anhis-endocrine2009

8/7/2019 anhis-endocrine2009

http://slidepdf.com/reader/full/anhis-endocrine2009 1/51

The Endocrine System



The Endocrine SystemGeneral Functions of Hormones

� Help regulate:

± extracellular fluid

± metabolism

± biological clock

± contraction of cardiac &

smooth muscle

± glandular secretion

± some immune functions

� Growth & development

� Reproduction



� The thyroid gland: located just inferior to the larynx, it has two lobes that give it theappearance of butterfly wings. It is the largest endocrine gland and it releases thyroidhormones and calcitonin.

� a. Thyroid hormone: T4 and T3, amino acid based hormones that contain iodine,main function is to increase metabolic rate.

� b. Calcitonin- reduces excessive levels of calcium ion in the blood by slowing downosteoclast activity, actively secreted during childhood.



Thyroid Gland



Formation of

Thyroid Hormone

� Iodide trapping by follicular cells

� Synthesis of thyroglobulin(TGB)

� Release of TGB into colloid� Iodination of tyrosine in

colloid

� Formation of T3 & T4 bycombining T1 and T2

together � Uptake & digestion of TGB

by follicle cells

� Secretion of T3 & T4 intoblood



Histology of Thyroid Gland� Follicle = sac of stored

hormone (colloid)surrounded by folliclecells that produced it

± T3 & T4

� In between cells calledparafollicular cells

± produce calcitonin



Histology of Thyroid Gland



Actions of Thyroid

Hormones� T3 & T4 = thyroid hormones

responsible for our

metabolic rate, reakdown of

fats, use of glucose for A

TPproduction

� Calcitonin = responsible for

building of bone & stopsreabsorption of bone (lower

blood levels of Calcium)



Tortora & Grabowski 9/e

Control of T3 & T4

Secretion

� Negative feedback

system

� Low blood levels of

hormones stimulate

hypothalamus

� It stimulates pituitary

to release TSH

� TSH stimulates gland

to raise blood levels



Parathyroid Glands

� 4 pea-sized glands found on back of thyroid gland



� The parathyroid gland: yellowish in color, lie posterior or the thyroid gland.There are at least two pairs of glands but some may have as many as four pairs. The hormone it releases is parathyroid hormone (PTH) which has theopposite effect if calcitonin. It increase calcium ion levels in the blood byeither activating the osteoclast, stimulating the kidney to reabsorb more

calcium, or activation vitamin D production for calcium to be absorbed fromfood.



18-12

Histology of Parathyroid Gland

� Chief (principal)

cells produceparathyroid

hormone (PTH)

� Oxyphil cellfunction is

unknown



HistologyHistology of of ParathyroidParathyroid GlandGland



Parathyroid Hormone

� Raise blood calcium levels± increase activity of osteoclasts

± increases reabsorption of Ca+2 by kidney

± promote formation of calcitriol (vitamin D3) bykidney which increases absorption of Ca+2 and

Mg+2 by intestinal tract

� Opposite function of calcitonin



Regulation of Calcium Blood Levels

� High or low blood levels of Ca+2 stimulate the release of different hormones --- PTH or CT



The pancreas: located in the abdominal cavity it contains endocrine cells called theislets of Langerhans that produce amino acid based hormones. The cells releaseinsulin which stimulates absorption of glucose by tissue cells when blood glucoselevels are high, and also releases glucagon that stimulates the liver to release sugar into the blood when blood glucose levels are low.



Anatomy of Pancreas

� Organ (5 inches) consists of head, body & tail

� Cells (99%) in acini produce digestive enzymes

� Endocrine cells in pancreatic islets produce hormones



Histology of the pancreas




Cell Organization in PancreasCell Organization in Pancreas

� Exocrine acinar cells surround a small duct

� Endocrine cells secrete near a capillary




Histology of the Pancreas

� 1 to 2 million pancreatic islets

� Contains 4 types of endocrine cells



Tortora & Grabowski 9/e 18-21

Cell Types in the Pancreatic Islets

� Alpha cells (20%) produce glucagon

� Beta cells (70%) produce insulin� Delta cells (5%) produce somatostatin

� F cells produce pancreatic polypeptide



Tortora & Grabowski 9/e ¥2000 JWS 18-22

Regulation of Glucagon & Insulin Secretion

� Low blood glucose

stimulates release of

glucagon

� High blood glucose

stimulates secretion

of insulin



18-23

Cell Types in the Pancreatic Islets

� Alpha cells (20%) produce glucagon

� Beta cells (70%) produce insulin� Delta cells (5%) produce somatostatin

� F cells produce pancreatic polypeptide



� The thymus: located in lower neck, anterior thorax, and posterior to the sternum. Itsecretes amino acid based hormones called thymic hormones like thymopoeitin andthymosin that stimulate T-lymphocytes to become immunocompetent.




Thymus Gland

� Important role in maturation of T cells

� Hormones produced by gland promote the

proliferation & maturation of T cells± thymosin

± thymic humoral factor

± thymic factor

± thymopoietin



� The gonads: testes and ovaries are organs that secret steroid sex hormones.Androgens released by these glands are changed into testosterone, estrogen, andprogesterone. They maintain primary and secondary sex characteristics and cellsinvolved in reproduction.




Ovaries and Testes

� Ovaries

± estrogen, progesterone, relaxin & inhibin

± regulate reproductive cycle, maintain pregnancy

& prepare mammary glands for lactation

� Testes

± produce testosterone± regulate sperm production & 2nd sexual

characteristics




Adrenal Glands

� One on top of each kidney

� 3 x 3 x 1 cm in size and weighs 5 grams

� Cortex produces 3 different types of hormones from 3 zones of cortex

� Medulla produces epinephrine & norepinephrine




Structure of Adrenal Gland

� Cortex derived from mesoderm

� Medulla derived from ectoderm




Histology

of Adrenal

Gland

� Cortex

± 3 zones

� Medulla



The adrenal (suprarenal) gland: These are two glands located superiorly to the kidney

and are actually two different glands within one structure.

� 1. adrenal medulla: considered part of the autonomic nervous system, it releases

adrenaline or epinephrine to assist in the ³fight or flight´ response.




Adrenal Medulla

� Chromaffin cells receive direct innervationfrom sympathetic nervous system± develop from same tissue as postganglionic

neurons

� Produce epinephrine & norepinephrine� Hormones are sympathomimetic

± effects mimic those of sympathetic NS

± cause fight-flight behavior

� Acetylcholine increase hormone secretion by

adrenal medulla



� 2. adrenal cortex: secretes steroids called corticosteroids.Aldosterone(mineralocorticoid) is secreted in response to a decrease in blood volume or bloodpressure stimulating the kidneys to reabsorb more water or sodium. Another group of hormones is called the glucocorticoids which include cortisol. These hormones keepblood glucose levels high to maintain brain activity during stressful situations. They

can direct lymphocytes, or decrease inflammation.




Androgens from Zona Reticularis

� Small amount of male hormone produced

± insignificant in males

± may contribute to sex drive in females

± is converted to estrogen in postmenopausal

females




Regulation of Aldosterone




Mineralocorticoids

� 95% of hormonal activity due to aldosterone� Functions

± increase reabsorption of Na+ with Cl- ,

bicarbonate and water following it± promotes excretion of K+ and H+

� Hypersecretion = tumor producing

aldosteronism± high blood pressure caused by retention of Na+

and water in blood




Glucocorticoids

� 95% of hormonal activity is due to cortisol� Functions = help regulate metabolism

± increase rate of protein catabolism & lipolysis

± conversion of amino acids to glucose

± stimulate lipolysis± provide resistance to stress by making nutrients

available for ATP production

± raise BP by vasoconstriction

± anti-inflammatory effects reduced (skin cream)� reduce release of histamine from mast cells

� decrease capillary permeability

� depress phagocytosis

R l ti f




Regulation of

Glucocorticoids

� Negative feedback




� Thyroid develops ---floor of pharynx 2nd pouch

� Parathyroid & thymus --3 & 4 pharyngeal pouches

� Pancreas from foregut

Development of the Endocrine SystemDevelopment of the Endocrine System




General Adaptation SyndromeGeneral Adaptation Syndrome



Other Other endocrineendocrine structuresstructures::

� A. The heart has sensory cells in the atria that stimulate the kidneys toproduce more urine containing salt. Getting rid of the excess fluid and

salt reduces excess blood volume and salt blood levels, and reducesblood pressure.

� B. The GI tract has scattered cells that release amino acid/peptidehormones chemically similar to neurotransmitters. They affect functionsrelated to regulating digestion, blood chemistry, and blood flow.

� C. The placenta is produced only when conception occurs, it secretshormones that prevent the uterus from getting rid of the nutrient layer towhich it is attached. It also produces other steroid hormones: estrogen,progesterone, corticotropin-releasing hormone, and human chorionicgonadotropin.

� D. The kidneys release rennin which regulates blood pressure anderythropoietin which stimulates erythrocyte production.

� E. When exposed to UV rays, the skin produces a steroid hormoneprecursor to vitamin D. Vitamin D helps in the absorption of calcium.




Miscellaneous HormonesMiscellaneous Hormones EicosanoidsEicosanoids

� Local hormones released by all body cells

� Leukotrienes influence WBCs & inflammation

� Prostaglandins alter

± smooth muscle contraction, glandular secretion, bloodflow, platelet function, nerve transmission, metabolism

etc.

� Ibuprofen & other nonsteroidal anti-inflammatory

drugs treat pain, fever & inflammation byinhibiting prostaglandin synthesis




NonsteroidalNonsteroidal AntiAnti--inflammatory Drugsinflammatory Drugs

� Answer to how aspirin or ibuprofen works

was discovered in 1971

± inhibit a key enzyme in prostaglandin synthesis

without affecting the synthesis of leukotrienes

� Treat a variety of inflammatory disorders

± rheumatoid arthritis

� Usefulness of aspirin to treat fever & pain

implies prostaglandins are responsible for

those symptoms




Growth FactorsGrowth Factors

� Substances with mitogenic qualities± cause cell growth from cell division

� Many act locally as autocrines or paracrines

� Selected list of growth factors (Table 18.12)

± epidermal growth factor

± platelet-derived growth factor

± fibroblast growth factor

± nerve growth factor

± tumor angiogenesis factors

± transforming growth factors




Stress and DiseaseStress and Disease

� Stress can lead to disease by inhibiting theimmune system

± hypertension, asthma, migraine, gastritis, colitis,

and depression

� Interleukin - 1 is secreted by macrophages

± link between stress and immunity

± stimulates production of immune substances

± feedback control since immune substance

suppress the formation of interleukin-1




Aging and the Endocrine SystemAging and the Endocrine System

� Production of human growth hormone decreases± muscle atrophy

� Production of TSH increase with age to try and

stimulate thyroid

± decrease in metabolic rate, increase in body fat &

hypothyroidism

� Thymus after puberty is replaced with adipose

� Adrenal glands produce less cortisol & aldosterone� Receptor sensitivity to glucose declines

� Ovaries no longer respond to gonadotropins

± decreased output of estrogen (osteoporosis &

atherosclerosis)




Pituitary Gland Disorders

� Hyposecretion during childhood = pituitary

dwarfism (proportional, childlike body)

� Hypersecretion during childhood = giantism± very tall, normal proportions

� Hypersecretion as adult = acromegaly

± growth of hands, feet, facial features &thickening of skin




Thyroid Gland Disorders

� Hyposecretion during infancy results indwarfism & retardation called cretinism

� Hypothyroidism in adult produces

sensitivity to cold, low body temp. weightgain & mental dullness

� Hyperthyroidism (Grave¶s disease)

± weight loss, nervousness, tremor &exophthalmos (edema behind eyes)

� Goiter = enlarged thyroid (dietary)




Addison¶s disease

� Hypersecretion of glucocorticoids

± hypoglycemia, muscle weakness, low BP,

dehydration due to decreased Na+ in blood

± mimics skin darkening effects of MSH

± potential cardiac arrest




Diabetes Mellitus & Hyperinsulinism

� Diabetes mellitus marked by hyperglycemia

± excessive urine production (polyuria)

± excessive thirst (polydipsia)

± excessive eating (polyphagia)

� Type I----deficiency of insulin (under 20)

� Type II---adult onset

± drug stimulates secretion of insulin by beta

cells

± cells may be less sensitive to hormone




Cushing¶s Syndrome

� Hypersecretion of glucocorticoids

� Redistribution of fat, spindly arms & legs due to muscle loss

� Wound healing is poor, bruise easily

anhis-endocrine2009

Documents