for Teachers for Schools for Enterprise
for Teachers for Schools for Enterprise
Course Navigator
Major Blood Vessels Between the Heart and Lungs: Pulmonary Trunk, Arteries & VeinsNext Lesson 

Blood Vessel Layers: Tunica Intima, Tunica Media & Tunica Adventitia

Chapter 4 /  Lesson 2   Transcript
Start Your Free Trial Today

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Major Blood Vessels Between the Heart and Lungs: Pulmonary Trunk, Arteries & Veins

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

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:06 Blood Vessels
  • 0:50 Layers of Blood Vessel Walls
  • 1:08 Tunica Intima
  • 2:09 Tunica Media
  • 3:58 Tunica Adventitia
  • 4:30 Lesson Summary
Add to Add to Add to

Want to watch this again later?

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

Login or Sign up

Timeline
Autoplay
Autoplay

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

In this lesson, you will take a microscopic look at the three layers, or tunics, that make up your blood vessels. Follow along and learn how the different cells within these tunics help the vessels contract and relax as blood moves through your circulatory system.

Blood Vessels

We previously learned that blood is carried to your cells through transportation tubes called blood vessels, and your heart is the pumping station that propels that blood. Every time your heart beats, blood is pumped into large arteries to start the one-way journey around your body. From the large arteries, blood moves into smaller arteries called arterioles and then into the capillary beds, and it's in these capillary beds where you have the exchange of gases and nutrients. Your blood is then drained out of the capillary beds and ready for its return trip to the heart by first going into small veins called venules and then merging into larger veins, which eventually flow back into the heart.

Layers of Blood Vessel Walls

Like a busy highway, your blood vessels have to be well-constructed to withstand all the pressure that comes with circulating your blood every minute of every day. To help stand up to the high demand, the walls of the blood vessels are constructed of three layers known as tunics.

Tunica Intima

The tunica intima is the innermost layer of the arteries and veins. You can easily recall this term by remembering that 'intima' and 'innermost' both start with the letters 'in.' The tunica intima is composed of a thin layer of endothelial cells and lines the entire circulatory system, from your heart and the large arteries all the way down to the very tiny capillary beds.

The tunica intima is the innermost layer of arteries and veins
Tunica Intima

As we previously learned, capillaries are comprised of only one layer of endothelial cells, and therefore, capillaries only have a tunica intima. This ultra-thin design is what allows for nutrients and gases to be exchanged in the capillary beds, and it's a unique feature of capillaries. The walls of arteries and veins have two additional layers, or tunics, forming too big of a barrier for there to be an exchange of gases and nutrients. So, why don't we go ahead and take a look at those two additional layers found within the walls of your arteries and veins.

Tunica Media

Working our way from the inside of the vessel out, we see the next layer, called the tunica media. This is the muscular middle layer of the arteries and veins. You can easily recall this by remembering that 'media' and 'middle' and 'muscular' all start with the same letter, which is 'm.' The tunica media of arteries contains more smooth muscle than the tunica media of their counterpart, the veins, and this allows the arteries to constrict and dilate to adjust the volume of blood needed by the tissues that they feed.

When the smooth muscle found within the tunica media is stimulated, it contracts, squeezing the walls of the artery and narrowing the vessel. The term vasoconstriction is used to describe the narrowing of the blood vessel due to contraction of the muscular wall. When an artery constricts, the flow of blood decreases and the pressure within the vessel rises. Vasoconstriction is a mechanism your body uses to regulate important functions in the body, such as body temperature and blood pressure.

Cross section of the tunica media layer
Tunica Media Cross Section

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

Register for a free trial

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back
What teachers are saying about Study.com
Free 5-day trial
Description

Earning College Credit

Did you know… We have over 160 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? Study.com 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.

Research Schools, Degrees & Careers

Get the unbiased info you need to find the right school.

Browse Articles By Category

Browse an area of study or degree level.

Recommended Articles
You are viewing lesson Lesson 2 in chapter 4 of the course:

 Back To Course

Biology 105: Anatomy & Physiology

16 chapters | 179 lessons | 15 flashcard sets

Ch 4. Blood Vessels
Ch 5. Digestive System

Blood Vessel Layers: Tunica Intima, Tunica Media & Tunica Adventitia Related Study Materials

Create an account to start this course today
Try it free for 5 days!
Create an account

Explore our library of over 75,000 lessons

Browse by subject
Support