11.20.11+-+Endocrine+System


 * **Define hormone, target organ, endocrine, paracrine, autocrine, juxtacrine.**
 * Hormone: chemical (protein or lipid) that communicates signal
 * target organ: target of hormone
 * Endocrine: ductless glands/tissues derived from epithelia that produce hormones to be secreted into blood (connective tissue); global effect with feedback mechanisms
 * Paracrine: hormones secreted, received by receptors in neighboring cells
 * Autocrine: hormones secreted, received by receptors on secreting cell
 * Juxtacrine: message transfered via two cellular membrane proteins (e.g. MHCII - CD4+)
 * **List 5 structural (chemical) classes of hormones.**
 * Three amino acid (aa) based classes
 * amino acid (1 aa)
 * Small peptide chain (few aa)
 * protein or glycoprotein (many aa)
 * Two lipid based classes
 * cholesterol based
 * arachidonic (polyunsaturated omega-6 fatty) acid based
 * **Define neuroendocrine hypothalamo-hypophyseal system and hypophyseal portal system.**
 * Neuroendocrine hypothalamo-hypophyseal system has two parts, the hypothalamus (a part of the diencephalon) and the hypophysis (a two part adeno/neurohypophysis endocrine structure). The hypothalamus sends hormones that regulate the activity of the adenohypophysis, directly supplies the hormones of the neurohypophysis, directly modulates the activity of the adrenal medulla. The adenohypophysis releases six hormones (FLAT PeG). The cells that produce FSH, LH, ACTH, and TSH are basophilic. The cells that produce prolactin and GH are acidophilic
 * The hypophyseal portal system is one of the three portal systems in the body (penis, kidney). Blood flows into the hypothalamus and spreads into capillaries. The hypothalamus releases its regulatory factors that enter the blood through the capillary walls, travel through venules, and enter another capillary bed in the adenohypophysis, where they modulate the activity of the endocrine cells of the adenohypophysis.
 * **Describe the embryonic origins of the adenohypophysis and neurohypophysis.**
 * Adenohypophysis originates from Rathke's pouch, diverticulum of roof of oral cavity.
 * Heurohypophysis originates from diverticulum of diencephalon.
 * **Describe the parts of the pituitary gland.**
 * There are two names for the pituitary gland, the pituitary gland and the hypophysis. When speaking of the pituitary gland, it is subdivided into the anterior and posterior lobes. These lobes correlate with the adeno (anterior) and neuro (posterior) portions of the hypophysis. Two names, each with two parts, describing the same thing.
 * The adenohypophysis is divided into three parts: the pars intermedias, the pars distalis, and the pars tubularis.
 * The neurohypophysis is also divided into three parts: the pars nervosa, infundibular stem, and median eminence.
 * Describe staining properties of acidophils, basophils and chromophobes of the adenohypophysis.
 * Acidophils stain pink
 * Basophils stain blue
 * Chromophobes don't stain
 * Acidophils, basophils, and cromophobes are all present in the pars distalis of the adenohypophysis.
 * Cords and follicles of basophils are present in the pars intermedias of the adenohypophysis.
 * Only gonadotrophs (basophils) are present in the pars tubularis of the adenohypophysis.
 * List five endocrine cell types of the adenohypophysis based on staining characteristics and specific hormone products. List the hormones secreted by each cell type and their effect on target organs.
 * Chromophobe - none, unknown function
 * Gonadotroph - FSH, LH - Basophil - FSH stimulates follicular (egg/sperm) development; LH stimulates either androgen release (Male) or ovulation (female)
 * Corticotroph - ACTH - Basophil - ACTH stimulates activity of adrenal cortex
 * Thyrotroph - TSH - Basophil - TSH stimulates thyroid activity (T3, T4 production/release)
 * Somatotroph - GH - Acidophil - GH mainly acts on liver, which in turn releases somatomedins, which makes bones grow
 * Mammotroph - Prolactin - Acidophil - Goes to breasts, stimulates milk secretion
 * Describe the histologic appearance of the pars intermedia and pars nervosa.
 * The pars intermedia (part of adenohypohysis) is a region of basophils surrounding micro cysts (remnants of Rathke's pouch), arranged in follicles.
 * The pars nervosa (part of neurohypophysis) has three important structures: fibers of nervous tissue that not very stained; highly stained basophilic nuclei that are pituicytes (branching glial cell); Herring bodies: storage bodies of hormones transported from hypothalamus to neurohypophysis
 * Name two products released from the pars nervosa. State where these products are synthesized and list their functions.
 * Oxytocin and Vasopressin are the two products released from the pars nervosa. These products are stimulated in the hypothalamus and sent via nerve fibers to be stored in the pars nervosa of the neurohypophysis in Herring bodies.
 * Oxytocin causes contractions of smooth muscle in the vagina, penis, uterus, and breast myoepithelial cells for ejaculation, childbirth, and milk secretion. All at the same time!
 * Vasopressin causes increased retention of water, raising blood pressure.
 * Describe the functions of Herring bodies and pituicytes.
 * Herring bodies: store products of hypothalamus (oxytocin and vasopressin) in pars nervosa of neurohypophysis.
 * Pituicytes: structural support of pars nervosa
 * List the layers of the adrenal cortex. Describe the histologic arrangement of each.
 * Salt: glomerulusa, arranged as balls on the outside, thin layer, produces aldosterone, which increase Na+ retention through angiotensin cycle
 * Sugar: fasciculata, arranged as columns with capillaries in the mid-cortex, thick layer, produces cortisol, which causes amino acid and lipid uptake, and insulin release
 * Sex: reticularis, arranged in network like layer in deep cortex, mid-sized layer, produces androgens, women and children important development effects
 * Name the hormone(s) elaborated by each layer of the adrenal cortex. Describe the function and regulation of these hormones.
 * Done
 * Describe the histologic organization of the adrenal medulla. Identify the cell types forming it. Name the substances released by these cells.
 * Histologic organization: clumps and cords of basophilic (slightly granulated) cells. Highly vascularized by venules.
 * Cell types: called chromaffin cells due to an old stain, but they are neural crest derived modified post-ganglionic sympathetic neurons
 * Norepinephrine, epinephrine, and enkephalins (serotonin)
 * Describe the relationships implied in the mnemonic: salt - sugar - sex - sympathetics.
 * Glomerulosa - Salt
 * Fascisulosa - Sugar
 * Reticular - Sex
 * Medulla - Sympathetics
 * Name two hormonal products released by the thyroid gland.
 * T3 and T4 and calcitonin
 * Describe the histologic structure of the thyroid gland. Identify the location of and products released by thyroid follicular and parafollicular cells.
 * Histologic Structure: Big pink follicles filled with thyroglobuilin, surrounded by follicular cells (and parafollicular cells that are not visible in our stain). Follicular cells are separated by many fenestrated capillaries.
 * Products: Thyroid follicular cells secrete T3 and T4
 * Products: Thyroid parafollicular cells secrete calcitonin
 * Describe the nature of thyroid colloid/thyroglobulin.
 * Thyroglobulin is a protein produced by follicular cells. It is stored in the thyroid colloid. It is very acidophilic.
 * Sequentially describe the steps in the synthesis and accumulation of thyroid hormone by follicular cells.
 * Functionally, thyroglobulin is the storage precursor of T3 and T4. Iodide is released into the follicular lumen and tyrosine residues that are a part of thyroglobulin are iodized by thyroid peroxidase to produce MIT and DIT. At this point, MIT and DIT are still part of the thyroglobulin chain. When ready for release, MIT and DIT are pinocytozed by the follicular cells, cleaved from thyroglobulin, and released into capillaries.
 * Describe the functions and regulation of thyroxine and calcitonin.
 * Thyroxine upregulates metabolism (catabolism, development). Regulated by TSH.
 * Calcitonin decreases plasma Ca2+ levels by inhibiting action of osteoclasts. Regulated by Ca2+ serum levels.
 * Identify two parenchymal cell types found in parathyroid glands.
 * Chief cells: pale, smaller, very common
 * Oxyphil cells: pink, larger, less common
 * Stroma formed by reticular fibers. Also, unilocular adipocytes present.
 * Name the hormone elaborated by the parathyroid glands. Describe the function and regulation of this hormone.
 * Parathyroid hormone (Parathormone). Increases serum Ca2+ levels by stimulating activity of osteoclasts. Regulated by Ca2+ serum levels.
 * Identify three target organs/cells of parathormone.
 * osteoclasts - stop!
 * kidney - uptake Ca2+!
 * intestine - uptake Ca2+!
 * Describe the histologic structure of the pineal gland, name its primary endocrine product, and describe brain sand.
 * Melatonin - secreted by mass of pink cells pinealocytes. Pinealocytes are modified neurons
 * Brain Sand - Big blue cells that have accumulated Ca and Mg deposits, function unknown, histologic marker
 * Capsule (made of pia mater), with septa (filled w/ vessels/nerves). Glial cells (astrocytes, support structure). Fibroblasts.
 * Identify the following microanatomical structures in photomicrographs of histological sections:
 * Thyroid Gland
 * Medulla
 * Follicular Cell
 * Medullary Cells
 * Colloid/Thyroglobulin
 * Parathyroid Gland
 * Pituitary Gland
 * Principal Cell
 * Pars Distalis
 * Oxyphil Cell
 * Acidophils
 * Adrenal Gland
 * Basophils
 * Capsule
 * Chromophobes
 * Cortex
 * Pars Intermedia
 * Zona Glomerulosa
 * Pars Nervosa
 * Zona Fasciculata
 * Pituicytes
 * Zona Reticularis
 * Herring Bodies