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The septum pellucidum (
Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...
for "translucent wall") is a thin, triangular, vertical double membrane separating the anterior horns of the left and right
lateral ventricles The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively. Each lateral ventricle resemble ...
of the
brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...
. It runs as a sheet from the
corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...
down to the fornix. The septum is not present in the syndrome
septo-optic dysplasia Septo-optic dysplasia (SOD), known also as de Morsier syndrome, is a rare congenital malformation syndrome that features a combination of the underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum (a ...
.


Structure

The septum pellucidum is located in the
septal area The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loca ...
in the midline of the brain between the two
cerebral hemisphere The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres. Each of these hemispheres ...
s. The septal area is also the location of the
septal nuclei The septal area (medial olfactory area), consisting of the lateral septum and medial septum, is an area in the lower, posterior part of the medial surface of the frontal lobe, and refers to the nearby septum pellucidum. The septal nuclei are loca ...
. It is attached to the lower part of the
corpus callosum The corpus callosum (Latin for "tough body"), also callosal commissure, is a wide, thick nerve tract, consisting of a flat bundle of commissural fibers, beneath the cerebral cortex in the brain. The corpus callosum is only found in placental mam ...
, the large collection of nerve fibers that connect the two cerebral hemispheres. It is attached to the front forward part of the fornix. The
lateral ventricle The lateral ventricles are the two largest ventricular system, ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right ventricle, respectively. Each lateral ...
s sit on either side of the septum. The septum pellucidum consists of two layers or ''laminae'' of both
white White is the lightest color and is achromatic (having no hue). It is the color of objects such as snow, chalk, and milk, and is the opposite of black. White objects fully reflect and scatter all the visible wavelengths of light. White on ...
and
gray matter Grey matter is a major component of the central nervous system, consisting of neuronal cell bodies, neuropil (dendrites and unmyelinated axons), glial cells (astrocytes and oligodendrocytes), synapses, and capillaries. Grey matter is distinguis ...
. During fetal development, there is a space between the two laminae called the
cave of septum pellucidum The cave of septum pellucidum (CSP), cavum septi pellucidi, or cavity of septum pellucidum is a slit-like space in the septum pellucidum that is present in fetuses but usually fuses during infancy. The septum pellucidum is a thin, laminated transl ...
that, in ninety percent of cases, disappears during infancy. The ''cavum'' was occasionally referred to as ''the fifth ventricle'', but this is no longer used because the space is usually not continuous with the
ventricular system The ventricular system is a set of four interconnected cavities known as cerebral ventricles in the brain. Within each ventricle is a region of choroid plexus which produces the circulating cerebrospinal fluid (CSF). The ventricular system is con ...
. The fifth ventricle is recognised as the terminal enlargement of the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...
.


Clinical significance

Absence of the septum pellucidum occurs in
septo-optic dysplasia Septo-optic dysplasia (SOD), known also as de Morsier syndrome, is a rare congenital malformation syndrome that features a combination of the underdevelopment of the optic nerve, pituitary gland dysfunction, and absence of the septum pellucidum (a ...
, a rare developmental disorder usually characterized by abnormal development of the
optic disk Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
and
pituitary In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypop ...
deficiencies. Symptoms of septo-optic dysplasia are highly variable and may include vision difficulties, low muscle tone, hormonal problems, seizures, intellectual problems, and
jaundice Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...
at birth. Management is directed at the symptoms a person is affected with.


Additional images

File:Gray744.png, Cross-section of the brain showing the septum pellucidum sitting between the two lateral ventricles, and beneath the corpus callosum File:Slide5oo.JPG, Septum pellucidum (labelled "septum lucidum") seen in a specimen from a
cadaver A cadaver or corpse is a dead human body that is used by medical students, physicians and other scientists to study anatomy, identify disease sites, determine causes of death, and provide tissue to repair a defect in a living human being. Stud ...
.


See also


References


External links

{{Authority control Cerebrum Ventricular system