TY - CHAP M1 - Book, Section TI - Endocrine Glands A1 - Mescher, Anthony L. PY - 2021 T2 - Junqueira's Basic Histology Text and Atlas, 16e AB - Endocrine Glands SUMMARY OF KEY POINTSPituitary GlandThe pituitary gland has two major parts: the posterior part called the pars nervosa develops as a downgrowth of the developing brain and is attached in the hypothalamus by the infundibulum.The anterior pituitary includes the large pars distalis, the pars tuberalis that surrounds the infundibulum, and the thin pars intermedia adjacent to the pars nervosa.Blood vessels of the hypothalamic hypophyseal portal system are important in carrying peptide factors from hypothalamic neurons to cells of the anterior pituitary where they control cell secretion.This portal system includes a primary capillary plexus in the infundibulum and lower hypothalamus and a secondary plexus in the pars distalis, connected by portal veins and draining to the hypophyseal vein.Endocrine cells of the anterior pituitary can be called acidophils, basophils, or chromophobes based on their general staining properties; the latter lack secretory granules and stain poorly.Acidophils and basophils can be identified as to which pituitary hormone they produce using immunohistochemistry and antibodies against specific hormones.Acidophils are primarily somatotrophs producing somatotropin (growth hormone), or lactotrophs (or mammotrophs) producing prolactin (PRL).Basophils include gonadotrophs producing FSH and LH and thyrotrophs making TSH.A third type of basophil is the corticotroph, synthesizing POMC that is cleaved by proteases to make ACTH and β-LPH.The hypothalamic hypophyseal tract includes bundles of nerve axons that run from supraoptic nucleus (SON) and paraventricular nucleus (PVN) in the hypothalamus to the posterior pituitary.Hypothalamic neurons in the SON synthesize vasopressin/ADH and those of the PVN synthesize oxytocin, both of which are stored in axonal dilations called Herring bodies before release to capillaries in the posterior pituitary.Adrenal GlandsThe adrenal cortex of each adrenal gland consists of three concentric zones, all histologically distinct but with cells producing steroid hormones and all drained by the same system of capillaries.The most superficial zona glomerulosa has round clusters of cells producing mineralocorticoids such as aldosterone regulating electrolyte levels.The wider, middle zona fasciculata has elongated strands of cells producing glucocorticoids such as cortisol, which regulates several aspects of carbohydrate metabolism.The innermost zona reticularis has a network of cells making the weak androgen DHEA that is converted to testosterone in men and women.The adrenal medulla contains neural crest-derived chromaffin cells synthesizing either epinephrine or norepinephrine that regulate the stress response.Pancreatic IsletsPancreatic islets of Langerhans are small clusters of pale cells embedded within the exocrine tissue; they have primarily β cells making insulin, α cell (glucagon), and δ cells (somatostatin).Thyroid GlandThe thyroid gland consists mainly of spherical follicles composed of simple epithelium of thyrocytes surrounding a lumen with thyroglobulin.Thyroglobulin is a large glycoprotein in which tyrosine residues are iodinated as precursors of the thyroid hormones thyroxine and tri-iodothyronine, which are released when the precursor is degraded.Thyroid follicles also contain a few smaller and paler cells called parafollicular cells, or C cells, which produce the polypeptide hormone calcitonin.Parathyroid GlandsOn the posterior side of the thyroid glands are four small parathyroid glands, each consisting primarily of principal cells that secrete PTH that raises blood Ca2+ levels.Pineal GlandThe pineal gland develops from embryonic neuroectoderm, remains ... SN - PB - McGraw Hill CY - New York, NY Y2 - 2024/03/28 UR - accessmedicine.mhmedical.com/content.aspx?aid=1184201680 ER -