Anterior pituitary
From Wikipedia, the free encyclopedia
| Anterior pituitary | |
|---|---|
| The anterior pituitary is the anterior, glandular lobe of the pituitary gland. | |
| Latin | lobus anterior hypophyseos |
| Precursor | oral mucosa |
| MeSH | Anterior+Pituitary+Gland |
| Dorlands/Elsevier | a_14/12111161 |
The anterior pituitary (also called the adenohypophysis) comprises the anterior lobe of the pituitary gland and is part of the endocrine system.
Under the influence of the hypothalamus, the anterior pituitary produces and secretes several peptide hormones that regulate many physiological processes including stress, growth, and reproduction.
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[edit] Regions
The term "pars distalis" is sometimes used as a synonym for the the anterior pituitary, but this is not quite correct. The anterior pituitary is usually divided into two regions:
- "pars distalis" - the majority of the anterior pituitary
- "pars tuberalis" - a sheath extending up from the pars distalis and wrapping around the pituitary stalk
The function of the tuberalis is not well characterized, and most of the rest of this article refers primarily to the distalis.
[edit] Embryology
Unlike the pars nervosa, which originates from neural ectoderm, the anterior pituitary arises from the oral mucosa.
This differentiation is exhibited by the fact that while the pars nervosa merely secretes those hormones produces in the brain (ADH and oxytocin), the anterior pituitary actually produces its hormones, while being under control of the hypotalamus as to when they should be secreted.
[edit] Major hormones secreted
| Secretory Cells | Hormone | Target | Effect |
| Corticotrophs | Adrenocorticotropic hormone (ACTH) | Adrenal gland | Secretion of glucocorticoids |
| Gonadotrophs | Follicle-stimulating hormone (FSH) | Ovaries, Testes | Growth of reproductive system |
| Somatotrophs | Growth hormone (GH) | Liver, adipose tissue | Promotes growth; lipid & carbohydrate metabolism |
| Gonadotrophs | Luteinizing hormone (LH) | Ovaries, Testes | Sex hormone production |
| Lactotrophs (aka Mammotrophs) | Prolactin (PRL) | Ovaries, mammary glands | Secretion of estrogens/progesterone; milk production |
| Thyrotrophs | Thyroid-stimulating hormone (TSH) | Thyroid gland | Secretion of thyroid hormones |
[edit] Hypothalamic releasing and release-inhibiting factors
Hormone secretion from the anterior pituitary gland is regulated by hormones secreted by the hypothalamus. Neuroendocrine neurons in the hypothalamus project axons to the median eminence, at the base of the brain. At this site, these neurons can release substances into small blood vessels that travel directly to the anterior pituitary gland (the hypothalamo-hypophysial portal vessels).
| Name | Abbreviation | Location | Function |
| Somatostatin | - | is expressed in neuroendocrine neurons of the periventricular nucleus and | inhibits the secretion of growth hormone |
| Growth hormone-releasing hormone | GHRH | is expressed in arcuate nucleus neuroendocrine neurons | stimulates the secretion of growth hormone |
| Gonadotropin-releasing hormone (or luteinising-hormone releasing hormone) | GnRH (or LHRH) | is expressed in neuroendocrine neurons in the medial preoptic and arcuate nuclei | stimulates the secretion of LH and FSH |
| Thyrotropin-releasing hormone | TRH | is expressed in parvocellular neuroendocrine neurons in the paraventricular and anterior hypothalamic nuclei | stimulates the secretion of TSH |
| Corticotropin-releasing hormone (or corticotropin-releasing factor) | CRH (or CRF) | is expressed in parvocellular neuroendocrine neurons in the paraventricular nucleus | CRH and vasopressin, from an overlapping population of parvocellular neuroendocrine neurons are stimulators of ACTH secretion. These two factors have synergistic effects on ACTH secretion. |
| Dopamine | - | from neuroendocrine neurons of the arcuate nucleus | inhibits prolactin secretion. |
[edit] Additional images
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[edit] External links
| Endocrine system - Pituitary gland - edit |
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| Posterior pituitary: Pars nervosa | Median eminence | Infundibular stalk |
| Anterior pituitary: Pars intermedia | Pars tuberalis | Pars distalis | Somatotropes | Lactotropes | Thyrotropes | Gonadotropes | Corticotropes |
| Diencephalon - edit |
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third ventricle, interventricular foramina, optic chiasm, subfornical organ epithalamus: pineal body, habenula, habenular nuclei anterior hypothalamus: anterior hypothalamic nucleus, paraventricular nucleus, preoptic area, supraoptic nucleus, suprachiasmatic nucleus intermediate/middle/tuberal/pituitary hypothalamus: infundibulum, median eminence, arcuate nucleus, ventromedial nucleus, dorsomedial hypothalamic nucleus, tuber cinereum, pituitary gland (anterior pituitary, posterior pituitary) posterior/lateral hypothalamus: posterior nucleus, mammillary body, lateral nucleus subthalamus: subthalamic nucleus thalamus: pulvinar, medial geniculate nucleus, lateral geniculate nucleus, list of thalamic nuclei |
