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• e First & e Only Franchise in the Iraq

  Presented by Assistant professor Dr. Ali Al-najjar General Surgeon
• Pineal Gland


  • Attached to roof of third ventricle beneath the posterior end of corpus callosum
  • Undergoes involution (shrinkage) after age 7, down 75% by end of puberty
  • Tiny mass of shrunken tissue in adults
  • May synchronize physiological function with 24-hour circadian rhythms of daylight and darkness
  • Synthesizes melatonin from serotonin during the night
  • Fluctuates seasonally with changes in day length
• Thymus


  • Plays a role in three systems: endocrine, lymphatic, immune
  • Located in the mediastinum superior to the heart, goes through involution after puberty
  • Site of maturation of T cells important in immune defense
  • Secretes hormones (thymopoietin, thymosin, and thymulin) that stimulate development of other lymphatic organs and activity of thyroid
• Thyroid Gland


  • Largest endocrine gland
  • Composed of two lobes and an isthmus below the larynx
  • Dark reddish brown color due to rich blood supply
  • Normally not palpable and not visible
  • If enlarged in size called Goiter

  
• Thyroid Gland


  Secretes thyroxine (T4) and triiodothyronine (T3)<|>Increases metabolic rate, O2 consumption, heat production (calorigenic effect), appetite, growth hormone secretion, alertness, quicker reflexes<|>Parafollicular (C or clear) cells secrete calcitonin with rising blood calcium, stimulates osteoblast activity and bone formation
• The thyroid gland is the largest endocrine gland

  
• The thyroid gland has two lobes and an isthmus below the larynx

  
• The thyroid gland secretes thyroxine (T4) and triiodothyronine (T3)
• Thyroid hormones increase metabolic rate, O2 consumption, heat production, appetite, growth hormone secretion, alertness, and quicker reflexes
• Parafollicular (C or clear) cells in the thyroid gland secrete calcitonin with rising blood calcium, which stimulates osteoblast activity and bone formation
• Parathyroid Glands


  • Usually four glands partially embedded in posterior surface of thyroid gland
  • Secrete parathyroid hormone (PTH)
  • Increases blood Ca2+ levels
  • Promotes synthesis of calcitriol
  • Increases absorption of Ca2+
  • Decreases urinary excretion
  • Increases bone resorption
• Parathyroid hormone (PTH) increases blood Ca2+ levels, promotes synthesis of calcitriol, increases absorption of Ca2+, decreases urinary excretion, and increases bone resorption
• Adrenal Glands


  • Small gland that sits on top of each kidney, retroperitoneal like the kidney
  • Adrenal cortex and medulla formed by merger of two fetal glands with different origins and functions
  • Connective tissue capsule

  
• Adrenal Medulla


  • Inner core, 10% to 20% of gland
  • Acting as an endocrine gland and sympathetic ganglion of sympathetic nervous system
  • Innervated by sympathetic fibers
  • When stimulated release catecholamines (epinephrine and norepinephrine) and a trace of dopamine directly into the bloodstream
  • Effect is longer lasting than neurotransmitters
  • Increases alertness and prepares body for physical activity
  • Increases blood pressure, heart rate, blood flow to muscles, pulmonary airflow, and metabolic rate
  • Decreases digestion and urine production
• Adrenal Cortex


  • Surrounds adrenal medulla and produces more than 25 steroid hormones called corticosteroids or corticoids
  • Secretes five major steroid hormones from three layers of glandular tissue:

  Zona glomerulosa (thin, outer layer) secretes mineralocorticoids like aldosterone to regulate electrolyte balance

  Zona fasciculata (thick, middle layer) secretes glucocorticoids like cortisol, which stimulate fat and protein catabolism, gluconeogenesis, and have anti-inflammatory effects

  Zona reticularis (narrow, inner layer) secretes sex steroids like androgens and small quantities of estradiol
• Pancreatic Islets


  • Exocrine digestive gland and endocrine cell clusters (pancreatic islets) found retroperitoneal, inferior and posterior to stomach

  Glucagon secreted by A or alpha cells, released between meals when blood glucose is falling

  Insulin secreted by B or beta cells, secreted during and after meals when glucose and amino acid levels are rising to lower blood glucose

  Somatostatin secreted by D or delta cells, partially suppresses secretion of glucagon and insulin

  Gastrin secreted by G cells, stimulates stomach acid secretion, motility, and emptying
• The pancreas contains both exocrine digestive gland tissue and endocrine cell clusters called pancreatic islets
• The pancreatic islets secrete hormones like glucagon, insulin, somatostatin, and gastrin that regulate blood glucose levels and digestive function
• Gonads


  • Ovarian hormones include estradiol, progesterone, and inhibin. Functions include developing female reproductive system and physique, regulating menstrual cycle and pregnancy, preparing mammary glands for lactation.

  Testicular hormones include testosterone, other androgens, estrogen, and inhibin. Testosterone stimulates development of male reproductive system and sex drive, and sustains sperm production.
• Endocrine Functions of Other Tissues and Organs

  • Skin: Keratinocytes convert cholesterol-like steroid into cholecalciferol using UV from sun

  Liver: Secretes calcidiol, angiotensinogen, hepcidin

  Kidneys: Convert calcidiol to calcitriol, secrete renin and erythropoietin

  Heart: Cardiac muscle secretes natriuretic peptides to decrease blood volume and pressure

  Stomach and small intestine: Secrete at least 10 enteric hormones to coordinate digestive motility and glandular secretion