THE PITUITARY GLAND

INTRODUCTION: The pituitary gland (or hypophysis) hangs by a short stalk also known as, infundibulum, from the hypothalamus and is enclosed by the sella turcica of the sphenoid bone. Despite its small size, the pituitary gland regulates many body functions. Its two major portions are the posterior pituitary gland also known as neurohypophysis, which is an extension of the nerve tissue of the hypothalamus, and the anterior pituitary gland also known as, adenohypophysis, which is separate glandular tissue.

POSTERIOR PITUITARY GLAND: The two hormones of the posterior pituitary gland are actually produced by the hypothalamus and simply stored in the posterior pituitary until needed. Their release is stimulated by nerve impulses from the hypothalamus.

Antidiuretic Hormone: Antidiuretic hormone, ADH, also called vasopressin, increases the reabsorption of water by kidney tubules, which decreases the amount of urine formed. The water is reabsorbed into the blood, so as urinary output is decreased, blood volume is increased, which helps maintain normal blood pressure. ADH also decreases sweating, but the amount of water conserved is much less than that conserved by the kidneys. The stimulus for secretion of ADH is decreased water content of the body. 

PATHOPHYSIOLOGY: If too much water is lost through sweating or diarrhea, for example, osmoreceptors in the hypothalamus detect the increased “saltiness” of body fluids. The hypothalamus then transmits impulses to the posterior pituitary to increase the secretion of ADH and decrease the loss of more water in urine. Any type of dehydration stimulates the secretion of ADH to conserve body water. In the case of severe hemorrhage, ADH is released in large amounts and will also cause vasoconstriction, especially in arterioles, which will help to raise or at least maintain blood pressure. This function gives ADH its other name, vasopressin.

ALCOHOL AND PITUITARY HORMONES: Ingestion of alcohol inhibits the secretion of ADH and increases urinary output. If alcohol intake is excessive and fluid is not replaced, a person will feel thirsty and dizzy the next morning. The thirst is due to the loss of body water, and the dizziness is the result of low blood pressure.

RELATED;

1. HORMONES

2. BLOOD PRESSURE

3. ALCOHOL AND ITS USE

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