Organs and organ systems in the human body

 The five vital organs in the human body are the brain, heart, lungs, kidneys, and liver. Other organs include the gallbladder, pancreas, and stomach. Organ systems, such as the nervous system, support these organs.

Keep reading to learn more about the organs of the body, the various organ systems, and some guidelines on how to maintain optimum health.

Organs of the body and their functions 

Vital organs 

The vital organs are those that a person needs to survive. A problem with any of these organs can quickly become life threatening. The five vital organs are as follows:

• brain
• heart
• lungs
• liver
• kidneys

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.

Brain

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 brain consists 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 areasTrusted Source of the brain 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 parietal lobe: Situated in the middle of the brain, the parietal lobe supports identifying objects and doing spatial reasoning.
• The frontal lobe: The frontal lobe, 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.
• 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 cerebral hemispheres. The corpus callosum connects these two hemispheres.

Heart

The heart is the most important organTrusted Source of the circulatory system, which helps deliver blood to the body. It 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) and then 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 blood flows in the right direction. The heart valves are:

• the tricuspid valve
• the pulmonary valve
• the mitral valve
• the aortic valve

Lungs

The lungs work with the heartTrusted Source to oxygenate blood. They do this by extracting oxygen from inhaled air and exhaling carbon dioxide released from the tissues.

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.

The diaphragm is a thick band of muscle directly under the lungs. It helps the lungs expand and contract when a person breathes.

Liver

The liver is the most important organ of the metabolic system, but it also plays a role in almost everyTrusted Source other organ system. It helps convert nutrients into usable 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.

Most 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
• making cholesterol
• aiding immune function
• clearing bilirubin from the blood
• regulating blood clotting

The liver partners with the gallbladder to deliver bile to the small intestine. The liver pours bile into the gallbladder, which then stores it and later releases it when the body needs it to help with digestion.

Kidneys

The kidneys are a pair of bean-shaped organs, each 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 millionTrusted Source tiny units for filtration, known as nephrons. They help filter waste into the urine and then return the filtered blood to the body through the renal vein.

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

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.

The non-vital organs are the:

• gallbladder
• pancreas
• stomach
• large intestine
• appendix

Injuries to non-vital organs may also affect vital organs, such as when a gallstone undermines liver function.

Gallbladder

The gallbladder is small and pear-shaped. It 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 digestionTrusted Source.

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.

Pancreas

The pancreas is located in the upper left portion of the abdomen. It has two important roles: It functionsTrusted Source 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. 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.

Stomach

The stomach is a J-shaped organ near the top of the abdomen.

The muscles of the stomach help break downTrusted Source and digest food. Within its lumen lining, certain stomach regions also produce enzymes that help digest food. The enzyme pepsin, for example, breaks down proteins so they can become amino acids.

The stomach also helps store chyme until it moves to the intestines. Chyme refers to food that is mixed with stomach secretions.

Anatomists usually divide the stomach into five subparts. These are:

• The cardia: This portion of the stomach is located just beneath the esophagus. It 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: This is where food begins breaking down. It is 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.

Intestines

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 ileumTrusted Source. 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 the colon, and ends with the rectum. The rectum is the last stop for feces before expulsion occurs from the anus.

Organ systems

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 body’s organ systems are the:

• nervous system
• reproductive system
• respiratory system
• urinary system
• lymphatic system
• integumentary system
• musculoskeletal system
• endocrine system
• immune system
• digestive system
• circulatory system

The sections below will outline the body’s organ systems in more detail.

Nervous system

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 nervous system helps the body regulate every functionTrusted Source, including every other organ system.

The nervous system also includes an extensive network of neurons throughout the body — the peripheral nervous system. For example, nerve fibers in the hand tell the brain when there is an injury in that area.

Also, other nerves interact with muscles, which helps coordinate movement.

Reproductive system

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 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 female reproductive system organs include:

• the mammary glands in the breasts
• the ovaries
• the fallopian tubes
• the uterus
• the vagina
• the vulva
• a system of various glands, such as the Bartholin glands, that help lubricate the vagina
• the cervix

Skin

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 layersTrusted Source:

• The epidermis: This is the outer layer of skin.
• The dermis: This is the middle layer of skin.
• The subcutaneous fat layer: This is the deepest layer of the skin.

Muscular system

The muscular system includes a vast network of muscles. There are three types of muscles:

• Skeletal muscles: These are voluntary muscles, meaning 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.

Endocrine system

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.

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

Immune system

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.

Digestive system

The digestive systemTrusted Source is the group of organs that digest food, as well as the various structures within that release substances to aid digestion and absorption.

It includes:

• 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

Circulatory system

The circulatory system includes the many blood vessels circulating 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 fluid balance by collecting excess fluid and other particles from the blood. Lymph nodes are present within this system.

Summary

Each organ in the body is a 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 specialize in a single organ or organ system. For example, cardiologists treat heart issues, while pulmonologists study the lungs.

Anyone suspecting a problem with one of their organs or organ systems should consult a specialist or ask a healthcare professional for a referral.

Source - Medical News Today