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Thread: Pars Distalis, Intermedia, and Nervosa picture - Endocrine Histology Atlas

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    Default Pars Distalis, Intermedia, and Nervosa picture - Endocrine Histology Atlas

    Although classification of cells as acidophils or basophils is useful in some situations, specific identification of anterior pituitary cells requires immunostaining for the hormone in question.

    In addition to differential staining characteristics, the size of secretory granules varies among different types of cells in the anterior pituitary. Somatotropes and lactotropes tend to have the largest size granules. The electron microscopic image below of ovine adenohypophysis depicts cells with several densities and sizes of granules.

    The portion of the adenohypophysis known as the pars tuberalis contains cords of epithelial cells and is filled with hypophyseal portal vessels. It reportedly contains gonadotropes and thyrotropes, plus other secretory cells of unknown function.
    Pars Distalis, Intermedia, Nervosa picture attachment.php?s=20fda2adc9acae2b3aebdf397fcb1a93&attachmentid=1339&d=1439157804

    The pars intermedia is closely associated with pars nervosa and separated from the pars distalis by the hypophyseal cleft. This lobe of the pituitary shows considerable variation in size among species. It is small in man, but much larger in species such as amphibians. The pars intermedia contains large pale cells that often surround follicles filled with ill-defined "colloid". Melanocyte-stimulating hormone is the predominant hormone secreted by the pars intermedia. The images below show pars intermedia from a cat at low and higher magnification. The hypophyseal cleft is seen in the middle of the left image. In the right image, the three round, clear areas are follicles characteristic of this tissue.

    In the mouse, the pituitary gland (hypophysis) is attached to the ventral surface of the brain (see Diagram of Endocrine Organs in Head – In Situ) and is heavier in females than in males; its size also differs between strains. The pituitary gland has three well-defined regions: pars distalis (anterior lobe), pars intermedia (intermediate lobe), pars nervosa (neural lobe or neurohypophysis). Pars distalis and pars intermedia are also known as adenohypophysis. They are separated from each other by the hypophyseal (residual) cleft, which is lined by low cuboidal epithelium. The pars distalis is the largest and most vascular lobe. The secretory cells of the pars distalis are grouped in cord separated by sinusoids. They are classified, based on their staining with hematoxylin and eosin, into chromophobe cells, acidophils, and basophils.

    The 4X micrograph is an overview of the pituitary gland and its surroundings. The 10X micrograph exhibits the three different lobes of the pituitary gland with the hypophyseal cleft separating pars intermedia and pars distalis. The 20X micrograph shows the cuboidal epithelial lining of the hypophyseal cleft. The 40X micrograph displays the different cells present in the pars distalis.

    The Endocrine System

    The endocrine system functions as a means of communication among the different cells and organs of the body. The other major communications system is the nervous system. In contrast to the nervous system, the endocrine system elicits a slower response, but its effects are of longer duration. The cells of endocrine organs secrete and release hormones, which are carried in the bloodstream to their target cells in widely separated organs and tissues. The endocrine system is therefore a ductless secretory system. All endocrine organs are richly supplied with blood vessels.

    The hormones of the endocrine system are chemically divided into several categories. (1) The steroid hormones are derived from cholesterol and are produced by the gonads and the adrenal cortex. (2) Most hormones are small peptides, or proteins or glycoproteins. Such hormones are produced by the hypothalamus, pituitary (hypophysis), parathyroid, pancreas, and the enteroendocrine cells of the gastrointestinal tract and lungs. (3) The catecholamines of the adrenal medulla, epinephrine and norepinephrine, are derivatives of a single amino acid, tyrosine. (4) The thyroid hormones thyroxine (T4) and T3 are derived from the oxidative coupling of two molecules of modified, iodinated tyrosine. (The thyroid hormones are sometimes lumped with category 2 or 3).

    The endocrine system and the nervous system function in conjunction with one another, and most biological phenomena are under the overlapping control of both systems. The nervous and endocrine elements are generally regarded as constituting a single neuroendocrine system.

    In the laboratory sessions, we look at the pituitary gland, adrenal gland, endocrine pancreas, thyroid and parathyroid glands.

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    Last edited by Medical Photos; 08-09-2015 at 10:03 PM.

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