2Thyroid Gland Largest of the endocrine glands. Situated on the front sides of the trachea.Butterfly-shaped, has two lobes connected by a tissue band called the isthmus.
3Thyroid Gland Thyroid gland contains two types of cells: Follicular cells-located within the thyroid follicle. Secrete T3 and T4 (discussed later)Parafollicular cells-located between the follicles.Each type of cells secrete a particular hormone.
4Thyroid Gland Composed of secretory units called follicles. Each follicle is filled with a clear, viscous substance called colloid.Follicular cells secrete two thyroid hormones:(1) triiodothyronine (T3)(2) tetraiodothyronine (T4 or thyroxine)
5Thyroid Gland Functions of T3 and T4: Regulate all phases of metabolism and are necessary for the proper functioning of all other hormones.Thyroid hormones are necessary for the normal maturation of the nervous system and for normal growth and development.T3 and T4 have similar functions but T3 is the more potent of the two.
6Hypothyroidism Adult-results in a condition called Myxedema. Myxedema-slowed metabolic state.Skin becomes thick and puffy due to accumulation of a thick fluid under the skin.
7Hypothyroidism Signs/Symptoms: Slow heart rate Sluggish peristalsis ConstipationLow body temperatureLow energyLoss of hairWeight gain
8Hypothyroidism Cretinism-infant born with no thyroid gland. Fails to develop both physically and mentally.Child will be short and stocky with abnormal skeletal development and severe mental retardation.Early diagnosis and and prompt treatment with thyroid hormone will prevent further developmantal delay.
9HyperthyroidismHyperthyroidism-caused by an excess of thyroid hormone.Metabolic state is “sped-up”.At risk for developing fast rhythm disorders of the heart.
10Hyperthyroidism Grave’s disease-common type of hyperthyroidism. Signs/Symptoms:Increased heart rateIncreased peristalsis/diarrheaElevation in body temperatureHyperactivityWeight lossEmotional swings
11HyperthyroidismGrave’s disease is also characterized by bulging eyes (exophthalmia).Bulging of eyes is caused by fat pads behind the eyeballs pushing the eyeballs forward in the eye socket.If the bulging is severe , it may be difficult for the patient to close eyelids over cornea. The exposed cornea may then dry out, ulcerate, and scar, leading to loss of vision.
12Iodine Synthesis of T3 and T4 requires iodine. Iodine in the body comes from dietary sources.Most of the iodine in the blood is pumped into the follicular cells of the thyroid hormones where it is used in the synthesis of thyroid hormones.
13Iodine DeficiencyIodine deficient state –T3 and T4 production decreases because iodine is necessary for the synthesis of the thyroid hormones.With insufficient iodine, negative feedback is not possible.Persistent stimulation of the thyroid gland by TSH causes thyroid to enlarge.With insufficient iodine, thyroid hormones cannot be made in quantities great enough to shut off the secretion of TSH through negative feedback.
14Iodine Deficiency Enlarged Thyroid gland is called a goiter. Diagnosis is usually made by ultrasound.
15CalcitoninCalcitonin-secreted by the parafollicular cells of the thyroid gland.Calcitonin helps regulate blood levels of calcium.
16Parathyroid GlandsFour tiny glands that lie along the posterior surface of the thyroid gland.Secretes parathyroid hormone (PTH).
17Parathyroid GlandsLow blood level of calcium stimulates the release of PTH.PTH has three target organs:BoneDigestive tractKidneysOverall effect of PTH is to increase calcium levels.
18Parathyroid Gland Hypocalcemia-low calcium levels. Calcium deficiency results in continuous muscle contraction known as tetany.Contorts the wrist , can cause sustainedcontraction of the muscles of the larynx(laryngospasm).
19Hypercalcemia Increased calcium level. PTH stimulates osteoclastic activity in the bones, moves calcium out of the bone causing hypocalcemia.Hypercalcemia depresses the nervous, cardiac and GI systems causing fatigue, bradycardia, anorexia and constipation.
20Adrenal Glands small glands located above the kidneys. Consists of two regions:Inner medullaOuter cortex
21Adrenal MedullaInner region of the adrenal gland, considered an extension of the sympathetic nervous system “fight or flight”.Catecholamines- Hormones that are secreted in emergency situations. They are:Epinephrin (adrenaline)Norepinephrine
22Adrenal Medulla Catecholamines help the body respond to stress by: Elevating blood pressure.Increasing heart rate.Convert glycogen to glucose in the liver, more glucose available to the cells.Increases metabolic rate, making more energy.Opens up the bronchial passages.
23Adrenal Cortex Outer region of the adrenal gland. Secretes hormones called steroids.Three steroids-GlucocorticoidsMineralcorticoidsSex hormones
24Adrenal Cortex Adrenal cortical hormones are essential for life. Adrenal cortical hormones regulate:Glucocorticoids sugarMineralcorticoids saltSex hormones sex
25Adrenal CortexGlucocorticoids-convert amino acids into glucose (gluconeogenesis).Maintain blood glucose levels between meals.Ensures steady supply of glucose for the brain and other cells.Chief glucocorticoid is cortisol.
26Adrenal CortexCortisol is secreted in greater amounts during stress. (physiological stress, disease, physical injury, emotional stress).Has an anti-inflammatory effect.Ex. Cortisol-like drug-prednisone, used in treatment of arthritis or severe allergic response.
27Adrenal Cortex Mineralocorticoids: Aldosterone-chief mineralocorticoid.Plays a role in the regulation of blood volume and blood pressure and in the concentration of electrolytes.Called salt retaining hormone.
28Adrenal Cortex Sex hormones: Secreted in small amounts. Female hormones-estrogens.Male hormones-androgens.
29Adrenal GlandAdrenal insufficiency is life threatening and must be treated with steroids and replacement of fluids and electrolytes.Hypersecretion-excess of adrenal cortical hormones.Cushing’s syndrome-elevated blood levels of steroids, such as prednisone.
30Adrenal Cortex Cushing’s syndrome s/s: Truncal obesity. Rounded facial appearance (moon face).Excess fat deposition between the shoulders (buffalo hump).Facial hair (hirsutism).Thin skin that bruises easily.Bone loss .Muscle weakness.
32Adrenal GlandHyposecretion-adrenal gland fails to secrete adequate amounts of adrenal cortical hormones.Addison’s disease-adrenal insufficiency.s/s-generalized weakness, muscle atrophy, bronzing of the skin, severe loss of fluids and electrolytes.
34The PancreasLong slender organ that lies transversely across the upper abdomen.Functions as an endocrine and exocrine gland.Secretes two hormones: insulin and glucagon.Islets of Langerhans-hormone-secreting cells of the pancreas.
36Pancreas Islets of Langerhans contain two types of cells: Alpha cells-secrete glucagon.Beta cells-secrete insulin.Both regulate blood sugar.
37PancreasInsulin is released in response to increased blood levels of glucose as occurs following a meal.Secretion of insulin decreases as blood levels of glucose decrease.Insulin has many target tissues, exerts widespread effects.
38Insulin and Blood Glucose Insulin decreases blood glucose levels for two reasons:Increases transport of glucose from the blood into the cells.Stimulates the cells to burn glucose as fuel.Insulin is the only hormone that lowers blood glucose.
39Pancreas Hyperglycemia-excess glucose in the blood. Signs/symptoms: Glucosuria-glucose in the urine.Polyuria-excretion of large volumes of urine.Polydipsia-excessive thirst.Polyphagia-excessive eating.Acidosis-due to the rapid breakdown of fatty acids.
41Gonads Sex glands: Ovaries in female. Testes in male. Ovaries secrete : estrogen and progesterone.Females appear female because of estrogenTestes secrete : testosteroneMales appear male because of testosterone.
42Thymus GlandThymus gland-lies in the thoracic cavity behind the sternum.Larger in child than in an adult, becomes smaller as child hits puberty.Secretes the hormones called thymosins, play a role in immunity.
47ProstaglandinsHormones derived from a fatty acid called arachidonic acid- a fatty acid found in the membranes of body cellsProduced by many tissues.Chemical mediators of pain and inflammation, increase sensitivity of nerve endings to painAspirin and ibuprofin block synthesis of prostaglandins-useful in pain control.
48As we Age Alteration in the secretion of hormones. Decrease in the levels of secretion of the glands.Decrease in the level of thyroid hormones and decreased metabolic rate.Decrease in the amount of growth hormone, decrease in muscle mass and increase in storage of fat.Diminished circadian control.