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A&P Chapter 17 Endocrine System
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What glands in the body are considered endocrine glands?


·         They are the glands that have a very well defined structure and function.  Some examples include:  Pituitary gland, Thymus gland, Thyroid gland, Parathyroid glands, Adrenal glands, Pancreas, and Gonads


What is the hormone produced by the anterior pituitary gland and what is its target tissue?



Hormone/target tissue

GH Hormone/All cells

ACTH/Adrenal cortex

TSH/Thyroid gland

PRL/Mammary glands

Gonadotropins/Ovaries and testes




What is the hormone produced by the posterior pituitary gland and what is its target tissue?



Oxytocin (OT)/Uterus, mammary glands in female. Reproductive tract of male.

Antidiuretic Hormone (ADH)/Kidneys


What is the hormone produced by the thyroid gland and what is its target tissue?


Thyroxine and Triiodothyronine (T4 / T3)/All cells.

Calcitonin (CT)/Bones and kidney


What is the hormone produced by the Parathyroid glands and what is its target tissue?


Parathyroid Hormone (PTH)/Bones and kidneys



What is the hormone produced by the Adrenal Cortex and what is its target tissue?


Glucocorticoids (hydrocortisone (cortisol) and corticosterone)/Most cells

Mineralocorticoid (aldosterone)/Kidneys and sweat glands


What is the hormone produced by the adrenal medulla and sympathetic nervous system and what is its target tissue?


Catecholamines (epinephrine and norepinephrine)/Most cells


What is the hormone produced by the Pancreas and what is its target tissue?


Pancreas :- Beta cells

Insulin/Most cells

Pancreas :- Alpha cells

Glucagon/Liver and Adipose tissues


What hormones use the cyclic AMP system and which use the IP3 or DAG systems of second messengers/  How does insulin differ in its mechanism of action on cell receptors?


·         Hormones that use cAMP systems:  ACTH, FSH, LH, PTH, TSH, Glucagon, Calcitonin and Catecholamines.

·         Hormones that use Diacylglycerol (DAG) / Inositol triphosphate (IP3) systems:  ADH, TRH, OT, LHRH and Catecholamines


What is a Paracrine secretion/hormone?


·         These are released by one cell, diffuse to nearby cells in the same tissue, and stimulate their physiology.  Some call them “local hormones”


How are endocrine and exocrine glands different?


·         The classical distinction between exocrine and endocrine glands ahas been the presence or absence of ducts.  Most exocrine glands secrete their products by way of a duct onto an epithelial surface such as the skin or the mucosa of the digestive tract.  Endocrine glands are ductless and release their secretions into the bloodstream.

·         Endocrine glands:  have a very well defined structure and function.  Examples include the pituitary gland, thymus gland, thyroid gland, parathyroid glands, adrenal glands, pancreas, and gonads


What types of capillaries are associated with endocrine glands?


·         Endocrine glands have an unusually high density of blood capillaries, which serves to pick up and carry away their hormones.  These vessels are an especially permeable type called fenestrated capillaries, which have patches of large pores in their walls allowing for an easy uptake of matter from the gland tissues


Briefly compare and contrast the endocrine and the nervous system.


·         Nervous System

o        Communicates by means of electrical impulses and neurotransmitters

o        Releases neurotransmitters at synapses at specific target cells

o        Usually has relatively local, specific effects

o        Reacts quickly to stimuli, usually within 1-10 msec

o        Stops quickly when stimulus stops

o        Adapts relatively quickly to continual stimulation

·         Endocrine System

o        Communicates by means of hormones

o        Releases hormones into bloodstream for general distribution throughout the body

o        Sometimes has very general, widespread effects

o        Reacts more slowly to stimuli, often taking seconds to days

o        May continue responding long after stimulus stops

o        Adapts relatively slowly; may respond for days or weeks


What is the hypophyseal portal system?  What is the adenohypophisis?


·         Hypophyseal portal system:  the anterior pituitary has no nervous connection to the hypothalamus but is linked to it by a complex of blood vessels called the hypophyseal portal system.  This system consists of a network of primary capillaries in the hypothalamus, a group of small veins called the portal venules that travel down the stalk and a complex of secondary capillaries in the anterior pituitary by secreting hormones that enter the primary capillaries, travel down the portal venules, and diffuse out of the secondary capillaries into the pituitary tissue.  The hypothalamic hormones regulate secretion by various types of pituitary cells.

·         Adenohypophisis:  constitutes the anterior three quarters of the pituitary. It has two parts, a large anterior lobe, called the pars distalis because it is most distal to the pituitary stalk, and a less important pars tuberalis, a small mass of cells that wraps around the stalk. 


What is the hypothalamo-hypophyseal tract?  What is the neurohypophysis?


·         The neurohypophysis constitutes the posterior one quarter of the pituitary.  It has three parts:  the median eminence, and extension of the floor of the brain; the infundibulum mentioned earlier; and the largest part, the posterior lobe (pars nervosa).  The neurohypophysis is actually nervous tissue (nerve fibers and neuroglial, not a true gland.  The nerve fibers arise from certain cell bodies in the hypothalamus, passing down the stalk as a bundle called the hypothalamo-hypophyseal tract, and end in the posterior lobe.

·         The hypothalamic neurons synthesize hormones and transport them down the axons to the posterior pituitary.  Here they are stored until a nerve signal coming down those same axons triggers their release into the blood.


What hormones are produced and released by the hypothalamus and act on the anterior lobe of the pituitary gland?


1.       Thyrotropin-releasing hormone (TRH):  Promotes secretion of thyroid stimulating hormone (TSH) and prolactin (PRL)

2.       Corticotropin-releasing hormone (CRH):  Promotes secretion of adrenocorticotropic hormone (ACTH)

3.       Gonadotropin-releasing hormone (GnRH):  Promotes secretion of follicle stimulating hormone (FSH) and luteinizing hormone (LH)

4.       Growth hormone-releasing hormone (GHRH):  promotes secretion of growth hormone (GH)

5.       Prolactin-inhibiting hormone (PIH):  Inhibits secretion of prolactin (PRL)

6.       Somatostatin:  Inhibits secretion of growth hormone (GH) and thyroid stimulating hormone (TSH)


What hormones are produced in the hypothalamus and stored in the posterior lobe of the pituitary gland?


·         Antidiuretic hormone (ADH):

o        Target tissue:  Kidney

o        Principle Effect:  Water retention

·         Oxytocin (OT)

o        Target tissue:  uterus, mammary glands

o        Principle Effects:  Labor contractions, milk release; possibly involved in ejaculation, sperm transport, sexual affection, and mother-infant bonding


What is the cause and what are the characteristics of giantism?


·         Caused by Growth hormone hypersecretion in  infants and children resulting in body height of over 8 feet. Every single part of the body grows.


What is the cause and what are the characteristics of acromegaly?


·         Caused by hypersecretion in adults resulting in distorted facial features.  Cannot effect the long bones, all soft bone continue to grow.  The skull, jaws, fingers, etc.


What are the functions of thymopoietin?


·         The thymus is a site of maturation for certain white blood cells called T cells that are critically important for immune defense.  It secretes thymopoietin, which stimulates the development of other lymphatic organs and regulates the development and activity of T cells.


What is thyroglobulin?  What is T3 and T4?  Describe the negative feedback control system for thyroid hormone?

See worksheet

What disorder is caused by insufficient thyroid hormone during infancy?


·         Thyroid dwarfism:  (Cretinism:  the growth hormone is fine, the thyroid hormone secretion is messed up)

o        To little secretion of thyroid hormones during fetal development and infancy

o        Severe forms of mental and physical retardation in the newborn (this does not occur in other dwarfism)

o        Retardation is reversible if hormonal replacement therapy is started during the first four months of life.  Without this, life expectancy is less than 2-3 years


What are the basic characteristics in adults of hypothyroidsm and hyperthyroidism?


·         Hypothyroidism

o        Decreased metabolic rate

o        Bradycardia

o        Decrease body temperature

o        Lethargy (low in energy)

o        Goiter (large thyroid gland)

o        Cold intolerance (body temperature)

o        Weight gain

o        Myxedema (bough, scaly skin)

·         Hyperthyroidism (Grave’s disease)

o        Increased metabolic rate

o        Tachycardia

o        Increased body temperature

o        Anxiety and irritability

o        Goiter (large thyroid gland)

o        Heat intolerance

o        Weight loss

o        Exophthalmia (bulging eyeballs)


What hormones are responsible for control of blood calcium?


·         Calcitonin:  (CT) from the thyroid gland lowers blood calcium by adding it to the bones

·         Parathyroid hormone: from the parathyroid gland, increases blood calcium by removing it from the bones.


What are the consequences of hypo and hyperparathyroidism?


·         Hypoparathyroidism:  Caused by the surgical excision during thyroid surgery.  Results in fetal tetanus within 3-4 days.  There is a decrease in calcium concentration in the blood.  In three to four days, muscular tetanus occurs, and freezes muscles.

·         Hyperparathyroidism:  caused by gland tumors.  Results in soft, fragile and deformed bones.  Increased blood calcium levels, formation of renal calculi. 


What are the three zones of the adrenal cortex and the main hormones produced by each?


·         Zona glomerulosa:  secretes mineralocorticoids. 

o        Aldosterone is the most important

o        Regulates blood sodium and potassium levels plus acid-base balance.  It tells the kidney to get K out and Na in.

·         Zona Fasciculata:  Secretes Glucocorticoids(mainly cortisol)

o        Actions

§         Reduce inflammation

§         Response to stress by increasing energy mobilization.  It affects glucose, protein, and fat metabolism

·         Zona Reticularis (Androgens)

o        Secrete male sex hormones.  Only produces about 5% of the androgens.  The other 95% comes from the reproductive system


What is Addison’s disease?  What is Adrenogenital syndrome?


·         Adrenogenital Syndrome

o        Excessive androgens secretion

o        Female virilization and masculinization

o        Male early puberty and rapid masculinization

·         Addison’s Disease

o        Insufficient Glucocorticoids

o        Lack of energy

o        Weight loss

o        Inability to resist stress


What are the typical characteristics of Cushing’s syndrome?


·         Opposite of Addison’s disease

·         Excessive Glucocorticoids

·         Muscle wasting

·         Fat redistribution

·         Spindly arms and legs

·         Large abdomen with stretch marks

·         Rounded moon face

·         Fatty buffalo hump between shoulder


What are the hormones of the adrenal medulla?


·         Catecholamines

·         Epinephrine and norepinephrine

o        Targets are most body cells

o        React quickly to stress by

§         Increase heart rate and strength

§         Increase blood flow to skeletal muscles, heart and brain

§         Dilation of airways

§         Increase fuel for energy

§         Increase blood pressure


What are the different cell types of the islet of the endocrine pancreas?


·         Alpha cells (20%) produce glucagon

·         Beta Cells (70%) produce insulin

·         Delta cells (5%) produce somatostatin (control how much insulin/glucagon is produced)

·         PP cells (5%):  produce pancreatic polypeptide (unknown function)


What are the actions/functions of insulin verses glucagon?  Discuss the regulation and feeback mechanisms.


·         Actions of Insulin

o        Insulin decreases blood glucose by:

§         Increasing uptake of glucose into the cells

§         Increasing synthesis of liver glycogen for storage

o        Insulin also increases proteins and fat synthesis

·         Actions of Glucagon

o        Increasing synthesis of glucose from amino acids in the liver

o        Increasing breakdown of liver glycogen into glucose

o        Increasing release of glucose from liver into blood

·         Regulation of Insulin and Glucagon Secretion

o        High blood glucose after a meal stimulates secretion of insulin and inhibits secretion of glucagon (Fed State)

o        Low blood glucose when fasting stimulates release of glucagon and inhibits secretion of insulin (Fasting State)


What is type I diabetes?  What is type II diabetes?  What are the common signs of diabetes?  What are the complications of diabetes?  Read pages 674-675 and understand Diabetes Mellitus types, treatments, and pathogenesis as described in the textbook in addition to the lectures?


·         Type I (Insulin Dependent Diabetes Mellitus or Juvenile DM)

o        Beta cells destroyed by own immune system

o        Insulin levels low or absent (not enough insulin)

o        Insulin injections required

o        Usually develops in people younger than 2, 5, 10

o        Can cause kidney problems because of excess glucose concentration in the blood

·         Type II (Non Insulin Dependent Diabetes Mellitus or maturity onset DM)

o        Most common type (90%)

o        Insulin may still be secreted but cells may be less sensitive

o        Insulin injections may not be required

o        Mostly in people over 35 who are obese

o        May be controlled by diet

o        Obese tissue produces lipoprotein.  In obese people, there is an increase in lipoprotein which blinds to and blocks insulin receptors.  If the Beta cells die, the change is irreversible because the beta cells are working overtime.  They die from exhaustion.  Once they die, they become Type I diabetic.

·         Common Signs of Diabetes (3 P’s of DM)

o        Polyuria

§         Excessive urination

o        Polydipsia

§         Excessive water drinking

o        Polyphagia         

§         Excessive eating

·         Complications of DM

o        Cardiovascular disease

o        Loss of vision

o        Kidney disease

§         Most complications linked to high blood glucose levels and acidosis

§         Acidosis caused by excessive use of fat for energy instead of glucose


What is the consequence of hyperinsulinism?


·         From excess insulin injection or pancreatic islet tumor

·         Causes hypoglycemia , weakness and hunger

o        Triggers secretion of epinephrine, GH and glucagon

§         Side effects:  anxiety,. Sweating and increased Heart rate

·         Insulin Shock

o        Uncorrected hyperinsulinism with disorientation, convulsions,  and unconsciousness


What cells mainly produce progesterone in the female?  What is inhibin?  What are the functions of estradiol and progesterone?


·         Corpus Luteum:  follicle after ovulation

o        Produces mainly progesterone for 12 days if no pregnancy or 8-12 weeks with pregnancy

·         Sustentacular Sertoli cells

o        Secrete inhibin which suppresses FSH secretion and stabilizes sperm production rates

·         Estradiol/progesterone: 

o        Development of female reproductive system, bone growth and secondary sexual characteristics

o        Regulate menstrual cycle and sustain pregnancy

o        Prepare mammary glands for lactation


In the male what cell produce testosterone?  What is the function of this hormone?  What function do Sustentacular (Sertoli) cells have in the testes?


·         Interstitial cells (between seminiferous tubules)

o        Produce mainly testosterone and some estrogen

§         Functions in the development of male reproductive system and male secondary sexual characteristics.  It sustains sperm production and sex drive.

·         Sustentacular Sertoli cells

o        Secrete inhibin which suppresses FSH secretion and stabilizes sperm production rates


What are the products of the endocrine tissues in the heart, skin, kidneys, and liver?


·         Heart:  Atrial Natriuretic Peptide (ANP) lowers blood pressure by increasing sodium and water loss

·         Skin:  Produce Vitamin D3

·         Liver: 

o        15% of Erythropoietin for RBC’s production

o        Angiotensinogen prohormone synthesis

o        Hepcidin to promote intestinal absorption of iron

o        Convert vitamin D3 to Calcidiol

Addison’s disease

·         Addison’s disease:  Hyposecretion of adrenal Glucocorticoids and mineralocorticoids, causing hypoglycemia, hypotension, weight loss, weakness, loss of stress resistance, darkening or bronzing (metallic discoloration) of the skin, and potentially fatal dehydration and electrolyte imbalance.

Congenital hypothyroidism

·         Congenital hypothyroidism:  Thyroid hormone hyposecretion present from birth, resulting in stunted physical development, thickened facial features, low body temperature, lethargy, and irreversible brain damage in infancy


·         Hyperinsulinism:  Insulin excess caused by islet hypersecretion or injection of excess insulin, causing hypoglycemia, weakness, hunger, and sometimes insulin shock, which is characterized by disorientation, convulsions, or unconsciousness


·         Myxedema:  a syndrome occurring in severe or prolonged adult hypothyroidism, characterized by low metabolic rate, sluggishness and sleepiness, weight gain, constipation, dry skin and hair, abnormal sensitivity to cold, hypertension, and tissue swelling


·         Pheochromocytoma:  a tumor of the adrenal medulla that secretes excess epinephrine and norepinephrine. Causes hypertension, elevated metabolic rate, nervousness, indigestion, hyperglycemia, and glycosuria

Toxic goiter (Graves disease)

·         Toxic goiter (Graves disease):  thyroid hypertrophy and hypersecretion, occurring when autoantibodies mimic the effect of TSH and overstimulate the thyroid. Results in elevated metabolic rate and heart rate, nervousness, sleeplessness, weight loss, abnormal heat sensitivity, and sweating, and bulging of the eyes (exophthalmos) resulting from eyelid retraction and edema of the orbital tissues.