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 pea that sits in a small, bony cavity (pituitary fossa) covered by a dural fold (sellar diaphragm) at the base of the brain. The pituitary fossa, in which the pituitary gland sits, is situated in the sphenoid bone in the middle cranial fossa at the base of the brain.

The pituitary gland secretes hormones regulating homeostasis, including trophic hormones that stimulate other endocrine glands. It is functionally connected to the hypothalamus by the median eminence. 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 hypophysial-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 important endocrine hormones, such as ACTH, TSH, prolactin, growth hormone, endorphins, FSH, and LH. Most of 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.

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 a part of the brain called 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. Hypothalamic neurons fire such hormones, releasing them into the capillaries of the pituitary gland.

The hormones secreted by the posterior pituitary are

• Oxytocin comes from the paraventricular nucleus in the Hypothalamus
• Antidiuretic hormone (ADH, also known as vasopressin and AVP, arginine vasopressin), comes from the supraoptic nucleus in the Hypothalamus

Intermediate lobe

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

Functions

The pituitary gland helps control the following body processes:

• Growth
• Blood pressure
• Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth
• Breast milk production
• Sex organ functions in both women and men
• Thyroid gland function
• The conversion of food into energy (metabolism)
• Water and osmolarity regulation in the body.

Pathology

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

• Gray516.png

  The arteries of the base of the brain.

• Gray715.png

  Mesal aspect of a brain sectioned in the median sagittal plane.

• Gray994.png

  Sagittal section of nose mouth, pharynx, and larynx.

See also

• Head and neck anatomy

External links

• Template:BrainInfo
• Template:BUHistology
• The Pituitary Gland, from the UMM Endocrinology Health Guide
• Oklamoma State, Endocrine System

Template:Pituitary gland {{endocrine_system

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