| Posterior pituitary | |
|---|---|
 Labeled diagram of the pituitary gland | |
| Details | |
| Precursor | Neural tube (downward-growth of thediencephalon)[1] |
| Artery | Inferior hypophyseal artery |
| Vein | Hypophyseal vein |
| Identifiers | |
| Latin | pars nervosa glandulae pituitariae, pars nervosa hypophyseos, lobus posterior hypophyseos |
| MeSH | D010904 |
| NeuroNames | 401 |
| NeuroLex ID | birnlex_1586 |
| TA98 | A11.1.00.006 |
| TA2 | 3859 |
| FMA | 74636 |
| Anatomical terminology | |
Theposterior pituitary (orneurohypophysis) is theposterior lobe of thepituitary gland which is part of theendocrine system. Unlike theanterior pituitary, the posterior pituitary is not glandular, but largely a collection ofaxonal projections from thehypothalamus that terminate behind the anterior pituitary, and serve as a site for the secretion ofneurohypophysial hormones (oxytocin andvasopressin) directly into the blood.[2] Thehypothalamic–neurohypophyseal system is composed of the hypothalamus (theparaventricular nucleus andsupraoptic nucleus), posterior pituitary, and these axonal projections.[2]
The posterior pituitary consists mainly ofneuronal projections (axons) ofmagnocellular neurosecretory cells extending from thesupraoptic andparaventricular nuclei of thehypothalamus. These axons store and release neurohypophysial hormonesoxytocin andvasopressin into the neurohypophyseal capillaries, from there they get into thesystemic circulation (and partly back into thehypophyseal portal system). In addition to axons, the posterior pituitary also containspituicytes, specializedglial cells resemblingastrocytes assisting in the storage and release of the hormones.[3]
Classification of the posterior pituitary varies, but most sources include the two regions below:
Also called the neural lobe or posterior lobe, this region constitutes the majority of the posterior pituitary and is the storage site of oxytocin and vasopressin. Sometimes (incorrectly) considered synonymous with the posterior pituitary, the pars nervosa includesHerring bodies andpituicytes.[4]
Also known as the infundibulum or pituitary stalk, the infundibular stalk bridges the hypothalamic and hypophyseal systems.
Themedian eminence is only occasionally included as part of the posterior pituitary. Other sources specifically exclude it from the pituitary.[5]
A few sources include thepars intermedia as part of the posterior lobe, but this is a minority view. It is based upon the gross anatomical separation of the posterior and anterior pituitary along the cystic remnants of Rathke's pouch, causing the pars intermedia to remain attached to the neurohypophysis.
Two hormones are classically considered as being related to the posterior pituitary: oxytocin and vasopressin. These hormones are created in the hypothalamus and released in the posterior pituitary. After creation, they are stored in neurosecretory vesicles regrouped intoHerring bodies before being secreted in the posterior pituitary via the bloodstream.
| Hormone | Other names | Symbol(s) | Main targets | Effect | Source |
|---|---|---|---|---|---|
| Oxytocin | OT, OXY | Uterus,mammary glands | Uterine contractions;lactation | supraoptic andparaventricular nuclei | |
| Vasopressin | Arginine vasopressin, antidiuretic hormone | VP, AVP, ADH | Kidneys andarterioles | Stimulates water retention; raises blood pressure by contracting arterioles | supraoptic andparaventricular nuclei |
Insufficient secretion ofvasopressin underliesdiabetes insipidus, a condition in which the body loses the capacity to concentrate urine. Affected individuals excrete as much as 20 liters of dilute urine per day. Oversecretion of vasopressin causes thesyndrome of inappropriate antidiuretic hormone (SIADH).
•The hypothalamic–neurohypophyseal system secretes two peptide hormones directly into the blood, vasopressin and oxytocin. ...
•The hypothalamic–pituitary–adrenal (HPA) axis. It comprises corticotropin-releasing factor (CRF), released by the hypothalamus; adrenocorticotropic hormone (ACTH), released by the anterior pituitary; and glucocorticoids, released by the adrenal cortex.
•The hypothalamic–pituitary–thyroid axis consists of hypothalamic thyrotropin-releasing hormone (TRH); the anterior pituitary hormone thyroid–stimulating hormone (TSH); and the thyroid hormones T3 and T4.
•The hypothalamic–pituitary–gonadal axis comprises hypothalamic gonadotropin–releasing hormone (GnRH), the anterior pituitary luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and the gonadal steroids.
| International | |
|---|---|
| Other | |
