Introduction•The endocrine system is made up of the cells, tissues, and organs that secrete hormones into body fluids.

•The body has two kinds of glands

•Exocrine - secretes products into ducts

•Endocrine - secrete products into body fluids to affect target cells

•The endocrine system’s function is to communicate with cells using chemicals called hormones.

•Endocrine glands and their hormones regulate a number of metabolic processes within cells, and the whole body.

•Their actions are precise, they only affect specific target cells.

•There are two main types of hormones:

•Steroidal Hormones – can pass through cell membrane and affect the nucleus directly.

•Nonsteroidal Hormones – must first bind to receptor in cell membrane and initiate a Signal Transduction Pathway.

•Requires multiple chemical messengers inside cell

Control of Hormonal Secretions

•Hormone levels are very precisely regulated.

•Negative Feedback Systems

•Commonly, negative feedback mechanisms control hormonal releases.

•In a negative feedback system, a gland is sensitive to the concentration of the substance it regulates or which regulates it.

Major Endocrine Glands and Their Products

Pituitary Gland

•Releasing hormones from the hypothalamus control the secretions of the anterior pituitary.

•A small gland located in the brain that is important for puberty and sexual cycles.

•Growth hormone (GH) stimulates body cells to grow and reproduce; it also speeds the rate at which cells use carbohydrates and fats.NFL

•Prolactin (PRL) promotes milk production following the birth of an infant.

•Thyroid-stimulating hormone (TSH) controls the secretion of hormones from the thyroid gland.

•Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) affect the male and female gonads.

•Antidiuretic hormone (ADH) produces its effect by causing the kidneys to conserve water.

•Oxytocin contracts muscles in the uterine wall and forces milk into ducts from the milk glands.

Thyroid GlandThyroid Gland

• The thyroid gland is The thyroid gland is located below the located below the larynx and consists of larynx and consists of two broad lobes two broad lobes connected by an connected by an isthmus.isthmus.

Thyroid Gland

•The thyroid gland is located below the larynx and consists of two broad lobes connected by an isthmus.

ThyroidThyroid

Consists of follicles Consists of follicles that are vesicles that are vesicles filled with fluid filled with fluid called colloidcalled colloid

The follicles The follicles produce hormones produce hormones that are stored in that are stored in the colloid and the colloid and released into released into capillariescapillaries

Thyroid Gland

Produces two Produces two iodine-iodine-containing containing hormones:hormones:

thyroxinethyroxine (T4)(T4)

triiodothyrine triiodothyrine (T3)(T3)

• These two These two hormones hormones together together increase the rate increase the rate at which the at which the metabolism of a metabolism of a cell runs. cell runs.

• Use of carbs, fats Use of carbs, fats and protein and protein synthesissynthesis

Thyroid Gland

• calcitonin

•Inhibits osteoclasts from breaking down bone and calcium emptying into blood.

•this lowers blood levels of calcium and phosphate ions when they are too high.

Thyroid Gland DisordersThyroid Gland Disorders

HyperthyroidismHyperthyroidism Too much thyroid hormone can cause the Too much thyroid hormone can cause the

body’s metabolism to speed upbody’s metabolism to speed up Most common form is known as Grave’s Most common form is known as Grave’s

DiseaseDisease SymptomsSymptoms

Muscle weakness, trembling hands, rapid Muscle weakness, trembling hands, rapid heart rate, fatigue, weight loss, diarrhea or heart rate, fatigue, weight loss, diarrhea or frequent bowel movements, vision frequent bowel movements, vision problems, menstrual irregularities problems, menstrual irregularities

Graves diseaseGraves disease

Exophthalmos may occur with Exophthalmos may occur with GravesGraves

+

Thyroid Gland Disorders Thyroid Gland Disorders (cont.)(cont.)

HypothyroidismHypothyroidism Too little thyroid hormone can cause the Too little thyroid hormone can cause the

body’s metabolism to slow downbody’s metabolism to slow down Physical and mental functions become Physical and mental functions become

sluggishsluggish SymptomsSymptoms

Fatigue, mental depression, sluggishness, Fatigue, mental depression, sluggishness, feeling cold, weight gain, dry skin and feeling cold, weight gain, dry skin and hair, constipation, menstrual hair, constipation, menstrual irregularities irregularities

With hypothyroidism With hypothyroidism Without hypothyroidism Without hypothyroidism

Thyroid Gland Disorders Thyroid Gland Disorders (cont.)(cont.)

Goiters Goiters Enlargement of the thyroid gland itself Enlargement of the thyroid gland itself Typically caused by lack of iodine in the Typically caused by lack of iodine in the

diet or by a disease that affects the thyroid diet or by a disease that affects the thyroid glands ability to produce thyroid hormone glands ability to produce thyroid hormone

SymptomsSymptoms Swelling of neck (range from small nodule Swelling of neck (range from small nodule

to massive lump), feeling of tightness in to massive lump), feeling of tightness in throat area, difficulty breathing and throat area, difficulty breathing and swallowing, hoarseness, dizziness when swallowing, hoarseness, dizziness when hands raised above head hands raised above head

Parathyroid Glands

•The four, tiny parathyroids are located on the posterior of the thyroid.

•Parathyroid hormone (PTH) increases blood calcium ion concentration.

Adrenal Glands

•The adrenal glands sit atop the kidneys enclosed in a layer of fat.

Epinephrine and Norepinephrine

•They are used in times of stress and trigger the “Fight or Flight” response.

Aldosterone

•Causes the kidneys to conserve water.

•Secreted in response to decreasing blood volume and blood pressure.

Cortisol

•Influences the metabolism of glucose, protein, and fat in response to stress.

•High concentrations cause increase in use of fatty acids for energy.

•Stress triggers cortisol release.

Pancreas

•The pancreas is both an endocrine gland and a digestive gland located superior to your belly button, medial to the kidneys.

•Glucagon increases the blood levels of glucose by stimulating the breakdown of glycogen.

•Insulin decreases the blood levels of glucose by shuttling glucose into cells and stimulating the liver to form glycogen.

•These two hormones operate to keep the blood glucose levels relatively constant.

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Hormonal Control of Female Hormonal Control of Female ReproductiveReproductive

FunctionsFunctions A.A. Hormones secreted by the Hormones secreted by the

hypothalamus, the hypothalamus, the anterior pituitary, and anterior pituitary, and the ovaries control female reproduction and the ovaries control female reproduction and development of secondary sexual development of secondary sexual characteristics.characteristics.

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B. B. Female Sex HormonesFemale Sex Hormones

1.1. At about 10 years of age, the At about 10 years of age, the hypothalamus begins to secrete hypothalamus begins to secrete more more GnRH (GnRH (Gonadotropin-releasing hormone), ), which in turn stimulates the anterior which in turn stimulates the anterior pituitary to produce LH and FSH.pituitary to produce LH and FSH.

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2.2. At puberty, the ovaries synthesize At puberty, the ovaries synthesize estrogens in response to FSH.estrogens in response to FSH.a.a. EstrogensEstrogens are responsible for the are responsible for the female secondary sexual characteristics, female secondary sexual characteristics, such as breast development, increased such as breast development, increased adipose tissue deposition, and increased adipose tissue deposition, and increased vascularization of the skin.vascularization of the skin.b.b. Ovaries also secrete Ovaries also secrete progesteroneprogesterone, , which triggers uterine changes during the which triggers uterine changes during the menstrual cycle. menstrual cycle.

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C.C. Female Reproductive Cycle Female Reproductive Cycle

1.1. MenarcheMenarche is characterized by is characterized by monthly changes in the uterine lining that monthly changes in the uterine lining that lead to menstrual flow as the endometrium lead to menstrual flow as the endometrium is shed.is shed.

2.2. A menstrual cycle is started by FSH, A menstrual cycle is started by FSH, which stimulates the maturation of a which stimulates the maturation of a follicle in the ovary.follicle in the ovary.

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3.3. Follicular cells surrounding the Follicular cells surrounding the developing oocyte secrete estrogen, which developing oocyte secrete estrogen, which is responsible for maintaining secondary is responsible for maintaining secondary sexual sexual characteristics as well as the characteristics as well as the thickening of the uterine lining.thickening of the uterine lining.4.4. Ovulation is triggered by a mid-Ovulation is triggered by a mid-cycle surge in LH.cycle surge in LH.5.5. Following ovulation, follicular cells Following ovulation, follicular cells turn into a glandular turn into a glandular corpuscorpus luteumluteum that that secretes increasing amounts of estrogen secretes increasing amounts of estrogen and progesterone.and progesterone.

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6.6. If pregnancy does not occur, the If pregnancy does not occur, the corpus luteum degenerates, hormone corpus luteum degenerates, hormone levels decline, and the uterine lining levels decline, and the uterine lining disintegrates and is shed, the remnant is disintegrates and is shed, the remnant is called the called the corpus albicanscorpus albicans..7.7. During the cycle, estrogen and During the cycle, estrogen and progesterone inhibit the increased release progesterone inhibit the increased release of FSH and LH; when estrogen and of FSH and LH; when estrogen and progesterone levelsprogesterone levels fall, the secretion of fall, the secretion of FSH and LH FSH and LH increases. increases.

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Fig19.13

Days

Days

Menstruation MenstruationProliferative phase Secretory phase

1

LH

Estrogens

Estrogens

Progesterone

Progesterone

Developingfollicle

Follicular phase Luteal phaseCorpusalbicansOvulation

Maturefollicle

Earlycorpus luteum

Regressivecorpus luteum

FSH

FSH LH

Ovarian activity

Uterine activity

7

1 3 5 9 11 13 15 17 19 21 23 25 27

21 28

1 37

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D.D. MenopauseMenopause

1.1.Menstrual cycles continue throughout Menstrual cycles continue throughout middle age until middle age until menopausemenopause, when the , when the cycles cease.cycles cease.

2.2.The cause of menopause is the aging The cause of menopause is the aging of of the ovaries when follicles no longer the ovaries when follicles no longer mature and estrogen levels decline. mature and estrogen levels decline.

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Birth ControlBirth Control A.A. Birth control refers to the Birth control refers to the

voluntary regulation voluntary regulation of the number of of the number of offspring produced, offspring produced, requiring the use of requiring the use of contraceptioncontraception. The following slide lists . The following slide lists the different methods.the different methods.

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1.1. Coitus InterruptusCoitus Interruptus2.2. Rhythm MethodRhythm Method3.3. Mechanical BarriersMechanical Barriers4.4. Chemical BarriersChemical Barriers5.5. Oral ContraceptivesOral Contraceptives6.6. Injectable ContraceptionInjectable Contraception7.7. Contraceptive ImplantsContraceptive Implants88 Intrauterine DevicesIntrauterine Devices9.9. Surgical MethodsSurgical Methods

Regulation of Menstrual Cycle

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Fig19.15

©The McGraw-Hill Companies, Inc./Jill Braaten, photographer ©The McGraw-Hill Companies, Inc./Jill Braaten, photographer

©PhotoLink/Getty Images ©Don Farrall/Getty Images ©The McGraw-Hill Companies, Inc./Jill Braaten, photographer

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a) (b)

(c) (d) (e)

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Fig19.16

Cut and ligatedductus (vas) deferens

Scrotum

Ovary

Uterus

Cervix

Vagina

Path of sperm

Cut and ligateduterine tubes

Path of egg

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

(a)

(b)

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Hormonal Control of Male Hormonal Control of Male ReproductiveReproductive

FunctionsFunctions A.A. Hormones secreted by the Hormones secreted by the

hypothalamus, the anterior pituitary, and hypothalamus, the anterior pituitary, and the testes control male reproduction and the testes control male reproduction and development of secondary sexual development of secondary sexual characteristics.characteristics.

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B.B. Hypothalamic and Pituitary Hypothalamic and Pituitary HormonesHormones

1. At the time of puberty, the hypothalamus 1. At the time of puberty, the hypothalamus controls the many changes that lead to controls the many changes that lead to the development the development of a reproductively of a reproductively functional adult.functional adult.

2.2.The hypothalamus releases (GnRH), The hypothalamus releases (GnRH), which triggers the production of the which triggers the production of the gonadotropinsgonadotropins luteinizing luteinizing hormone hormone (LH), and (LH), and follicle-stimulating hormonefollicle-stimulating hormone (FSH) from the anterior pituitary.(FSH) from the anterior pituitary.

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a.a. LH promotes the development of LH promotes the development of interstitial cells of the testes andinterstitial cells of the testes and they, they, in turn, secrete male in turn, secrete male hormones hormones ((testosteronetestosterone).).

b.b. FSH stimulates the supporting cells FSH stimulates the supporting cells of the seminiferous tubules where of the seminiferous tubules where spermatozoa are created.spermatozoa are created.

c.c. FSH and testosterone stimulate FSH and testosterone stimulate spermatogenesis. spermatogenesis.

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C.C. Male Sex Hormones Male Sex Hormones

1.1. The male sex hormones are called The male sex hormones are called androgensandrogens, of which , of which testosteronetestosterone is the is the most abundant.most abundant.

2.2. Testosterone is secreted in a fetus Testosterone is secreted in a fetus until birth, and then not again until until birth, and then not again until pubertypuberty, after which it is continuously , after which it is continuously secreted.secreted.

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3.3. Actions of Testosterone Actions of Testosterone a.a. Testosterone stimulates the Testosterone stimulates the development of the male reproductive development of the male reproductive organs and causesorgans and causes the testes to descend.the testes to descend.b.b. Testosterone is also responsible for Testosterone is also responsible for male secondary sexual characteristicsmale secondary sexual characteristics (deep voice, body (deep voice, body hair, thickening of hair, thickening of the skin, and so forth).the skin, and so forth).

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4.4. Regulation of Male Sex Hormones Regulation of Male Sex Hormones a.a. A negative feedback system involving A negative feedback system involving the hypothalamus regulates the quantity of the hypothalamus regulates the quantity of testosterone.testosterone.b.b. As the concentration of blood As the concentration of blood testosterone increases, the hypothalamus testosterone increases, the hypothalamus becomes inhibited, and its stimulation of the becomes inhibited, and its stimulation of the anterior pituitary anterior pituitary declines.declines.c.c. As the amount of LH drops in response, As the amount of LH drops in response, the amount of testosterone is reduced. the amount of testosterone is reduced.