Overview of the pineal gland.
is a pinecone-shaped neuroendocrine gland about 8 mm
in length that produces
and is covered by a capsule of pia mater.
The pineal gland is part of the epithalamus (a diencephalic structure) that
extends caudally from its attachment immediately superior to the poste-
rior commissure into the superior (quadrigeminal) cistern. It is superior
to the colliculi of the midbrain. Secretion of melatonin is stimulated by
darkness and inhibited by light. The level of this hormone increases dur-
ing sleep. Connective septa divide the pineal into poorly deF ned lobules.
This gland contains
CalciF ed concretions called
may also be present in the pineal gland, especially in older patients.
Pinealocytes and brain sand of the pineal gland.
is composed of two types of cells:
are modiF ed neurons, which have
round or ovoid nuclei with pale-stained cytoplasm containing granules
F lled with
. The pinealocytes synthesize
, which is
important in the regulation of the
(day and night
cycles). The pinealocytes are larger than the neuroglial cells and have
a long cytoplasmic process that extends to the capillaries; their secre-
tory granules are released into the capillaries. The
supportive cells with small, dark nuclei. They are also called
and are commonly found near the capillaries. The particles
of brain sand assume various sizes as shown here; their function is not
known. Other functions of the pineal gland may relate to promoting
sleep and sexual development; enhancing mood and slowing the aging
process; and, possibly, inhibiting the growth of some tumors.
) within the pineal gland increase with
age. These calciF cations appear white in computed tomography
scan and magnetic resonance imaging and are commonly used as a
natural landmark by radiologists and neurologists.
is an aggressive malignant tumor in children, which
arises in the pineal gland. Because it commonly consists of cellular
sheets that lack an architectural pattern, it is described as a
. The term
is also used to emphasize the rudi-
mentary developmental stage of the tumor, although in some tumors
the cells begin to show differentiation into neurons, or glial cells, or
even rods and cones. The earliest stages of such specialization may
be detectable before any architectural alteration.
protein associated with synapses. An antibody to this marker protein,
conjugated to the enzyme peroxidase, creates a colored metabolite
wherever synaptophysin appears in cell cytoplasm or membranes. In
the image on the
, a brown compound marks the
contain synaptophysin. Tumor treatments can be individually formu-
lated based on the different cellular components.
tumor cell cytoplasm