In the human body, there are five vital organs that people need to stay alive. These are also a number of other organs that work together with these vital organs to ensure that the body is functioning well.
Keep reading to learn more about the organs of the body, the various organ systems, and some guidelines on how to maintain optimum health.
The interactive body map below shows the organs of the body and which systems they play a role in. Click on the map to learn more.
The vital organs are those that a person needs to survive. A problem with any of these organs can quickly become life threatening.
It is not possible to live without these organs. That said, in the case of the paired kidneys and lungs, a person can live without one of the pair.
The sections below will look at the five vital organs in more detail.
The brain is the body’s control center. It forms the core of the central nervous system by creating, sending, and processing nerve impulses, thoughts, emotions, physical sensations, and more.
The skull encloses the brain, protecting it from injury.
Neurologists are doctors who study the nervous system. Over time, they have identified numerous parts of the brain, including systems within the brain that function similarly to independent organs.
The brain is made up of three main subparts: the cerebrum, the cerebellum, and the brainstem. Within these areas, there are several key components of the brain that, together with the spinal cord, comprise the central nervous system.
The major areas of the central nervous system include:
- The medulla: This is the lowest part of the brainstem. It helps control heart and lung function.
- The pons: Located above the medulla in the brainstem, this area helps control eye and facial movement.
- The spinal cord: Extended from the base of the brain and down the center of the back, the spinal cord helps with many automatic functions, such as reflexes. It also sends messages to and from the brain.
- The parietal lobe: Situated in the middle of the brain, the parietal lobe supports the identification of objects and spatial reasoning. It also plays a role in interpreting pain and touch signals.
- The frontal lobe: The frontal lobe, which is located in the front of the head, is the largest section of the brain. It plays a role in many conscious functions, including personality and movement. It also helps the brain interpret smells.
- The occipital lobes: Positioned near the back of the brain, the occipital lobe primarily interprets vision signals.
- The temporal lobes: Located on either side of the brain, the temporal lobes play a role in numerous functions, including speech, scent recognition, and short-term memory.
The brain’s two halves are called the right and left hemispheres. The corpus callosum connects these two hemispheres.
The heart also has an electrical system within. Electrical impulses within the heart help ensure that it beats with a consistent rhythm and proper rate.
The heart rate increases when the body needs more blood, such as during intense exercise. It decreases during times of rest.
The heart has four chambers. The two upper chambers are called atria, and the two lower chambers are called ventricles.
Blood flows into the right atrium from the veins of the heart and body (except the lungs), then it flows into the right ventricle. From there, it flows into the pulmonary artery, which has branches that reach the lungs. The lungs then oxygenate the blood.
This oxygenated blood travels from the lungs, through pulmonary veins that lead back and join together, to the left atrium, and then through the left ventricle. From there, the heart pumps the blood through an artery that branches to distribute blood to itself and other body parts (except the lungs).
The heart has four valves that ensure that blood flows in the right direction. The heart valves are:
- the tricuspid valve
- the pulmonary valve
- the mitral valve
- the aortic valve
The lungs work with the heart to oxygenate blood. They do this by filtering the air a person breathes, then removing excess carbon dioxide in exchange for oxygen.
Several parts of the lungs help the body take in air, filter it, and then oxygenate the blood. These are:
- The left and right bronchi: The trachea splits into these tubes, which extend into the lungs and have branches. These smaller bronchi split into even smaller tubes called bronchioles.
- The alveoli: The alveoli are tiny air sacs at the end of the bronchioles. They work like balloons, expanding when a person inhales and contracting when they exhale.
- The blood vessels: There are numerous blood vessels in the lungs for carrying blood to and from the heart.
With extensive medical care, a person can live without one lung, but they cannot survive with no lungs.
The diaphragm, which is a thick band of muscle directly under the lungs, helps the lungs expand and contract when a person breathes.
The liver is the most important organ of the metabolic system. It helps convert nutrients into usable substances, detoxifies certain substances, and filters blood coming from the digestive tract through a vein before it joins venous blood flow from other parts of the body. Oxygenated blood reaches the liver via an artery.
The majority of liver mass is in the upper right side of the abdomen, just under the rib cage.
The liver plays many roles in digestion and filtering the blood, including:
- producing bile
- helping the body filter out toxic substances, including alcohol, drugs, and harmful metabolites
- regulating blood levels of various important chemicals, including amino acids
- making cholesterol
- removing some bacteria from the blood
- making some immune factors
- clearing bilirubin from the blood
- regulating the process of blood clotting, so that a person does not bleed too much and does not develop dangerous blood clots
The liver partners with the gallbladder to deliver bile to the small intestine. The liver pours bile into the gallbladder, which then stores and later releases the bile when the body needs it to help with digestion.
A person can live without portions of their liver, but the liver itself is vital for life.
The kidneys are a pair of bean shaped organs, and each is about the size of a fist. They are located on either side of the back, protected inside of the lower part of the rib cage. They help filter blood and remove waste from the body.
Blood flows from the renal artery into the kidneys. Each kidney contains about a million tiny units for filtration known as nephrons. They help filter waste to the urine and then return the filtered blood to the body through the renal vein.
The kidneys also produce urine when they remove waste from the blood. Urine flows out of the kidneys through the ureters, then down to the urinary bladder.
A person can live with just one kidney. When a person is experiencing severe kidney failure, dialysis can filter the blood until they get a kidney transplant or their kidney recovers some function. Some people need to undergo hemodialysis long term.
Non-vital organs are those that a person can survive without. However, this does not mean that conditions affecting these organs are never life threatening or dangerous. Many infections and cancers in non-vital organs are life threatening, especially without prompt treatment.
Injuries to non-vital organs may also affect vital organs, such as when a gallstone undermines liver function.
The sections below will outline the body’s non-vital organs in more detail.
Small and pear shaped, the gallbladder sits in the right upper quadrant of the abdomen, just under the liver. It contains cholesterol, bile salts, bile, and bilirubin.
In a healthy person, the liver releases bile into the gallbladder, which the gallbladder stores and then releases to travel down the common bile duct into the small intestine to aid digestion.
However, some people develop gallstones that block the gallbladder or biliary tree, causing intense pain and interfering with digestion. Also, this can sometimes interfere with liver or pancreas function.
Located in the upper left portion of the abdomen, the pancreas has two important roles: It functions as both an exocrine gland and an endocrine gland.
As an exocrine gland, the pancreas produces enzymes a person needs to help digest their food and convert it into energy. Those enzymes include amylase, lipase, trypsin, and chymotrypsin.
In its role as an endocrine gland, the pancreas also produces and releases insulin, which helps the body remove glucose from the blood and convert it into energy.
Problems with insulin can lead to a dangerously high level of blood glucose and the onset of diabetes.
The pancreas also produces and releases glucagon, which raises blood glucose levels.
The main pancreatic duct connects to the common bile duct, which flows from the liver and gallbladder. Therefore, problems within the biliary tree, liver, or gallbladder may also affect the pancreas.
The stomach is a J shaped organ near the top of the abdomen.
Food begins its journey to the stomach soon after a person swallows. The food moves down from the throat and into the esophagus. The stomach is located at the end of the esophagus.
The muscles of the stomach help it break down and digest food. Within its lumen lining, certain regions of the stomach also produce enzymes that help digest food. The enzyme pepsin, for example, breaks down proteins so that they can become amino acids.
The stomach also helps store chyme until it moves to the intestines. Chyme refers to food that has mixed with stomach secretions.
Anatomists usually divide the stomach into five subparts. These are:
- The cardia: Located just beneath the esophagus, this portion of the stomach includes the cardiac sphincter. The sphincter prevents food from flowing back up the esophagus or into the mouth.
- The fundus: This is situated to the left of the cardia and underneath the diaphragm.
- The body: Food begins breaking down in the body, which is also the largest part of the stomach.
- The antrum: This is the lower part of the stomach. It contains partially digested food before it flows to the small intestine.
- The pylorus: This portion of the stomach connects to the small intestine. It includes a muscle called the pyloric sphincter, which controls when and how much stomach content flows into the small intestine.
The intestines are a group of tubes that help filter out waste, absorb water and certain electrolytes, and digest food.
Partially digested food first travels through the small intestine, which comprises three parts: the duodenum, the jejunum, and the ileum. Most digestion and absorption of food happens here.
Food then becomes feces as it travels within and through the large intestine. This begins with the cecum, extends to the rest of colon, and ends with the rectum. The rectum is the last stop for feces before expulsion occurs from the anus.
Doctors usually list dozens of organs, though the definition of an organ varies from expert to expert. Most organs play a role in organ systems, which work together to perform specific functions.
The sections below will outline the body’s organ systems in more detail.
The brain and spinal cord form the central nervous system, which works to process and send nerve signals, interpret information, and produce conscious thought.
The portion of nervous system that communicates with the central nervous system is called the peripheral nervous system. Overall, the peripheral and central nervous systems also include an extensive network of neurons. Located throughout the body, these fibrous bundles send information about sensation, temperature, and pain.
The nervous system helps the body regulate every function, including every other organ system.
For instance, the stomach releases the hormone ghrelin, which signals to the brain that it is time to eat. This causes feelings of hunger and encourages a person to eat, which leads to the beginning of the process of digestion.
The nervous system integrates with virtually every other part of the body. For example, nerve fibers in the hand tell the brain when there is an injury in that area.
Meanwhile, nerves in the skin relay information about external temperature. This may cause the brain to initiate involuntary responses that control body temperature, such as sweating or shivering.
Also, other nerves interact with muscle, which helps coordinate movement.
The reproductive system includes the organs that enable a person to reproduce and experience sexual pleasure. In females, the reproductive system also supports the growth of a fetus.
The reproductive system works closely with other organs and organ systems. For example, the hypothalamus and pituitary gland help regulate the production and release of hormones such as estrogen and testosterone.
The male reproductive system organs include:
- the testes
- the epididymis
- the vas deferens
- the ejaculatory ducts
- the prostate gland
- the seminal vesicles
- the penis
- the bulbourethral glands
- the mammary glands in the breasts
- the ovaries
- the fallopian tubes
- the uterus
- the vagina
- the vulva
- the clitoris
- a system of various glands, such as the Bartholin glands, which help lubricate the vagina
- the cervix
The skin is the body’s largest organ. It is part of the integumentary system, which includes skin, hair, nails, and fat.
The integumentary system helps regulate body temperature, protect the body from dangerous pathogens, make vitamin D from sunlight, and provide sensory input.
The skin comprises three layers:
- The epidermis: This is the outer layer of skin. It contains three types of cells. Squamous cells are the outer layer of skin, which the body constantly sheds. Basal cells are the next layer, located under the squamous cells. Melanocytes produce melanin, which is skin pigment. The more melanin the melanocytes produce, the darker a person’s skin is.
- The dermis: This is the middle layer of skin, located under the epidermis. It contains blood vessels, lymph vessels, hair follicles, sweat glands, nerves, sebaceous glands, and fibroblasts. A flexible protein called collagen holds the dermis together.
- The subcutaneous fat layer: This is the deepest layer of the skin. It helps keep the body warm and reduces the risk of injury by absorbing heavy blows.
The muscular system includes a vast network of muscles. There are three types of muscles:
- Skeletal muscles: These are voluntary muscles, which means that a person can decide when to move them. The biceps and triceps are examples of skeletal muscles.
- Cardiac muscles: These are involuntary muscles that help the heart pump blood.
- Smooth muscles: These are also involuntary muscles. Smooth muscles line the bladder, intestines, and stomach.
The endocrine system is a network of glands throughout the body. These glands release important chemicals called hormones, which help regulate the function of virtually every organ and organ system in the body.
For example, progesterone helps regulate the menstrual cycle and plays an important role in sustaining a pregnancy.
The endocrine system includes several major glands, including:
- the pancreas
- the thyroid
- the adrenal glands
- the pituitary
- the parathyroid
- the thyroid
- the hypothalamus
- the pineal gland
- the ovaries
- the testes
The immune system helps the body prevent infections and fights them off when they do occur.
Many organs play a role in the immune system. For example, the skin prevents dangerous pathogens from entering the body, and the salivary glands release saliva that can help break down some dangerous sources of infection in food.
The lymphatic system plays a key role in the immune system by releasing lymphocytes that fight disease. There are many lymph nodes throughout the body. Some people notice that their lymph nodes enlarge when they get sick.
The digestive system is the group of organs that digest food, as well as the various structures within that release substances to aid digestion and absorption.
- the mouth
- the esophagus
- the salivary glands
- the gallbladder
- the liver
- the pancreas
- the stomach
- the small and large intestines
- the appendix
- the rectum
- the anus
The circulatory system includes the many blood vessels that circulate blood throughout the body. It includes veins, arteries, capillaries, venules, and arterioles.
The lymphatic system is also part of the circulatory system. It helps maintain the body’s balance of fluid by collecting excess fluid and other particles from the blood. Lymph nodes are present within this system.
Each organ in the body is its own complex system, made up of numerous smaller parts. Many organs also depend on several other body parts. For example, to properly breathe, the lungs must work with the nose, mouth, throat, windpipe, and sinuses.
This complexity of each organ and organ system means that some doctors choose to specialize in a single organ or organ system. For example, cardiologists treat heart issues, while pulmonologists study the lungs.
Anyone who thinks that they have a problem with one of their organs or organ systems should see a specialist or ask a healthcare provider for a referral.