Functions of the Exocrine and Endocrine Systems

The endocrine system is made up of glands that produce hormones to influence and regulate growth, reproduction, sexual development and function, metabolism, mood, and sleep. Glands in the endocrine system include the pancreas, thyroid gland, adrenal glands, parathyroid glands, pituitary gland, and the ovaries or testicles. The various glands produce hormones. Organs have receptors for specific hormones, so the exocrine system functions by releasing hormones to instruct these organs through their receptors.

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The exocrine system consists of glands that secrete substances to lubricate and protect the body. These glands include the sweat, salivary, mucous, mammary, gastric, prostate, bile, ceruminous, sebaceous, and lacrimal glands. Substances produced by exocrine glands flow through ducts to epithelial surfaces. The three shapes of epithelial cells are squamous, columnar and cuboidal. These cell types make up hair, skin and other tissue types on or near the body's surface.

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Hormones produced by endocrine glands are released and travel through the bloodstream so they can reach any organ or tissue in the body. Hormones are often specifically targeted to perform a task or reach one specific organ. Exocrine glands have a much shorter range. Their secretions cannot go anywhere beyond one small area on the skin, or mucous membranes inside cavities such as the mouth. Some exocrine glands do not have ducts, so they release secretions directly on or into the targeted area.

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Exocrine and endocrine glands both secrete proteins, and the glands themselves are epithelial tissues. We feel and see the effects of exocrine gland secretions more quickly. Salivating while smelling a tasty food and crying in response to an upsetting event are endocrine functions managed by the salivary and lacrimal glands. Hormonal changes can take place over days or years.

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The adrenal glands are an exception within the endocrine system: we feel the effects of their actions immediately. They release epinephrine and norepinephrine, the hormones responsible for the fight-or-flight response. The effects include increased heart rate, dilated pupils, and rapid breathing. The digestive and excretory systems are slower because the adrenal hormones are directing energy to bodily functions required to escape or fight a threat.

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The endocrine system works in tandem with the nervous system. The endocrine system manages long-term changes such as puberty, menopause, and producing breast milk. The exocrine system handles body temperature regulation and keeping the eyes lubricated. Both systems share functions in processes such as sexual intercourse and digestion. Hormones influence sexual maturity; the secretions during intercourse and arousal are short-term effects of the exocrine glands.

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The endocrine system plays a major role in pregnancy at every stage. Hormones determine when the ovaries release an egg and regulate menstrual cycles. Intercourse implants a fertilized egg in the uterus. The developing placenta is a temporary endocrine gland, in addition to its many other functions. The endocrine system guides a complex process involving almost all of the body's organs and tissues, to carry a pregnancy to term.

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Endocrine disorders can sometimes be difficult to diagnose and treat. Problems with the pituitary gland interrupt menstruation, metabolism, bone growth, and many other processes; the pituitary -- or master gland -- strongly affects on the rest of the endocrine system. Diabetes is a well-known illness related to damage or poor function of the pancreas. Disorders of the ovaries or testes interfere with reproduction and cause abnormal testosterone, estrogen, and progesterone levels. A disorder in any of the endocrine glands may be serious because these glands control or influence almost every process in the body.

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Exocrine disorders are localized. There are several glands of each type in the exocrine system, and most disorders only impact a single gland. Acne, cysts and other minor infections are very common. Blocked or infected ducts cause most exocrine disorders. Doctors treat these with topical medication or by removing the blockage and infected material. Blocked or overactive cerumen glands can impact hearing because the ear canal fills with secretions or dead skin cells. Sometimes infections of exocrine glands are more serious. They can turn into abscesses, although these are not unique to the endocrine system. Abscesses usually require treatment with antibiotics and a procedure to drain the infection.

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The pancreas is a unique gland that engages both the exocrine and endocrine systems. Enzymes that break down lipids, proteins, and other molecules come from exocrine functions. The region of the pancreas known as the Islets of Langerhans produces insulin, glucagon, and somatostanin. These secretions serve endocrine functions. Insulin and glucagon regulate blood sugar; somatostanin influences production of the other secretions.

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