Anatomy of the Endocrine System PDF

ANATOMY OF THE ENDOCRINE SYSTEM Taty Anna Kamarudin Department of Anatomy Faculty of Medicine, UKM.  Objectives Differentiate the exocrine and endocrine glands Describe the gross anatomy of the thyroid and parathyroid glands Describe the gross anatomy of the...

ANATOMY OF THE ENDOCRINE SYSTEM Taty Anna Kamarudin Department of Anatomy Faculty of Medicine, UKM.  Objectives Differentiate the exocrine and endocrine glands Describe the gross anatomy of the thyroid and parathyroid glands Describe the gross anatomy of the pituitary gland Explain the importance of hypothalamo- hypophyseal portal system Describe the gross anatomy of the adrenal glands Describe the gross anatomy of the pineal gland Apply the clinical significance of the endocrine glands, e.g.: goitre and pituitary adenoma Differences Between Exocrine And Endocrine Glands Exocrine Gland Endocrine Gland Presence of duct No duct; directly into blood Mucous or serous Hormone secretion  Endocrine glands Thyroid gland Parathyroid gland Pituitary gland Suprarenal/Adrenal gland Pineal gland Pancreas Thymus Testes Ovaries  Thyroid Gland Lies in anterior region of the neck C5 – T1 vertebrae Two lobes connected by isthmus Lateral lobes extend from oblique line of thyroid cartilage to 5th to 6th tracheal ring Isthmus : 2nd ,3th and 4th tracheal rings Surfaces : Lateral, medial and posterior Poles : upper and lower poles Coverings: Pretracheal fascia : (outer false capsule) larynx & trachea True capsules (inner) : closely adhered Between these : nerve and blood vessels (+) Thuroid gland: Relations Lateral : infra-hyoid muscles anterior border of sterno-mastoid muscle Medial : upper pole contact with inferior constrictor muscle of pharynx - larynx and trachea with pharynx and oesophagus - recurrent laryngeal nerve in tracheo-oesophageal groove - external laryngeal nerve –medial to the upper pole Posterior : prevertebral muscles - medial part of carotid sheath and its contents - sympathetic trunk - parathyroid glands Relations of thyroid gland  Anterolateral relations C5-T1 vertebrae  Posterolateral relations C5-T1 vertebrae Common carotid artery, internal jugular vein, vagus nerve Posterior relations larynx, trachea pharynx, oesophagus cricothyroid muscle and its nerve supply external laryngeal nerve recurrent laryngeal nerve C5-T1 vertebrae  Thyroid: Arterial supply Superior thyroid artery (branch of external carotid) and passes to the upper pole Inferior thyroid artery (branch of thyrocervical trunk) and passes behind the carotid sheath to the back of the gland Thyroid "ima" artery (variable) when present it arises from the aortic arch or the brachiocephalic artery Thyroid ima artery Arises from brachio- cephalic trunk, arch of aorta, right common carotid, subclavian or internal thoracic artery Unpaired ; in 10% of people Supplied isthmus Potential source of bleeding during tracheostomy  Thyroid: Venous drainage Superior thyroid veins - drains the upper pole to the internal jugular vein Middle thyroid veins - drains from the lateral side of the gland to the internal jugular vein Inferior thyroid veins - often several – drain the lower pole to the brachiocephalic veins  Superior thyroid artery and superior laryngeal nerve during thyroidectomy The superior thyroid artery (STA) is the first branch of the external carotid artery. STA runs with the external branch of the superior laryngeal nerve High ligation of the STA (away from thyroid gland) during thyroidectomy places this nerve at risk of injury, which would produce dysphonia by altering pitch regulation.  Inferior thyroid artery and recurrent laryngeal nerve The inferior thyroid artery (ITA) arises from the thyrocervical trunk, a branch of the subclavian artery. As the artery approaches the thyroid gland it crosses the recurrent laryngeal nerve. During thyroidectomy, ITA should be ligated away from the gland, where the recurrent laryngeal nerve is not close by to avoid nerve injury. Recurrent laryngeal nerve injury will cause vocal cord paralysis and hoarseness. Histology of thyroid gland Covered with capsule Septa extend into gland with blood vessels, nerve, lymphatic Thyroid follicles: -Lined by single layer of cuboidal epithelium -Lumen contains eosinophilic colloid -Inactive stage – lining cells are flat or cuboidal -Active stage – cells become columnar In aging thyroid – infiltration of thyroid by lymphocytes. Thyroid C cell -Neuroendocrine cells -Small clumps in between the follicles -In H&E – pale staining cells with granular cytoplasm -Secrete Calcitonin Thyroid disorders Goiter – abnormal enlargement Causes: Hyperplasia Nodular Diffuse Grave disease Iodine deficiency Cancer Effects: Hyperthyroidism Hypothyroidism  Parathyroid glands 2 pairs (superior and inferior) Lie at posterior aspect of thyroid Embedded in thyroid’s true capsule Within the pretracheal fascia Between the capsule and fascia: nerve and blood vessels Parathyroid glands: Blood supply Branches of the inferior thyroid artery Also the superior thyroid arteries, thyroid ima artery, laryngeal arteries, tracheal arteries or oesophageal arteries Blood drain into the plexus of veins on the anterior surface of the thyroid comprising the superior, middle and inferior thyroid veins Parathyroid gland: Histology Capsule –fibro-elastic capsule incomplete lobules carried blood, nerve and lymph Parenchyma Cells : chief cells – small round -central nuclei -pale eosinophilic cytoplasm -Synthesizes parathyroid hormone : oxyphil cells – eosinophilic cytoplasm - increase in number with age -larger than chief cells -nuclei small and condensed Parathyroid disorders Hyperparathyroidism (parathyroid adenoma) Hypoparathyroidism : due to inadvertent surgical removal during throidectomy. low Ca+ level. tetany Pituitary gland Location: hypophyseal fossa (sella turcica) Lies below the hypothalamus; Connected by infundibulum Covered by diaphragma sella (fold of duramater) Pituitary gland: relations cavernous sinus optic chiasma sphenoid bone & air sinus Pituitary gland Pituitary gland Lobes : anterior – pars distalis pars tuberalis pars intermedia posterior – pars nervosa infundibular stalk median eminence Pituitary gland  Pituitary gland: blood supply Superior and inferior hypophyseal arteries, branches of internal carotid artery. The veins drain into the cavernous sinuses.  Pituitary Gland: Connections with hypothalamus Two pathways: 1. Nerve fibres from supraoptic and paraventricular nuclei to posterior lobe (hypothalamo- hypophyseal tract). 2. Long and short portal blood vessels that connect sinusoids in the median eminence and infundibulum with capillary plexus in the anterior lobe (hypothalamo-hypophyseal portal system).  anterior lobe - receives venous blood from the hypothalamus via hypothalamo- hypophyseal portal system of veins Hypothalamus - transmits releasing factors to the pituitary Pituitary gland: Histology Pituitary gland HISTOLOGY Covered by fibro-elastic capsule Trabeculae carried blood vessels into pars distalis PARS DISTALIS (Anterior pituitary) Chromophobes : ovoid, scanty cytoplasm; with few granules - Indistinct cell membrane - Appears as NUCLEAR HEAPS Chromophil cells : distinct cell boundaries; granular cytoplasm 1.Acidophils – Alpha and Epsilon 2.Basophils -Beta, Gamma, Delta cells Pituitary gland PARS TUBERALIS Cuboidal cells with central nuclei Finely granular cytoplasm PARS INTERMEDIA -Secrete melanocyte stimulating hormone (MSH) -basophilic; small cystic space with eosinophilic materials Posterior pituitary (Pars nervosa) Non-myelinated axon Cells bodies present in supraoptic and paraventricular nuclei of hypothalamus Expanded terminal end of neurones – herring bodies (H) Pituicytes Specialized neuroglial cells Short and branching process Distinct cell membrane Cytoplasm contains granules and lipid vacuoles Nucleus – ovoid with pink chromatin granules Pituitary gland (posterior pituitary) H – Herring bodies Hormones produced by pituitary gland and their effects Anterior pituitary 1.Growth hormone –produced from orangeophil – acts on overall growth 2.Follicular Stimulating hormone –from delta cells – promotes growth of ovarian follicles - testes to produce spermatozoa 3.Luteinizing hormone – gamma cells – promotes ovulation - stimulates interstitial cells of testes 4.Lutetrophic hormone – gamma cells – acts on corpus luteum to secrete progesterone - activates secretion of milk (prolactin) 5.Thyroid stimulating hormone – beta cells – on thyroid gland 6.Adreno – Cortico-trophic hormone – beta cells – on suprarenal cortex Posterior pituitary 1.Antidiuretic hormone (vasopressin) – constricts arterioles ͢ - raise blood pressure 2.Oxytoxin – acts on uterine muscle, duct of mammary gland Disorders of pituitary gland Adenoma – excessive production of hormone ACTH – Cushing’s disease GH - gigantism or acromegaly - pressure symptom on optic chiasma and nerve - visual disturbance and blindness Panhypopituitarism - failure of production of hormone - rare ; blockage of arterial supply - necrosis of cells  Suprarenal/Adrenal glands Paired, yellowish retroperitoneal lie on the upper poles of the kidneys. Separated from kidney by perirenal fat. Surrounded by renal fascia & pararenal fat. Pararenal fat Perirenal fat Coronal section  Right adrenal gland Pyramidal in shape. Base is related to the superior pole of the right kidney. rests posteriorly on the diaphragm. lies behind the right lobe of the liver and extends medially behind the inferior vena cava.  Left adrenal gland Crescentic in shape. Extends along the medial border of the left kidney from the superior pole to hilum. rests posteriorly on the diaphragm. lies behind the pancreas, lesser sac, and the stomach Adrenal gland: Arterial supply A. Superior suprarenal arteries from the inferior phrenic artery. B. Middle suprarenal (one or more) from the aorta. C. Inferior suprarenal (one or more) from the renal artery. Adrenal gland: Venous drainage Venous drainage is via the suprarenal veins. The left suprarenal vein drains into the renal vein The right suprarenal vein drains into the inferior vena cava. Adrenal gland: Lymphatic drainage Lateral (para-aortic) lumbar nodes. Adrenal gland: Internal structure Each gland has a pale cortex and a dark brown medulla. Adrenal gland: Histology Adrenal gland: Histology Adrenal gland Histology - Outer layer: dense fibrous capsule - Central vein located in the center of medulla. Adrenal cortex 3 Zones : Zona glomerulosa -beneath the capsule -cells arranged in round clusters / groups separated by fibrous trabeculae - contain capillaries. - cells cytoplasm contain smooth ER & numerous mitochondria. -produce mineralocoticoid ( Aldosterone ) Adrenal cortex: Zona Fasciculata – cells arranged in parallel cord; right angle to the capsule. – cytoplasm abundant & pale staining – lipid droplet. – mitochondria & SER. – secrete glucocorticoid ; also secrete small amount of sex hormone. Adrenal cortex: Zona Reticularis – innermost cortical layer. – small closely packed cells – arranged in irregular cords. – clusters of cells are separated by wide diameter capillaries. – less cytoplasm (few lipid droplets) – darker staining. – small quantities of androgen & glucocorticoid. Adrenal medulla Secretes catecholamines (adrenaline & noradrenaline (NA)) H&E stain – chromaffin cells: granular, faintly basophilic cytoplasm – numerous capillaries. – venous channels – central vein. Chrome salt fixation H&E – cells containing NA–strong positive chromaffin reaction. Physical & psychological stress – release of adrenal medullary hormone. Adrenal gland: Blood supply – superior, middle & inferior arteries – plexus under capsule Cortex capillaries sinusoids descend between cords of secretory cells in the ZF. - into deep plexus in ZR. - small venules - central vein. Medulla – long cortical arteries rich network of capillaries - surround the secretory cells. - drain into central vein  Adrenal gland disorders Hypoadrenalism – due to autoimmune adrenalitis: failure of secretion of cortical hormone - Addison’s disease (weakness, tiredness, skin pigmentation, postural hypotension, hypovolaemia and low blood sodium) Hyperadrenalism -(adenoma or carcinoma) -Ectopic ACTH syndrome (neuroendocrine tumour in lungs) – produce excess amount of glucocorticoid Cushing’s syndrome – due to excess amount of glucocorticoid Conn’s syndrome – due to excessive production of aldosterone Pineal gland  Pineal gland Small spherical Lies in midline of the brain Inferior to the posterior end of corpus callosum Represents an evagination of posterior part of roof of 3rd ventricle Connected to the brain by a stalk containing nerve fibres Synthesizes melatonin – induced by darkness Histology Cells – pinealocytes – modified neurons; many branched processes - arranged in clusters - surrounded by fenestrated capillaries - granular cytoplasm; contain melatonin and its precursor serotonin - round nuclei with prominent nucleoli - neuroglial cells – likes astrocytes Matrix – calcium and magnesium phosphate - Aging pineal gland contains basophilic extracellular bodies (Pineal sand) In a cranial radiography, pineal gland used to mark the midline  Pancreas Exocrine & endocrine gland Longnecker, Daniel S. 2021. Lies posterior to peritoneum, Lies across the transpyloric plane Head, neck and tail regions Arterial supply: splenic artery and superior & inferior pancreaticoduodenal arteries Venous drainage: splenic vein and superior & inferior pancreaticoduodenal veins that drain into portal system  Pancreas Possesses ducts for its exocrine function: main duct & accessory duct Lymph drains into the lymph nodes along its arteries and finally into coeliac and superior mesenteric nodes Pancreas: Histology Exocrine secretory acini : darkly stained Islets of Langerhans – clumps of endocrine cells scattered in exocrine tissue - more numerous in tail of pancreas - appear as area of pale epithelial mass - arranged in irregular, anastomosing cellular plates around a rich capillaries network Consists of polygonal or rounded cells Alpha cells – lies at periphery ; produce glucagon Beta cells – at the center ; produce insulin Delta cells – larger cells ; produce gastrin.  a temporary organ Thymus largest at puberty After puberty, it ceases to grow, gradually reduces in size and finally replaced by fatty tissue Produces hormones that regulate immune cells production Responsible for maturing T cells  Thymus consists of two lateral lobes placed in close contact along the middle line located partly in the thorax, partly in the neck, and upward extending from the 4th costal cartilage, as high as the lower border of the thyroid gland. Derived from the ventral wing of 3rd pharyngeal pouch Thymus: Histology Capsule:loose collagenous; invested by epithelial cells Epithelial cells serve as supporting framework Septa – separating lobes Cortex –basophilic, contain T lymphocytes (thymocytes),macrophages, Cortical epithelial cells – nurse cells Medulla – eosinophilic epithelial cells, Hassal corpuscles Histology of thymus gland Capsule-loose collagenous; invested by epithelial cells Epithelial cells serve as supporting framework Septa – separating lobes Cortex –basophilic, contain T lymphocytes (thymocytes),macrophages Cortical epithelial cells – nurse cells Thymus gland Medulla – eosinophilic - contain robust epithelial cells (large pale nucleus with eosinophilic cytoplasm) - Hassall’s corpuscle – groups of keratinised epithelial cells After puberty, lipid infiltration occurs Cords of epithelial cells persists and produce thymic hormones through life Cortex Medulla Thymus in fetus  Testes In the scrotum Oval shaped Encapsulated in dense fibrous tissue: tunica albuginea Gives rise to fibrous septa- divide testes to testicular lobules Each lobule consist of a seminiferous tubule Supplied by testicular arteries Testes : histology Leydig cells - In between the seminiferous tubules - produce testosterone  Disorders Testicular cancer Varicocoele: enlargement of testicular veins (pampiniform plexus) due to impaired venous drainage Hydrocoele testis: accumulation of fluid in the tunica vaginalis  Ovaries Location: pelvis (ovarian fossa) Paired Oval shaped Encapsulated by fibrous capsule: tunica albuginea Supplied by ovarian arteries Ovaries :Germinal epithelium –simple cuboidal cells Cortex – peripheral zone; constitude follicles - corpus luteum ( oestrogen and progesterone) - corpus albican - tunica albuginea is surface cortex Medulla – loose fibro elastic tissue and vascular Growing follicles is surrounded by theca externa and theca interna Egg cells - large spheroidal cells with vesicular nucleus and prominent nucleoli , surrounded by granulosa cells  Ovarian disorders Ovarian cysts : eggs failed to released from follicle Polycystic ovary syndrome : irregular menstrual cycle Ovarian cancer : metastasized Menopause : shrunken ovaries with scars  Any question? [email protected] Acknowledgement: PM Dr. Elvy Suhana Mohd Ramli Department of Anatomy, UKM