Histology Lecture 3: Endocrine System PDF

University of Alkafeel, College of Medicine, Year 2, Course 2 Histology - Lecture 3 Endocrine system By: Assistant Professor Dr. Rasha Dosh 1...

University of Alkafeel, College of Medicine, Year 2, Course 2 Histology - Lecture 3 Endocrine system By: Assistant Professor Dr. Rasha Dosh 1  Learning objectives 1. Classify endocrine glands based on chemical components of their secretion. 2. Describe the basic histological characteristics of all endocrine glands. 3. Identify & describe the glandular and nervous tissue components of the pituitary gland. 4. Identify & describe the microscopic structures of anterior and posterior pituitary. 5. Identify & describe the structure and function of the thyroid gland, parathyroid gland, adrenal gland, pineal gland. Email :[email protected] Website :http://Alkafeel.edu.iq 2  Endocrine system  This system is comprised of a variety of ductless glands.  All endocrine glands secrete their products (hormones) into the connective tissue surrounding the secretory elements; from there, those products enter bloodstream through capillaries and reach target organs.  Molecules that have an effect on specific organs called target organs  Only cells with specific receptors for the hormone respond to that hormone called target cells  Organs, tissues, or cells lacking the specific receptor do not respond to its stimulating effects.  Paracrine control-act on adjacent cells that express specific receptors for that particular hormone  Autocrine control- cells express receptors for hormones that they secrete. Email :[email protected] Website :http://Alkafeel.edu.iq 3 Distributed in three ways: Major Endocrine glands Pituitary gland, Thyroid, Parathyroid, Adrenal, Pineal Organs contain group of endocrine cells Islets of Pancreas, Gonads (Testes ,Ovary), Thymus, hypothalamus Isolated endocrine cells / APUD / Neuroendocrine system Lining epithelium of GIT, Respiratory tract Email :[email protected] Website :http://Alkafeel.edu.iq 4 Development of glands Email :[email protected] Website :http://Alkafeel.edu.iq 5 Email :[email protected] Website :http://Alkafeel.edu.iq 6 Types of endocrine glands Email :[email protected] Website :http://Alkafeel.edu.iq 7 Email :[email protected] Website :http://Alkafeel.edu.iq 8 Major endocrine glands Email :[email protected] Website :http://Alkafeel.edu.iq 9 Email :[email protected] Website :http://Alkafeel.edu.iq 10 Pituitary gland/ Hypophysis Cerebri Email :[email protected] Website :http://Alkafeel.edu.iq 11 Subdivisions of pituitary gland Email :[email protected] Website :http://Alkafeel.edu.iq 12  Pituitary gland/ Hypophysis cereberi The hypophysis consists of glandular (Adenohypophysis) & nervous portions (Neurohypophysis) At low power, identify: Adenohypophysis (anterior pituitary)  Pars anterior (pars distalis;).  Pars intermedia( remnant of rathke pouch rudimentary in human beings).  Pars tuberalis Neurohypophysis:  Pars nervosa ( posterior pituitary) consist of median eminence and infundibulum. Email :[email protected] Website :http://Alkafeel.edu.iq 13 Email :[email protected] Website :http://Alkafeel.edu.iq 14 Email :[email protected] Website :http://Alkafeel.edu.iq 15 Connections of pituitary gland Email :[email protected] Website :http://Alkafeel.edu.iq 16 Blood supply of pituitary gland Email :[email protected] Website :http://Alkafeel.edu.iq 17 Connections with Hypothalamus Email :[email protected] Website :http://Alkafeel.edu.iq 18 Email :[email protected] Website :http://Alkafeel.edu.iq 19  Anterior Pituitary  (Distalis /Pars Anterior) Cells can be divided into two classes on the basis of their staining characteristics: Chromophils ("color-loving"), and chromophobes ("color-fearing"). Chromophils are further classified as acidophils and basophils. Each cell type produces only one type of hormone. parenchyma consists of secretory epithelial cells arranged in anastomosing cords and clusters. Abundant sinusoidal capillaries with fenestration Email :[email protected] Website :http://Alkafeel.edu.iq 20 Anterior Pituitary Email :[email protected] Website :http://Alkafeel.edu.iq 21 Anterior Pituitary Email :[email protected] Website :http://Alkafeel.edu.iq 22  Neurohypophysis Is a down growth from the hypothalamus Exhibits characteristics of nervous tissue. Axon terminals within this area originate from cells in the hypothalamus; those in the supraoptic nucleus produce ADH (vasopressin), while those in the paraventricular nuclei produce oxytocin. Cell bodies of these neurons are located in the hypothalamus, The pars nervosa contains no neuronal cell bodies. Pituicytes  Glial cells, variable in cell size and shape.  Herring bodies:  large unmyelinated axon terminals, containing large numbers of neurosecretory granules.  Rich capillary network present in pars nervosa Email :[email protected] Website :http://Alkafeel.edu.iq 23 Email :[email protected] Website :http://Alkafeel.edu.iq 24 Neurohypophysis Email :[email protected] Website :http://Alkafeel.edu.iq 25 Neurohypophysis Email :[email protected] Website :http://Alkafeel.edu.iq 26 Email :[email protected] Website :http://Alkafeel.edu.iq 27 Thyroid gland- general structure Email :[email protected] Website :http://Alkafeel.edu.iq 28 Email :[email protected] Website :http://Alkafeel.edu.iq 29 Thyroid Follicles Email :[email protected] Website :http://Alkafeel.edu.iq 30 Email :[email protected] Website :http://Alkafeel.edu.iq 31  Follicular epithelium  Vary from high cuboidal to low cuboidal ; reflects the level of follicle secretory activity.  Follicle cells (principal cells) have large, centrally- or basally-located nuclei,  Cells active in protein secretion.  Storage and release of thyroid hormones involves the protein thyroglobulin.  Parafollicular cells  Found scattered singly or in small groups, present in periphery of the follicles  Cells are responsible for production of calcitonin, a peptide hormone that is synthesized and secreted independently of thyroid hormone.  Also called C, clear or light cells.  Can be distinguished from follicular cells because they are large, oval, have eccentrically-placed nuclei and extensive, but lightly-stained cytoplasm. Email :[email protected] Website :http://Alkafeel.edu.iq 32 Email :[email protected] Website :http://Alkafeel.edu.iq 33 Parathyroid Glands Email :[email protected] Website :http://Alkafeel.edu.iq 34  Parathyroid Glands General structure:  Thin C.T. capsule that surrounds each gland and gives rise to internal septa.  glands are actually embedded in the capsule of the thyroid gland. Parenchyma  Present as a mass of crowded single cells, not arranged as follicles. It consist of 2 type of cells:  Chief cells (principal cells):  Numerous ,small cells with prominent nuclei, and the pale, scant cytoplasmic staining. Secrete parathyroid hormone.  Oxyphil cells:  single or clumps of larger cells with acidophilic (oxyphilic), cytoplasm with dark staining nucleus.  Number increase with age. Email :[email protected] Website :http://Alkafeel.edu.iq 35 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 36 Email :[email protected] Website :http://Alkafeel.edu.iq 37 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 38 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 39 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 40 Email :[email protected] Website :http://Alkafeel.edu.iq 41 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 42 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 43 Adrenal/ suprarenal gland Email :[email protected] Website :http://Alkafeel.edu.iq 44  Pineal gland  It is an neuroendocrine gland that regulates daily body rhythm.  The human pineal gland relates light intensity and duration to endocrine activity.  Melatonin is a pineal gland hormone  Pineal gland is a flattened, pine, cone–shaped structure  The pineal gland contains two types of parenchymal cells: pinealocytes and interstitial (glial) cells. Email :[email protected] Website :http://Alkafeel.edu.iq 45  Pinealocytes:  Chief cells, arranged in clumps within lobules formed by connective tissue septa that extend into the gland from the pia mater.  It is a neuro secretory cell.  It has nucleated cell body like structure and also possess short and long processes like neuron.  Two types of Pinealocytes: Light and Dark Pinealocytes  Light Pinealocytes are many and large cell types. Nucleus is greatly lobulated.  Dark Pinealocytes are few in number and comparatively small in size. Nucleus is comparatively less lobulated. Email :[email protected] Website :http://Alkafeel.edu.iq 46  Pineal gland  Interstitial (glial) cells  Constitute 5% of the cells in the gland.  Astrocytes present in between the Pinealocytes.  Nucleus is elongated and dense in nature.  Corpora arenacea or brain sand  Are calcified structures in the pineal gland and other areas of the brain such as the choroid plexus.  These structures consist of calcium phosphates and carbonates in an organic matrix deposited in concentric layer Email :[email protected] Website :http://Alkafeel.edu.iq 47  References 1- Junqueira’s Basic Histology: Text and Atlas, 16th Edition, by Anthony L. Mescher. 2- A Text and Atlas: With Correlated Cell and Molecular Biology, 8th edition, by Wojciech Pawlina, Michael H. Ross Email :[email protected] Website :http://Alkafeel.edu.iq 48