Lesson 4- Blood Vessels

I. Learning Objectives:

    1. What are the different types of blood vessels?
    2. What are the function of the blood vessels?
    3. Draw the blood vessels and label it

II. Concept or Terminologies:             

              a. Artery- carries the blood away from the heart. It is thick-walled.    

                b. Vein – carries the blood back to the heart. It is thin-walled.

      c. Capillary- is the smallest blood vessels that has wall that is only one cell thick.  
    • d. Arteriole – is a smaller branch of the artery. It connects an artery to the capillary.
    • e. Venule- is a small branch of the vein. It connects the vein to the capillary.

III. References:

    1.Into the Future: Science & Health VI, pp.17-18

IV. Review of Related Lesson:                

      What are the parts of the heart?

V. Lecture Presentation:                  

 Identify the parts of the heart by labeling them.   

                                         heart 2.jpg                                                       

    1. Motivational Question:
        Today we will discuss about the other parts of the circulatory system. Thay are the pipes or tubes. What are they called?
    Study the picture below.
                                    blood_vessels 1.jpg
  1.   Presentation:
    The Blood Vessels In class we talked about three types of blood vessels:
    Arteries are blood vessels that carry oxygen rich blood AWAY from the heart. Remember, A A Arteries Away, A A Arteries Away, A A Arteries Away.


    Capillaries are tiny blood vessels as thin or thinner than the hairs on your head. Capillaries connect arteries to veins. Food substances(nutrients), oxygen and wastes pass in and out of your blood through the capillary walls. 

                                           veins 1.jpg

    Veins carry blood back toward your heart.

    In a general sense, a vessel is defined as a hollow utensil for carrying something: a cup, a bucket, a tube. Blood vessels, then, are hollow utensils for carrying blood. Located throughout your body, your blood vessels are hollow tubes that circulate your blood. There are three varieties of blood vessels: arteries, veins, and capillaries. During blood circulation, the arteries carry blood away from the heart. The capillaries connect the arteries to veins. Finally, the veins carry the blood back to the heart.If you took all of the blood vessels out of an average child, and laid them out in one line, the line would be over 60,000 miles long! An adult's vessels would be closer to 100,000 miles long!Besides circulating blood, the blood vessels provide two important means of measuring vital health statistics: pulse and blood pressure. We measure heart rate, or pulse, by touching an artery. The rhythmic contraction of the artery keeps pace with the beat of the heart. Since an artery is near the surface of the skin, while the heart is deeply protected, we can easily touch the artery and get an accurate measure of the heart's pulse.When we measure blood pressure, we use the blood flowing through the arteries because it has a higher pressure than the blood in the veins. Your blood pressure is measured using two numbers. The first number, which is higher, is taken when the heart beats during the systole phase. The second number is taken when the heart relaxes during the diastole phase. Those two numbers stand for millimeters. A column of mercury rises and falls with the beat of the heart. The height of the column is measured in millimeters. Normal blood pressure ranges from 110 to 150 millimeters (as the heart beats) over 60 to 80 millimeters (as the heart relaxes). It is normal for your blood pressure to increase when you are exercising and to decrease when you are sleeping. If your blood pressure stays too high or too low, however, you may be at risk of heart disease.

Blood vessels are hollow tubes that carry blood through miles and miles of blood vessels in a never ending stream. If you could take all the blood vessels of a average size child and line them up they could reach about 60,000 miles long. In an adult the blood vessels could reach 100,000 miles long. The blood vessels carry blood between the heart, different tissues, and organs of the body. There are three types of blood vessels: arteries, veins, and capillaries. These blood vessels have the ability to expand to allow more blood to flow through them. They can also contract to help control the flow of blood. The blood flows through the big arteries into smaller ones. The smallest arteries, called arterioles, direct the blood flow into the capillaries. The capillaries connect to the smallest veins called venules. The Veins then return blood to the heart.


The arteries are elastic, muscular tubes that carry the blood from the left ventricle of the heart to the capillaries. The walls of the arteries are thicker than the other vessels because of the high pressure. The largest artery is the aorta it is about 1 inch in diameter. The walls of the arteries are 3 layers thick. The inner layer, or tunica intima, consists of single flatten cells called endothelium. The middle layer, or tunica media, is the thicker part of the artery wall. The outer layer, or tunica externa is composed of fibrous connective tissue that give strength to the wall of the artery. The thickness of arteries depends on where it is located within the arterial system. The wall thickness of the arteries prevent the arteries from collapsing. Sometimes there is a weakness in a wall of an artery and this causes the artery to bulge. This abnormal expansion of the artery is called an aneurysm. There is also a problem of the arteries that involves lack of elasticity. This disease comes about because the wall of arteries becoming harden. This abnormal harding is called arteriosclerosis.


The veins carry blood from capillaries to the heart. The veins increase in size as they progress toward the heart. The veins that connect to the capillaries are venules.They are the smallest of the veins. The veins tend to follow a path parallel with the arteries. However, there are more veins than arteries this is due to the draining of large areas when needed. The veins at any one moment carries about 70 percent of the blood. The veins are like the arteries in that they have three layers in their walls. However, they are not as thick as arteries. This would also correlate with the lower pressure of blood within them. Located with the veins are valves that allow blood to flow toward the heart but does not allow blood to flow backwards. The veins that are in the lower part of the body tend to have more valves to counteract the force of gravity. The only vein that does not have valves is the vena cava. The valves in the legs sometimes breakdown and allow the blood to flow backwards. This is called varicose veins and is more prevalent in person who stand for long periods of time on hard surfaces.


The capillaries are the smallest working unit in the blood vessels that connect the arterioles to the venules. The walls of the capillaries are only 1 cell thick this allows for the exchange of nutrients and other substances like oxygen and carbon dioxide. Each of the cells in the walls of the capillaries have openings between them so that the exchange can take place. The number of capillaries vary depending on the need for oxygen and other nutrients. The blood flow through the capillaries is regulated by a sphincter, a ring of muscle, that contracts to control the flow of blood through the capillaries. This is important because there would not be enough blood to fill all the blood vessels at one time. This is understandable when one sees that an individual could have between 25,000 to 60,000 miles of capillaries

3. Summary:    

a. What are the three kinds of blood vessels?    

b. Differentiate the three kinds of blood vesels from one another?    

c. why do arteries appear reddish while veins appear bluish?   

d. How do blood flows in the capillaries?   

e. Why does blood do not flow backward?

 f. How are veins connected to the capillaries? Arteries to Capillaries?

 g. Which blood vessels will have a greater pressure, the vein or the artery?

h. Why do you think so?

i. What blood vessels that have valve?

j. Why do you think does the blood squirts when the artery is cut?

k. Why can exchange of gases, nutrients, water,and waste occur in the capillaries?

VI. Learning activities.

     For more Learning activities log on to  www.teacherlink.ed.usu.edu/units

and     www.syvum.com/cgi

VII. Evaluation

      Log on to www.prongo.com.quiz/station.

VIII. Assignment:

     Prepare a comic strip of the 3 kinds of blood vessels. Each of them should argue regarding who is more important.


4 Responses to “Lesson 4- Blood Vessels”

  1. Shermae Curioso Javier Says:


  2. Shermae Curioso Javier Says:

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    […]Lesson 4- Blood Vessels « Science[…]…

  4. June Says:

    I think it is safe to say that from about 20 years ago, I had this assignment (from God) to study the Blood. I was reminded of it earlier this week and decided to begin. (I was missing too much blessings for not obeying.) From the Search Engine, I first clicked on the Wikipedia site… I soon thought that the structure was too boring for my not yet conditioned brain. So back to the SE I went… This time rather than just inserting the one word “Blood”, I typed “Grade 3 Lesson on Blood”. (I am a college grad.) Voila! I discovered this lesson. I am thoroughly enjoying it… So I will be coming back again..

    Thank You, WordPress… You’ve Set Me on my Way to Goodness!

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