ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

The Organ Systems of the Human Body

Updated on December 31, 2012

What Are Organ Systems?

An organ system is a level of organisation found in our body. There are four levels of organisation within the body:

  • A cell is a group of organelles working together to perform a particular function;
  • A tissue is a group of cells working together;
  • An organ is a group of tissues working together;
  • An organ system is a group of organs working together to perform a particular task.

Most of my science pupils know the names of several organs by the time they arrive in high school at 11 years old. My first job when teaching human biology is to teach my pupils how these organs work together and why they work together.

So why do we need our organ systems to work together? The usual response from the kids is "to keep us alive!" Whilst correct, this is a very simplistic view that needs improvement. All living things perform the same 7 life processes:

  • Movement
  • Reproduction
  • Sensing
  • Growth
  • Respiration
  • Excretion
  • Nutrition

Our organ systems divide up the different life processes between them. Each organ system relies on all the others to carry out the tasks it cannot do by itself.

Organ Systems and the Life Processes

Organ System
Life Process
Musculoskeletal System
Reproductive System
Nervous System, Integumentary System
Endocrine System
Respiratory System, Cardiovascular System
Urinary System
Digestive System
You are a living organism, and therefore must exhibit all the features of a living thing (MRS GREN). Your organ systems help you accomplish this! The only system not to contribute is the immune system, which defends us from foreign invaders

The Circulatory System

Organs of the Circulatory system:

  • Heart (CV)
  • Blood Vessels (CV)
  • Lymph Glands (L)
  • Thymus (L)
  • Spleen (L)

The circulatory system is made up of the cardiovascular system (CV) and the Lymphatic system (L). This system is responsible for transporting nutrients and gases to the cells and tissues of the body, and removing waste products.

Fast Fact: The tissue that makes up your heart is myogenic - it will beat on its own!

Pigs lungs
Pigs lungs | Source

The Respiratory System

Organs of the Respiratory System:

  • Trachea
  • Lungs
  • Diaphragm
  • Intercostal muscles

The respiratory system provides oxygen for all your cells, and removes carbon dioxide from the body. The lungs are adapted to provide as large a surface area as possible to maximise diffusion. The small sacs in the lungs (alveoli) are only a cell thick to allow oxygen to diffuse into the blood and carbon dioxide to diffuse out.

Fast Fact: The lungs provide a surface area of over 70m2 in an adult - this is the size of a tennis court!


The Gastrointestinal System

Organs of the GI System:

  • Mouth
  • Oesophagus
  • Stomach
  • Small and Large Intestine
  • Rectum
  • Pancreas
  • Liver

The gastrointestinal system is responsible for digestion of our food. Digestion is the process of breaking down food into nutrients that can be readily absorbed and used by the body. Most of the nutrients are absorbed in the small intestine, whereas the large intestine reabsorbs as much water as possible. The liver and pancreas aid digestion by producing bile (to digest fat) and enzymes, respectively.

Fast Fact: The small intestine can be up to 20ft (6m) in length!


The Musculoskeletal System

Organs of the musculoskeletal system:

  • Muscles
  • Bones in skeleton.

The musculoskeletal system is a combination of the muscles and skeleton. The skeleton not only provides a rigid structure for the muscles to pull on, but provides protection to vulnerable internal organs such as the brain, lungs and heart. Muscles come in two varieties: skeletal and smooth. Skeletal muscle is under our conscious control and are attached to bones by rings of tissue called ligaments. Smooth muscle forms the walls of organs such as the stomach; this muscle cannot be controlled and is called involuntary.

Fast Fact: There are 206 bones in an adult body, but babies have more than 300 bones or cartilage elements!

Organ Systems in Our Body - Detailed Video


The Urinary/Excretory System

Organs of the Excretory System:

  • Kidneys
  • Bladder
  • Ureter
  • Vena Cava and Aorta
  • Urethra

The kidneys are the major organs of the excretory system; they filter the blood removing urea, excess salt and water. These waste products are stored in the bladder until they can be excreted from the body. The two major blood vessels of the body, the aorta and vena cava supply the kidneys with blood.

Fast Fact: Healthy urine is sterile - it contains fluids and salts, but no bacteria or it is safe to drink?

Organs of the Reproductive Systems

Male Reproductive System
Female Reproductive System
Fallopian tubes
Vas deferens
Seminal vesicle

The Reproductive Systems

The human reproductive system is the only organ system that differs between the sexes. It allows couples to produce fertile offspring to continue the species. Women are born with their full complement of immature eggs (between 400,000 and 2 million), inside their ovaries*. Men constantly produce sperm from puberty at the rate of around 1,500 sperm per second.

Fast Fact: While a woman may be born with 2 million eggs, only around 500 eggs will develop over the course of her fertile life.

The Endocrine System

Organs of the Endocrine System:

  • Pineal Gland
  • Pituitary gland
  • Thyroid gland
  • Thymus
  • Pancreas
  • Adrenal glands
  • Testis/Ovaries

The human endocrine system is a collection of glands that secrete hormones - the chemical messengers of the human body. These molecules cause chemical changes in cells with the appropriate receptors. For example, growth hormones secreted by the pituitary gland signal certain cells to divide for growth. The adrenal glands release adrenaline (epinephrine) under stress to trigger the fight-or-flight response. The endocrine system works together with the nervous system to send messages around the body.

Fast Fact: There are around 50 different hormones in the human body.

Two monocytes (stained with Giemsa in blue)
Two monocytes (stained with Giemsa in blue) | Source

The Immune System

Organs of the Immune System:

  • Tonsils and adenoids
  • Lymph nodes
  • Thymus
  • Bone Marrow
  • White blood cells (not an organ)

The immune system defneds the body against attacks from foreign bodies (bacteria and viruses). The lymph glands and bone marrow work together to create and store the various types of white blood cell required to properly defend the body.

Fast Fact: It is thought that new cancer therapies can be developed by modifying and targetting the body's own immune system - this could lead to cancer treatments with no side-effects.

The Nervous System

Organs of the Nervous System:

  • Brain
  • Spinal cord

The nervous system is high-speed broadband compared to the postal service that is the endocrine system. It transmits electrical messages at high speed from throughout the body. There are four different types of nerves:

  1. Cranial nerves run from the brain to the sense organs of the head.
  2. Central nerves are found in the brain and spinal cord.
  3. Autonomic Nerves run from the spinal cord to the lungs, heart, digestive, bladder and sex organs. These send messages that are not under conscious control.
  4. Peripheral nerves connect the spinal cord to the limbs - these messages are under conscious control and are used for things such as movement.

Fast Fact: The brain contains over 100 billion neurons!


The Integumentary System

The integumentary system includes:

  • Skin
  • Blood vessels
  • Sweat and oil glands
  • Nerves
  • Hair
  • Fingernails

The skin is the largest organ of the body - it makes up 16% of your body weight - and one of our most important sense organs. It also regulates body temperature, provides a physical barrier to pathogens, protects internal organs and helps to retain moisture.

Fast Fact: The outer layer of the skin is made of dead cells - we shed around 30,000-40,000 an hour (out of 1.6 trillion skin cells). This forms most of the dust in your house. Over a year you shed around 3.6kg (8lbs) of dead skin.


    0 of 8192 characters used
    Post Comment
    • Marcy Goodfleisch profile image

      Marcy Goodfleisch 

      6 years ago from Planet Earth

      Excellent and detailed information! I wish resources like this had been available when I studied this type of thing in high school and college. I like the way you've given us visual as well as academic details here. Voted up and up!


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)