Organs — Definition & Overview

Organs: Tissues Working Together

When tissues work together, they form an organ.

Organs are the third step in the levels of biological organization. They are found between tissues and organ systems, as shown in the graphic below. Let's take a look at that.

As the graphic shows, an organ is made from a collection of tissues working together. Organs can also combine to form higher levels of organization like organ systems.

Different Organisms, Different Organs

The human body has almost 80 organs, each performing a very specific job. For example, your heart is an organ that needs many different tissues to work together to perform its vital functions. It needs muscle tissue to contract and release. The heart also has specialized cardiac tissue which is responsible for the signals that tell your heart when to contract. Those are just two types of tissues, but the heart contains many more.

You might also hear the term vital organ, which refers to an organ that is absolutely necessary for survival (that is, you cannot survive without it). They are usually identified as the heart, lungs, brain, kidneys, and liver.

The picture below shows a really basic drawing of some of the human body's larger organs.

The largest organ of your body is your skin.

It's important to remember, too, that not all organisms have the same organs. For instance, here's a diagram of snail organs:

Different organisms may use different organs, but you might be surprised to know that many of those snail organs are similar to those of humans.

Insects also have many organs. Here's a diagram of spider organs:

One more thing: Plants have organs too. The same definition applies. In plants, organs are tissues working together to perform a specific function.

Most plants have four organs: the root, stem, flower, and leaf.

Key Vocabulary:

1. Cell
2. Tissue
3. Organ
4. Function

Organ (Level of Organization)

Organs are made of building blocks called tissues.

Many organisms have organs that are essential to their survival. You might be surprised to know that the snail has many organs that are similar to those of humans.

Each of our organs consist of many types of tissues that help perform a specific function. For example, your heart is an organ that needs many different tissues to work together to perform its vital functions. It needs muscle tissue to contract and release. The heart also has specialized cardiac tissue which is responsible for the signals that tell your heart when to contract. Those are just two types of tissues, but the heart contains many more.

Each type of tissue found in an organ is essential to its function.

(Video) Cells, Tissues, and Organs

by funsciencedemos

Organs are made up of tissues, which are made up of cells. This video explores the organs of the human body, how organs work together, and what they are made up of.

Examples of Organs

Organs are the next level of complexity. Organs are made of two or more tissues working together closely to perform functions.

Organs are things such as your skin, your heart, and your brain. They can be very complex, hence we still aren't completely certain how the brain works.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Cell}}$ : Simplest level of organization and the smallest unit of life

$\color{#8925AE}{\text{Tissue}}$ : A group of specialized cells that do specific jobs

$\color{#8925AE}{\text{Organ}}$ : A structure made up of specialized tissues

$\color{#8925AE}{\text{Organism}}$ : An individual living thing