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A major organ of the endocrine system, the anterior pituitary (also called the adenohypophysis or pars anterior), is the glandular, anterior lobe that together with the posterior lobe (posterior pituitary, or the neurohypophysis) makes up the pituitary gland (hypophysis). The anterior pituitary regulates several physiological processes including stress, growth, reproduction and lactation. Proper functioning of the anterior pituitary and of the organs it regulates can often be ascertained via blood tests that measure hormone levels. ==Structure== The pituitary gland is a pea-sized gland that sits in a protective bony enclosure called the sella turcica (''Turkish chair/saddle''). It is composed of three lobes: the anterior, intermediate, and posterior lobes. In many animals, these 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 as part of the anterior pituitary. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary. The anterior pituitary is composed of three regions: :; Pars distalis: The pars distalis, (distal part), comprises the majority of the anterior pituitary and is where the bulk of pituitary hormone production occurs. The pars distalis contains two types of cells including chromophobe cells and chromophil cells. The chromophils can be further divided into acidophils (alpha cells) and basophils (beta cells).〔 These cells all together produce hormones of the anterior pituitary, and release them into the blood stream. :; Pars tuberalis: The pars tuberalis, (tubular part), forms a part of the sheath extending up from the pars distalis which joins with the pituitary stalk (also known as the infundibular stalk or infundibulum), arising from the posterior lobe. (The pituitary stalk connects the hypothalamus to the posterior pituitary). The function of the pars tuberalis is poorly understood. However it has been seen to be important in receiving the endocrine signal in the form of TSHB (a β subunit of TSH) informing the pars tuberalis of the photoperiod (length of day). The expression of this subunit is regulated by the secretion of melatonin in response to light information transmitted to the pineal gland.〔Ikegami K, Iigo M and Yoshimura T. Circadian clock gene Per2 is not necessary for the photoperiodic response in mice. ''PLoS One'' 2013;8(3).PMID 23505514〕〔Dardente H. Melatonin-dependent timing of seasonal reproduction by the pars tuberalis: pivotal roles for long daylengths and thyroid hormones.J.Neuroendocrinol.2012.Feb;24(2)〕 Earlier studies have shown a localisation of melatonin receptors in this region.〔Morgan PJ and Williams LM.The pars tuberalis of the pituitary: a gateway for neuroendocrine output. RevReprod 1996 Sep;1(3) PMID 9414453〕 :; Pars intermedia: The pars intermedia, (intermediate part), sits between the pars distalis and the posterior pituitary, forming the boundary between the anterior and posterior pituitaries. It is very small and indistinct in humans. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「anterior pituitary」の詳細全文を読む スポンサード リンク
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