Ingegneria delle tecnologie per la salute Fondamenti di anatomia e istologia Apparato endocrino homeostasis homeostasis overview Cellular signalling Lipid-soluble hormones Water soluble hormone overview Negative feedback Positive feedback X-RH : releasing hormones X-SH : stimulating hormones (acting on endocrine gland) X : Hormones (acting on target cell) Pituitary gland-hypophysis Pituitary gland-hypophysis Pituitary gland-hypophysis ectoderm endoderm Pituitary gland-hypophysis Size of a pea, 0.5 g wheigth On the basis of the hypothalamus, in the sella turcica (sphenoid bone) Strictly related with the optic chiasm (bitemporal hemianopsia in pineal adenomas Posterior pituitary gland Posterior hypophysis: hormones ADH: peptide, anti-diuretic hormone, aka Arginine-Vasopressine (AVP). Stop water reabsorption in collector tubules of kidney. Weak vasoconstriction. OT: oxytocin, peptide, uterine contraction in childbirth. Positive feedback Anterior pituitary gland Portal system Anterior hypophysis: hormones Pineal gland - epiphysis Produces melatonin that regulates circadian rythm thyroid Anterior to the trachea, two lobes, under the cricoid cartilage. Endodermic origin Anterior: platisma and skin Posterior: trachea, superior and inferior laringeal nerves, parathyroids lateral: great vessel of the neck parathyroids Four glands, endodermic, 6x3x1mm, posterior to the thyroid. Produce parathormone (PTH) in that regulate calcium metabolism PTH: increases serum calcium levels Calcitonin: produced by parafollicolars cell of thyroid Vitamin D Calcium reabsorption stimulates osteoclasts Adrenal glands Medial to the kidney, 5x3 cm Two different components: medulla and cortex. Medulla: ectodermal origin (nervous system) Cortex: mesodermic origin Adrenal glands Cortex: under the control of CRH and ACTH secerned by hypothalamus and hypophysis Medulla: ddriven by autonomous nervous system, it can considered a special sympathetic ganglion Adrenal glands Corticoids hormones: all derived from cholestherol, lipid hormones Mineralcorticoids: Aldosterone, regulates Na reabsorption in kidneys and regulates angiotensin secretion blood pressure Glucocorticoids: cortisol, stress hormone, reguates glucose levels and metabolism Androgens: dehydroepiandrosterone, androstenedione. In female they are converted into estrogens periferically. Endocrine pancreas Pancreatic islets Pancreatic islets About 3.000.000, 0.1 mm diameter 4.5% of the pancreatic volume Endodermic origin Alpha cells: produce glucagon (15–20% of total islet cells). Arise serum glucose Beta cells producing insulin and amylin (65–80%): reduce serum glucose Delta cells producing somatostatin (3–10%): inhibits all secretions PP cells (gamma cells) producing pancreatic polypeptide (3–5%): inhibits pancreatic secretions Epsilon cells producing ghrelin (<1%): hunger hormone Paracrine function: glucagon inhibits beta cell, insulin inhibits alpha cell, somatostatin inhibits alpha and beta. Enteroendocrine cells Enteroendocrine cells are specialized endocrine cells of the gastrointestinal tract and pancreas. They produce gastrointestinal hormones or peptides in response to various stimuli and release them into the bloodstream for systemic effect, diffuse them as local messengers, or transmit them to the enteric nervous system K cell: secrete incretin that promotes trygliceride storage I cell: secrete Cholecystokinin, secretion of bile G cell: (stomach), secrete gastrin N cell: neurotensin, smooth muscle contraction S cell: secrete secretin, stimulates exocrine pancreas secretion .