Internal Organs

When we think about what makes up the human body, we could name a few things. Cells is a good answer, as is tissues.’ But, what about important parts like our heart, brain, or stomach? These kinds of structures are the internal organs. They’re what perform most of our body’s main functions! Sure, they’re made up of groups of tissues. But, as we’ll learn, internal organs also do essential things that tissues can’t.

An image showingthe internal organs of the body.

These are the bodies internal organs.

Organs: The Engines of Life

Imagine a specific thing that the body can do, complex or simple. Wave a hand, read a book, run, or just blink. All these things are possible because of the actions of our organs. That’s because organs are what makes us, well, us.  Most basically, they keep us alive! 

An image of a little boy looking in a mirror.

When we look in the mirror, we probably don’t think about organs. But, we need them to do everything!

Really, organs do SO much that it can be hard to decide what isn’t an organ. To help here’s a full definition: An organ is a group of specialized tissues which work together to do something cells or tissues can’t do alone. As an example, the brain has many different tissues. But, tissues can’t think or remember. Only the complete organ has this function.
 
That said, all external and internal organs have special types of cells to help them do their jobs. While we have about 80 organs, we have 216 different kinds of cells. Most specialize to help one specific organ. For instance, heart cells, called cardiac cells, are only in the heart. 
 

These cells can actually beat on their own, like the heart. Yet, they cannot do the heart’s unique job, which is to pump blood. It’s only when many of these cardiac cells work together that they form a whole, beating heart.

An illustration of a brain neuron.

Each organ has unique types of cells. These are brain cells, called neurons.

Why internal organs?

Now that we’ve gone over what an organ is, we come to a new question. Why are some organs internal while others are external? The answer relies on a concept called homeostasis.
 
Homeostasis is the perfect state for the body; it’s when everything is just right. This state is what allows many of our organs to work best. But, to maintain it, our body needs to close itself off from the rest of the world. That’s why our skin keeps in our internal organs.
 
Before we go into that, note that most of our organs are actually internal. The few that are outside include the skin and sense organs. All of the rest are inside, for a few reasons.
 

One is that they need to stay warm. The inside of our body is actually quite hot at about 98.6°F. Internal organs need this high temperature to do important chemical reactions. These reactions include making proteins and breaking down food.

An image showing a thermometer reading normal temperature of a body.

The inside of our bodies is very warm! You’ll see its temperature listed by biologists as 38 degrees Celsius. This is equal to about 98.6 degrees Fahrenheit.

Next, our internal organs need the fluids inside of our body. The internal environment of our body is very wet. This is partially because organs need specific fluids coating them at all times. These help them perform their function. For example, the lungs have a type of fluid called a surfactant that covers them. This fluid helps them manage the movement of air into our body.
 

Organ Systems

 
Finally, even though each organ has its own job, none of them are very useful on their own. The heart needs other organs to pump blood to. The stomach needs the mouth to chew food as well as the large intestines to process food waste. 
 
Because they depend on each other, organs form organ systems. Organ systems are groups of two or more organs. They work together to do something the individual organs can’t do alone. Each organ in the system still keeps its own function. But, the combining of organ functions allows the system to do something new.
 
An example would be the digestive system. This organ system includes nine organs, two of which are the stomach and mouth. On their own, the mouth chews food and the stomach digests it. But, because they’re connected by the esophagus, they form a system. Chewed food reaches the stomach where it can be more easily digested.