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

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• Superior thyroid

• Inferior thyroid artery

• Arteria thyroidea ima

•

• Superior, middle and

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