The Great Communicator
The Endocrine System
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• The endocrine system is composed of ductless glands that secrete chemical messengers called hormones into the bloodstream
– endo- means within
– -crine means secrete or separate
• Hormones enter the bloodstream and are carried throughout the body to affect a variety of tissues and organs
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• The glands of the normal endocrine system include
– one pituitary gland
– one thyroid gland
– four parathyroid glands
– two adrenal glands
– one pancreas
– one thymus
– one pineal gland
– two gonads
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• The pituitary gland is located at the base of the brain just below the hypothalamus
– The hypothalamus secretes releasing and inhibiting factors that affect the release of substances from the pituitary gland
– The combining form for the pituitary gland is pituit/o
– The pituitary gland has two lobes: the anterior and posterior
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• The anterior pituitary gland secretes
– thyroid stimulating hormone (TSH)
– adrenocorticotropic hormone (ACTH)
– follicle-stimulating hormone (FSH)
– luteinizing hormone
(LH)
– Interstitial cellstimulating hormone
(ICSH)
– prolactin
– growth hormone (GH)
– melanocyte-stimulating hormone (MSH)
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• The posterior pituitary gland secretes
– antidiuretic hormone
(ADH)
– oxytocin
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• The thyroid gland is a butterflyshaped gland that secretes
– triiodothyronine
(T
3
)
– thyroxine (T
4
)
– calcitonin
• The combining forms for the thyroid gland are thyr/o and thyroid/o
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• The parathyroid glands are usually four glands located on the surface of the thyroid gland
• The parathyroid glands secrete parathromone
• The combining form for the parathyroid glands is parathyroid/o
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• The adrenal glands are two glands located cranial to each kidney that consist of a cortex and medulla
– ad- means toward
– ren/o means kidney
• The adrenal cortex secretes mineralocorticoids, glucocorticoids, and androgens
• The adrenal medulla secretes epinephrine and norepinephrine
• The combining forms for the adrenal glands are adren/o and adrenal/o
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• The pancreas is a gland located near the proximal duodenum that has both exocrine and endocrine functions
• The endocrine functions of the pancreas maintains blood glucose levels
• The pancreas secretes insulin and glucagon
• The combining form for the pancreas is pancreat/o
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• The thymus is a gland predominant in young animals located near midline in the cranioventral portion of the thoracic cavity
• The thymus secretes thymosin
• The combining form for the thymus is thym/o
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• The pineal gland is located near midline in the central portion of the brain and functions in maintaining circadian rhythm
• The thymus secretes melatonin
• The combining form for the pineal gland is pineal/o
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• The gonads are glands that produce gametes (sex cells)
• The gonads are the ovaries in females and the testes in males
• The combining form for the gonads is gonad/o
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• The ovaries are the female gonads
• The ovaries secrete
– estrogen
– progesterone
• The ovaries are covered in more detail in the chapter on reproduction
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• The testes are the male gonads
• The testes secrete
– testosterone
• The testes are covered in more detail in the chapter on reproduction
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• Additional terms for endocrine system tests, pathology, and procedures can be found in the text
• Review the Flash! CD program to make sure you understand these terms
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