Lecture 16 - Endocrine Anatomy & Histology PDF

ENDOCRINE ANATOMY & HISTOLOGY Thomas Wilson Graphics from Grant’s Method of Anatomy, Netters Atlas of Human Embryology, Larsen’s Anatomy, Human Embryology and Developmental Biology, Moore’s Before We Are Born, Analysis of Vertebrate Structure, McMinn’s & Abrahams Clinical A...

ENDOCRINE ANATOMY & HISTOLOGY Thomas Wilson Graphics from Grant’s Method of Anatomy, Netters Atlas of Human Embryology, Larsen’s Anatomy, Human Embryology and Developmental Biology, Moore’s Before We Are Born, Analysis of Vertebrate Structure, McMinn’s & Abrahams Clinical Atlas of Anatomy, Human Anatomy Colour Atlas & Textbook [email protected] Goal: To understand how development of endocrine glands influences their adult structure and function Outline: Outcomes: Anatomy and histology of: Describe the histological appearance and structure of endocrine organs from a low magnification perspective Pituitary gland Pineal gland Identify different endocrine organs and cell types in histological section, and describe the secretion of that organ and/or cell type. Thyroid gland Identify the gross anatomy of endocrine organs, as well as their Parathyroid gland blood supply, nerve supply and venous drainage. Adrenal gland Endocrine pancreas  sits in pituitary µ fossa suprachiasmatic nucleus ] ventricular para nucleus ✓ Pineal gland o↑;Easm pituitary gland PART 2: In fund ibulum clinoid process spenoid air sinus Anatomy &/or Histology Pituitary Gland: Anatomy Sits in sella turcica (AKA pituitary fossa) of sphenoid bone In the middle of a ‘4-poster bed’ (clinoid processes) Posterior to sphenoid air sinus Surrounded by cavernous dural sinus 6 5 I Posterior pituitary connected to hypothalamus via Infundibulum (means funnel) Hypothalamic hypophyseal tract connects neurons of hypothalamic nuclei to their release site in P.Pit → capillary bed → capillary bed Pituitary has a ‘portal venous system’ connecting the venous drainage of the hypothalamus to the pituitary gland Mechanism for how hypothalamic hormones act on A.Pit Pituitary Gland: Histology Anterior pituitary (adenohypothysis, cerebral hypophysis) A P Epithelial glandular tissue (remember how it developed?) " " stalk heads down → infvndibulum ' towards Pars nervosa ' Pars tuberalis (pars: ‘a share of’): Wrapped around infundibulum Brings more vasculature to the infundibulum → acidic cytoplasm Mostly basophilic cells secreting AdenoCorticoTrophic Hormone (ACTH), Follicle Stim.Horm (FSH), Luteinising Hormone (LH; ‘L’ means yellow) Pars distalis Largest component of pituitary I → more basic cytoplasm Acidophils: Secrete Growth hormone (GH) & prolactin Basophils: Secrete ACTH, FSH, LH, Thyroid Stim.Horm (TSH) Pars intermedia → goes back & works on pineal gland as well Mostly basophils: Secrete Melanocyte Stimulating Hormone (MSH) Chromophobe cells → clear cytoplasm Can have colloid (fluid filled) cysts which are remnants of Rathke’s pouch Remnant from ↳ fluid with macromolecule material dispersed throughout Fhathke's pouch Note: cells can also be named based on function ← can't see function Somatotrophs, lacto/mammotrophs, corticotrophs, gonadotrophs, thyrotrophs ↳ relate to growth ↳thyroid ↳ lactation ↳ act on cortex ↳ gonads of adrenal gland Posterior pituitary (neurohypophysis) Stores Anti-Diuretic Hormone (ADH) & Oxytocine, which are Infundibulum: Hypothalamic hypophyseal tract synthesised in the hypothalamus Pars nervosa: Herring bodies and pituicytes ADH: From supraoptic nucleus of hypothalamus to just above optic nerve cross over Herring bodies are swollen secretory terminals that store ADH Oxytocin (means quick birth): From paraventricular nucleus because nerve cells OR oxytocin, not both in one H.body (WHY?) from either hypo - ↳ beside the ventricle nuclei are Pituicytes regulate release of herring body contents specific ↳ specialised type of glial cell  Copyright © McGraw-Hill Education. Permission required for reproduction or display. Blood vessel Basophil Acidophil Chromophobe (a) Anterior pituitary "" "" Hormone stored in nerve endings (Herring bodies) Glial cells (pituicytes) Anterior pituitary Nerve fibers (b) Posterior pituitary (a–b): © Biophoto Associates/Science Source Pineal Gland: Histology Location: Posterior wall of third ventricle, midsagittal Astrocytes → dendritic projections ‘Star-shaped’ glial cells with very dark nuclei Pinealocytes → large , clear A maintenance cell Large cells with pale round nuclei surrounded by pale cytoplasm ↳ attach onto neighbouring pinealoocytes & blood vessels ↳ are apart of BBB Secrete melatonin rhythmically on 12hr light/dark cycle Brain sand: Corpora arenacea Directed by retinal light detection… Composition of calcium & magnesium salts ‘Stringy’ appearance made by astrocytes & pinealocytes  r " " "" "" Thyroid Gland: Anatomy " ;; Vagus m. thy ro cervical Location: trunk Deep to the cervical strap muscles Sits just inferior to the thyroid & cricoid cartilages * m 2 lobes connected by an Isthmus (a narrowing between 2 seas) i i Pyramidal lobe: Remnant of thyroid migration Hence, usually found to be pointed to the midline, superiorly ⑧O Blood supply: """ " " External carotid  Superior thyroid arteries ↑ Subclavians (thyrocervical trunk)  Inferior thyroid arteries superior thyroid a. Which nerves relate to this trunk, and what side does each pass? (branch of external carotid) Drainage: Superior / middle / inferior thyroid veins Superior & middle thyroid veins  Internal Jugular Vein superior Inferiors can drain anywhere from brachiocephalic, IJV, SVC thyroid V. ʰ middle thyroid v. Innervation: Concerning bloodsupply and sensation """ "" Sympathetics from cervical ganglia (Sup/mid/inf) ← 1¥ inferior thyroid v. Vagus (CN X, laryngeal & recurrent laryngeal branches) post - sympathetic branches ganglia GVA: Visceral sensation supply vasculature NO PARASYMPATHETIC INNERVATION, just sympathetic tone (apologies for the error in recording) Thyroid Gland: Histology Thyroid lobule: Bunch of follicles separated into a fascial capsule Thyroid follicles: Extracellular colloid storage lakes Follicular cells (simple cuboidal epithelial border of ‘lake’) produce: Thyroglobulin: Large protein that binds many different THs I 4. abundant Tetraiodothyronine (T4) (aka thyroxine) ↳ just call 1-3/4 → , less potent Triiodothyronine (T3): The more potent, but less abundant one →thyroid stimulating hormone TSH (from A.Pit) stimulates follicular cells to ingest thyroglobulin via endocytosis from the ‘lake’ Also stimulates further synthesis of T3 & T4 (to replace cleared /exocytosed) → exocytosed T3 & T4 are cleaved from thyroglobulin & released into bloodstream Follicle Effect: ↑ metabolic rate in almost all body tissues " " Lake Parafollicular cells (aka C-cells): Grainy cells between follicles Secrete calcitonin: Acts by inhibiting osteoclasts, which reduces serum [Ca2+] a Parathyroid Gland " " takes posterior vein Parathyroid Gland ☆ has dense capillary bed passing through due PTH importance to Location: 2 on posterior side of each thyroid lobe About the size a grain of rice (130mg) Not easily observed, often hidden within thyroid tissue 2 cell types present: - Chief cells: Most abundant Small with round nucleus, pale acidophilic cytoplasm ← chief cells & Oxyphi tic cells & Secrete ParaThyroid Hormone (PTH) when [Ca2+] is low Counters calcitonin by stimulating osteoclast activity which raises serum [Ca2+] via bone resorption Also increases GIT absorption of calcium Oxyphilic Cells: Less abundant, often clustered Only appear after 6-7yoa & increase in number with age Only observed in some mammals… Very acidophilic cytoplasm, uniform nuclei, and BIG More cytoplasm visible compared to chief cells What do they do? ↳ unknown - stop producing PTH Adrenal Gland: Anatomy Location: on top of the kidney Primary Retroperitoneal Blood supply: Paired adrenal arteries from abdominal aorta Can have branches from inferior phrenic & renal arteries Arteries enter through external capsule, supplying cortex first Drainage: In a cortex  medulla direction (not counter current like many other organs) Central adrenomedullary vein  renal veins (caval system) The right A.G. can drain directly into IVC as well Innervation: lesser splanchnic Sympathetics from aorticorenal ganglion (T10-11) Parasympathetics (blood vessels) from Vagus nerve ↳ Vasoconstrict to minimise the release of things into the blood Adrenal Gland: Medulla Histology in medulla Many large blood vessels centrally, with Chromaffin cells so fenestrated capillaries spreading throughout the Light pale nucleus, pale basophilic cytoplasm medulla  towards the cortex Synthesise and secrete Adrenaline & Nor Adrenaline (catecholamines) AKA Epinephrine Nor epinephrine Quite clear border with the cells of the cortex Involved in stress responses regulated by sympathetic activation Longer lasting & systemic effect, compared to normal sympathetic nerve NAdr ↳ not specific target MEDULLA venue ✗ ,,, µ central mealy Hary. Adrenal Gland: Cortex Histology Fibrous capsule Superficial Deep: all have acidophilic cytoplasm 1. Zona Glomerulus (ball of thread) Small curved cell columns, dark round nuclei Spongy appearance, but not as much as Z.F. Secretes mineralocorticoids, mainly Aldosterone " " water retension 2. Zona Fasciculata (Bunched) Roughly ¾ of cortex Radially orientated fascicle-like tubes of cells Separated by fenestrated capillaries Very pale contents that appear ‘spongy’ (cholesterol = steroid precursor) Secretes glucocorticoids, mainly cortisol Tumours/hyperplasia of this zone can result in Cushing’s disease 3. Zona Reticularis (Network) Branched cords of cells with sinusoidal space between Smaller cells Least ‘spongy’ looking Secretes androgens (gonadocorticoids), mainly DHEA Not fully present until 3yoa  Which layer belongs to which image, & WHY? B: Zona reticularis A: Zona glomerulus C: Zona Fasci cut ata ENDOCRINE Pancreas: Histology Pancreatic islets (of Langerhan’s) make up the endocrine pancreas ~1-2% total pancreatic cell count Higher blood supply /gram of tissue than the exocrine pancreas Pan: Bread Kreas: flesh, due to it being entirely ‘flesh’, AKA sweetbread Made up of 4 cell types, which secrete: 1. Alpha (~20% total Islet cells) – Glucagon ↑serum glucose – utilise the store 2. Beta (~70% total Islet cells) – Insulin ↓serum glucose - store islet 3. Delta (~5-10% total Islet cells) – Somatostatin (‘body static’) Inhibits glucagon and insulin secretion Inhibits gastric parietal cells (HCl secretion) Inhibits growth hormone and TSH 4. PP-cells (aka epsilon cells; ~1%) – Pancreatic polypeptide ftp.rotiolytic Upregulates gastric chief cells (pepsinogen secretion) Inhibits bile, pancreatic enzyme, bicarbonate secretions & intestine motility Pancreas stained with red anti-insulin antibody visualising beta " " cells alpha " " cells visualising Pancreas stained with red anti-glucagon antibody Micrographs taken by Dr. Jamie Chapman of University of Tasmania Clinical relevance PREGNANCY! The End! Hyperthyroidism with ‘goiter’ (iodine deficiency in this case) Adrenogenital Syndrome (AGS) Cushing’s Syndrome JFK had Addison’s disease