Pituitary Gland - Assignment Point
One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis). J Physiol (Paris). ;43(4) [Hypothalamo-hypophyseal relationship and its role in gonadostimulation in domestic duck]. [Article in Undetermined. The pituitary gland (hypophysis) is intimately connected to the hypothalamus in both an anatomical and functional close relationship. . by a gland collector from the local fish market during or just before the breeding season, mainly from dead .
It secretes hormones from both the front part anterior and the back part posterior of the gland. Hormones are chemicals that carry messages from one cell to another through our bloodstream.
Relationship Between Hypothalamus and Pituitary Gland | Definition, Anatomy, Physiology
The pituitary is divided into three sections: The anterior lobe is mainly involved in development of the body, sexual maturation, and reproduction. The intermediate lobe of the pituitary gland releases a hormone that stimulates the melanocytes, cells which control pigmentation like skin color through the production of melanin. The posterior lobe produces antidiuretic hormone, which reclaims water from the kidneys and conserves it in the bloodstream to prevent dehydration.
Structure and Function of Pituitary Gland The pituitary gland has two parts, the anterior and posterior lobes, which are under the control of a part of the brain known as the hypothalamus.
Nerve cells in the hypothalamus secrete two hormones that pass down nerve fibres to be stored in the posterior lobe until they are needed. The pituitary gland has an anterior lobe and a posterior lobe. It is linked to the hypothalamus, which lies directly above it, by a short stalk that contains nerve fibres and a specialized network of blood vessels known as a portal system. 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. Anterior pituitary contains several different types of cells that synthesize and secrete hormones.
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The posterior pituitary or neurohypophysis is not a separate organ, but an extension of the hypothalamus. It is composed largely of the axons of hypothalamic neurons which extend downward as a large bundle behind the anterior pituitary.
It also forms the so-called pituitary stalk, which appears to suspend the anterior gland from the hypothalamus.
The image to the right shows a frontal view of a pig pituitary gland and hypothalamus. The posterior gland can be seen peeking out behind the anterior gland; pass your mouse cursor over the image for labels image courtesy of Dr. The anterior and posterior pituitary have separate embryological origins. In many mammals, there is also an intermediate lobe pars intermedia between the anterior and posterior pituitary. A key to understanding the endocrine relationship between hypothalamus and anterior pituitary is to appreciate the vascular connections between these organs.
As will be emphasized in later sections, secretion of hormones from the anterior pituitary is under strict control by hypothalamic hormones. These hypothalamic hormones reach the anterior pituitary through the following route: A branch of the hypophyseal artery ramifies into a capillary bed in the lower hypothalamus, and hypothalmic hormones destined for the anterior pituitary are secreted into that capillary blood.
Blood from those capillaries drains into hypothalamic-hypophyseal portal veins.