Video Transcript
Which of the following best defines an organ? (A) A group of different cells that work together to carry out multiple different
functions. (B) A group of similar cells that work together to carry out a particular
function. (C) A mass of the same tissue that multiplies to form a large structure inside the
body. (D) A group of different tissues that work together to perform a certain
function. Or (E) a group of tissues bound together by a membrane.
While you’re probably familiar with the term organ, you may not be quite sure of its
scientific definition, so let’s have a quick review of what organs actually are.
There are more than 70 organs in the human body. They can be grouped into organ systems, for example, the respiratory system and the
cardiovascular system. The organs involved in each system work together to conduct basic life processes. An example of an organ within the respiratory system is the lungs, which contain
several different tissue types. For example, epithelial tissues cover the surface of the lung. Connective tissues provide stability and structure. And pleural tissue lines the lobes of the lungs and the chest cavity. In fact, not only the lungs but all organs are made up of multiple types of
tissues.
Tissues, which are groups of similar specialized cells, come together to form organs
with specific functions. For example, one function of the lungs is to inhale oxygen. The heart and blood vessels of the cardiovascular system then deliver this oxygen to
every cell in the body and pick up waste products like carbon dioxide. The lungs then perform a second function of exhaling the waste gases. This illustrates the fact that just as organs within a system interact, entire organ
systems also interact with each other.
Now, let’s have another look at our answer options. We have learned that organs are made up of different tissue types. Therefore, we can rule out answers (A) and (B) because they refer to groups of cells,
which are the building blocks of tissues, not organs. We can also eliminate answer option (C), because organs are made up of different
tissue types, not the same. Answer (E) does refer to a group of tissues. But as you may remember, cells and organelles are structures that are bound by a
phospholipid membrane. Entire organs are not membrane bound, so this answer is incorrect.
The best definition of an organ is found in option (D). An organ is a group of different tissues that work together to perform a certain
function.
