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The pituitary gland (or hypophysis cerebri) is an endocrine gland in vertebrates. In humans, the pituitary gland is located at the base of the brain, protruding off the bottom of the hypothalamus. The human pituitary gland is oval shaped, about the size of a chickpea, and weighs 0.5 grams (0.018 oz) on average. Hormones secreted from the pituitary gland help to control growth, blood pressure, energy management, all functions of the sex organs, thyroid glands, metabolism, as well as some aspects of pregnancy, childbirth, breastfeeding, water/salt concentration at the kidneys, temperature regulation, and pain relief. Structure In humans, the pituitary gland rests upon the hypophyseal fossa of the sphenoid bone, in the center of the middle cranial fossa. It sits in a protective bony enclosure called the sella turcica, covered by the dural fold diaphragma sellae. The pituitary gland is composed of the anterior pituitary lobe, the posterior pituitary lobe, and an intermediate lobe that joins them. The intermediate lobe is avascular and almost absent in humans. In many animals, these three lobes are distinct. The intermediate lobe is present in many animal species, particularly in rodents, mice, and rats, which have been used extensively to study pituitary development and function. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary, which is an extension of the hypothalamus. The height of the pituitary gland ranges from 5.3 to 7.0 mm. The volume of the pituitary gland ranges from 200 to 440 mm3. Anterior The anterior pituitary lobe (or adenohypophysis) arises from an invagination of the oral ectoderm (Rathke's pouch). This contrasts with the posterior pituitary, which originates from neuroectoderm. Endocrine cells of the anterior pituitary are controlled by regulatory hormones released by parvocellular neurosecretory cells in the 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. The anterior lobe of the pituitary can be divided into the pars tuberalis (pars infundibularis) and pars distalis (pars glandularis) that constitutes ~80% of the gland. The pars intermedia (the intermediate lobe) lies between the pars distalis and the pars tuberalis, and is rudimentary in the human, although in other species it is more developed. It develops from a depression in the dorsal wall of the pharynx (stomal part) known as Rathke's pouch. The anterior pituitary contains several different types of cells that synthesize and secrete hormones. Usually there is one type of cell for each major hormone formed in anterior pituitary. With special stains attached to high-affinity antibodies that bind with distinctive hormone, at least 5 types of cells can be differentiated. Posterior The posterior lobe develops as an extension of the hypothalamus, from the floor of the third ventricle. The posterior pituitary hormones are synthesized by cell bodies in the hypothalamus. The magnocellular neurosecretory cells, of the supraoptic and paraventricular nuclei located in the hypothalamus, 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. Functions The anterior pituitary regulates several physiological processes by secreting hormones. This includes stress (by secreting ACTH), growth (by secreting GH), reproduction (by secreting FSH and LH), metabolism rate (by secreting TSH) and lactation (by secreting prolactin). The intermediate lobe synthesizes and secretes melanocyte-stimulating hormone. 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). It regulates hydroelectrolytic stability (by secreting ADH), uterine contraction during labor and human attachment (by secreting oxytocin). Anterior The anterior pituitary synthesizes and secretes hormones. All releasing hormones (-RH) referred to can also be referred to as releasing factors (-RF). Somatotropes: Human growth hormone (HGH), also referred to as 'growth hormone' (GH) or somatotropin, is released under the influence of hypothalamic growth hormone-releasing hormone (GHRH), and is inhibited by hypothalamic somatostatin. Corticotropes: Cleaved from the precursor proopiomelanocortin protein, and include adrenocorticotropic hormone (ACTH), and beta-endorphin, and melanocyte-stimulating hormone are released under the influence of hypothalamic corticotropin-releasing hormone (CRH).: 1210  Thyrotropes: Thyroid-stimulating hormone (TSH) is released under the influence of hypothalamic thyrotropin-releasing hormone (TRH) and is inhibited by somatostatin. Gonadotropes: Luteinizing hormone (LH). Follicle-stimulating hormone (FSH), both released under influence of Gonadotropin-releasing Hormone (GnRH) Lactotropes: Prolactin (PRL), 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. 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. There is also a non-endocrine cell population called folliculostellate cells. Intermediate The intermediate lobe synthesizes and secretes the following important endocrine hormone: Melanocyte–stimulating hormone (MSH). This is also produced in the anterior lobe. When produced in the intermediate lobe, MSHs are sometimes called "intermedins". Posterior The posterior pituitary stores and secretes (but does 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 poste.... Discover the Lisa Whittle popular books. Find the top 100 most popular Lisa Whittle books.