1. The Endocrine System

2. Major functions of the Endocrine System
By releasing chemicals called hormones into the bloodstream, Endocrine glands control:
Metabolism
Growth
Development
Puberty
Tissue function
Mood

3. Exocrine vs. Endocrine Endocrine Glands Exocrine Glands
Secrete into the blood
Secrete into the external environment or an organ
Ductless (no ducts)
Have ducts
Secrete hormones
Secrete other stuff (sweat, oil, enzymes etc.)

4. The Endocrine System: a Gland System
Endocrine glands utilize blood vessels to transport hormones as a means of regulating hundreds of physiologic processes, maintaining homeostasis.

5. Endocrine Glands

6. The Hypothalamus
The hypothalamus is an incredibly complex portion of the midbrain which bridges the gap between the nervous system and the endocrine system. It secretes a number of different “releasing” hormones which, in turn, activate Pituitary Gland function.

7. The Hypothalamus (cont.)
The Hypothalamus is connected to the pituitary via a funnel shaped stalk called the infundibulum.
In addition to ‘releasing hormones,’ the hypothalamus secretes inhibitory hormones which halt the secreation of various stimulatng hormones into the capillary beds of the pituitary.

9. Endocrine Glands: The Master Gland
About the size of a walnut, the Pituitary Gland receives messages from the hypothalamus and releases many different hormones into the bloodstream in response.
These hormones target other glands, organs and/or tissues usually elliciting a cascade of responses.

11. Pituitary Gland Hormones
Abbreviation
Target
Effect
Growth Hormone GH
Bones and muscles
Growth/ cell reproduction
Prolactin
N/A
Mammary Glands
Milk production
Adrenocorticotropic Hormone
ACTH
Adrenal Glands
Releases androgens
Melanocyte Stimulating Hormone
MSH
Melanocytes
(in the dermis)
Produces melanin
Follicle Stimulating Hormone
FSH
Ovaries/Testes
puberty
Luteinizing Hormone LH
Ovaries
ovulation
Oxytocin
Uterus
Uterine contraction during pregnancy
Antidiuretic Hormone
ADH
Kidneys
Water retention
Thyroid Stimulating Hormone
TSH
Thyroid
Metabolism regulation

12. Pituitary/Hypothalamus Interaction

13. Classification of Hormones: 3 Basic Categories
The simplest group of hormones are modified amino acids.
Hormones may also include much more larger and intricate protein complexes.
Finally, some lipid hormones are considered steroids, and actually diffuse across cell membranes.
EXAMPLES

14. The Pineal Gland
The pineal gland is about the size of the tip of your little finger, and is located deep inside the brain.
Secretes melatonin, which regulates sleep patterns.
Its other functions remain a mystery….

15. Did You Know?...
The Pineal Gland is the smallest of all your organs.

16. The Thyroid Gland
Located at the base of the throat, and shaped like a butterfly, the Thyroid Gland is actually 2 glands in one…
Secretes the hormone thyroxine to regulate metabolism of carbohydrates, fats, and proteins in the bloodstream. Iodine is an integral element in this hormone.
Secretes calcitonin to regulate Calcium (Ca+) and phosphate ion levels in blood and bone.

17. The Thyroid (cont.) C Cells- (extrafollicular cells): Calcitonin
follicular cells surrounding lumen filled with thyroglobulin T3, T4

18. The Parathyroid glands
Embedded in the posterior surface of the thyroid, there are 4 raisin sized parathyroid glands.
Parathormone (PTH) governs osteoblast and osteoclast activity, while aiding the thyroid maintaining appropriate calcium concentration in the blood.

20. Challenge Question:
What is a “goiter?”

21. The Thymus Gland
the thymus is located in the upper anterior portion of the chest cavity just behind the sternum. Its primary function is to provide an area for Immune cell maturation, and is vital in immune system development. The thymus secrets a hormone called Thymosin, which controls T-Lymphocyte maturation.

22. The Pancreas
The Pancreas acts as both an endocrine and an exocrine gland. Its endocrine function regulates blood sugar levels by releasing insulin (lowers blood sugar) and/or glucagon (raises blood sugar) into the bloodstream.

23. The Adrenal Glands
Located on the top of the kidneys, the adrenal glands secrete adrenaline and cortisol.
These hormones initiate the “Fight or Flight” response as part of the sympathetic nervous system.

24. Adrenal Glands (cont.) Cortex Zona glomerulosa: mineralcorticoids
Zona fasciculata: glucocorticoids
Zona reticularis: sex steroids
Medulla:
epinepherine and
norepinepherine

26. The Testes
testes are components of both the reproductive system and the endocrine system. The respective functions of the testes are:
producing sperm
producing male sex hormones of which testosterone is the best-known.
Testosterone is responsible for the appearance of secondary sex characteristics in males.

27. The Ovaries
Just like the testes, the ovaries have both a reproductive function as well as endocrine.
Producing eggs
Secretion of estrogen and progesterone
Estrogen is responsible for the appearance of secondary sex characteristics in females at puberty as well as the development and maintenance of the reproductive organs

28. The Endocrine System and Interdependence: Negative Feedback Loops
The primary function of the Endocrine System is to maintain homeostasis (equilibrium) among all body systems by using “negative feedback” to control hormone secretion.

29. Negative Feedback: Blood Sugar

30. Negative Feedback: Calcium

31. Negative Feedback: Temperature

33. Negative Feedback: Metabolism

34. Practice Quiz: Name These Glands1. 3. 2. 4. 5. 6. 7. 8. 9.