Endocrine system part II

Histology 2016-2017
Department of Anatomy &Histology: Dr.Rajaa Ali
***********************************************************
Endocrine system part II
Hypothalamus:
The hypothalamus regulates pituitary gland activity.
The hypothalamus is located in the middle of the base of the brain, and it encapsulates the ventral portion of the third ventricle.
It coordinates most endocrine functions of the body and serves as one of the major controlling centers of the autonomic nervous system.
Some of the functions that it regulates include blood pressure, body temperature, fluid and electrolyte balance, body weight, and appetite.
The hypothalamus produces numerous neurosecretory products. In addition to oxytocin and ADH, hypothalamic neurons secrete polypeptides that promote and inhibit the secretion and release of hormones from the anterior lobe of the pituitary gland.

Pineal Gland:
The pineal gland (pineal body, epiphysis cerebri) is an endocrine or neuroendocrine gland that regulates daily body rhythm.
It develops from neuroectoderm of the posterior portion of the roof of the diencephalon and remains attached to the brain by a short stalk, it is located at the posterior wall of the third ventricle near the center of the brain.
The pineal gland is a flattened, pine cone–shaped structure, hence its name.
The pineal gland contains two types of parenchymal cells:
Pinealocytes and interstitial (glial) cells.
Pinealocytes are the chief cells of the pineal gland. They are arranged in clumps or cords within lobules formed by connective tissue septa that extend into the gland from the pia mater that covers its surface.
The interstitial (glial) cells constitute about 5% of the cells in the gland. They have staining and ultrastructural features that closely resemble those of astrocytes. In addition to the two cell types, the human pineal gland is characterized by the presence of calcified concretions, called corpora arenacea or brain sand (Fig. 1).
The human pineal gland relates light intensity and duration to endocrine activity.The pineal gland is a photosensitive organ and an important timekeeper and regulator of the day/night cycle (circadian rhythm).