Adrenal Glands The adrenal glands are closely associated

Adrenal Glands • The adrenal glands are closely associated with the kidneys • The gland sits like a cap on each kidney • Hormones are secreted from two different areas of the gland, the adrenal cortex and the adrenal medulla • Numerous hormones are secreted by the adrenal glands 1

Adrenal Cortex Hormones • The adrenal cortex secretes three groups of corticoids • Mineralocorticoids: aldosterone speeds up reabsorption of sodium into blood circulation and increasing excretion of potassium from the blood; also speed up reabsorption of water by kidneys • Glucocorticoids: cortisone and cortisol increase amount of glucose in blood • Androgens: male sex hormones that bring about masculine characteristics in combination with similar hormones from gonads; present in males and females 2

Hormones of the Adrenal Cortex 3

Adrenal Medulla Hormones • The adrenal cortex secretes two hormones • Epinephrine: powerful cardiac stimulant; release of more glucose from stored glycogen for muscle activity and increasing the force and rate of heartbeat • Norepinephrine: acts as vasocontrictor; not as powerful as epinephrine 4

Hormones of the Adrenal Medulla 5

Structure of the Glands Surface of adrenal gland Capsule Zona glomerulosa Connective tissue capsule Adrenal gland Zona lomerulosa Kidney Cortex Zona fasciculata Adrenal cortex Adrenal medulla Medulla Zona reticularis Zona fasciculata Zona reticularis (a) (b) Adrenal medulla Chromaffin cells © Ed Reschke 6

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Pancreas • Located behind stomach • The pancreas has two major types of secretory tissue– why it is a dual functioning organ as both an exocrine gland endocrine gland • Three hormones are secreted from the islet cells: • Alpha cells secrete glucagon (antagonistic or opposite to that of insulin; increase level of glucose in bloodstream) • Beta cells secrete insulin (promote utilization of glucose in cells; lack of insulin causes diabetes mellitus) 8

Structure of the Gland Pancreatic islet (Islet of Langerhans) Gallbladder Common bile duct Pancreatic duct Duct Pancreas Small intestine Digestive enzymesecreting cells Pancreatic islet (Islet of Langerhans) Capillary Hormone-secreting islet cells From Kent M. Van De Graaff and Stuart Ira Fox, Concepts of Human Anatomy and Physiology, 2 nd ed. © 1989 Wm. C. Brown Publishers, Dubuque, Iowa. All Rights Reserved. Reprinted with permission 9

Hormones of the Pancreatic Islets 10

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Other Endocrine Glands Pineal Gland Thymus Gland Gonads Other organs: digestive glands, heart, and kidney 13

Gonads • Sex glands including the ovaries in the female and testes in the male • Ovary: responsible for producing the egg or ova and hormones estrogen and progesterone • Estrogen-stimulates development of reproductive organs including breasts and secondary sex characteristics • Progesterone-works with estrogen to build up lining of uterus for fertilized egg • Testes: responsible for producing sperm and hormone testosterone • Testosterone: development of male reproductive organs and secondary sex characteristics 14

Pineal Gland • Attached to the roof of the third ventricle of the brain • Produces melatonin • The amount of light affects the amount of melatonin secreted—the darker it is, the more melatonin is produced…the lighter it is, the less melatonin is produced • Causes body temperature to drop 15

Thymus Glands • Endocrine gland lymphatic organ located under sternum • Fairly large during childhood but begins to disappear at puberty • Secretes large number of hormones • Major hormone is thymosin that stimulates lymphoid cells that are responsible for production of T cells that fight certain diseases • Critical to development of immune system 16

Stress and Its Effects • Physical or physiological stress • Survival depends on maintaining homeostasis • Factors that change the internal environment are potentially life-threatening • Sensing such dangers directs nerve impulses to the hypothalamus • This can trigger a loss of homeostasis 17

Responses to Stress results from changes in the external environment Hormonal signals Neural signals Signals from sensory receptors Sympathetic impulses Hypothalamus Adrenal medulla Epinephrine and norepinephrine released CRH released Anterior pituitary Norepinephrine released Short-term “fight or flight” or alarm stage. • Blood glucose increases. • Blood glycerol and fatty acids increase. • Heart rate increases. • Blood pressure rises. • Breathing rate increases. • Air passages dilate. • Pupils dilate. • Blood flow redistributes. ACTH released Adrenal cortex Cortisol released Long-term adjustment or resistance stage • Increase in blood concentration of amino acids. • Increased release of fatty acids. • Increased glucose formed from noncarbohydrates—amino acids (from proteins) and glycerol (from fats). 18

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Lifespan Changes • Endocrine glands decrease in size • Muscular strength decreases as GH levels decrease • ADH levels increase due to slower break down in liver and kidneys • Calcitonin levels decrease; increase risk of osteoporosis • PTH level changes contribute to risk of osteoporosis • Insulin resistance may develop • Changes in melatonin secretion affect the body clock • Thymosin production declines increasing risk of infections 20