The anterior pituitary produces seven hormones: growth hormone (GH), prolactin (PRL), thyroid-stimulating hormone (TSH), melanin-stimulating hormone (MSH), adrenocorticotropic hormone (ACTH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). A portal system carries blood from one capillary network to another therefore, the hypophyseal portal system allows hormones produced by the hypothalamus to be carried directly to the anterior pituitary without first entering the circulatory system. This capillary network is a part of the hypophyseal portal system that carries substances from the hypothalamus to the anterior pituitary and hormones from the anterior pituitary into the circulatory system. The anterior pituitary gland, or adenohypophysis, is surrounded by a capillary network that extends from the hypothalamus, down along the infundibulum, and to the anterior pituitary. (credit a: modification of work by NCI credit b: modification of work by Gray’s Anatomy) The pituitary gland is located at (a) the base of the brain and (b) connected to the hypothalamus by the pituitary stalk. The posterior lobe of the pituitary gland contains axons of the hypothalamic neurons. The pituitary has two distinct regions-the anterior pituitary and the posterior pituitary-which between them secrete nine different peptide or protein hormones. The anterior portion of the pituitary gland is regulated by releasing or release-inhibiting hormones produced by the hypothalamus, and the posterior pituitary receives signals via neurosecretory cells to release hormones produced by the hypothalamus. It is attached to the hypothalamus via a stalk called the pituitary stalk (or infundibulum). The pituitary gland, sometimes called the hypophysis or “master gland” is located at the base of the brain in the sella turcica, a groove of the sphenoid bone of the skull, illustrated in Figure 18.15. The hypothalamus contains autonomic centers that control endocrine cells in the adrenal medulla via neuronal control. It synthesizes and secretes regulatory hormones that control the endocrine cells in the anterior pituitary gland. The hypothalamus acts as an endocrine organ, synthesizing hormones and transporting them along axons to the posterior pituitary gland. It receives input from the body and other brain areas and initiates endocrine responses to environmental changes. The hypothalamus is an endocrine organ located in the diencephalon of the brain.
The hypothalamus in vertebrates integrates the endocrine and nervous systems.
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