Corpora arenacea (''
singular
Singular may refer to:
* Singular, the grammatical number that denotes a unit quantity, as opposed to the plural and other forms
* Singular homology
* SINGULAR, an open source Computer Algebra System (CAS)
* Singular or sounder, a group of boar ...
'': corpus arenaceum, also called brain sand or acervuli or psammoma bodies
or pineal concretions
) are
calcified structures in the
pineal gland
The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal ...
and other areas of the
brain
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head ( cephalization), usually near organs for special ...
such as the
choroid plexus
The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central ne ...
. Older organisms have numerous corpora arenacea, whose function, if any, is unknown. Concentrations of "brain sand" increase with
age, so the pineal gland becomes increasingly visible on
X-rays
X-rays (or rarely, ''X-radiation'') are a form of high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 and named it ' ...
over time, usually by the third or fourth decade. They are sometimes used as anatomical landmarks in
radiological examinations.
Chemical analysis shows that they are composed of
calcium phosphate
The term calcium phosphate refers to a family of materials and minerals containing calcium ions (Ca2+) together with inorganic phosphate anions. Some so-called calcium phosphates contain oxide and hydroxide as well. Calcium phosphates are wh ...
(later characterized as
hydroxyapatite
Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca5(PO4)3(OH), but it is usually written Ca10(PO4)6(OH)2 to denote that the crystal unit cell comprises two entities ...
),
calcium carbonate,
magnesium phosphate
Magnesium phosphate is a general term for salts of magnesium and phosphate appearing in several forms and several hydrates:
* Monomagnesium phosphate (Mg(H2PO4)2).xH2O
* Dimagnesium phosphate (MgHPO4).xH2O
* Trimagnesium phosphate (Mg3(PO4)2 ...
, and
ammonium phosphate
Ammonium phosphate is the inorganic compound with the formula (NH4)3PO4. It is the ammonium salt
Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the fo ...
. Recently,
calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...
deposits have been described as well.
References
Further reading
*
*
*
*
External links
*
* - "Pineal gland"
Epithalamus
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