Difference Between Tissue and Organ

The key difference between tissue and organ is that tissue is a collection of cells that serves the same function while organ is a collection of tissues that functions as a unit.

The cell is the basic structural and functional unit of all living organisms. Some organisms have only one cell (unicellular organisms) whereas others contain numerous cells (multicellular organisms). A single cell is capable of growth and development, gaining nutrition, respiration, excretion, recognizing and acting on stimulations as well as reproduction. When considering the animal kingdom, all organisms except protozoans are multicellular. The cells in a multicellular organism are specialized to carry out different functions. This specialization of the cells has enabled the efficient functioning of the body. Tissues and organs are two kinds of organizational units of cells in a multicellular organism. Moreover, an organ occupies a higher level of organization than a tissue. Let’s discuss the difference between tissue and organ.

CONTENTS

1. Overview and Key Difference
2. What is a Tissue 
3. What is an Organ
4. Similarities Between Tissue and Organ
5. Side by Side Comparison – Tissue vs Organ in Tabular Form
6. Summary

What is a Tissue?

Similar cells operate collectively and become specialized functionally to form a tissue. Therefore, a tissue can be defined as a collection of similar cells that serve the same function. Formation of tissue is a way of differentiation or division of labour within an organism, and it may be extensive. The major advantage of tissues is that generally, tissues are able to carry out specific tasks more efficiently than individual cells. The cells in a tissue are not always identical, but they have the same embryonic dermal origin and specialization for the same function.

Histology is the study area of tissues. The main techniques used to recognize and differentiate different components of tissue are embedding, sectioning, and staining. There are four basic types of animal tissues. They are connective, muscle, nervous, and epithelial tissues. They make up all the systems and the whole body of an animal.

What is an Organ?

An organ is a collection of tissues that work together as a functional unit. Generally, the cells of a tissue function as a unit due to the coordination of cellular activity. Therefore, different tissues get together to form organs and carry out major functions of multicellular organisms. Heart, lungs, stomach, kidney, skin, liver and bladder are some examples of organs that we have. The heart pumps blood throughout the body, lungs exchange oxygen and carbon dioxide while kidneys filter blood and excrete wastes.

In an organ, there can be many types of tissues. But there is usually a main tissue and sporadic tissues. The main tissue for the skin is epithelial tissue while connective tissues, nerves and blood are sporadic tissues. In addition, an organ can be described as a hollow organ when it takes the shape of a tube or has a cavity within it.

What are the Similarities Between Tissue and Organ?

• Cells are the basic structural units of tissue and organ.
• They are found in multicellular organisms.
• Both carry out different functions within an organism.
• Furthermore, they are specialized in their functions.

What is the Difference Between Tissue and Organ?

A tissue is a collection of cells with a similar structure that carries out a specific function. In contrast, an organ is a collection of tissues that functions as a unit. Therefore, this is the key difference between tissue and organ. Another difference between tissue and organ is that the general size of a tissue is smaller than that of an organ. A tissue always carries out a specific function. But, an organ can perform various bodily functions; for example, the heart pumps blood throughout the body, receives deoxygenated blood and sends blood for oxygenation to the lung.

Furthermore, organs can be hollow in structure, but tissues are always even in shape without gaps between cellular components. Another difference between tissue and organ is that tissues are the major structural components of an organ while organs are the major functional components of an organ system.

Summary – Tissue vs Organ

The levels of organization of an organism start from a cell. Cells make up tissues. Tissues make up organs. Organs make up organ systems. Finally, organ systems make up an organism. Therefore, tissue is a collection of cells that function as a unit while an organ is a collection of tissues that functions as a unit. Connective tissue, nerve tissue, epithelial tissue and muscle tissue are examples of tissues while heart, kidney, lungs, skin and stomach are organs. This is the summary of the difference between tissue and organ.

Reference:

1.“Boundless Anatomy and Physiology.” Lumen, Available here.
2.“Tissues, Organs, & Organ Systems.” Khan Academy, Khan Academy, Available here.

Image Courtesy:

1. “Diagram of the human heart (cropped)” By Wapcaplet – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Four types of tissue” By MedlinePlus –  (Public Domain) via Commons Wikimedia