Adrenal Gland ENDOCRINE AND EXOCRINE SYSTEMS

ADRENAL GLAND

1. Differences Between Endocrine and Exocrine Systems Group 2 Assignment

2. Classifications A gland consists of one or more cells that make and secrete a particular product. This product, called a secretion , is an aqueous (water-based ) fluid that usually contains proteins. These glands can be divided into two main types namely endocrine and exocrine glands. NB: The term secretion can refer to both the gland’s product and the process of making and releasing that product.

3. Glands Endocrine System ( endo - within) secrete their products (hormones ) into the interstitial fluid surrounding the secretory cells rather than into ducts. From the interstitial fluid, hormones diffuse into blood capillaries and blood carries them to target cells throughout the body. Exocrine System ( exo - outside) secrete their products into ducts that carry the secretions into body cavities, into the lumen of an organ, or to the outer surface of the body . Eg . sebaceous glands, mammary glands, mucus producing glands

4. Differences Endocrine System These are ductless glands They pour secretion directly into bood They secrete hormones The response of the endocrine glands is generally delayed due to the release of substances in the blood which then transported to the target tissues Exocrine System They may or may not have ducts The Secretion is poured directly at the site of action They secret enzymes Exocrine glandular secretion however possesses a quicker response time as they are released directly at the target site .

5. Duration of action Endocrine System the secretions of endocrine glands have longer duration of action. This happens because the blood containing released substances is passed from kidneys for the purpose of filtration where they are reabsorbed and again transported to the target site Exocrine System On the contrary, the secretions of exocrine glands are not passed to kidney so there is no reabsorption hence the duration or effect is shorter .

6. Examples Endocrine System Examples include : Thyroid gland, parathyroid gland, pituitary gland, pineal gland, testes and ovaries, hypothalamus and adrenal glands Exocrine System Examples : Gastric gland, Salivary gland, mammary glands, sweat glands, digestive system glands

7. Functions Endocrine System The released chemicals of the endocrine system help in regulation and maintenance of multiple physiological events, such as body metabolism, menstrual flow and uterine changes, reproductive functioning, etc. Exocrine System The secretions produced by exocrine glands help in the regulation of multiple phenomena such as regulation of body temperature through sweat glands. Likewise, the lacrimal glands in the eyes help preventing the eyes from dying out .

8. Significance Knowing the difference between endocrine and exocrine glands helps with a better understanding as to what is normal and what is diverted from the normal physiology. Crying and sweating are short term phenomenon and usually stops after some time but if such secretions persists for a longer period of time (such as constant sweating or lacrimal fluid) then it indicates that a person is suffering from some pathological condition.

9. Transportation Of Hormones in Blood Group 2 Assignment

10. Most water-soluble hormone molecules circulate in the watery blood plasma in a “free” form (not attached to other molecules), but most lipid-soluble hormone molecules are bound to transport proteins . The transport proteins, which are synthesized by cells in the liver, have three functions:

11. 1. They make lipid-soluble hormones temporarily water-soluble, thus increasing their solubility in blood.

12. 2. They retard passage of small hormone molecules through the filtering mechanism in the kidneys, thus slowing the rate of hormone loss in the urine.

13. 3. They provide a ready reserve of hormone, already present in the bloodstream.

14. In general, 0.1–10% of the molecules of a lipid-soluble hormone are not bound to a transport protein. This free fraction diffuses out of capillaries, binds to receptors, and triggers responses . As free hormone molecules leave the blood and bind to their receptors, transport proteins release new ones to replenish the free fraction.

15. Adrenal Glands Group 2

16. Description Adrenal glands are triangular shaped endocrine glands that measure about 3 inches in length, and a half inch in height. The two glands are separated with one being on each kidney. They are made up of an inner layer called the adrenal medulla and an outer layer called the adrenal cortex . Group 2

17. The adrenal cortex The adrenal cortex is subdivided into three zones, each of which secretes different hormones The outer zone, is the zona glomerulosa secrete hormones called mineralocorticoids The middle zone, or zona fasciculata is the widest of the three zones and consists of cells that secrete mainly glucocorticoids , (so named because they affect glucose homeostasis). The cells of the inner zone, the zona reticularis , synthesize small amounts of weak androgens , steroid hormones that have masculinizing effects.

18. Mineralocorticoids Aldosterone is the major mineralocorticoid. It regulates homeostasis of two mineral ions, namely sodium ions (Na + ) and potassium ions ( K + ), and helps adjust blood pressure and blood volume. Aldosterone also promotes excretion of Hydrogen ions in the urine; this removal of acids from the body can help prevent

19. The renin–angiotensin–aldosterone or RAA pathway controls secretion of aldosterone

20. Glucocorticoids The glucocorticoids, functions to regulate metabolism and resistance to stress, include: cortisol (hydrocortisone), corticosterone , and cortisone. Of these three hormones secreted by the zona fasciculata , cortisol is the most abundant, accounting for about 95% of glucocorticoid activity.

21. Effects of Glucocorticoids 1. Protein breakdown. Glucocorticoids increase the rate of protein breakdown , mainly in muscle fibers, and thus increase the liberation of amino acids into the bloodstream. The amino acids may be used by body cells for synthesis of new proteins or for ATP production . 2. Glucose formation. Upon stimulation by glucocorticoids, liver cells may convert certain amino acids or lactic acid to glucose , which neurons and other cells can use for ATP production. Such conversion of a substance other than glycogen or another monosaccharide into glucose is called gluconeogenesis

22. 3 . Lipolysis. Glucocorticoids stimulate lipolysis, the breakdown of triglycerides and release of fatty acids from adipose tissue into the blood . 4 . Resistance to stress. Glucocorticoids work in many ways to provide resistance to stress. The additional glucose supplied by the liver cells provides tissues with a ready source of ATP to combat a range of stresses, including exercise, fasting, fright, temperature extremes, high altitude, bleeding, infection, surgery, trauma , and disease. Because glucocorticoids make blood vessels more sensitive to other hormones that cause vasoconstriction, they raise blood pressure. This effect would be an advantage in cases of severe blood loss, which causes blood pressure to drop.

23. 5. Anti-inflammatory effects. Glucocorticoids inhibit white blood cells that participate in inflammatory responses. Unfortunately, glucocorticoids also retard tissue repair, and as a result , they slow wound healing. Although high doses can cause severe mental disturbances, glucocorticoids are very useful in the treatment of chronic inflammatory disorders such as rheumatoid arthritis. 6. Depression of immune responses. High doses of glucocorticoids depress immune responses. For this reason, glucocorticoids are prescribed for organ transplant recipients to retard tissue rejection by the immune system.

24. Androgens Small amounts of weak androgens are secreted in both male and females. The major androgen secreted by the adrenal gland is dehydroepiandrosterone Adrenal androgens are responsible for sexual characteristics at puberty: it stimulates growth of axillary and pubic hair in boys and girls and contribute to the prepubertal growth spurt . In females,They promote libido (sex drive) and are converted into estrogens (feminizing sex steroids) by other body tissues. After menopause, when ovarian secretion of estrogens ceases, all female estrogens come from conversion of adrenal androgens. the main hormone that stimulates its secretion is ACTH

25. Adrenal Medulla It is the inner region of the adrenal gland a modified sympathetic ganglion of the autonomic nervous system (ANS). Rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones . The adrenal medulla is made up of chromaffin cells which are the bodies main source of catecholamine hormones . These hormones are adrenaline (epinephrine) and noradrenaline (norepinephrine). These are powerful “fight or flight” hormones initiated by the sympathetic nervous system that play a key role in short-term stress reaction.

26. Summary Take Home Message……….