1. Module 8 Intro

1.21. Lab

Lesson 3

Module 8—Circulation, Immunity, and Excretion

Lab: Identifying Blood Cells

 

You will now perform a modified version of “Investigation 8.C: Identifying Blood Cells” from page 285 in the textbook. Note: You will not be using the light microscope as described in the textbook lab, but rather a set of ten prepared online slides.

 

You will be assuming the role of a lab technician in this virtual investigation. Virtual slides with smears of different blood samples will be presented to you so you can identify what kinds of cells are present.

 

Background Information

 

Have you ever had a blood test? It is common that a complete blood count, or CBC, is ordered as part of the test. The CBC measures the number of red blood cells, the number of white blood cells, the total amount of hemoglobin in red blood cells, and the fraction of the blood composed of red blood cells (the hematocrit). The hematocrit part of the CBC test measures the number and size of red blood cells. It gives a measure of the proportion of the whole blood that is made up of red blood cells. The value is then given as a percentage, such as 45%, which means that red blood cells take up 45% of the blood volume.

 

How the Test Is Performed

 

Blood is usually drawn from the inside of the elbow or the back of the hand. The site is cleaned with antiseptic and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood.

 

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

 

In the laboratory, some of the blood is centrifuged (spun in a machine). This forces the cells to the bottom of the container. The cellular portion is compared with the total amount of blood and expressed as a percent. The cellular portion is composed almost entirely of red blood cells. The percentage of white blood cells is very small.

 

What Abnormal Results May Mean

 

Low hematocrit may indicate

  • anemia
  • blood loss (hemorrhage)
  • bone marrow failure (affects stem cell production) (e.g., due to radiation, toxin, fibrosis, tumour)
  • destruction of red blood cells
  • leukemia
  • malnutrition or specific nutritional deficiency
  • multiple myolema (cancer of plasma cells in the bone marrow)
  • rheumatoid arthritis

High hematocrit may indicate

  • dehydration
  • burns
  • diarrhea
  • erythrocytosis (excessive red blood cell production)

Procedure

 

In order to more easily identify the blood cells found in the histology slides, click on the following link and read about the characteristics of a blood smear.

 

If you need more help distinguishing between white and red blood cells, look at the following link.

 

Work through the four different suggestions to differentiate the leukocyte cell types.

 

Suggestions:

  1. Are cytoplasmic granules present or absent?

  2. Determine the colour of the granules (red or blue).

    You can read about this in the following link.

  3. What does the nucleus look like?

    You can read about this in the following link.

  4. Use RBCs as a size comparison.

    You can read about this in the following link.

    Once you are confident that you are able to differentiate between the cells, continue with the investigation.

    Perform the Differential Counts activity, and view the ten fields or slides.

Now continue with the Lab in the Assignment.


Read

 

Transport: Plasma

 

Plasma carries all of the blood cells as well as transporting wastes, nutrients, and hormones. Without the bloodstream to serve as a pathway for hormones, the body is unable to respond effectively to fluctuations in its external or internal environment. Many regulatory feedback systems are dependent on the presence of hormones. If feedback systems are out of balance, many different parts of the body will cease to function together. If so, your body will break down.

 

You may want to read more on the role of plasma in the transport of matter on pages 284 and 285 of the textbook.

 

Self-Check

 

SC 1. Complete this Self-Check activity about blood.

 

Now continue with the Lab in the Assignment.