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An organ is a collection of tissues joined in a structural unit to serve a function. The number of organs depends on who in the medical field is asked and how they count it. The general count is 78 organs. Bones and teeth are each counted only once. Counting each bone and tooth separately increases the organ list to 315 organs. Counting every ligament and tendon would further dramatically increase the total number of organs. Not every organ is necessary for survival. The brain, heart, liver, and at least one kidney and lung are absolutely essential for living. Losing the total function of any one of these five vital organs can result in death.
List organ system and their functions
Respiratory system
The system is a network that coordinates together to perform the process of breathing. The respiratory system comprises the following organs:
- Mouth and nose: Openings that pull air from outside the body into the respiratory system.
- Sinuses: Hollow areas between the bones in the head that help regulate the temperature and humidity of the inhaled air.
- Pharynx (throat): Tube that delivers air from the mouth and nose to the trachea.
- Trachea (windpipe): Passage connecting throat and lungs.
- Larynx (voice box): Hollow organ that allows to talk and make sounds when air moves in and out.
- Bronchial tubes: Tubes at the bottom of the windpipe that connect into each lung.
- Lungs: Lungs are paired organs that help in the exchange of gases. They remove oxygen from the inhaled air, pass it into the blood, and exhale carbon dioxide.
Cardiovascular or circulatory system
The following organs are part of the cardiovascular or circulatory system:
- Heart: It is a muscular organ that works to pump blood throughout the body via an intricate network of blood vessels.
- Arteries: The thick-walled blood vessels carry oxygenated blood from the heart.
- Veins: They are blood vessels that carry deoxygenated blood back to the heart.
- Capillaries: These tiny blood vessels facilitate the exchange of oxygen, nutrients, and waste between the circulatory system and organs and tissues.
Musculoskeletal system
The system is mainly involved in locomotion, protection of internal organs, mineral storage, and blood formation. The internal skeleton serves as a framework for the body. It consists of:
- Bones: The bones are calcium-loaded organs that support the organ and muscles.
- Muscles: The three types of specialized contractile tissue, namely cardia, skeletal, and smooth muscles, are responsible for movement and heat production, maintaining posture, and protecting internal organs of the body.
- Tendons and ligaments: They are a band of fibrous connective tissues that connect bone to bone and bones to muscles.
Gastrointestinal system
The system is mainly involved in the breakdown and absorption of food. It comprises the following organs:
- Esophagus (food pipe): A hollow tubular organ that connects the mouth to the stomach. Muscles here propel food into the stomach.
- Stomach: A large organ that holds and digests food using enzymes and acids.
- Liver: It helps filter toxins from the blood and produces bile, which helps break down proteins, carbohydrates, and fats.
- Gallbladder: This sac-like organ stores bile produced by the liver and then releases it when necessary.
- Small intestine: The small intestine receives food from the stomach and begins to break down the food while absorbing most of its nutrients.
- Large intestine: This organ is filled with billions of harmless bacteria that turn food into feces while removing water and electrolytes for the body’s use.
- Rectum: It is located at the end of the large intestine, this small space is a temporary storage area for feces.
- Anus: This is the external opening of the rectum through which feces are expelled.
Urinary system
The urinary system, also known as the renal system, produces, stores, and eliminates urine. Urine is the fluid waste excreted by the kidneys. The following organs are the parts of this system:
- Kidneys: These are located below the ribs and function mainly to remove waste products, balance the body’s fluids, control red blood cell (RBC) production, and release hormones to regulate blood pressure.
- Ureters: Narrow tubes that carry urine from the kidneys to the bladder. The muscles in their walls continually tighten and relax forcing urine downward.
- Bladder: Muscular sac that stores the urine and allows to control urination.
- Urethra: The tube that transports urine from the urinary bladder to the outside of the body.
Endocrine system
The system is made up of glands that secrete chemicals into the blood that act as chemical messengers that control many body functions including growth, metabolism, etc. The organs in this system are:
- Hypothalamus: Produces multiple hormones that control the pituitary gland. It is also involved in regulating the sleep-wake cycles, body temperature, and appetite. It can also regulate the function of other endocrine glands.
- Pituitary: It is located below the hypothalamus. The hormones it produces affect growth and reproduction. They can also control the function of other endocrine glands.
- Pineal: It is found in the middle of the brain. It is important for regulating sleep-wake cycles.
- Thyroid: It is located in the front part of the neck. It controls the metabolism of each cell in the body.
- Parathyroid: Also located in the front of the neck, it is important for maintaining and controlling calcium levels in the bones and blood.
- Thymus: Located in the upper torso, it is active until puberty and produces hormones important for the development of T cells (a type of white blood cell or WBC).
- Adrenal: It is located on top of each kidney. These glands produce hormones important for regulating functions, such as blood pressure, heart rate, and stress response.
- Pancreas: It is located in the abdomen behind the stomach. It helps control blood sugar levels.
Nervous system
It receives information, processes it, and transmits appropriate responses to the organs of the body. The organs of the nervous system are:
- Brain: It controls memory, speech, thoughts, movement, and various organ functions.
- Spinal cord: It carries signals to the brain and is responsible for movement and sensation.
- Eyes, ears, nose, tongue, and skin: They are the five main sense organs that enable sight, hearing, smell, taste, and touch.
Lymphatic system
The system consists of organs and vessels that aid in immune response, collect fluids, and help get rid of toxins of the body. The organs that comprise this system are:
- Bone marrow: The spongy tissue inside the bones of the hip, ribs, and skull and contains stem cells that produce RBC and WBC.
- Spleen: The lymphoid tissue that plays a major role in the production of WBC and filtration of blood to remove microbes and old or damaged RBCs.
- Thymus: This gland is crucial for the production, maturation, and differentiation of T cells.
- Tonsils: Located at the back of the mouth. It enables protection against inhaled and swallowed foreign bodies.
Reproductive system
Female reproductive organs are:
- Ovaries: These are responsible for producing eggs and hormones in females.
- Uterus: Pear shaped organ that receives fertilized egg and supports its development during pregnancy.
Male reproductive organs are:
- Testis: Oval shaped organ that produces sperm cells.
- Epididymis: Long coiled tube that rests on the back of each testicle transports and stores sperm cells produced in the testes.
- Prostrate: It has a walnut-sized structure that secretes fluids to nourish the sperm.
Skin
The skin is the body's largest organ. It covers the entire body. It is a protective shield against heat, light, injury, and infection. Skin also helps regulate the body’s temperature.