Tissues (Biology) — Definition & Overview

Tissue (Level of Organization)

A tissue is a group of similar cells working together to perform a specialized function (job).

Tissues are the second step in the levels of biological organization. They are found between cells and organs, as shown in the graphic below. Let's take a look at that.

As the graphic shows, a tissue is a bunch of cells working together.

You may be familiar with muscle tissue, but the human body actually has four main types, including nervous tissue, epithelial tissue, and connective tissue. They all have specific functions:

Key Vocabulary:

1. Cell
2. Function
3. Tissue

(Video) What Are Tissues?

by Don't Memorise

Tissues aren't just something you blow your nose into. This video explains what a biological tissue is and where it fits into the organization of a multicellular organism. It also goes through some examples of tissues in the human body as well as in plants.

What Are Tissues Made Of?

Take a look at the image below. At the very top, we see the chemical level. This includes atoms like hydrogen and oxygen. Below that is the molecular level, when those atoms combine to make molecules.

After that, we have the cellular level. Here, we see a smooth muscle cell with organelles inside. Finally, we see that tissues are made up of similar cells performing the same function. There are an astounding number of different kinds of tissues in your body.

The patterns and shapes of the cells that make up tissues are absolutely amazing. Just think about it; the cells had to evolve to fit a specific niche in the body and over time became these intricate, almost otherworldly tissues.

Look at the dense connective tissue picture below. It's kind of beautiful. The cells are tightly packed and elongated because this kind of tissue is needed for things like tendons.

One more type is bone tissue, which is found in—you guessed it—bones. You can see it in the picture below as the sponge-like fibers within the bone. Although it may look squishy, this type of tissue is actually very hard.

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

$\color{#8925AE}{\text{Cell}}$ : The smallest unit of life

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

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

What Are Biological Tissues?

There are many types of cells in the human body. When cells that are similar in structure and function join together in large groups, they can form tissues. Much like how building blocks or bricks can form a wall, single cells can gather together in sheets or clumps that eventually give form to larger structures like organs (or, in the case of bricks, houses).