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navpreet sin
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Exams, Education & References
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7:48 PM on November 28, 2008
Arvind Pal's Answer
The parts that traditionally comprise the hypothalamus are not usually considered as a gland. However, a part of the pituitary gland -- which is a type of gland called an endocrine gland -- is actually just an extension of part of the hypothalamus. So technically, it'd be perfectly reasonable to say that that part of the hypothalamus is also part of an endocrine gland.
Glands come in two types: endocrine and exocrine. Endocrine glands secrete chemicals into the bloodstream, whereas exocrine glands secrete chemicals and fluids out of the body.
The pituitary gland (also called the hypophysis) is one of the body's major endocrine glands. In fact, it is considered the "master gland" of the endocrine system. The pituitary gland can be divided into parts; two major parts are called the anterior pituitary gland and the posterior pituitary gland. "Anterior" means that part is towards the front of the gland; "posterior" means it is towards the back.
Both parts of the pituitary gland, both anterior and posterior, are endocrine glands. But they have very different structures. The structure of the anterior pituitary is reflected in its other name, adenohypophysis; "adeno-" means glandular and refers to the glandular appearance of the anterior pituitary when viewed under a microscope. In contrast, the posterior pituitary is also called the neurohypophysis; "neuro-" refers to the fact that the posterior pituitary resembles tissue of the nervous system when viewed under a microscope.
The two major pieces of the pituitary gland have different microscopic appearances because they come from different areas of the body. The anterior pituitary actually develops from an outpouching of the roof of the mouth early in development. In contrast, the posterior pituitary comes from the gradual extension of the hypothalamus, which lies directly on top of the pituitary gland.
During development, nerve cells (called neurons) of the hypothalamus send long projections (called axons) to form the posterior pituitary. Once they reach the right spot, they set up shop next to a blood vessel. There they organize themselves so that the ends of their projections (called axon terminals) sit right next to the blood vessel wall. These terminals contain little sacs of hormones that get released into the bloodstream whenever the nerve cell is excited.
So yes, it's definitely fair to consider at least a part of the hypothalamus as an endocrine gland.
Answered at
8:20 PM on November 28, 2008
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