Introduction
The cardiovascular system consists of the heart and blood vessels, from the largest veins and arteries down to the smallest capillaries. It also circulates hormones that are released by the endocrine system--a system of glands--throughout the body. Hormones function by producing their effects only when they attach to a suitable target receptor. Even though hormones circulate freely throughout the cardiovascular system, aside from the target receptors, the rest of the body's systems are essentially unaffected by their presence. The following 10 kinds of glands form the endocrine system. All secrete their hormones into the cardiovascular system at large.
Adrenal glands
The two adrenal glands are at the top of the kidneys. Each adrenal gland has an outer region called the cortex and an inner one called the medulla. The medulla secretes adrenaline into the blood stream and the cortex secretes steroid hormones. Adrenaline has the effect of increasing blood pressure and heart rate.
Hypothalamus
The hypothalamus is a part of the brain that secretes hormones that affect the pituitary--another endocrine gland in the brain--by traveling through the cardiovascular system to the pituitary and exerting control of hormonal releases by that gland.
Ovaries
The ovaries are female reproductive glands located near the uterus. They release hormones into the blood that course through the cardiovascular system and cause the development of female features, like breast development, and control the menstrual cycle and pregnancy.
Pancreas
The pancreas is near the stomach and has a sort of division of labor. Part of the pancreas is concerned with digestion and is not endocrine in nature. The other part does have an important endocrine function since it secretes insulin, a hormone that functions through the cardiovascular system to control blood sugar levels.
Parathyroid glands
Parathyroid glands are small and are four in number. They are usually located on the thyroid gland and affect the cardiovascular system by controlling blood calcium levels.
Pineal gland
The pineal gland is in the center part of the brain and is perhaps best known for producing melatonin, a hormone involved in wake and sleep cycles. The brain at large has a feature known as the blood-brain barrier. This barrier functions by restricting certain chemicals and microbes from entering the brain through the cardiovascular system while letting essential substances like oxygen through. Curiously, the pineal gland--though located within the brain--is not subject to this barrier.
Pituitary gland
The pituitary gland is roughly a pea-sized gland near the brain's base and is heavily involved in communicating with, and controlling, other endocrine glands throughout the cardiovascular system. There are anterior and posterior lobes to the pituitary and--as with the pancreas and the adrenal glands--there is a division of labor. Each lobe produces a different set of hormones. Through hormonal targets and receptors released into the cardiovascular system, the hypothalamus regulates hormones produced by one of the pituitary lobes.
Testes
The testes are paired male reproductive glands located in the groin. They produce mainly testosterone, a hormone that circulates in cardiovascular system and controls the development and regulation of male features.
Thymus
The thymus is in the chest and exerts its influence on the body by regulating the immune system. Certain lymphocytes (white blood cells) arrive in the thymus through the cardiovascular system. Here they mature and become T-cells which circulate through the cardiovascular system and impart immunity.
Thyroid gland
The thyroid gland secretes hormones into the cardiovascular system that have a wide range of functions, including influence over metabolism, bone growth, nervous system development, reproductive processes, digestion and the cardiovascular system itself by influencing heart rate and blood pressure.
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