Endocrine System Chapter 10. Endocrine Glands Endocrine glands are ductless glands and tissues that secrete hormones directly into the bloodstream. Hormone.

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Endocrine SystemChapter 10Endocrine GlandsEndocrine glands are ductless glands and tissues that secrete hormones directly into the bloodstream.HormoneHormon- gr. to excite.Chemical messengers.Released in small amounts.Affect target cells.General Functions of HormonesGrowth and developmentReproductionMetabolismBiological clockContraction of cardiac and smooth muscleGlandular secretionFeedback mechanisms regulate the secretion of hormonesNegative feedback- the outcome of a process feeds back on the system, shutting down the process.Antagonistic feedback- one hormone has an opposite effect of another hormone on the system.Positive feedback- the outcome of a process feeds back on the system, further stimulating the process.Negative FeedbackAntagonistic FeedbackPositive Feedback Im good enough, Im smart enough, and doggone it, people like me!Positive Feedback- Oxytocin (OCT)Sucking by the infant stimulates nerve receptors in the nipple.The resulting impulses travel along nerves to the hypothalamus.The hypothalamus signals the posterior pituitary to release OCT.OCT travels via the bloodstream to the mammary glands.Milk is ejected from the mammary glands.HypothalamusAnatomyPart of the diencephalon, inferior to the thalamus.FunctionsRegulates the internal environment through the autonomic nervous system.Controls glandular secretions of the pituitary gland.Pituitary Gland- anatomyAnatomyPea-shaped structure. inch in diameter.Lies in the sella turcica of the sphenoid bone.2 anatomically and functionally different portions.Posterior Anterior AnteriorPituitaryPosteriorPituitaryPineal GlandAnatomyPine cone shape.In the epithalamus.Covered by a capsule made of pia mater.FunctionSecretes melatonin that targets the brain; involved in regulating daily sleep-wake cycle.Thyroid GlandAnatomyInferior to the larynx.2 lobes, shield-shaped and deep red in color.Isthmus connects the lobes.30g in weight (=1 oz.).FunctionsIncreases metabolic rate.Regulate growth and development.Isthmus The Thyroid Gland Secretes Thyroid Hormone (TH)Hypothyroidism- undersecretion of the thyroid hormone.Fetus or infant- cretinism. Dwarfism and mental retardation.Adult- myxedema. Weight gain.Lethargy. Loss of hair.Lowered body temperature. Hyperthyroidism- oversecretion of thyroid hormone. Adult- Graves diseaseIncreased metabolic rate. Enlargement of the thyroid gland.Rapid heart rate.High blood pressure.Exophthalmos.Treatment for Graves diseaseSurgery.Ingestion of radioactive iodine.Parathyroid GlandsAnatomy- 4 small masses at the back of the thyroid gland.Hormones- parathyroid hormones. Target- bones, kidneys, intestines.Hormone FunctionsIncrease blood calcium level.Antagonistic action between calcitonin and parathyroid hormone maintains blood calcium levels.Thymus GlandAnatomyUpper mediastinum.Large in infants (70 g), atrophied in adult (3 g).2 lobed organ.Hormones- thymosins.Target- T lymphocytes (white blood cells).Hormone FunctionsPromote production and maturation of T lymphocytes. Adrenal GlandsAnatomyAlmond-shaped, located at the tops of the kidneys.Consists of adrenal medulla and adrenal cortex.Hormones and FunctionsAdrenal MedullaEpinephrine- adrenaline. Fight or flight.Norepinephrine- noradrenaline. Adrenal CortexSex Hormones. Development.Mineralocorticoids. Salt & water balance.Glucocorticoids. Regulate glucose levels.Targets- all tissues.PancreasAnatomy 5-6 inches long, 1 inch thick.Attached to the duodenum, posterior to the stomach.Two tissue types.Exocrine tissue- produce and secrete digestive juices.Endocrine tissue- produce and secrete insulin and glucagon directly into the blood.Target- liver, muscles, adipose tissue.Hormones and FunctionsInsulin- lowers blood sugar.Glucagon- increases blood sugar.TestesAnatomy Scrotum of male.2 oval glands.2 inches long, 1 inch in width.Hormone- testosterone.Target- gonads, skin, muscles, bones.Hormone FunctionStimulate male sex characteristics.OvariesAnatomyAbdomen of female5 cm X 2.5 cm (2 X 1 inch).HormonesEstrogens.Progesterone.TargetsGonads, skin, muscles, bones.Hormone FunctionStimulate female sex characteristics.*Figure: 10-06Title:The two lobes of the pituitary gland.Caption:The two lobes of the pituitary gland, their connections with the hypothalamus, and the hormones they secrete.

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