1. Endocrine System
Chapter 18

2. Introduction
The endocrine system consists of cells, tissues, & organs that secrete hormones into the blood
Hormone – an organic substance secreted by a cell that has an effect on the metabolic activity of another cell or tissue
Target cells – cells that are affected by the hormone
Have specific receptors for the hormones
Types of hormones
Steroid
Amino acid derivative
Peptide

3. Human Anatomy, 3rd edition
How Hormones Work
Activation of 2nd messengers
Hormone (first messenger) binds to receptor on cell membrane
Receptor/hormone complex activates another substance in the cell (2nd messenger)
Triggers cell’s response
Human Anatomy, 3rd edition
Prentice Hall, © 2001

4. Human Anatomy, 3rd edition
How Hormones Work
Activation of genes
Hormone crosses cell membrane
Hormone binds to a receptor
Cytoplasm
Nucleus
Receptor/hormone complex binds to DNA
Alters gene activity
Human Anatomy, 3rd edition
Prentice Hall, © 2001

5. The Hypothalamus & Endocrine Regulation
Sympathetic neurons
Adrenal medulla
Releases hormones
Antidiuretic hormone (ADH)
Oxytocin
Secretes regulatory hormones
Anterior pituitary gland
Releasing factors
Inhibiting factors
Human Anatomy, 3rd edition
Prentice Hall, © 2001

6. Overview of the Endocrine System
Human Anatomy, 3rd edition
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7. Human Anatomy, 3rd edition
The Pituitary Gland
aka hypophysis
Located in sella turcica
Infundibulm connects to hypothalamus
Master gland of the endocrine system
2 parts
Posterior pituitary = neurohypophysis
Anterior pituitary = adenohypophysis
Human Anatomy, 3rd edition
Prentice Hall, © 2001

8. Hypophyseal Portal System
Median eminence
Neurons secrete regulatory factors
2 capillary beds
#1 in hypothalamus
RFs diffuse in
#2 in anterior pituitary
RFs diffuse out
Portal veins connect the capillary beds
Human Anatomy, 3rd edition
Prentice Hall, © 2001

9. Posterior Pituitary Neurohypophysis is nervous tissue
Cell bodies in the hypothalamus make hormones
Axons run down the infundibulum
Carry hormones to axon terminals
Axon terminals in the posterior pituitary store hormones

10. Posterior Pituitary Produces 2 Hormones
Antidiuretic hormone (ADH)
Target – kidneys
Effect – reabsorption of water
Oxytocin
Targets – reproductive organs
Effects – contractions of smooth muscles (labor contractions, milk ejection; ductus deferens, prostate gland – ejaculations)

11. Anterior Pituitary Hormones
Gonadotropins stimulate growth & development of gonads
Follicle stimulating hormone (FSH) stimulates gametes
Targets – follicle cells (females), testes (males)
Effects – follicle development & estrogen secretion (females), sperm maturation (males)
Luteinizing hormone (LH)
Targets – follicle cells (females), interstitial cells of testes (males)
Effects – ovulation, formation of corpus luteum, secretion of progesterone (females), testosterone secretion (males)

12. Anterior Pituitary Hormones
Thyroid stimulating hormone (TSH)
Target – thyroid gland
Effect – triggers the release of thyroid hormones
Adrenocorticotropic hormone (ACTH)
Target – adrenal cortex
Effect – cells that produce glucocorticoids (steroid hormones)

13. Anterior Pituitary Hormones
Prolactin
Target - breast
Effect - stimulates milk production
Growth hormone
Target – all cells
Effect - stimulates growth in general and the skeletal system in particular
Melanocyte stimulating hormone (MSH)
Target - melanocytes
Effect – increases melanin production and distribution

14. Human Anatomy, 3rd edition
Pituitary Hormones
FG19_05.JPG
Title: Pituitary Hormones and Their Targets
Notes: This schematic diagram shows the hypothalamic control of the pituitary gland, the pituitary hormones produced, and the responses of representative target tissues.
Keywords: pituitary hormones, targets, adrenal medulla, adrenal cortex, thyroid, peripheral tissues, mammary glands, testes, ovaries, melanocytes, kidneys, anterior pituitary, posterior pituitary, ACTH, TSH, GH, PRL, FSH, LH, MSH, ADH, hypothalamus, oxytocin
Human Anatomy, 3rd edition
Prentice Hall, © 2001

15. Human Anatomy, 3rd edition
The Thyroid Gland
Location – inferior to thyroid cartilage
Thyroid follicles make thyroid hormones
Tyrosine + iodine
T4 (thyroxine) or (T3) (triiodothyronine)
Target cells – most cells
Effect of thyroid hormones
increase energy utilization, oxygen consumption, growth, development
Human Anatomy, 3rd edition
Prentice Hall, © 2001

16. Human Anatomy, 3rd edition
The Thyroid Gland
C cells
Produce calcitonin (CT)
Targets – bone, kidneys
Effect – lowers blood calcium levels
Human Anatomy, 3rd edition
Prentice Hall, © 2001

17. Control of Thyroid Hormones
FG19_08.JPG
Title: The Regulation of Thyroid Secretion
Notes: This negative feedback loop is responsible for the homeostatic control of thyroid hormone release.
Keywords: thyroid activity, regulation, homeostasis, anterior pituitary, TSH, thyroid gland, T3, T4, body temperature
Human Anatomy, 3rd edition
Prentice Hall, © 2001

18. The Parathyroid Glands
Location – posterior surfaces of thyroid gland
Principal cell
Chief cells produce parathyroid hormone (PTH)
Target cells – bone, kidneys, intestines
Effect
Increases blood calcium levels
Human Anatomy, 3rd edition
Prentice Hall, © 2001

19. Human Anatomy, 3rd edition
The Thymus Gland
Location – posterior to the sternum
Produces thymosins
Enhance lymphycyte production
Development
Childhood – large
Puberty – largest
Adulthood – decreases in size
Human Anatomy, 3rd edition
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20. Human Anatomy, 3rd edition
The Adrenal Glands
Location – on top of the kidney
Structure
Capsule
Cortex
Human Anatomy, 3rd edition
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21. Human Anatomy, 3rd edition
The Adrenal Medulla
Secretes epinephrine & norepinephrine
Target – most cells
Effect - stimulates heart beat & tissue metabolism, increases alertness, prepares body to deal with emergencies
Human Anatomy, 3rd edition
Prentice Hall, © 2001

22. Human Anatomy, 3rd edition
The Adrenal Cortex
Zona glomerulosa secretes mineralocorticoids, mostly aldosterone
Target – kidneys
Effect – increases blood sodium, decreases blood potassium
Zona fasciculata – secretes glucocorticoids (cortisol, corticosterone)
Target – most cells
Effect – conserve blood glucose, anti-inflammatory effects
Zona reticulares – secretes androgens
Effects are uncertain
Human Anatomy, 3rd edition
Prentice Hall, © 2001

23. Human Anatomy, 3rd edition
The Pancreas
Location – between the spleen and the duodenum
Functions – both exocrine and endocrine
Endocrine cells are in the Islets of Langerhans
Human Anatomy, 3rd edition
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24. Human Anatomy, 3rd edition
Islets of Langerhans
Alpha cells secrete glucagon
Targets – liver, adipose tissues
Effect - increase blood sugar levels
Beta cells secrete insulin
Targets - most cells
Effect - decrease blood sugar levels
Diabetes mellitis
Human Anatomy, 3rd edition
Prentice Hall, © 2001

25. Human Anatomy, 3rd edition
The Pineal Gland
Location = epithalamus
Pinealocytes secrete melatonin
Derived from seratonin
Light inhibits production
Regulates circadian rythms
Target – hypothalamus
Effects – Inhibits FSH & LH secretion
Human Anatomy, 3rd edition
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26. Human Anatomy, 3rd edition
The Testes
Divided into internal compartments containing seminiferous tubules
Spermatogenesis
Human Anatomy, 3rd edition
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27. Human Anatomy, 3rd edition
Seminiferous Tubules
Interstitial cells secrete androgens; testosterone is the most important
Target – most cells
Effects – maturation of sperm; protein synthesis in skeletal muscle; male secondary sex characteristics & behaviors
Some interstitial cells secrete inhibin
Target – anterior pituitary
Effect – inhibits the secretion of FSH
Human Anatomy, 3rd edition
Prentice Hall, © 2001

28. The Ovaries – Follicle Cells
Estrogen
Targets – most cells
Effects – follicle maturation; female secondary sex characteristics and behaviors
Inhibin
Target – anterior pituitary
Effect – inhibits secretion of FSH
Human Anatomy, 3rd edition
Prentice Hall, © 2001

29. The Ovaries – Corpus Luteum
Progesterone
Targets – uterus, mammary glands
Effects – prepare uterus for implantation, mammary glands for secretion
Relaxin
Targets – pubic symphysis, uterus, mammary glands
Effects – loosens pubic symphysis, relaxes cervical muscles, stimulates mammary gland development
Human Anatomy, 3rd edition
Prentice Hall, © 2001

30. Hormonal Regulation of the Female Reproductive System
FG27_18.JPG
Title: The Hormonal Regulation of Female Reproductive Function
Notes: A diagrammatic view of the hormonal regulation of female reproductive function.
Keywords: hormones, female reproductive functions, hypothalamus, pituitary, estrogens, progestins, GnRH, LH, FSH
Human Anatomy, 3rd edition
Prentice Hall, © 2001