Generality
The corpus callosum is the important cerebral commissure that, situated under the cerebral cortex, in the center of the two hemispheres of the brain, serves to join the latter.
Made of white substance, the corpus callosum is about 10 centimeters long, resembles C with the convexity facing upwards and includes more than 200 million commissural fibers.
According to the most classical of anatomical descriptions of the corpus callosum, this latter can be subdivided into 4 characteristic regions, which take the name of: rostrum, knee, trunk and splenium.
The main function of the corpus callosum allows the exchange of motor, sensory and cognitive information between the various lobes of the two cerebral hemispheres.
For reasons that are not yet entirely clear, some individuals are born without the corpus callosum. The total or partial absence of the corpus callosum is called agenesis of the corpus callosum.
Brief anatomical review of the brain proper
The brain proper, or telencephalon or more simply brain, is the most voluminous and important component of the 4 that make up the brain (NB: the other 3 are the cerebellum, the diencephalon and the brainstem).
Contained within the skull (or neurocranium ), the brain basically consists of two large masses mostly homologous of nervous tissue, called cerebral hemispheres, in the middle of which a deep one flows with anteroposterior direction ( axis or sagittal plane ) separatory groove, called interhemispheric groove . All this, therefore, results in the presence of a cerebral hemisphere to the right of the separator groove ( right cerebral hemisphere ) and of a cerebral hemisphere to the left of the separator groove ( left cerebral hemisphere ).
To conclude this brief review of the brain is a note on the subdivision of the brain into gray substance and white substance .
The gray substance corresponds to the most superficial layers of the cerebral hemispheres and constitutes, to all effects, the lamina of nerve cells which takes the name of cerebral cortex and which forms the so-called lobes of the brain ; the white substance, on the other hand, corresponds to the deeper layers of the cerebral hemispheres and represents, in fact, the base of the aforementioned cerebral cortex.
What is the corpus callus?
The corpus callosum, or commensura callosa, is the dense band of nerve fibers located below the cerebral cortex, in the center of the two hemispheres of the brain.
The corpus Callosum is an example of cerebral commissure
As can be guessed from its alternative name, the corpus callosum is an example of cerebral commissure (or cerebral commissure );
In neurology, the term "cerebral commissure" refers to any formation of white or gray substance, similar in appearance to a bundle, a lamina or a band, which associates two mostly homologous zones of the nervous system along the cerebro-spinal axis, by means of nerve fibers called, for the occasion, commissural fibers .
In light of all this, the previous definition of corpus callosum can thus be revised: "the corpus callosum is the band of commissural fibers, constituting the cerebral commissure located below the cerebral cortex, at the center of the two hemispheres of the brain".
Anatomy
The corpus callosum takes place at the center of the brain, between the two hemispheres, below the cerebral cortex.
Composed of about 200 million commissural fibers of small diameter (2 microns), the corpus callosum measures 10 centimeters in length, which makes it the largest commissura of the human nervous system.
Observing it along the sagittal plane (plane that, in the antero-posterior sense, divides the brain into two halves, a right and a left), the corpus callosum resembles a C where, however, the characteristic convexity is turned upwards.
Did you know that ...
The corpus callosum is the largest cerebral commissure of the human nervous system.
Relationships of proximity of the corpus Callosum
The corpus callosum is bordered by:
- The interhemispheric sulcus and the so-called cerebral sickle, above.
The cerebral sickle is a particular extension of the meningale dura mater, which creeps into the interhemispheric groove;
- The so-called induseum griseum, always superiorly.
Arranged so as to cover the corpus callosum, the induseum griseum is a thin layer of gray matter belonging to the dorsal section of the hippocampus (the latter being a nervous component of the temporal lobe);
- The callous furrow (or furrow of the corpus callosum ), on both sides.
This cerebral sulcus is the groove that separates the corpus callosum from the cingulate convolution (or circumvolution of the cingulum) of the frontal lobe ;
- The pellucid septum and the thalamus, below.
The pellucid septum is the lamina of white substance that contributes to form the medial wall of the lateral ventricle .
The thalamus is a portion of the diencephalon, which is one of the main components of the brain.
Composition of the Callous Body
The corpus callosum is a cerebral commissura of white substance.
In neurology, the term "white substance" refers to the central nervous system tissue composed of neurons whose axons are coated with the so-called myelin sheath (NB: this is in contrast to the gray substance, which is the central nervous system tissue composed of neurons whose axons are devoid of myelin sheath).
Subdivisions of the corpus Callosum
According to the most traditional of anatomical descriptions of the corpus callosum, this latter can be divided into 4 regions which, in the antero-posterior sense (ie proceeding from the front to the back of the head), are: the rostrum, the knee, the trunk and the splenium .
ROSTRUM
The rostrum of the corpus callosum is pointed and corresponds to the site of the commissural fibers, which connect the lower surface of the two frontal lobes, one on the right cerebral hemisphere and one on the left cerebral hemisphere.
It precedes the stretch called knee.
KNEE
Placed between rostrum and trunk, the knee of the corpus callosum is a gentle curvature, in which reside the commissural fibers that connect the medial and lateral surfaces of the two frontal lobes.
TRUNK
Including between knee and splenium, the trunk is the largest part of the corpus callosum. In the area of his competence, there is a part of the commissural fibers that connect the right temporal lobe with the left temporal lobe and the right occipital lobe with the left occipital lobe.
splenius
Next to the trunk, the splenium is the terminal part of the corpus callosum; it includes the remaining part of commissural fibers which bring the right temporal lobe into communication with the left temporal lobe and the right occipital lobe with the left occipital lobe.
Blood supply of the Callous Body
The influx of oxygenated blood to the corpus callosum, essential for keeping the latter alive, depends on the pericallosa artery and the posterior pericallosa artery .
In some individuals, the blood supply from the subcallary artery and / or the median callous artery may be added to the blood supply provided by the aforementioned arteries.
- The pericallosa artery is a branch of the anterior cerebral artery, which is one of the branches of the internal carotid artery; it is the main supplier of oxygenated blood of the corpus callosum.
- The posterior pericallosa artery is a branch of the posterior cerebral artery, which originates from the basilar artery; this artery supplies the splenium of the corpus callosum with oxygenated blood.
- The subcallus artery and the median callous artery are two branches of the anterior communicating artery. Both supply the rostrum and knee of the corpus callosum with oxygenated blood, but only the medium callous artery also nourishes the portion called the body.
Development
The corpus callosum usually takes place between the 12th and 16th week of gestation (in any case, within the first trimester of pregnancy). From this moment on, he is the protagonist of a slow process of growth and development, which continues even for several years after birth; the corpus callosum, in fact, grows throughout childhood and the first childhood, up to about 12 years .
Once the growth process is completed at the age indicated above, its size will remain unchanged for the rest of life.
Function
The corpus callosum covers various functions.
First of all, it has the task of joining the two cerebral hemispheres and allowing the exchange of motor, sensory and cognitive information between the various areas (eg: the lobes of the brain) of these two important masses of nervous tissue.
The passage of motor, sensory and cognitive information between the two cerebral hemispheres, deriving from the presence of the corpus callosum, is called interhemispheric communication.
Secondly, it supports eye movement, vision, attention and excitement management, and tactile localization.
Did you know that ...
The discovery of the functions of the corpus callosum dates back to 1955. The merit of this discovery belongs to Ronald Myers, a graduate of the University of Chicago.
diseases
From the clinical-pathological point of view, the corpus callosum is known for a congenital condition (ie present since birth) called agenesis of the corpus callosum .
The agenesis of the corpus callosum is, quite simply, the partial or total absence of the corpus callosum.
Causes of agenesis of the corpus callosum
The agenesis of the corpus callosum occurs when the fetal developmental process of the brain undergoes a hitch between the III and the XII week of gestation.
Although it requires several in-depth studies, the scientific research conducted up to now on the causes of the aforementioned hitch suggests that factors such as: prenatal infections, genetic aberrations, hereditary mutations, fetal exposure to toxic substances, the formation of a cyst at the encephalic etc.
Symptoms of corpus callosum agenesis
Possible symptoms of corpus callosum agenesis include: vision problems, muscular hypotonia, poor motor coordination, reduced perception of pain, difficulty in chewing and swallowing, delayed acquisition of motor skills such as sitting or walking, epilepsy, spasticity, hearing problems, facial abnormalities and abnormalities of the skull.
It should be pointed out that the symptomatological picture of callous body agenesis can vary considerably from patient to patient, therefore it is difficult to draw up a list of typical clinical manifestations.
Medical conditions associated with the agenesis of the corpus callosum
Corpus callosum agenesis is often associated with other medical conditions; among the latter deserve a mention: Aicardi syndrome, Andermann syndrome, Shapiro syndrome, acrocallosa syndrome, optic nerve hypoplasia, Menkes syndrome and Mowat-Wilson syndrome.
The reason for the frequent association between the aforementioned medical conditions and the agenesis of the corpus callosum is the subject of scientific studies.
