| Brain: Pituitary gland |
Located at the base of the brain, the pituitary gland is protected by a bony structure called the sella turcica of the sphenoid bone.
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Median sagittal through the hypophysis of an adult monkey. Semidiagrammatic.
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| Latin |
hypophysis, glandula pituitaria |
| Gray's |
p.1275 |
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Artery
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superior hypophyseal artery, infundibular artery, prechiasmal artery, inferior hypophyseal artery, capsular artery, artery of the inferior cavernous sinus[1] |
| MeSH |
Pituitary+Gland |
| NeuroLex ID |
birnlex_1353 |
In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 grams (0.018 oz) in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity (sella turcica) covered by a dural fold (diaphragma sellae). The posterior pituitary (or neurohypophysis) is a lobe of the gland that is functionally connected to the hypothalamus by the median eminence via a small tube called the pituitary stalk (also called the infundibular stalk or the infundibulum). The anterior pituitary (or adenohypophysis) is a lobe of the gland that regulates several physiological processes (including stress, growth, reproduction, and lactation). The pituitary gland sits in the hypophysial fossa, situated in the sphenoid bone in the middle cranial fossa at the base of the brain. The pituitary gland secretes nine hormones that regulate homeostasis.[citation needed]
Contents
- 1 Structure
- 1.1 Anterior
- 1.2 Posterior
- 2 Function
- 2.1 Anterior
- 2.2 Posterior
- 2.3 Intermediate
- 3 Functions
- 3.1 Diseases involving the pituitary gland
- 4 In other animals
- 5 Additional images
- 6 See also
- 7 References
- 8 External links
Structure[edit]
The pituitary gland is a pea-sized gland that sits in a protective bony enclosure called the sella turcica. It is composed of three lobes: anterior, intermediate, and posterior. In many animals, these three lobes are distinct. However, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a result, it is often considered part of the anterior pituitary. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary. It belongs to the diencephalon.
Anterior[edit]
Main article: Anterior pituitary
The anterior pituitary (adenohypophysis), arises from an invagination of the oral ectoderm and forms Rathke's pouch. This contrasts with the posterior pituitary (neurohypophysis), which originates from neuroectoderm.
Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in the hypothalamus. The latter release regulatory hormones into hypothalamic capillaries leading to infundibular blood vessels, which in turn lead to a second capillary bed in the anterior pituitary. This vascular relationship constitutes the hypothalamo-hypophyseal portal system. Diffusing out of the second capillary bed, the hypothalamic releasing hormones then bind to anterior pituitary endocrine cells, upregulating or downregulating their release of hormones.[2]
The anterior pituitary is divided into anatomical regions known as the pars tuberalis, pars intermedia, and pars distalis. It develops from a depression in the dorsal wall of the pharynx (stomodial part) known as Rathke's pouch.
Posterior[edit]
Main article: Posterior pituitary
The posterior lobe develops as an extension of the hypothalamus. The magnocellular neurosecretory cells of the posterior side possess cell bodies located in the hypothalamus that project axons down the infundibulum to terminals in the posterior pituitary. This simple arrangement differs sharply from that of the adjacent anterior pituitary, which does not develop from the hypothalamus. The release of pituitary hormones by both the anterior and posterior lobes is under the control of the hypothalamus, albeit in different ways. [2]
Function[edit]
Anterior[edit]
The anterior pituitary synthesizes and secretes the following important endocrine hormones. All releasing hormones (-RH) referred to, can also be referred to as releasing factors (-RF).
Somatotrophins:
- Human growth hormone (HGH), also referred to as 'growth hormone' (GH) , and also as somatotropin, is released under the influence of hypothalamic growth hormone-releasing hormone (GHRH), and is inhibited by hypothalamic somatostatin
Thyrotrophins:
- Thyroid-stimulating hormone (TSH), is released under the influence of hypothalamic thyrotropin-releasing hormone (TRH) and is inhibited by somatostatin.
Corticotropins:
- Adrenocorticotropic hormone (ACTH), and Beta-endorphin are released under the influence of hypothalamic corticotropin-releasing hormone (CRH).[3]
Lactotrophins:
- Prolactin (PRL), also known as 'Luteotropic' hormone (LTH), whose release is inconsistently stimulated by hypothalamic TRH, oxytocin, vasopressin, vasoactive intestinal peptide, angiotensin II, neuropeptide Y, galanin, substance P, bombesin-like peptides (gastrin-releasing peptide, neuromedin B and C), and neurotensin, and inhibited by hypothalamic dopamine.[4]
Gonadotropins:
- Luteinizing hormone (also referred to as 'Lutropin' or 'LH').
- Follicle-stimulating hormone (FSH), both released under influence of Gonadotropin-Releasing Hormone (GnRH)
These hormones are released from the anterior pituitary under the influence of the hypothalamus. Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophysial portal system.
Posterior[edit]
The posterior pituitary stores and secretes (not synthesize) the following important endocrine hormones:
Magnocellular Neurons:
- Antidiuretic hormone (ADH, also known as vasopressin and arginine vasopressin AVP), the majority of which is released from the supraoptic nucleus in the hypothalamus.
- Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus. Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which, in turn, increases uterine contractions. This positive feedback loop continues throughout labour.
Intermediate[edit]
The intermediate lobe synthesizes and secretes the following important endocrine hormone:
- Melanocyte–stimulating hormone (MSH), although this function is often (imprecisely) attributed to the anterior pituitary. MSHs are sometimes called "intermedins," as they are released by the pars intermedia.
Functions[edit]
Hormones secreted from the pituitary gland help 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 males and females
- Thyroid gland function
- The conversion of food into energy (metabolism)
- Water and osmolarity regulation in the body
- Water balance via the control of reabsorption of water by the kidneys
- Temperature regulation
- Pain relief
Diseases involving the pituitary gland[edit]
A normal sized hand (left) and the enlarged hand of someone with acromegaly (right).
Main article: Pituitary disease
Some of the diseases involving the pituitary gland are:
- Central diabetes insipidus caused by a deficiency of vasopressin.
- Gigantism and acromegaly caused by an excess of growth hormone.
- Hypothyroidism caused by a deficiency of thyroid-stimulating hormone.
- Hyperpituitarism, the increased (hyper) secretion of one or more of the hormones normally produced by the pituitary gland.
- Hypopituitarism, the decreased (hypo) secretion of one or more of the hormones normally produced by the pituitary gland.
- Panhypopituitarism a decreased secretion of most of the pituitary hormones.
- Pituitary tumours.
- Pituitary adenomas, noncancerous tumors that occur in the pituitary gland.
- (Citation needed) Calcified Pituitary glands due to consumption of fluoride in water
All of the functions of the pituitary gland can be adversely affected by an over or under production of associated hormones.
In other animals[edit]
The pituitary gland is found in all vertebrates, but its structure varies between different groups.
The division of the pituitary described above is typical of mammals, and is also true, to varying degrees, of all tetrapods. However, only in mammals does the posterior pituitary have a compact shape. In lungfish, it is a relatively flat sheet of tissue lying above the anterior pituitary, but in amphibians, reptiles, and birds, it becomes increasingly well developed. The intermediate lobe is, in general, not well developed in any species and is entirely absent in birds.[5]
The structure of the pituitary in fish, apart from the lungfish, is generally different from that in other animals. In general, the intermediate lobe tends to be well developed, and may equal the remainder of the anterior pituitary in size. The posterior lobe typically forms a sheet of tissue at the base of the pituitary stalk, and in most cases sends irregular finger-like projection into the tissue of the anterior pituitary, which lies directly beneath it. The anterior pituitary is typically divided into two regions, a more anterior rostral portion and a posterior proximal portion, but the boundary between the two is often not clearly marked. In elasmobranchs there is an additional, ventral lobe beneath the anterior pituitary proper.[5]
The arrangement in lampreys, which are among the most primitive of all fish, may indicate how the pituitary originally evolved in ancestral vertebrates. Here, the posterior pituitary is a simple flat sheet of tissue at the base of the brain, and there is no pituitary stalk. Rathke's pouch remains open to the outside, close to the nasal openings. Closely associated with the pouch are three distinct clusters of glandular tissue, corresponding to the intermediate lobe, and the rostral and proximal portions of the anterior pituitary. These various parts are separated by meningial membranes, suggesting that the pituitary of other vertebrates may have formed from the fusion of a pair of separate, but associated, glands.[5]
Most armadillos also possess a neural secretory gland very similar in form to the posterior pituitary, but located in the tail and associated with the spinal cord. This may have a function in osmoregulation.[5]
There is a structure analogous to the pituitary in the octopus brain.[6]
Intermediate lobe[edit]
Although rudimentary in humans (and often considered part of the anterior pituitary), the intermediate lobe located between the anterior and posterior pituitary is important to 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. The intermediate lobe produces melanocyte-stimulating hormone (MSH), although this function is often (imprecisely) attributed to the anterior pituitary.
The intermediate lobe is, in general, not well developed in tetrapods, and is entirely absent in birds.[5]
Additional images[edit]
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Location of the pituitary gland in the human brain
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Pituitary and pineal glands
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The arteries of the base of the brain.
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Mesal aspect of a brain sectioned in the median sagittal plane.
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Cerebrum.Inferior view.Deep dissection.
See also[edit]
- Dantian
- Head and neck anatomy
References[edit]
- ^ Gibo H, Hokama M, Kyoshima K, Kobayashi S (1993). "[Arteries to the pituitary]". Nippon Rinsho 51 (10): 2550–4. PMID 8254920.
- ^ a b Boron, Walter F.; Boulpaep, Emile L. (2009). Medical Physiology (2nd ed.). Philadelphia: Saunders Elsevier. pp. 1016–1017. ISBN 978-1-4160-3115-4.
- ^ Knepel W, Homolka L, Vlaskovska M, Nutto D. (1984). Stimulation of adrenocorticotropin/beta-endorphin release by synthetic ovine corticotropin-releasing factor in vitro. Enhancement by various vasopressin analogs. Neuroendocrinology. 38(5):344-50.
- ^ Shlomo Melmed (3 December 2010). The pituitary. Academic Press. p. 40. ISBN 978-0-12-380926-1.
- ^ a b c d e Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 549–550. ISBN 0-03-910284-X.
- ^ Wells, M. J.; Wells, J. (1969). "Pituitary Analogue in the Octopus". Nature 222 (5190): 293–294. doi:10.1038/222293a0.
External links[edit]
- NeuroNames hier-382
- BU Histology Learning System: 14201loa
- The Pituitary Gland, from the UMM Endocrinology Health Guide
- Oklahoma State, Endocrine System
- Pituitary apoplexy mimicking pituitary abscess
- [1] The Pituitary Foundation
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Human systems and organs
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TA 2–4:
MS |
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Skeletal system
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- Bone
- Carpus
- Collar bone (clavicle)
- Thigh bone (femur)
- Fibula
- Humerus
- Mandible
- Metacarpus
- Metatarsus
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Muscular system
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TA 5–11:
splanchnic/
viscus |
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mostly
Thoracic
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mostly
Abdominopelvic
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Digestive system+
adnexa
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- Mouth
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GU: Urinary system
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- Kidney
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GU: Reproductive system
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- Female
- Uterus
- Vagina
- Vulva
- Ovary
- Placenta
- Male
- Scrotum
- Penis
- Prostate
- Testicle
- Seminal vesicle
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Endocrine system
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- Pituitary
- Pineal
- Thyroid
- Parathyroid
- Adrenal
- Islets of Langerhans
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| TA 12–16 |
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Circulatory system
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Cardiovascular system
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- peripheral
- Artery
- Vein
- Lymphatic vessel
- Heart
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Lymphatic system
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- primary
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- CNS equivalent
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Nervous system
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Integumentary system
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- Skin
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Blood
(Non-TA) |
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General anatomy: systems and organs, regional anatomy, planes and lines, superficial axial anatomy, superficial anatomy of limbs
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Human anatomy, endocrine system: endocrine glands (TA A11, TH H3.08, GA 11.1269)
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| Islets of pancreas |
- Alpha cell
- Beta cell
- Delta cell
- PP cell
- Epsilon cell
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Hypothalamic/
pituitary axes
+parathyroid |
| Pituitary |
| Posterior pituitary |
- Pars nervosa
- Median eminence
- Infundibular stalk
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| Anterior pituitary |
- Pars intermedia
- Pars tuberalis
- Pars distalis
- Acidophil cell
- Somatotropic cell
- Prolactin cell
- Basophil cell
- Corticotropic cell
- Gonadotropic cell
- Thyrotropic cell
- Chromophobe cell
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| Thyroid axis |
| Thyroid gland |
- Thyroid isthmus
- Lobes of thyroid gland
- Pyramidal lobe of thyroid gland
- Follicular cell
- Parafollicular cell
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| Parathyroid gland |
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Adrenal axis:
Adrenal gland |
| Cortex |
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
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| Medulla |
- Medullary chromaffin cell
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| Gonadal axis |
- Gonad: Testes
- Ovaries
- Corpus luteum
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| Pineal gland |
- Pinealocyte
- Corpora arenacea
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| Other |
- Enteroendocrine cell
- Paraganglia
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noco (d)/cong/tumr, sysi/epon
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proc, drug (A10/H1/H2/H3/H5)
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Human brain: diencephalon (TA A14.1.08, GA 9.807)
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| Epithalamus |
| Surface |
- Pineal body
- Habenula
- Habenular trigone
- Habenular commissure
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| Grey matter |
- Pretectal area
- Habenular nuclei
- Subcommissural organ
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| Thalamus |
| Surface |
- Stria medullaris of thalamus
- Thalamic reticular nucleus
- Taenia thalami
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Grey matter/
nuclei |
- paired: AN
- Ventral
- Lateral
- Metathalamus
- midline: MD
- Intralaminar
- Midline nuclear group
- Interthalamic adhesion
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| White matter |
- Mammillothalamic fasciculus
- Pallidothalamic tracts
- Ansa lenticularis
- Lenticular fasciculus
- Thalamic fasciculus
- PCML
- Medial lemniscus
- Trigeminal lemniscus
- Spinothalamic tract
- Lateral lemniscus
- Dentatothalamic tract
- Acoustic radiation
- Optic radiation
- Subthalamic fasciculus
- Anterior trigeminothalamic tract
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| Hypothalamus |
| Surface |
- Median eminence/Tuber cinereum
- Mammillary body
- Infundibulum
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| Grey matter |
| Autonomic zones |
- Anterior (parasympathetic/heat loss)
- Posterior (sympathetic/heat conservation)
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| Endocrine |
- posterior pituitary: Paraventricular
- magnocellular
- parvocellular
- Supraoptic
- other: Arcuate (dopamine/GHRH)
- Preoptic (GnRH)
- Suprachiasmatic (melatonin)
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| Emotion |
- Lateral
- Ventromedial
- Dorsomedial
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| White matter |
- afferent
- SN → Medial forebrain bundle
- efferent
- Mammillothalamic fasciculus → AN, Stria terminalis → Amygdala, Dorsal longitudinal fasciculus → SC
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| Pituitary |
- Posterior is diencephalon, but anterior is glandular
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| Subthalamus |
- Subthalamic nucleus
- Zona incerta
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Ventricular system:
Third ventricle |
- recesses:
- Optic recess
- Infundibular recess
- Suprapineal recess
- Pineal recess
- Hypothalamic sulcus
- Tela chorioidea of third ventricle
- Apertures: Interventricular/Monro
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anat (n/s/m/p/4/e/b/d/c/a/f/l/g)/phys/devp
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noco (m/d/e/h/v/s)/cong/tumr, sysi/epon, injr
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proc, drug (N1A/2AB/C/3/4/7A/B/C/D)
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