Difference between revisions of "Pituitary gland" - New World Encyclopedia
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| − | The '''pituitary gland''', or '''hypophysis''', is an | + | The '''pituitary gland''', or '''hypophysis''', is an endocrine gland about the size of a bean that sits at the base of the [[brain]] in a small, bony cavity (the pituitary fossa), which is situated in the sphenoid bone in the middle cranial fossa. The gland is connected to the brain by the ''infundibulum'' and is covered by the sellar diaphragm fold. |
| + | |||
| + | The pituitary gland is two fused glands, each made up of different tissue types. The individual glands merge during embryonic development. The anterior pituitary is a true endocrine gland of epithelial origin that is made up of the same tissue that forms the roof of the mouth. The posterior pituitary, on the other hand, is an extension of neural tissue. | ||
The pituitary gland secretes [[hormone]]s regulating [[homeostasis]], including [[trophic hormone]]s 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. | The pituitary gland secretes [[hormone]]s regulating [[homeostasis]], including [[trophic hormone]]s 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. | ||
| Line 29: | Line 31: | ||
===Anterior pituitary (Adenohypophysis)=== | ===Anterior pituitary (Adenohypophysis)=== | ||
| − | |||
| − | The anterior lobe is derived from the | + | 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 [[hypothalamus|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. In that case, the first hormone is called a trophic hormone. | |
| − | The control of hormones from the | + | 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)=== | ===Posterior pituitary (neurohypophysis)=== | ||
| − | |||
| − | The posterior lobe is connected to | + | 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 | + | The hormones released by the posterior pituitary are: |
| − | *[[Oxytocin | + | *[[Oxytocin]] |
| − | *[[Antidiuretic hormone]] (ADH, also known as [[vasopressin]] and AVP, arginine vasopressin) | + | *[[Antidiuretic hormone]] (ADH, also known as [[vasopressin]] and AVP, arginine vasopressin) |
===Intermediate lobe=== | ===Intermediate lobe=== | ||
| − | There is also an | + | 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 [[cell]]s 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== | ==Functions== | ||
| Line 61: | Line 69: | ||
==Pathology== | ==Pathology== | ||
| − | + | Variances from normal secretion of hormones can cause disorders. 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: | |
{| class="wikitable" | {| class="wikitable" | ||
| '''Condition''' || '''Direction''' || '''Hormone''' | | '''Condition''' || '''Direction''' || '''Hormone''' | ||
|- | |- | ||
| − | | [[Acromegaly]] || overproduction || | + | | [[Acromegaly]] || overproduction || growth hormone |
|- | |- | ||
| − | | | + | | Growth hormone deficiency || underproduction || growth hormone |
|- | |- | ||
| − | | | + | | Syndrome of inappropriate antidiuretic hormone || overproduction || vasopressin |
|- | |- | ||
| − | | [[Diabetes insipidus]] || underproduction || | + | | [[Diabetes insipidus]] || underproduction || vasopressin |
|- | |- | ||
| − | | | + | | Sheehan syndrome || underproduction || prolactin |
|- | |- | ||
| − | | | + | | Pituitary adenoma || overproduction || any pituitary hormone |
|- | |- | ||
| − | | | + | | Hypopituitarism || underproduction || any pituitary hormone |
|} | |} | ||
Revision as of 23:55, 14 June 2007
| 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[1] |
| 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 in a small, bony cavity (the pituitary fossa), which is situated in the sphenoid bone in the middle cranial fossa. The gland is connected to the brain by the infundibulum and is covered by the sellar diaphragm fold.
The pituitary gland is two fused glands, each made up of different tissue types. The individual glands merge during embryonic development. The anterior pituitary is a true endocrine gland of epithelial origin that is made up of the same tissue that forms the roof of the mouth. The posterior pituitary, on the other hand, is an extension of neural tissue.
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 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. 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 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
Variances from normal secretion of hormones can cause disorders. 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
- 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
ReferencesISBN links support NWE through referral fees
- ↑ Gibo H, Hokama M, Kyoshima K, Kobayashi S (1993). [Arteries to the pituitary]. Nippon Rinsho 51 (10): 2550-4. PMID 8254920.
External links
- Template:BrainInfo
- Template:BUHistology
- The Pituitary Gland, from the UMM Endocrinology Health Guide
- Oklamoma State, Endocrine System
Template:Pituitary gland {{endocrine_system
Credits
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