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Pituitary gland

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Pituitary gland
Gray1180
Located at the base of the skull, the pituitary gland is protected by a bony structure called the sella turcica of the sphenoid bone.
Latin hypophysis, glandula pituitaria
Gray's subject #275 1275
System
MeSH A06.407.747
Gray1181
Median sagittal through the hypophysis of an adult monkey. Semidiagrammatic.

The pituitary gland, (or hypophysis or Hypophysis cerebri), 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.

It is regarded as the 'master gland' because of its role of regulating the activity of other endocrine glands. 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.

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).

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

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 hypothalamo hypophyseal system 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 hormones, and the hypothalamic hormones that modulate their release are listed below, along with the associated cell types.

Anterior pituitary hormone Hypothalamic hormone Staining type Cell type
growth hormone release caused by GHRH (growth hormone releasing hormone) acidophil somatotrope
prolactin release INHIBITED by DA (dopamine, "prolactin inhibiting factor"/PIF) acidophil lactotroph (or mammotroph)
follicle-stimulating hormone release caused by GnRH (gonadotropin-releasing hormone) basophil gonadotrope
luteinizing hormone release caused by GnRH (gonadotropin-releasing hormone) basophil gonadotrope
thyroid-stimulating hormone release caused by TRH (thyrotropin-releasing hormone) basophil thyrotrope
adrenocorticotropic hormone (ACTH) release caused by CRH (corticotropin-releasing hormone) chromatophobe corticotrope
endorphins - - -

The hypothalamic hormones travel to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophyseal portal system.

There is also an interaction between the hormones from the hypothalamus, i.e. TRH induces the release of prolactin.

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

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:

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

See also

References


External links

Endocrine system - Pituitary gland - edit
Posterior pituitaryPars nervosa | Median eminence | Infundibular stalk
Anterior pituitaryPars intermedia | Pars tuberalis | Pars distalis | Somatotropes | Lactotropes | Thyrotropes | Gonadotropes | Corticotropes


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