adenohypophysis n : the anterior lobe of the pituitary body; primarily glandular in nature [syn: anterior pituitary, anterior pituitary gland]

English

Noun

adenohypophysis (plural adenohypophyses)

1. the anterior lobe of the pituitary gland, producing and secreting several peptide hormones that regulate many physiological processes including stress, growth, and reproduction.

Synonyms

• anterior lobe
• anterior pituitary

Derived terms

• adenohypophyseal
• adenohypophysial

The anterior pituitary (also called the adenohypophysis, from Greek adeno, "gland"; hypo, "under"; physis, "growth"; hence, glandular undergrowth) comprises the anterior lobe of the pituitary gland and is part of the endocrine system. Unlike the posterior lobe, the anterior lobe is genuinely glandular, hence the root adeno in its name.

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.

Regions

The term "pars distalis" is sometimes used as a synonym for the anterior pituitary, but this is not quite correct. The anterior pituitary is usually divided into three regions:

• pars distalis ("distal part") - the majority of the anterior pituitary
• pars tuberalis ("tubular part") - a sheath extending up from the pars distalis and wrapping around the pituitary stalk
• pars intermedia ("intermediate part") - sits between the bulk of the anterior pituitary and the posterior pituitary and is often very small in humans

The function of the tuberalis is not well characterized, and most of the rest of this article refers primarily to the distalis.

Embryology

Unlike the posterior pituitary (pars nervosa), which originates from neural ectoderm, the anterior pituitary arises from an invagination of the oral mucosa called Rathke's pouch (which is itself ectoderm derived).

This differentiation is exhibited by the fact that while the posterior pituitary merely secretes those hormones produced in the hypothalamus (ADH and oxytocin), the anterior pituitary actually produces its hormones, while being under control of the hypothalamus as to when they should be secreted.

Major hormones secreted

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).

Additional images

glandular lobe of the pituitary gland. Image:Nasennebenhöhlen.gif

See also

• Tropic hormones
• Pituitary adenoma
• Triple bolus test

External links

• Embryology at unc.edu