1. The Endocrine System  Structures  Functions

2. The Endocrine System  Homeostasis: the harmonious coordination and integration of all body functions  Maintaining homeostasis: involves growth, maturation, reproduction and metabolism  Endocrine system: body system responsible for coordinating homeostasis through hormone secretion and chemical excretion

3. The Endocrine System  Composed of numerous glands throughout the body that secrete hormones into the bloodstream and secrete chemicals to rid the body of wastes.  Chemicals and hormones  Regulate growth  Regulate sexual production & development  Metabolize nutrients in cells  Maintain homeostasis

4. Hormones  Delivered to target cells within the body  Fit into each cell like a lock and key  Body sends a signal for a certain hormone when needed (negative feedback)  Body responds by producing enzymes  Enzymes create and release the hormone needed until correction is complete then secretion stops  Hormones are made up of four major chemical groups

5. Hormones - four major groups  Fatty acids  Control hormones involved in estrus  includes prostaglandins  Steroids  Occur naturally in the body and regulate chemicals, like cholesterol, that control essential life functions  Amino acids  Control thyroid gland functions  Simplest of the hormones  Peptides  Control proteins in the body  Largest of the hormones (example: Oxytocin)

6. Lock and Key

7. Hypothalamus  Located in front of the thalamus  Serves as a reservoir for hormones  Closely associated with pituitary gland  Secretes releasing and inhibiting factors that affect the release of substances from the pituitary gland  Produces antidiuretic hormone (ADH) and oxytocin  Provides a link between the nervous and endocrine systems

8. Hypothalamus

9. Endocrine Glands  Secrete hormones directly into the bloodstream and then transported to all areas of the body  Include the following:  Pituitary  Thyroid  Parathyroid  Adrenal  Thymus  Pancreas  Pineal  Gonads

10. Pituitary Gland  Main endocrine gland  Often called the “master gland” because it controls the thyroid gland.  Works with hypothalamus to control the endocrine system and create a link with the nervous system  Located at the base of the brain  Has an anterior and posterior lobe

11. Hormones Secreted by the Hypothalamus HORMONEFUNCTION Corticotropin Releasing Hormone (RH) Signals release of Adrenocorticotropic Hormone (ACTH) Gonadatropin RH Signals release of  Follicle Stimulating Hormone (FSH)  Luteinizing Hormone (LH) Growth Hormone RH Signals release of Growth Hormone (GH) Growth Inhibiting RH Signals inhibition of GH Thyrotropin RH Signals release of Thyroid-stimulating hormone (TSH) Prolactin Inhibiting RH Signals inhibition of Prolactin production Oxytocin Synthesized Antidiuretic Hormone Synthesized

12. Hormones Secreted by the Anterior Pituitary Gland HORMONEFUNCTION ACTH Glucocorticoid Release FSH Follicular Development LH Ovulation Corpus Luteum Androgen Secretion Growth Hormone (GH) Promotes growth CHO Protein Lipid Metabolism TSH Thyroxine Release Prolactin (PRL) Promotes Lactation Interstitial Cell Stimulating Hormone (ICSH) Stimulates ovulation in females Stimulates androgen release in males Melanocyte-stimulating Hormone (MSH) Stimulates melanin synthesis in melanocytes

14. Pituitary Gland – Anterior Lobe  Controlled by the hypothalamus  Produces and secretes… Thyroid-stimulating hormone (TSH): affects growth and secretions of the thyroid gland Adrenocorticotropic hormone (ACTH): affects growth and secretions of the adrenal cortex Follicle-stimulating hormone (FSH): affects the secretion of estrogen and growth of eggs in the ovaries & production of sperm in the testes Lutenizing hormone (LH): affects ovulation and aids in maintenance of pregnancy in females Interstitial cell-stimulating hormone (ICSH): stimulates testosterone secretion in males Prolactin (lactogenic hormone-LTH): affects milk secretion and influences maternal behavoir Growth hormone (somatotropin-STH): accelerates body growth Melanocyte-stimulating hormone (MSH): affects skin pigmentation

15. Pituitary Gland – Posterior Lobe  Connects to the hypothalamus  Does not produce hormones but stores and secretes them  Secretes… Oxytocin: stimulates uterine contractions during parturition and milk letdown from the mammary ducts Antidiuretic hormone (ADH): maintains water balance in the body by increasing water reabsorption in the kidneys

16. Thyroid Gland  Regulates metabolism, iodine uptake, and blood calcium levels  Located in the neck, contains two lobes, one on each side of trachea  Can become overactive (hyperthyroid) or underactive (hypothyroid)  Only endocrine gland that can be palpated when enlarged  Produces and secretes…  Triiodothyronine (T3) and Thyroxine (T4)  Increases metabolic rate in tissues (increases oxygen consumption)  Increases heart rate  Makes heart more sensitive to epinephrine  Stimulates the breakdown of adipose tissue  Stimulates erythropoiesis  Necessary for normal growth and development  Calcitonin: promotes the absorption of calcium from blood into bones

17. Thyroid Gland  Butterfly shaped gland HORMONES SECRETED BY THE THYROID GLAND HormoneFunction Thyroxine (T 4 )Metabolism Triiodothyrodine (T 3 ) ATP generation Oxygen consumption CalcitoninCa metabolism

18. Parathyroid Glands  Four glands located on the surface of the thyroid gland  Produces and secretes…  Parathormone (parathyroid hormone-PTH)  Increases blood calcium levels by reducing bone calcium levels (calcium is regulated in the body by the antagonistic actions of PTH and calcitonin.  Regulates phosphorus content of blood and bones

19. Adrenal Glands  Located cranial to the kidneys  Regulate electrolytes, metabolism, sexual functions and the bodies response to injury  Consist of 2 parts  Adrenal cortex  Adrenal medulla

20. Adrenal Glands - A drenal Cortex  Hormones classified as steroids  Produces and secretes corticosteroids…  Mineralcorticoids: regulate electrolyte and water balance by affecting ion transport in the kidney. Aldosterone (is the principal mineralcorticoid) which regulates sodium and potassium.  Glucocorticoids: regulate carbohydrate, fat and protein metabolism; resistance to stress; and immunologic functioning. Example is hydrocortisone (cortisol) which converts fat and protein into glucose, increasing blood sugar.  Androgens: aid in the development and maintenance of male sex characteristics. Example is testosterone which increases strength and muscle mass.

21. Adrenal Glands – Adrenal Medulla  Produces and secretes…  Epinephrine (adrenaline): stimulates the sympathetic nervous system (flight or flight system) and increases blood pressure, heart rate, and blood glucose.  Norepineherine (noradrenaline): stimulates the sympathetic nervous system and increases blood pressure, heart rate, and blood glucose.

22. Thymus  Gland that operates in young animals  Located near midline in the cranioventral portion of the thoracic cavity.  Immunologic function through its role in the maturation of t-lymphocytes  Produces and secretes...  Thymosin: promotes full development of T-lymphocytes

23. Pancreas  Located near the proximal duodenum  Has both endocrine and exocrine functions  Produces and secretes…  Insulin: decreases blood glucose levels by transporting blood glucose into body cells or into storage as glycogen (main carbohydrate)  Glucagon: increases blood glucose levels by breaking down glycogen

24. Pineal Gland  Located in the central portion of the brain  Functions are not fully understood but has to do with circadian rhythm (events occurring in a 24-hour period)  Produces and secretes…  Melatonin: controls circadian rhythm and plays a role in sleep, behavior, coat growth, seasonal rituals, aging and reproduction

25. Gonads  Associated with reproduction  Ovaries in females and testes in males  Produces gametes (sex cell)  Ovaries secrete…  Estrogen: aids in the development of secondary sex characteristics (example is mammary gland development) and regulates ovulation  Progesterone: aids in the maintenance of pregnancy, also secreted from the corpus luteum and placenta.  Testes secrete…  Testosterone: increases the development of secondary sex characteristics (example is horn growth in rams, shoulder girth in cattle and horses). It is thought to also be secreted from ovaries and adrenal cortex but in very small amounts.

26. HORMONES SECRETED BY THE GONADS OrganHormoneFunction OvaryEstrogenHeat cycle ProgesteronePregnancy InhibinInhibit FSH TestesTestosteroneLibido UterusProstiglandinsLuteolytic Equine Chorionic Gonadotropin (ECG) Accessory Corpus Luteum RelaxinRelaxes uterine/cervical muscles in preparation for parturition

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