Organ System Examples & Functions | What is an Organ System?

Amanda Robb, Stephen Christensen
  • Author
    Amanda Robb

    Amanda has taught high school science for over 10 years. They have a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. They also are certified in secondary special education, biology, and physics in Massachusetts.

  • Instructor
    Stephen Christensen
What is an organ system? Learn about the organ system definition and see organ system examples. Learn about the 11 body systems and organ system functions. Updated: 04/14/2021

Table of Contents


Organ System Definition

What is an organ system? Organ systems are collections of anatomical structures in the body that work together to achieve a function. Organ systems include multiple organs, but organs may be involved in more than one organ system. Each organ system depends on the others, but scientists find it helpful to divide the body into organ systems for study.

Organ systems and their functions are important for multicellular organisms to maintain homeostasis, or a balance in the body. These specialized systems allow for complex functions to be carried out to maintain life, such as gas exchange, nutrient absorption and distribution and more. There are 11 organ systems in the human body. Some organ system examples include the respiratory system, the digestive system and the cardiovascular system.

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  • 0:02 Organ Systems
  • 1:54 Integumentary,…
  • 3:14 Nervous, Circulatory &…
  • 4:47 Respiratory, Endocrine…
  • 6:44 Reproductive &…
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Human Organ Systems

How many organ systems are there? Human organ systems include the following:

  1. Integumentary system
  2. Muscular system
  3. Skeletal system
  4. Circulatory system
  5. Respiratory system
  6. Nervous system
  7. Urinary/Excretory system
  8. Digestive system
  9. Reproductive system
  10. Lymphatic system
  11. Endocrine

The different types of organ systems are explained in detail below.

Integumentary System

The integumentary system is the organ system made up of our skin, nails and hair. The main function of the integumentary system is to protect the body. Our skin is the largest organ in the body and the dead, keratinized layer on the outside helps to shield the body from environmental changes and pathogens. The inner layers of the skin help regulate temperature homeostasis. Specialized sensory neurons help the body detect changes in the environment, such as temperature, pressure and pain.

Muscular System

The muscular system is the organ system that includes all of our muscles and its main function is to facilitate movement. There are three main types of muscle: cardiac, skeletal and smooth. Cardiac muscle makes up the heart. Skeletal muscle is attached to the skeleton and is responsible for voluntary movement. Lastly, smooth muscle makes up hollow organs, such as the stomach, intestines and uterus and is involuntary.

Skeletal System

The skeletal system is the organ system that includes the bones, joints and cartilage. This body system's main function is for structure, support and movement. For example, the skull encases the brain and provides protection from the environment. Other skeletal components act like anchors for the muscular system and allow for movement. Cartilage is more flexible than bone and both acts as a flexible barrier and provides cushioning between bones, such as between the vertebrae of the spine.

Circulatory System

The circulatory system, also known as the cardiovascular system, includes the heart, blood vessels and blood. The main function of the circulatory system is to bring oxygen and nutrients to all of the cells in the body and remove metabolic waste. The heart is the main organ of the circulatory system and uses its muscular action to pump blood through the blood vessels to the body. Blood is pumped to the body through the arteries and returns to the heart through the veins.

The circulatory system includes the heart, blood and blood vessels
human body organ systems

Respiratory System

The respiratory system includes the lungs and accessory organs. The main function of the respiratory system is to carry out gas exchange. Air enters the lungs through the nose and mouth and travels through the trachea to the bronchi. Each bronchi branches into smaller bronchioles and eventually dead-ends in the alveoli, where gas exchange occurs. Here, carbon dioxide diffuses into the lungs for exhalation and oxygen diffuses from the lungs into the blood.

Nervous System

The nervous system is the body system that includes the brain, spinal cord, and nerves. The main function of the nervous system is communication. The brain acts as the processing center for all information and communicates with the body by sending messages through the spinal cord. Nerves in the body control our motor function and sense changes in both the external and internal environment and communicate this information to the brain. Neurons are the main cell of the nervous system and are specialized for sending and receiving information.

Neurons are the main cell type in the nervous system
organ system examples

Urinary/Excretory System

The urinary/excretory system is the body system that removes metabolic waste from the body and regulates water homeostasis. It includes the kidneys, which filter metabolic waste from the blood to produce urine. Urine is stored in the bladder and carried out of the body through the urethra. The urinary system plays an important role in maintaining blood pressure. When our blood pressure is too high, extra water can be released as urine to regulate our water and salt balance. If water levels in the body are low, less urine is produced.

Digestive System

The digestive system is the body system responsible for breaking down food and absorbing nutrients. The digestive system is also known as the gastrointestinal system and includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, anus and accessory organs, like the pancreas, gall bladder and liver. Together, these organs work to break down food and absorb macromolecules into the blood.

Reproductive System

The reproductive system is the body system responsible for creating offspring, or reproduction. The male reproductive system includes the testes and penis and the main function is to produce sperm for reproduction. The female reproductive system includes the ovaries, uterus, vagina and vulva and its main purpose is to incubate a fetus during gestation and birth of the child.

Lymphatic System

The lymphatic system, also known as the immune system, protects the body from pathogens and maintains homeostasis of fluids inside the body. The lymphatic system includes the lymph fluid, lymphatic vessels, lymph nodes and leukocytes, or white blood cells. Fluid expelled from the circulatory system accumulates in the tissues and is returned to the heart via the lymphatic vessels. The lymph system also produces mature white blood cells, which are needed to identify and fight off pathogens.

Endocrine System

The endocrine system is the organ system that produces hormones, chemical messengers that regulate body functions and maintain homeostasis between organ systems. The endocrine system consists of endocrine glands and the hormones they produce. Examples of endocrine organs include the pituitary gland, adrenal glands, testes and ovaries. These organs produce hormones. Examples of hormones include:

  • Estrogen
  • Testosterone
  • Insulin
  • Antidiuretic hormone
  • Oxytocin

Body Systems and Functions

Body systems and functions are interdependent, meaning that all organ systems depend on each other. Organ systems and functions require coordinated communication. Without such, homeostasis in the body can be disrupted.

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