Endocrine system MUDr. Hisham El Falougy, PhD. [email protected] Thyroid gland • Brownish-red • C5 – T1 • Pretracheal layer of deep cervical fascia • Right lobe, left lobe, isthmus • 25g Thyroid gland • Lobes are conical • Apex – oblique line of thyroid lamina • Base – 4th or 5th tracheal cartilages • 5cm long, transverse 3cm, anteroposterior 2cm • Isthmus (1.25 transverse and vertical) • Pyramidal lobe – towards the hyoid bone Thyroid gland • Lateral surface is covered by • Sternothyroid • Sternohyoid • Superior belly of omohyoid • Sternocleidomastoid • Medial surface is adapted to • Larynx • Trachea Thyroid gland • Superior pole contacts • Inferior pharyngeal constrictor • cricothyroid • External laryngeal nerve – medially • Recurrent laryngeal nerve and oesophagus – posteriorly • Posterolateral surface of the gland - carotid sheath Thyroid gland • Highly vascular • Arteries • Superior thyroid artery • Inferior thyroid artery • Arteria thyroidea ima • Veins • Superior, middle and inferior thyroid veins Thyroid gland • Capsule • Irregularly sized and shaped lobules • Follicles – functional units • Spherical and cyst-like (0.02 – 0.9 mm) • Colloid sorrounded by epithelium • Precursor of thyroid hormons T3, T4 Thyroid gland • Stroma • Parafollicular cell • C (clear)cells • Thyrocalcitonin • Lowers blood calcium • Amine precursor uptake and decarboxylation system (APUD) • TSH Parathyroid glands • Yellowish-brown, ovoid structures • Between posterior lobar borders and capsule of the thyroid gland • 6mm long, 3-4 mm across, 1-2mm posteroanterior • 50mg • 2 superior, 2 inferior glands Parathyroid glands • Chief (principal) cells • Parathyroid hormone • Oxyphil cells • Metabolism of Calcium and Phosphorus Suprarenal glands (adrenal glands) • Superior renal pole • Golden yellow • Two functional and structural areas • Cortex (outer) • Medulla (inner) • Enclosed in the renal fascia • Sorrounded by the perinephric fat • Seperated from kidneys by fibrous tissue Suprarenal glands (adrenal glands) • Mean Transverse dimensions – 61 mm (right), 79 mm (left) • Each weigh 5g • Right gland – pyramidal shape with 2 limbs • Left gland - semilunar Suprarenal glands (adrenal glands) • The right gland • Posterior to inferior vena cava, right hepatic lobe, • Anterior to right crus of diaphragm • The left gland • Anterior to left crus of diaphragm Suprarenal glands (adrenal glands) • Arteries • Superior suprarenal artery • Middle suprarenal artery • Inferior suprarenal artery • Veins • Right and left suprarenal veins Suprarenal glands (adrenal glands) • Cortex • Yellowish • Main mass • Medulla • Dark red or greyish • Completely enclosed by cortex except at the hilum Suprarenal glands (adrenal glands) • Cortex • Zona glomerulosa – mineralocorticoids (aldosterone) • Zona fasciculata – glucocorticoids (cortisol) • Zona reticularis – sex hormones (progesterone, oestrogens, androgens) Suprarenal glands (adrenal glands) • Medulla • Chromaffin cells • Catecholamines – adrenalin (epinephrine), noradrenalin (norepinephrine) Testicular interstitial tissue • The tissue between the seminiferous tubules • Connective tissue • Myoid cells • Leydig cells • Polyhedral cells • Androgens (testosterone) • Stimulated by LH, prolactin • Fetal life – development of genital tract • Growth and and division of germinal cells • Adult primary and secondary sexual characteristics Female endocrine structures • Ovarian medulla • Rich of blood vessels • Nerve fibers • Endocrine hilar cells - androgens Female endocrine structures • Corpus luteum • Remainder of the tertiary follicle • Granulosa lutein cells • Progesterone and oestradiol • Receptors for human chorionic gonadotropin • Corpus luteum of menstruation – 12 to 14 days • Corpus albicans – scar like body after 2 months • Corpus luteum of pregnancy - 25 mm at 8th week of gestation • Largely replaced by placenta after 8th week Female endocrine structures • Placenta • Chorion frondosum (embryonic/fetal) • Decidua basalis (maternal ) • Discoid structure (20 cm diameter, 3-4 cm thick) • Weighs 350 – 700g • Placental barrier Endocrine pancreas • Pancreatic islets of Langerhans • Spherical clusters of cells • More than 1 million islets • Mainly in the tail • Rich blood supply and autonomic innervation • Alpha cells – glucagon • Beta cells – insulin • Delta cells – gasterin and somatostatin • F cells – pancreatic polypeptide Diffuse endocrine cells • 40 different types • Absorb and decarboxylate the amine precursors (APUD) • Open-type cells • Closed-type cells Diffuse endocrine cells • Gastroenterpancreatic system • Stomach – closed type cells • Small intestine – crypts and intestinal villi • Large intestine – base of the crypts • Respiratory system • Epithelium of trachea and bronchi • Neuroepithelial bodies • Urogenital system – urethra and urethral glands .