Adrenal, pancreas, thyroid

Adrenal, pancreas, thyroid

The adrenal gland

The adrenal gland• Adrenal CortexOuter glandderived from mesodermproduces steroid hormones• Adrenal MedullaInner region of glandproduces epinephrine and norepinephrinederived from neural crest

Adrenal gland•Ad, adjacent to, next to; renal,kidney•First hormone purified from agland, adrenalin- epinephrine(IUPAC)- 1901 by JokichiTakamine purified from the adrenalmedulla•Adrenal medulla- derived fromneural crest•Adrenal cortex- derived fromurogenital mesoderm

3 layers of adrenal cortex• Zona glomerulosa (outer zone)-producesaldosterone• Zona fasciculata (middle zone)- producescortisol• Zona reticularis (inner zone)- produces theweak androgen DHEA

Figure 21—4. Fine structure of2 steroid-secreting cells fromthe zona fasciculata of thehuman adrenal cortex. Thelipid droplets (L) containcholesterol esters. M,mitochondria withcharacteristic tubular andvesicular cristae; SER, smoothendoplasmic reticulum; N,nucleus; G, Golgi complex; Ly,lysosome; P, lipofuscinpigment granule. x25,700.

CatecholamineSynthesis-Synthesized from the amino acidtyrosine, which is taken up intomedulla cells by active transport.

Cortisol• Increases blood glucose but spares liverglycogen stores.• Increases conversion of fats and aminoacids into glucose.• Increases liver glycogen.

Aldosterone• Removing the adrenal gland (adrenalectomy)causes death in 2 weeks due to lack ofaldosterone• Aldosterone increases Na+ and waterretention by kidney• Water and Na+ retention are required fornormal blood pressure• Decrease blood volume leads to decreasedcardiac output, decreased blood pressure,and death.

Stress- Historical Background• Claude Bernard (1813-1878)- the concept of maintaining a constantinternal environment• Walter Cannon (1871-1945)The concept of “homeostasis” and thediscovery of the role of adrenaline• Hans Selye (1907-1982)Introduced the term “stress”

Hans Selye• Canadian physician, studied the effects ofovarian extracts on rats• Found that many different treatmentsresult in the same effects:Enlargement of the adrenal glandReduction in thymus sizeDevelopment of GI ulcers

controlstressThe triadLarger AdrenalsSmaller ThymusSmaller Lymph nodesPeptic ulcersFrom Selye, H. “The Stress of Life”

General adaptation syndrome• Alarm phase• Adaptation phase• Exhaustion

Diversity of Stressors“Systemic Stressor”(interoceptive or visceralstressors) Reflexive,visceral sensorypathways•Ether•Hemorrhage•Formalin•Cholecystokinin•Surgery•Bacteria (LPS), “immunestress”“Neurogenic Stressor”Higher brain processing• Restraint• Confinement• Novelty• Unpredictability• Social status• Grief


Pancreas• Exocrine and Endocrine organ• Endocrine cells:Islets of Langerhans (several cell types)• Beta cells (70%)- insulin• Alpha cells –glucagon• Delta cells-somatostatin

Figure 21—10.Photomicrograph of an isletof Langerhansshowing alpha(A) cells andbeta (B) cells.Gomori’strichromestain. Highmagnification.


PC, prohormone convertase

History of diabetes• Clinicians have reported for years the presence ofglucose in the urine (glucosuria). The Indian physicianSushruta in 400 B.C. described the sweet taste of urinefrom affected individuals.• In 250 B.C., the name "diabetes" was first used. It is aGreek word that means "to syphon", The complete term"diabetes mellitus" was coined in 1674 by Thomas Willis,physician to King Charles II. Mellitus is Latin for honey.• Up until the mid-1800s, the most successful treatmentswere starvation diets in which caloric intake was severelyreduced.

History• 1869, Paul Langerhans,discovered islets• 1860s Miring and Minkowski Removing pancreas causesdiabetes Tie off pancreatic duct in dogs,the exocrine pancreas digestsitself, but the islets are left intact. These dogs did not developdiabetesPaul Langerhans(1847-1888)

History• Islets were required for blood glucoseregulation and that diabetes involvedloss of the islets.• Early 1920s. Fred Banting M.D. andCharles Best (Grad student) use dogsto develop first insulin preparation• Worked in the laboratory of JohnMcLeod, University of Toronto

Dr. J. Collip

Teddy Ryder, 5 yr old, receivedinsulin July 10, 1922Contract with Eli Lilly, 1922

The thyroid gland• Lays over the larynx• Accumulates tyrosine and iodide• Hollow, soccer-ball shaped structurescalled follicles

Thyroid hormones• Act on intracellular receptors• T3 is 10x more potent than T4• Increase metabolic rate by increasingoxygen consumption• Increase heat production by “uncoupling”oxidative phosphorylation, ie. Make lessATP, more heat

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