Thymus: Definition, Functions & Location

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Male Reproductive System: Functions, Organs & Anatomy

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
Your next lesson will play in 10 seconds
  • 0:01 Definition of the Thymus
  • 0:25 Location of the Thymus
  • 1:09 Functions of the Thymus
  • 2:53 Lesson Summary
Save Save Save

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Log in or Sign up

Speed Speed

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Derrick Arrington

Derrick has taught biology and chemistry at both the high school and college level. He has a master's degree in science education.

The human immune system is responsible for protecting the body from foreign invaders as well as internal problems. In this lesson, you will learn about part of the immune system known as the thymus.

Definition of the Thymus

We could not exist without the immune system. It is our line of defense against any material that can cause sickness or disease. The immune system is composed of specialized cells, glands, and organs. One important part of the immune system is the thymus, which is a pyramid-shaped organ of the immune system that is involved in producing T cells, or lymphocytes.

Location of the Thymus

The thymus is located in the chest in an area in front of the heart and directly behind the sternum. If you use your finger to feel the top of your sternum in the center of your chest, the thymus will be positioned about two centimeters behind the location of your finger.

Structurally, the thymus is composed of two lobes of tissue that are mirror images of each other and are joined at the top to form a pyramid-like shape. The thymus is a collection of tissues. In the center is the group of tissues known as the medulla. The medulla is surrounded by loosely packed tissue known as the cortex, which is enclosed by an outer capsule.

Functions of the Thymus

One critical part of the immune system is a group of white blood cells known as lymphocytes. And one of the types of lymphocyte cells actively involved in immunity is the T cells. These cells get their name because they are derived from the thymus. These T cells attack foreign substances in the body that are known as antigens.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account