Life Cycle - Human Biology (4B)
Post Lab

   
OBJECTIVES:
  • Exploring the components of blood.
  • Defining the components of blood. 
VOCABULARY:
  • arteries 
  • plasma
  • platelet
  • red blood cells
  • veins
  • white blood cells
MATERIALS:

Students measure arteries and veins.

BACKGROUND:

Blood is composed of a solid portion and a liquid portion.  The liquid portion or plasma provides a medium in which the solid portion can be transported.  Within plasma are found many substances, including water, inorganic salts, proteins, nitrogen bearing substances including fats, cholesterol, sugars, hormones, and dissolved gases.  The cellular solid portion includes red blood cells, a variety of different types of white blood cells and platelets.

Four major parts to blood are plasma, red blood cells, white blood cells, and platelets. On the worksheet the students will identify each of the components after you discuss the characteristics of each part. 

About 55% of blood is plasma.  Plasma is about 90% water.  Food, nutrients, and oxygen are dissolved in plasma.  Plasma also contains antibodies.  Antibodies help fight disease.

Red blood cells are saucer shaped cells found in the plasma that carry oxygen.  They are the most plentiful blood cells found in the human body.  Red blood cells are also called erythrocytes.  White blood cells are used by the blood to destroy harmful germs.  White blood cells are also called leukocytes.

Platelets are smaller than red blood cells and colorless.  Platelets help stop bleeding by  producing blood clots that stop blood from escaping a blood vessel.

Blood travels through veins and arteries.  On the students' worksheets they will measure the widths of the various blood vessels and rank them in order of largest width to smallest width.  The largest artery (aorta) and the two largest veins (vena cava) measure about 2-3 cm wide.  Because of their muscle tissue, the walls of arteries are thicker and firmer than those of veins. 

PROCEDURE:
  1. Give students the worksheet and have them measure the different cross sections of arteries and veins.   See if the students know what each of the cross sections represent before you give them the answer.
      
  2. Remind students that when you measure in metric you can record in decimal by recording the whole number, place decimal, and then count the spaces.  The answers are in centimeters.  However, students can record .1 cm as 1 mm.

    ANSWERS: 
         1. aorta - 2.8 cm
         2. large artery - 1.3 cm
         3. small artery - .5 cm 
         4. arteriole - .2 cm 
         5. capillary - .1 cm
         6. venule - .2 cm
         7. small vein - .3 cm
         8. small vein 1.2 cm
         9. vena cava - 2 cm 
        
  3. The second picture goes over the names of the arteries and veins.  Notice that veins have “v” in front of the name and arteries have “a” in front of the name.  Students are fascinated with an understanding of the different parts of the body.  The names may be difficult, but they represent a part of their body. 

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