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Thread: Basophils and Acidophils picture - Endocrine Histology Atlas

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    Default Basophils and Acidophils picture - Endocrine Histology Atlas

    Pituitary Gland

    The pituitary (also known as the hypophysis) is found at the base of the brain, about 1cm in diameter, lying beneath the third ventricle in a bony cavity (sella turcica) in the base of the skull. It has a complex structure. This diagram of the pituitary shows its main features.

    The adenohypophysis can be further subdivided into the pars distalis, pars intermedia, and pars tuberalis. The pars distalis is the anterior lobe of the pituitary. The adenohypophysis is regulated by releasing hormones from the hypothalamus.

    The adenohypophysis (more specifically, the pars distalis of the adenohypophysis or anterior pituitary) secretes tropic hormones.

    On a histology slide, it is apparent that there are several cell types in the pars distalis of the adenohypophysis (anterior pituitary).

    The cells of the pars distalis (anterior pituitary) can be classified as acidophils or basophils depending on their affinity for acidic histology dyes or basic histology dyes, respectively. The acidophils are the somatotropic cells and the lactotropic cells. Thus, growth hormone and prolactin are secreted by acidophilic cells. The basophils are the gonadotropic cells, corticotropic cells and thyrotropic cells. Thus, the basophils secrete FSH, LH, ACTH, and TSH.

    Lactotropic cells secrete prolactin. Thyrotropic cells secrete thyroid stimulating hormone (TSH). Somatotropic cells secrete growth hormone. Corticotropic cells secrete adrenocorticotropic hormone (ACTH) and melanocyte-stimulating hormone (MSH). Gonadotropic cells secrete follicle stimulating hormone (FSH) and luteinizing hormone (LH)

    Histology hint Sarah Bellham: there are two mnemonics to use when thinking of acidophils and basophils of the anterior pituitary.

    "GPA" (growth hormone and prolactin are secreted by the acidophils).

    "B-FLAT" (basophils secrete FSH, LH, ACTH, and TSH).
    Basophils Acidophils picture Endocrine Histology attachment.php?s=ed97b974b0a69ba693cf7ae530a4004f&attachmentid=1324&d=1439064900
    But acidophilic and basophilc cells aren’t only characterized by different pattern of production of hormones, but also by they localization in the anterior pituitary. Acidophilic cells are most adboundant in the antero-lateral area, the basophilic cells in the posterior-central area.
    Even after differentiation, pituitary cells continue to undergo mitosis and this process could be augmented under certain conditions in adulthood.
    There is increasing evidence indicating that some anterior pituitary cells are multifunctional in nature and could exhibit mixed phenotypes. Interestingly, multifunctional cells are found to be more abundant in females than in males, indicating that the hormonal changes associated with the cyclical events in females may promote transdifferentiation.
    Pituitary cell differentiation and growth are dependent on many locally produced and released molecules acting in autocrine or paracrine manners. These include nitric oxide, ATP, acetylcholine and peptide factors such as endothelins, activins, neurotropins, leukemia inhibitory factor and insulin-like growth factors.

    Pituitary Development

    The cells destined to become the endocrine pituitary gland are located in the midline of the anterior neural ridge. The neural ridge forms a pocket (Rathke's pouch ) that comes into contact with, and invaginates into, the ventral diencephalon. Together they will form the pituitary, the anterior (endocrine) pituitary originating from Rathke's pouch, and the posterior (neural) pituitary originating from the ventral diencephalon.
    The three major stages in the formation of the anterior pituitary gland are: (1) extrinsic signals that cause cell proliferation and determination as pituitary; (2) intrinsic signaling gradients within Rathke's pouch activate a core group of transcription factors; and (3) commitment of cells to particular lineages through combinatorial associations of transcription factors.
    Stage 1: Initial proliferation and induction.
    The first stage of anterior pituitary growth and differentiation involves extrinsic paracrine signals from the diencephalon (dorsally) and from the pharyngeal (oral) ectoderm ventrolaterally (Figure 1). The diencephalon cells produce BMPs, Wnt5a, and FGF10. The oral ectoderm produces Sonic hedgehog. FGFs and sonic hedgehog are critically important at this stage. BMP4 is required for the cell division of Rathke's pouch. Sonic hedgehog is expressed throughout the oral ectoderm, except in the region that is destined to become Rathke's pouch. This combination of signals, from top and bottom, cause the Rathke's pouch cells to express the transcription factor LHX3, a critical factor for specifying these cells as the precursors of the endocrine cell types.

    Stage 2: Intrinsic signaling and specification.
    The patterning of Rathke's pouch is established by intrinsic gradients of paracrine factors within the ectoderm, itself, and from the condensing mesenchyme associated with the pouch. First a ventral-to-dorsal gradient of BMP2 and Indian hedgehog is established within the ventral ectoderm of the pouch (BMP2) and in the condensing ventral mesenchyme (BMP2, Ihh). In the opposite direction is a dorsal-to-ventral gradient of FGFs. These gradients cause overlapping sets of transcription factors to be synthesized in different populations of cells, according to their positions along the dorsal-ventral axis (Figure 2). Many of these transcription factors are required to regulate the expansion of particular sets of multipotent precursor cells.

    Stage 3. Cell commitment.
    The information in the transient gradients of paracrine factors becomes stabilized in the discrete pattern of transcription factor synthesis (Figure 3).

    References:
    Anterior Pituitary
    http://www.histology-world.com/facts...pituitary1.htm
    Histology Guide | Glandular











    Last edited by Medical Photos; 08-08-2015 at 08:15 PM.

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