Pineal gland, sheep - H&EThe parenchyma of the pineal gland looks rather homogeneous at low magnification. A few blood vessels are visible criss-crossing through the gland. At higher magnification three types of nuclei can be distinguished. Small dark nuclei belong to the astrocytes found in the pineal gland. Pinealocytes have larger, lighter and round nuclei, which are surrounded by a broad rim of light cytoplasm. Most nuclei present are the nuclei of pinealocytes. Endothelial cell nuclei are found in association with the vessels and capillaries traversing the tissue. Both pinealocytes and astrocytes have long processes which give the tissue between the nuclei its "stringy" appearance.Brain sand is not visible in this section.Draw a small part of the parenchyma of the pineal gland at high magnification. Label pinealocytes and astrocytes.
PINEAL GLAND<br /><ul><li>Also called Epiphysis Cerebri.
The pineal gland is a pine cone shaped gland of the endocrine system.
The gland is a conical, grey body measuring 5 to 8mm in length and 3 to 5mm in its greatest width.
A structure of the diencephalon of the brain, the pineal gland produces several important hormones including melatonin.</li></li></ul><li><ul><li>Melatonin influences sexual development and sleep-wake cycles.
The pineal gland is composed of cells called pinealocytes and cells of the nervous system called glial cells.
The pineal gland connects the endocrine system with the nervous system in that it converts nerve signals from the sympathetic system of the peripheral nervous system into hormone signals.</li></li></ul><li>
Function:<br />The pineal gland is involved in several functions of the body including: <br />Secretion of the Hormone Melatonin<br />Regulation of Endocrine Functions<br />Conversion of Nervous System Signals to Endocrine Signals<br />Causes Feeling of Sleepiness<br />Influences Sexual Development<br />
HISTOLOGICAL ORGANIZATION<br />Pia Mater - the delicate inner layer of connective tissue that covers the brain.<br />Surrounding the pineal body.<br />which functions as its capsule and which sends connective tissue septa into the pineal body, subdividing it into lobules.<br />In the pineal we find two cell types: pinealocytes (about 95% of the cells; large, light and round nuclei) and astrocytes (glial cells; dark, elongated nuclei).<br />
Aside from the cells the pineal gland also contains sand - well - brain sand (or acervulicerebri or - just for good measure - corpora arenacea). <br />These are calcium-containing concretions in the pineal parenchyma, which increase in size and number with age. These concretions are radioopaque, and, since the pineal is located in the midline of the brain, they provide a good midline-marker.<br />They have no other known function.<br />
Continuation..<br />Interstitial cells – cells of the second type found among the pinealocytes and in greater number in the stalk of the gland.<br />Their nuclei are elongated and stain more deeply than those of the pinealocytes.<br />They resemble the astrocytes of the brain in having long-cell process and an abundance of intermediate filaments throughout the cytoplasm.<br />The pineal gland of humans, and a few other species, concretions called CORPORA ARENACEA or BRAIN SAND.<br />
These bodies consist of calcium phosphates and carbonates in an organic matrix deposited in concentric layer.<br />They are not regarded as pathological fir they appear in early childhood and increase in size and number with advancing age.<br />Calcified corpora arenacea are visible in in X-rays or CAT scans of the head in 80% of individuals of 30 years of age. <br />
The most prominent secretory product of the pineal body is melatonin.<br />The cocktail of substances released by the pinealocytes can have several functions: <br />they may decrease secretory activity in most other endocrine glands (in part indirectly, by way of influencing hypothalamic neurones),<br />and they may "delay" puberty through antigonadotrophiceffects.<br />Secretory activity in the pineal gland is stimulated by darkness and inhibited by light. <br />
Via the effects of pineal hormones on the adenohypophysis and sex hormones it is likely that the pineal body is involved in phenomena associated with the circadian rhythm and seasonal phenomena (e.g. seasonal affective disorder, SAD).<br />The pineal body is innervated by postganglionic sympathetic fibres derived from the superior cervical ganglion.<br />