Pituitary gland

Pituitary gland
Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica of the sphenoid bone.
Median sagittal through the hypophysis of an adult monkey. Semidiagrammatic.
Latin	hypophysis, glandula pituitaria
Gray's	subject #275 1275
Artery	superior hypophyseal artery, infundibular artery, prechiasmal artery, inferior hypophyseal artery, capsular artery, artery of the inferior cavernous sinus
Precursor	neural and oral ectoderm, including Rathke's pouch
MeSH	Pituitary+Gland
Dorlands/Elsevier	h_22/12439692

The pituitary gland, or hypophysis, is an endocrine gland about the size of a bean that sits at the base of the brain. It is located in a small, bony cavity called the pituitary fossa, which is situated in the sphenoid bone in the middle cranial fossa. The pituitary gland is connected to the hypothalamus of the brain by the infundibulum and is covered by the sellar diaphragm fold.

The pituitary gland, often called the "master gland," is actually two fused glands, each made up of different tissue types. The individual glands merge during embryonic development. The tissue that forms the roof of the mouth also forms the anterior pituitary, a true endocrine gland of epithelial origin. The posterior pituitary, on the other hand, is an extension of neural tissue.

The pituitary gland secretes various hormones regulating homeostasis, including trophic hormones that stimulate other endocrine glands. It also secretes hormones for sexual eminence and desires.

Sections

Located at the base of the brain, the pituitary is functionally linked to the hypothalamus. It is divided into two lobes: the anterior or front lobe (adenohypophysis) and the posterior or rear lobe (neurohypophysis).

Anterior pituitary (adenohypophysis)

The anterior lobe is derived from the oral ectoderm and is composed of glandular epithelium. The anterior pituitary is functionally linked to the hypothalamus via the hypophyseal- portal vascular connection in the pituitary stalk. Through this vascular connection the hypothalamus integrates stimulatory and inhibitory central and peripheral signals to the five phenotypically distinct pituitary cell types.

The anterior pituitary synthesizes and secrets six important endocrine hormones:

• Adrenocorticotropic Hormone (ACTH)
• Thyroid stimulating hormone (TSH)
• Prolactin
• Growth hormone (also called somatotrophin
• Follicle stimulating hormone (FSH)
• Leutinizing hormone (LH).

These hormones are released from the anterior pituitary under the influence of hypothalamic hormones. The hypothalamic hormones travel to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophyseal portal system. Once the hormone is released, it either targets another gland (or organ) or it controls the secretion of another hormone from a gland. In that case, the first hormone is called a trophic hormone.

The control of hormones from the anterior pituitary exerts a negative feedback loop. Their release is inhibited by increasing levels of hormones from the target gland on which they act.

Posterior pituitary (neurohypophysis)

The posterior lobe is connected to the hypothalamus via the infundibulum (or stalk), giving rise to the tuberoinfundibular pathway. Hormones are made in nerve cell bodies positioned in the hypothalamus, and these hormones are then transported down the nerve cell's axons to the posterior pituitary. They are stored in the posterior pituitary in cell terminals until a stimulus reaches the hypothalamus, which then sends an electrical signal to the posterior pituitary to release the hormone(s) into circulation.

The hormones released by the posterior pituitary are:

• Oxytocin
• Antidiuretic hormone (ADH, also known as vasopressin and AVP, arginine vasopressin)

Intermediate lobe

There is also an intermediate lobe in many animals. For instance, in fish it is believed to control physiological color change. In adult humans it is just a thin layer of cells between the anterior pituitary and posterior pituitary, nearly indistinguishable from the anterior lobe. The intermediate lobe produces melanocyte-stimulating hormone or MSH, although this function is often (imprecisely) attributed to the anterior pituitary.

Functions

The pituitary gland helps control the following body processes through secretion and release of various hormones:

• Human development and growth — ACTH and GH
• Blood pressure (through water reabsorption)— ADH/vasopressin
• Some aspects of pregnancy and childbirth, including stimulation of uterine contractions during childbirth — oxytocin
• Breast milk production — prolactin
• Sex organ functions in both women and men — FSH and LH
• Thyroid gland function — TSH
• Metabolism (conversion of food into energy) — TSH
• Water and osmolarity regulation in the body (in kidneys)— ADH/vasopressin

Pathology

Variances from normal secretion of hormones can cause disorders in the human body. Hypersecretion of a hormone exaggerates its effects while hyposecretion of a hormone either diminishes or all together eliminates the effects of the hormone. Common disorders involving the pituitary gland include:

Condition	Direction	Hormone
Acromegaly	overproduction	growth hormone
Growth hormone deficiency	underproduction	growth hormone
Syndrome of inappropriate antidiuretic hormone	overproduction	vasopressin
Diabetes insipidus	underproduction	vasopressin
Sheehan syndrome	underproduction	prolactin
Pituitary adenoma	overproduction	any pituitary hormone
Hypopituitarism	underproduction	any pituitary hormone

Additional images

• 

  Pituitary and pineal glands

See also

• Hypothalamus
• Hormone

References

ISBN links support NWE through referral fees

• Silverthorn, D. 2004. Human Physiology, An Integrated Approach (3rd Edition). San Francisco: Benjamin Cummings. ISBN 013102153

External links

• The Pituitary Gland- overview, from the University of Maryland Medical Endocrinology Health Guide
• The Pituitary Foundation
• Pituitary Disorders- education and support

Template:Pituitary gland

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Pituitary_gland  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Pituitary gland"

Note: Some restrictions may apply to use of individual images which are separately licensed.