The human body contains intricate internal organ systems that have their own functions and perform particular tasks. However, each system depends upon the others, either directly or indirectly, in order for the body to function normally. The organs communicate with each other and adjust their performance, depending on what the body requires. There are eight separate internal organ systems found in the body which include:
The circulatory system acts like a highway and transports materials, such as water, nutrients, and oxygen, throughout the body to the cells. It also removes wastes produced by the body, including carbon dioxide that the body cells produce. Each organ within this system performs a circulatory task, and the three main organs in this system include the heart, blood vessels, and blood.
- Heart – Located in the center of the body’s chest just a little to the left, the heart pumps blood and keeps it moving throughout the body. As a muscle the size of a fist, the heart beats around 3 billion times during an average lifetime.
- Blood Vessels – The purpose of blood vessels is to carry nutrients and oxygen to the body’s tissues as well as to circulate the blood back to the heart. There are three types of blood vessels: arteries, which carry oxygen-rich blood away from the heart; veins, which carry blood back toward the heart; and capillaries, which connect the arteries to veins.
- Blood – As a necessary part of the body, blood constantly flows throughout it and carries nutrients, water, oxygen, and waste products to and from the body’s cells. Comprised of liquids, solids, and small amounts of carbon dioxide and oxygen, blood can travel thousands of miles along blood vessels.
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An essential part of the body, the digestive system runs from the mouth to the rectum. Food travels along this route, also referred to as the gastrointestinal tract (GI tract). During these travels, food becomes absorbed and broken down into nutrients that sustain the body’s cells. Other accessory organs located within the digestive system include:
- Gall Bladder
- Salivary Glands
The goal of this system is to convert food into energy and basic nutrients to feed the entire body, and it does this through six major functions. These specific functions include ingestion, secretion, mixing and movement, digestion, absorption, and excretion.
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The endocrine system is in charge of sending messages to the glands to notify them when to produce certain hormones. Affecting almost every organ and cell within the body, the endocrine system contains glands that select and remove materials from the blood. This system assists with the body’s metabolism, tissue function, growth and development, reproduction, sleep, and sexual function, among others. The organs found within this system include the pancreas, adrenal glands, ovaries in females and testicles in males, thyroid gland, pituitary gland, and parathyroid gland. The master gland in this system is the pituitary, which rests in the brain. It is in charge of all growth hormones and stimulates them as well as controls skin pigmentation.
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The excretory system removes liquid poisons within the body and turns them into urine or sweat. During circulation, blood passes through the kidneys where it deposits used minerals, water, and nitrogen-rich molecules called urea. As the most important organ in this system, the kidneys act as a filtering machine, remove wastes from the blood, and form a liquid called urine. The kidneys funnel urine to the bladder through ureters, where it sits until the body removes it as waste through the urethra tubes. Each day, the body produces on average about 1.5 liters of urine. Among the component organs found in this system, include:
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In charge of guarding the immune system against viruses, bacteria, and infections, the lymphatic system contains a group of organs, ducts, and nodes. It also transports a watery clear fluid called lymph, which is similar to blood plasma but contains lymphocytes and other white blood cells. This fluid distributes immune cells and interacts with the circulatory system to drain fluid from cells and tissues. As a subset of the circulatory system, the lymphatic system also removes interstitial fluid as well as transports white blood cells to and from the lymph nodes and antigen-presenting cells to the lymph nodes. Located in the neck, armpits, groin, and behind the ears, these lymph nodes filter lymph and attack potential infections. In addition to the lymph nodes, other organs found in this system include the spleen, tonsils, adenoids, thymus, and lymphoid tissue.
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Comprised of nerves, the brain, and specialized cells known as neurons, the nervous system transmits signals between different parts of the body. The brain controls all of the body’s functions, and it makes these movements possible by contacting the neurons. These neurons send signals to other cells within the body through thin fibers called axons, which release chemicals known as neurotransmitters. These neurons send back information about the body’s environment to either the central nervous system or the peripheral nervous system. The central nervous system contains the brain, spinal cord, and nerves, while the peripheral nervous system houses sensory neurons, clusters of neurons called ganglia, and nerves that all connect to each other and to the central nervous system.
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Unlike most internal organs, the reproductive system varies depending on the body’s gender. However, although the male and female systems remain different in structure and function, they both work together to produce offspring.
- The female reproductive system includes breasts, mammary glands, vulva, vagina, ovaries, fallopian tubes, and the uterus. The ovaries produce eggs and the body’s hormones, and about once a month, the ovaries release these eggs into the fallopian tubes. If the egg remains unfertilized, the body undergoes a menstrual cycle in which the egg as well as the blood and tissue lining the uterus leave the body.
- The male reproductive system consists of the spermatic ducts, testes, scrotum, sex glands, and penis. These organs work together to deliver semen out of the body into the woman’s vagina. That is where the sperm found within the semen seek out the woman’s egg for fertilization.
Interested in learning more about the reproductive system? Check out these resources below:
- The Reproductive System
- Diseases of the Female Reproductive System
- Diseases of the Male Reproductive System
The respiratory system controls the body’s breathing. The key parts of the respiratory system include the lungs, trachea, bronchi, mouth, nasal cavity, and the diaphragm. The lungs maintain the most responsibility as they bring in air and add fresh oxygen to the blood via red blood cells. The red blood cells also return carbon dioxide, which is a waste gas product produced by cells, back to the lungs for the body to breathe out. As the main muscle used in breathing, the diaphragm pulls the air in and reduces the air out of the lungs.
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