What is an organ?
Humans are multicellular organisms. This means that we are made up of billions and billions of tiny cells (like all other plants and animals on Earth). Each cell has a job, and they combine to create organs, muscles, and body parts.
- Cells are the basic unit of all life.
- When a group of cells works together to carry out a particular function, it is called tissue. For example, muscle tissue or brain tissue.
- An organ is the name of a group of different tissues working together to perform a job inside the body.
- Organs are grouped into organ systems – for example, the digestive system.
From largest to smallest, we can move down the hierarchy of the human body: The digestive system is made up of organs (like the intestine and liver), and those organs are made up of different tissues, and those tissues are made up of different cells.
How many organs are in the human body?
You would think that scientists agree on how many organs are in the human body, but some disagree over what counts as an organ. For example, do you count each tooth individually or as a set? Also, there are over 200 bones in the human body, is each counted once or as the whole system once?
Science is a continued discussion, so this question poses a great prompt to ask children what they think!
Though, the majority of scientists are in agreement that there are 78 human body organs.
Which human body organs do children learn about?
Through primary school learning, children will focus on the principal organs of the human body. These are the organs that carry out the body’s primary functions that we talk about in day-to-day life – from eating and digesting our food to moving around and thinking, feeling, and breathing.
A list of the main organs in the human body:
Kidneys
The kidney is a small organ; well, it is a pair. They are small; bean-shaped organs tucked into our abdomen’s sides.
The kidney is one of the most vital organs in our bodies; it is thought to be as important as the heart. The human body needs at least one kidney to survive. They are about 13 cm long and sit on each side of the lower back. One of the jobs of the kidneys is to filter out the waste in our blood. This waste is usually nutrients that our body already has enough of. This waste then travels to the bladder to be removed.
Skin
The skin is the largest human body organ and even rebuilds itself. The skin is constantly removing old cells and replacing them with brand-new cells. Every minute of the day, we lose about 30,000 to 40,000 dead skin cells from the surface of our skin.
The skin is the organ that allows us to have a sense of touch and helps to keep our body at just the right temperature. It is rugged, waterproof, and covers everything inside the body.
Heart
The heart is one of the essential organs in our bodies. It is the pump that allows blood to flow around your body. It is located in the center of the chest and is about the size of your fist. Not only that, but it pumps blood around each of the veins and arteries of your body to ensure that each muscle and organ is provided with oxygen and nutrients.
Liver
Our liver is located in the upper right of our abdomens and has around 500 functions! A few parts are that it stores energy in glycogen, cleans the blood in your body, and produces the fluid used to digest food.
Lungs
The lungs make use of the ample space behind our breastplate and ribcage. They expand and contract as they fill with air and as it is breathed out again. The lungs allow you to inhale and exhale. Breathing in allows fresh air and oxygen to enter your blood, and breathing out removes stale air, made up of carbon dioxide, from your blood.
Trachea
The trachea, also known as the windpipe, is a hollow tube that connects our lungs to the nose and mouth. It includes the voice box (known as the larynx), which allows us to use air to make different sounds.
The trachea allows air to flow easily from our nose and mouth to our lungs and back out.
Keep reading to find a human body organ diagram!
Brain
The brain is located inside our skull, at the top of our heads, and it is like a central computer for all the other functions in our body. The organ sends messages to the rest of the body (using the spinal cord to send the message incredibly quickly). Without the brain, all your muscles and organs would not function. So to protect the brain, we have the skull, a thick solid plate of bone, and a fluid surrounding it.
The brain has specific areas that complete different tasks in the body, such as helping us understand language, helping us move, and even helping us control all of those functions that we don’t think about (breathing, blinking, and digesting food).
Stomach
The stomach is a large processor of food and liquid in the body. Within the stomach, food is broken down into smaller pieces that are easier for the body to digest fully.
In terms of appearance, the stomach is ‘J’ shaped and is located near the top of the abdomen. Once a person swallows their food, it goes down to the stomach. This journey involves moving down the throat and into the esophagus. Once it has reached the end of the esophagus, the food enters the stomach.
A bunch of super strong muscles around the stomach walls helps break down and digest food. Moreover, within the lumen lining in certain stomach parts, a range of enzymes help with food digestion. Different enzymes are assigned to break down various components of food. For instance:
- Amylase enzymes break down carbohydrates and starches
- Protease enzymes break down proteins
- Lipase enzymes break down fats
- Maltase enzymes are released in the small intestine, not the stomach, but they break down maltose, malt sugar, into glucose, a simple sugar. The body then uses this simple sugar for energy.
- Lactase enzymes break down lactose, a sugar found in dairy products. The body turns lactose into glucose and galactose, which are simple sugars.
The stomach can be broken down into five main sections. These are as follows:
- The cardia: This stomach area is located just below the esophagus. The cardiac sphincter is found in this area, which stops food from flowing back up the esophagus and into the mouth. Without this sphincter, we would choke.
- The fundus: This stomach area is located to the left of the cardia and underneath the diaphragm. The fundus is responsible for collecting digestive gases.
- The body: This is the largest area of the stomach. In the stomach’s body, food starts to be broken down into smaller, digestible pieces.
- The antrum: This is located in the lower region of the stomach. This part of the stomach hold partially digested food before it travels to the small intestine.
- The pylorus: The pylorus connects the stomach to the small intestine. The pyloric sphincter is located in this stomach area and controls when and how much stomach content travels into the small intestine.
Small Intestine
The small intestine is a narrow, coiled-up tube (around six to seven meters long) that connects to the stomach and absorbs nutrients from the food after leaving it.
Large Intestine
Water and food that cannot be digested are passed from the small intestine into the large intestine, turning them into waste. The large intestine is around 1.5 meters long.
Bladder
The bladder is a bag that collects the urine that leaves the kidneys. When the bladder is complete, it sends a message to the brain, and you go to the toilet. Drinking plenty of water and avoiding rich foods will help keep the bladder and kidneys in good condition.
Where are the organs in the human body?
Each of the organs in the human body organs diagram below is organized into different organ systems. In each system, the organs that belong to it work together to perform a particular function.
The organ systems in the body are:
Circulatory System
Within the circulatory system, there are the following organs:
- Heart
- Blood vessels (arteries and veins)
- The blood
The circulatory system plays a vital role in keeping us alive, as it transports oxygen and nutrients throughout the body via the blood. This system also removes carbon dioxide and other waste products from the body.
Lymphatic System
The lymphatic system is also involved in transporting fluid around the body. Instead of blood, this system transports a fluid called lymph using the following organs:
- Lymph vessels
- Lymph nodes
- Lymph ducts
- Various glands
The purpose of the lymphatic system is to boost the body’s immunity, regulate blood pressure, and aid digestion. The lymphatic system also acts as the drainage system for the body, taking any excess fluid, proteins, fats, bacteria, and other substances away from the cells and spaces between cells.
Respiratory System
When we think of the respiratory system, we tend to think of breathing, but this system has many other functions. The organs within the respiratory system are:
- Lungs
- Trachea (windpipe)
- Airways of the respiratory tree
As mentioned, the respiratory system controls the body’s breathing. It also transports oxygen and carbon dioxide in and out of the bloodstream in a process called respiration.
Another lesser-known function of the respiratory system is to help regulate the body’s pH balance, i.e., the body’s balance of acids and bases.
Integumentary System
This is one of the body’s organ systems that people often forget about; however, it plays a crucial role in keeping the body running smoothly. The integumentary system includes the skin and all of the structures within it. The organs that make up the integumentary system are:
- Sweat glands
- Hair follicles
- Nails
- Nerves
A fun fact about the integumentary system is that it is the only single-organ system. This is because the skin is an organ and the entire organ system.
Endocrine System
The endocrine system comprises the body’s glands that secrete hormones into the bloodstream. Along with the nervous system, the endocrine system is regarded as one of the most complex systems in the body,
The endocrine system is responsible for regulating the body’s metabolism and using the products of digestion.
Digestive System
The digestive system, also known as the gastrointestinal system, is commonly referred to as the gut. Within this organ system are all the organs that transport food from where it enters the body to where it exits it. These organs are:
- Oesophagus
- Stomach
- Intestines
Urinary System
The urinary system, which is also known as the excretory system, contains the following organs:
- Kidneys
- Ureters
- Bladder
- Urethra
This organ system filters blood and removes toxins and waste from tissues. It also removes any excess fluid and aids in regulating the body’s blood pressure.
Musculoskeletal System
The following organs are included in the musculoskeletal system:
- Skeleton
- All the muscles, tendons, and ligaments attached to it
The musculoskeletal system is crucial in the human body as it provides the framework and fuel for our movement, posture, and physical abilities.
There are three different types of muscles in the body. They are:
- Skeletal – voluntary
- Smooth – involuntary (these are inside walls of organs such as the intestines)
- Cardiac – heart muscle
Nervous System
The nervous system is highly complex, made up solely of tissue that isn’t fed directly through contact with blood. The organs within the nervous system are:
- Brain
- Spinal cord
- All of the nerves connected to both of these organs
Reproductive System
The reproductive system is unique as it is the only system split into two parts. Half of us have female genitals, and the other half have male genitals. This means that the reproductive organ system is not complete in one body.
Immune System
All of the organs within the immune system are borrowed from other body organ systems. The primary organs that make up the immune system are:
- Lymph nodes
- Bone marrow
- Thymus
- Spleen
- Adenoids
- Tonsils
- Skin
As there is a great deal of overlap between the organs of various other systems and the immune system, it is one of the most complicated systems in the body.
