The adrenal glands are an integral part of the endocrine system, which means that they make hormones that are secreted into the bloodstream. Adrenal glands have a profound affect on tissues throughout the body. Adrenal gland activity is controlled both directly and indirectly by the central nervous system.
Anatomy
The adrenal glands are located on both kidneys, Pathology Outlines explains. Each gland is approximately 15 cubic cm in size and weighs between 4 and 6g. Blood is supplied to the adrenal glands by the inferior phrenic, aortic and renal arteries. Each adrenal gland is divided into two distinct zones: the cortex, which is located on the outside of the gland, and the medulla, which is the center of the gland. These two zones secrete two distinct classes of hormones.
Adrenal Cortex
The adrenal cortex makes three main types of hormones: corticosteroids, aldosterone and androgens. Corticosteroids, states the University of Maryland Medical Center, control how the body uses fats, carbohydrates and proteins. These hormones also regulate the body's immune system and block inflammation.
Aldosterone controls the amount of sodium in the blood, which also helps regulate blood volume and blood pressure. Androgens are hormones, such as testosterone, which promote the development of male features and characteristics. Normally, the adrenal cortex produces such a low amount of androgens that they have very little effect on the development of male features. Some disorders, however, can cause the hypersecretion of androgens by the adrenal cortex, leading to virilization in women or premature puberty in males. The hormones of the adrenal cortex are essential for life.
Medulla
The hormones the adrenal medulla produce are not essential for a person to stay alive, but they do play a critical role in how the body responds to stress, both emotional and physical. The adrenal medulla produces two different hormones, epinephrine and norepinephrine.
Epinephrine works to increase heart rate and the force with which the heart beats. It also causes the liver to make more glucose and causes smooth muscles to relax. Norepinephrine cause blood vessels throughout the body to narrow, causing an increase in blood pressure. Both hormones are responsible for generating the body's "fight or flight" response.
Control
Adrenocorticotropin hormone, or ACTH, controls the production of hormones by the cortex. The pituitary gland produces this hormone, according to Colorado State's Physiology Hypertexts. ACTH production is itself controlled by another hormone known as corticotropin-releasing hormone, or CRH. This hormone is made by the hypothalamus. This network allows the central nervous system to have control over the production of hormones from the adrenal cortex. The synthesis of hormones by the adrenal medulla is directly controlled by nerve signaling.
Disorders
Adrenal gland disorders can cause problems if they cause changes in hormone levels in the body. Addison's disease is a condition in which the adrenal cortex does not produce enough hormones, the Merck Manual explains. Conversely, Cushing's syndrome is marked by an increase in adrenal cortex hormones, which may be caused by over production of ACTH or because of a hormone-secreting tumor. Pheochromocytomas are rare tumors of the adrenal medulla that continuously secrete epinephrine and norepinephrine.
