Pituitary Gland

The pituitary gland includes the anterior pituitary and the posterior pituitary.The posterior pituitary stores and releases hormones that are actually produced by the hypothalamus, whereas the anterior pituitary produces and secretes its own hormones.The anterior pituitary, however, is regulated by hormones secreted by the hypothalamus, as well as by feedback from the target gland hormones.

The pituitary gland, or hypophysis, is located on the inferior aspect of the brain in the region of the diencephalon (chapter 8). Roughly the size of a pea—about 1.3 cm (0.5 in.) in diameter—it is attached to the hypothalamus by a stalklike structure called the infundibulum (fig. 11.12).

The pituitary gland is structurally and functionally divided into an anterior lobe, or adenohypophysis, and a posterior lobe called the neurohypophysis. These two parts have different embryonic origins. The adenohypophysis is derived from a pouch of epithelial tissue (Rathke's pouch) that migrates upward from the embryonic mouth, whereas the neurohypophy-sis is formed as a downgrowth of the brain. The adenohypophy-sis consists of two parts in adults: (1) the pars distalis, also known as the anterior pituitary, is the rounded portion and the major endocrine part of the gland, and (2) the pars tuberalis is the thin extension in contact with the infundibulum. These parts are illustrated in figure 11.12. A pars intermedia, a strip of tissue between the anterior and posterior lobes, exists in the fetus. During fetal development, its cells mingle with those of the anterior lobe, and in adults they no longer constitute a separate structure.

The neurohypophysis is the neural part of the pituitary gland. It consists of the pars nervosa, also called the posterior pituitary, which is in contact with the adenohypophysis and the infundibulum. Nerve fibers extend through the infundibulum along with small neuroglia-like cells called pituicytes.

Optic chiasma-

Anterior lobe (adenohypophysis)

Pars tuberalis Pars distalis

Pars tuberalis Pars distalis

Pars Tuberalis Pituitary Gland

Infundibulum

Posterior lobe (neurohypophysis)

Infundibulum

Posterior lobe (neurohypophysis)

■ Figure 11.12 The structure of the pituitary gland. The anterior lobe is composed of glandular tissue, whereas the posterior lobe is composed largely of neuroglia and nerve fibers.

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Responses

  • natalia hentinen
    Which gland is also called the neurohypophysis?
    8 years ago
  • toivo
    What type of tissue posterior lobe of the pituitary gland composed of?
    8 years ago
  • grazia pinto
    What are the embryonic origins of the anterior and posterior pituitary gland?
    7 years ago

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