on rodents have given results implying that the pineal gland can affect the secretion of the sex hormones (Follicle-stimulating hormone (FSH) and the Luteinizing hormone (LH)) and that it can affect the actions of drugs such as antidepressants and cocaine through the protective role its hormone melatonin has in reversing the neurodegeneration process.[7] The complete range of functions which can be attributed to the pineal gland is still very much a matter of more scientific research and debate and it will probably remain like that for some time in the future.[1]Clinical significance
A condition which is typically affecting the pineal gland is the calcification. This is a process which is thought to be very much connected with the so called “brain sand” or the corpora arenacea collecting inside the pineal gland, and it can easily be observed through the brain X-ray10. It is a condition which develops progressively with aging but it can also affect children as young as two years.[8] Some studies have also shown a connection between the calcification and Alzheimer’s disease, with the higher level of calcification of the pineal gland being present in patients suffering from Alzheimer’s than in those affected by other types of dementia. High levels of calcification in children have been connected with a more rapid development of bones and reproductive organs. Migraines have also been associated with the pineal gland calcification. Another relatively common imagenological finding related with the pineal gland are the cysts, as they can be present in up to 10% of patients that need an MRI or the CT scan examination for another cause. The presence of cysts in the pineal gland can be completely asymptomatic, in rare cases there are some symptoms that can be explained by the effect of the mass or the size of the cyst and this is the reason why the symptoms vary depending on the severity of the condition. These symptoms usually are:- Headache
- Migraine
- Parinaud syndrome (impossibility of moving the eyes in the up direction)
- Problem with the movement of the eyes.
- Vertigo
- Difficulties for moving
- Disrupted sleep pattern
- Secondary parkinsonism
- Epilepsy
- Chicken
- Turkey
- Almond
- Sweetcorn
- Peanuts
Published on June 27, 2017
Last updated on April 24, 2025
Last updated on April 24, 2025