Blood is a vital force in your body. In fact, over 5 litres of it courses through your arteries, capillaries, and veins carrying blood to your organs in order to keep them functioning and thriving. Blood has four main components, each with a different function. Red blood cells carry oxygen and nutrients, platelets stop bleeding and help heal wounds, white cells protect us against infection and the yellow plasma in which they are suspended carries an array of proteins that regulates bleeding and clotting.
Join the discussion
Explore the online questionnaire/eligibility quiz by the Canadian Blood Services to determine if you qualify to donate blood. What questions surprised you? Share your thoughts with the class.
Debrief:
- What are the screening questions that are used by the Canadian Blood Services?
- Do you agree with the screening criteria? Why or why not?
- Evaluate the screening criteria for their necessity in ensuring safe blood transfusions.
Transferable skills
One of the skills we are practicing in this learning activity is “Communication.” We will communicate using the appropriate digital tools, taking care to create a positive digital footprint. We will also ask effective questions to acquire knowledge; listen to all points of view and ensure that those views are heard; voice their own opinions; and advocate for ideas.
Blood circulation
The circulatory system has three major components: the heart, the blood vessels, and blood.
The heart
Your heart is a muscular system that pumps blood through the circulatory system to the lungs and body. The blood vessels form a system of hollow tubes that carry blood to and from your body tissues. Your blood is the bodily fluid in which blood cells are suspended, and is also the means for transporting nutrients, oxygen, carbon dioxide, and other materials throughout your body.
Blood vessels
There are three main types of blood vessels in the human body: arteries, veins, and capillaries. The arteries carry blood away from the heart, while veins carry blood to the heart.
Arteries
Arteries and veins are thicker and range in diameter from the thin ones connected to the capillaries (arterioles and venules) to the thick ones connected to the heart. Arteries carry oxygenated blood away from the heart, while veins carry deoxygenated blood to the heart. As blood travels through an artery, during contraction of the heart’s ventricles, the artery’s elasticity allows it to expand. The expansion and contraction of the artery allows the blood to keep flowing through the blood vessels. Try measuring your pulse on your wrist or neck. You will feel the rhythmic expansions and contractions of an artery as blood moves through it.
Veins
Veins have thinner walls than arteries, but a larger inner circumference. Veins are not as elastic as arteries. The contraction of your muscles keeps the blood flowing towards the heart. There are also one-way valves that prevent blood from flowing backwards. These one-way valves are very important, especially in the legs, because they ensure that your blood flows upward to your heart, against the pull of gravity. If you have ever experienced spider veins or varicose veins, they are the result of valves not working to their full potential in your veins.
Capillaries
Capillaries are the smallest of the blood vessels. They spread out through your body in a fine network. They are the width of a single cell, and are just large enough to allow blood cells to flow along them in single file. These narrow blood vessels allow for rapid diffusion of gases, nutrients, and wastes between the capillaries and the surrounding tissue cells.
Join the discussion
Before learning about the function of blood, brainstorm what the function of blood is, and why it is essential for our survival. Share your points with the class.
Debrief:
- What are the components in blood? What functions do these components add to the blood?
- Synthesize the problems that can occur if one or more of these components were missing.
Blood has many functions described as follow:
Drawing blood
A phlebotomy is the taking of blood from a vein. This procedure is often the first step in the work of a medical laboratory technologist. Blood samples are used for many of the laboratory tests ordered by physicians. Blood is usually drawn from a vein, usually from the inside of the elbow or the back of the hand.
The site is first cleaned with an antiseptic. The medical technologist wraps a wide, thick elastic band around the upper arm to apply pressure to the area and make the vein swell with blood. Then, a needle is inserted into the vein. To help hold the needle in place, a plastic strip is built around it, so that the technologist can place their thumb on it, as shown. Because of its shape, this needle is called a “winged” needle. The blood collects into an airtight vial or tube attached to the needle. The elastic band is then removed from the arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding. The blood collected in the vial is then sent to a laboratory for analysis.
Blood analysis
Blood can be analyzed in many ways, including chemical and visual methods. Visually examining a sample of blood can quickly tell a doctor a lot about a patient’s health. A microscope is used so that individual blood cells can be observed and counted. To prepare a blood sample for microscopy (the use of a microscope), a drop of blood is placed on a microscope slide to create a blood film or blood smear. A blood film is made by placing a drop of blood on one end of a slide, and using a spreader slide to spread the blood over the slide’s length.
The aim in preparing a thin film blood smear is to create a thin film of blood in which the cells are spaced far enough apart to be counted and differentiated. The slide is left to air-dry, after which the blood is fixed to the slide by immersing it briefly in methanol. The fixative is essential for good staining and presentation of cellular detail. After fixation, the slide is stained with various stains to distinguish the cells from each other.
A blood count test is relatively inexpensive and quick to do, and can reveal a lot about a patient’s health. Most laboratories routinely use automated equipment to dilute the blood, sample a measured volume of the diluted suspension, and count the cells in that volume. In addition to counting actual numbers of red cells, white cells, and platelets, the automated cell counters also measure the hemoglobin and calculate the hematocrit and red blood cell indices (measures of the size and hemoglobin content of their blood cells). Technologists then examine a stained blood smear under the microscope to identify any abnormalities in the appearance of the red blood cells and to report the types and percentages of white blood cells observed. A differential white cell count is done by staining a smear of the patient’s blood with a Wright’s stain, allowing the different types of white cells to be clearly observed under the microscope. A technologist then uses a microscope to count a minimum of 100 white blood cells and reports each type of white cell as a percentage of the total white blood cells counted. These values are recorded as a white blood count (WBC).
Checkpoint
Complete the following quick self-assessment before continuing.
| I can… | Yes! I’ve made notes on this, understand it and am good to continue. | I will need to review to strengthen my understanding. |
|---|---|---|
| Describe the function of blood | ||
| Compare the similarities and differences in structure and function of arteries, veins and capillaries | ||
| Explain the process involved in a phlebotomy |
Blood and its components
On average, you have five litres of blood flowing through your circulatory system. Blood consists of two distinct elements: a fluid portion and a solid portion. The fluid portion is called plasma and consists of water, plus dissolved gases, proteins, sugars, vitamins, minerals, and waste products. Plasma makes up 55% of the blood volume. The solid portion of blood consists of red blood cells, white blood cells, and platelets. These cells are produced in the bone marrow, which is inside your bones. This portion makes up 45% of your blood volume.
Separation of blood into plasma, white blood cells, and red blood cells. The three main types of blood cells differ in size and function.
Plasma
Plasma is a clear, yellowish liquid composed of 92% water and 7% dissolved blood proteins. The remaining 1% consists of other organic substances and inorganic ions, such as sodium, potassium, chloride, and bicarbonates. The main proteins in blood are albumin, globulin, and fibrinogen. Water in the plasma helps to dissolve and transport other substances, as well as helping to regulate body temperature. The plasma proteins help to maintain fluid balance in the plasma, and a slightly alkaline pH in the blood. The fibrinogen helps with clotting, and globulin proteins (your antibodies) help to strengthen immunity. The ions, such as bicarbonates, chlorides, calcium, magnesium, potassium, and sodium also help to maintain fluid balance and a slightly alkaline pH, as well as assisting in nerve and muscle function.
Join the discussion
With a partner, or in a group of 3, perform a quick internet search of what normal blood sugar levels are, and what levels are considered diabetic. Share your findings with the class.
Debrief:
- Why is extra sugar in the blood harmful for health?
- Why is the disorder called diabetes?
- Synthesize ways to reduce blood sugar levels and evaluate their effectiveness.
Red blood cells
Red blood cells are called erythrocytes and make up approximately 44% of the total blood volume. These cells are specialized for oxygen transport. The number of erythrocytes present and the amount of hemoglobin present in the red blood cells determines the amount of oxygen that can be carried. Red blood cells are produced in the bone marrow at the rate of two million per second. As a red blood cell matures, it loses its nuclei and mitochondria. The loss of these structures causes the red blood cell to become concave on each side, forming its distinctive biconcave or disc shape.
This structure provides a greater surface area for oxygen transfer. This shape also gives the red blood cell the flexibility to pass through blood vessels of different shapes and sizes. One drop of blood contains about five million red blood cells. Each red blood cell is packed with 280 million iron-containing molecules of the respiratory protein, hemoglobin. Hemoglobin binds oxygen in the lungs and releases oxygen in the cells that need it. Oxygen molecules bind to the iron portion of the hemoglobin molecule and this is what gives red blood cells their crimson colour. Hemoglobin also transports some of the carbon dioxide waste from the cells. As carbon dioxide diffuses into the blood, it enters the red blood cells where a small amount binds to the hemoglobin. Red blood cells live for approximately 120 days. As red blood cells age, they break down and the iron from the broken-down red blood cells is recycled in the bone marrow to become new red blood cells.
Platelets
Platelets—also called thrombocytes—are membrane-bound fragments of cells that form when larger cells in the bone marrow break apart. Platelets do not contain nuclei, and they break down in the blood within 7 to 10 days after they have formed. Platelets play a key role in blood clotting.
Blood clotting is a complex process involving several steps:
- When an injury occurs, chemicals are released from the injured cells that attract platelets to the site of the injury.
- The platelets form an initial plug to help stop the bleeding.
- The chemicals that are released also combine with other chemicals in the plasma to produce enzymes.
- These enzymes react with fibrinogen to produce fibrin. Fibrin is an insoluble protein that forms a fibrous mesh over the platelets at the site of the injury.
- This mesh forms a clot to prevent the loss of blood cells.
White blood cells
White blood cells are called leukocytes and are part of your body’s defence system for responding to infections, fighting parasites, and attacking bacteria. White blood cells make up 1% of your total blood volume, but they can increase to more than double the normal levels when your body is fighting an infection. Unlike red blood cells, white blood cells have a nucleus, appear to be colourless, and can live for a number of years. White blood cells are suspended in the blood plasma and are less abundant than red blood cells. On average, a healthy person has one white blood cell for every 500 red blood cells.
There are five main types of white blood cells. The first three, called neutrophils, eosinophils, and basophils, are known as granulocytes, because they have a granular or grainy appearance in their cytoplasm. The other two, called lymphocytes and monocytes, are known as agranulocytes, because of their smooth (non-granular) cytoplasm. These five types of white blood cells will be discussed in more detail in the sections that follow.
Join the discussion
What is a universal blood donor? Share your points with the class.
Blood types and their antigens
| Blood types | Rhesus factor | |||||
|---|---|---|---|---|---|---|
| Type A | Type B | Type AB | Type O | Type + | Type - | |
| Antigen(s) on red blood cell | A | B | A and B | No A No B |
D | No D antigen |
| Antibodies in plasma | Anti-B | Anti-A | No anti-A No anti-B |
Anti-A Anti-B |
No anti-D | Anti-D |
Debrief:
- What are the different blood types?
- What antigens are present on the various blood types?
- What are the antibodies present based on blood type?
- Predict the consequences of providing the improper blood type in a blood transfusion.
- Found in body tissues, as well as in the blood.
- They are formed in your bone marrow and are 9 to 16 μm (micrometres) in size.
- Neutrophils are the most abundant white blood cell, making up about 70% of the total number of white blood cells present.
- They are relatively short-lived, surviving only about six hours. Neutrophils are an essential part of the immune system.
- Neutrophils are easily recognizable because their nucleus is divided into 3 to 6 lobes. They also contain granules in their cytoplasm.
If you have a bacterial infection, neutrophils are among the first cells to respond and migrate to the site of inflammation. Neutrophils die in the process of fighting infection and the remains of their dead cells, along with dead bacteria, are the predominant cells in pus, which is the fluid that builds up around a wound.
- Eosinophils are found in the mucous lining of the digestive and respiratory tracts.
- Have a two-lobed nucleus and also contain granules.
- They measure about 12 to 17 μm across.
- Eosinophils are fairly rare, making up only 1% to 6% of the white blood cells.
- An increase in eosinophils is associated with allergies, asthma, hay fever, and parasitic diseases.
- As with neutrophils, they develop in the bone marrow before migrating into blood. The nucleus in eosinophils tends to stain a dark blue colour, as do the granules.
- Basophils help the immune system by secreting substances that attract phagocytes to destroy pathogens.
- Part of the granulocyte white blood cells, but are the least common of these, as they only represent about 0.01% to 0.3% of circulating white blood cells.
- Range in size from 10 to 14 μm.
- Stain a dark purple colour, on a slide. The granules in the cell are large and mask the nucleus.
- An increase in basophils is observed in allergic reactions, parasitic infections, hemolytic anemia, and chicken pox.
- Lymphocytes produce proteins called antibodies that can detect and destroy pathogens.
- There are two types: small and large cells. The large lymphocytes include natural “killer cells”. The small lymphocytes consist of T-cells and B-cells. T-cells act against virus-infected cells and tumour cells, while B-cells produce antibodies.
- They represent 25% to 30% of the white blood cell count.
- Range in size from 6 to 10 μm.
- These agranulocytes stain a reddish-purple to a blue colour. The large nucleus appears to almost fill the cell.
- An increase in lymphocytes may be observed in diseases like mononucleosis, and in chronic infections.
- Monocytes circulate in the bloodstream for only a few days before they become specialized as macrophages, which destroy bacteria.
- Move quickly (approximately 8 to 12 hours) to the sites of infection in the tissues and divide, or differentiate, into macrophages to elicit an immune response.
- Defend the body against viruses and bacteria.
- Usually identified in stained smears by its large two-lobed nucleus, sometimes shaped like a kidney, and its non-granular appearance. The nucleus stains a purple colour.
- Monocytes are the largest of all of the leukocytes and average between 16 and 20 μm in size.
- They are produced in the bone marrow and represent between 3% and 9% of the leukocytes in the blood.
- An increase in monocytes can be observed in cases of malaria, typhoid fever, and Rocky Mountain spotted fever cases.
Summary
The following table shows a comparison of the cellular components of blood.
| Comparison | Red blood cells | White blood cells | Platelets | |
|---|---|---|---|---|
| Granulocytes | Agranulocytes | |||
| Origin | Bone marrow | Bone marrow | Thymus, bone marrow | Bone marrow |
| Approximate # of cells present per cubic cm of blood | 5,500,000
(male) 4,500,000 (female) |
6,000 | 2,000 | 250,000 |
| Size | Small (8 µm diameter) | Largest (up to 25 µm) | Large (10 µm) | Smallest (2 µm) |
| Function | To carry oxygen and carbon dioxide to and from cells | To engulf foreign particles | To form antibodies | To clot blood |
| Lifespan | 120 days | A few hours to a few days | Unknown | 2–8 days |
| Type of white blood cell | Neutrophils, eosinophils | Lymphocytes, basophils | ||
Checkpoint
Complete the following quick self-assessment before continuing.
| I can… | Yes! I’ve made notes on this, understand it and am good to continue. | I will need to review to strengthen my understanding. |
|---|---|---|
| Explain the components of blood including red blood cells, plasma and platelets | ||
| Compare the different types of white blood cells based on structure and function | ||
| Explain the process of blood clotting |
Take a break!
Excellent work! You have just completed the section on cellular componentd of blood. Now is a great time to take a break before moving on to the rest of this lesson.
Complete blood count
A complete blood count (CBC) measures the number of red blood cells, the number of white blood cells, the total amount of hemoglobin, and the fraction of blood that is composed of red blood cells (the hematocrit). A white blood cell (WBC) count measures two components: the total number of WBCs (leukocytes), and the differential count. The differential count measures the percentages of each type of leukocyte present. White blood cells are composed of granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). White blood cells are a major component of the body’s immune system. The white blood cell count is part of the complete blood cell count. For example, if you were to examine a blood smear and measure 100 white blood cells, 70 of them would be neutrophils, 25 would be lymphocytes, three would be monocytes, one would be an eosinophil, and one would be a basophil.
Disorders of the blood
Click on the tabs to learn more about different blood disorders:
Hemophilia is an inherited disease and is caused by insufficient blood-clotting proteins in the blood. A person with hemophilia bleeds for a longer period of time and is at risk of dying from internal bleeding that may occur from a minor injury. The protein that is in short supply is known as factor VIII. Some hemophiliacs are treated with injections of this substance, which is acquired from the products of blood transfusions.
Hemophilia is sometimes referred to as the “Royal Disease”. The gene that codes for the protein factor VIII was passed from Queen Victoria of England in 1837 to the ruling families of Russia, Spain and Germany.
Another disorder, anemia occurs when the blood contains fewer than normal red blood cells. Anemia can be caused by blood loss and can occur when red blood cells do not carry enough hemoglobin (which is needed for transporting oxygen). The symptoms of anemia include dizziness, fatigue, shortness of breath, headache, and cold hands and feet. Many types of anemia are short-lived and are easily treated with dietary supplements. Severe or chronic anemia, however, can be life-threatening, because the lack of oxygen in the blood can damage the brain, heart, and other organs. A hematocrit test determines the percentage of an individual’s blood that is made up of red blood cells. For this test, a small blood sample is placed in a special hematocrit tube, which is then placed in a centrifuge. The centrifuge spins the tube at a high speed to separate the blood components. The red blood cells are forced to the bottom of the tube because they are the heaviest element in blood. A decreased volume of red blood cells indicates that the patient has anemia.
Sickle-cell anemia is a genetic disease that causes red blood cells to develop a deformity. Instead of the cells having a normal biconcave, circular shape, the red blood cells are in the form of a sickle or crescent shape. These cells are unable to carry oxygen and often get stuck in capillaries. As a consequence, people with this disease suffer from severe anemia. This disease occurs more often in people of African descent.
Many diseases result in an unusually high number of white blood cells in the blood. One of the most common results of disease or infection is an increase in the number of lymphocytes. Doctors can quickly check for signs of an infection by examining the white blood cell count during blood analysis.
Leukemia is a cancer of the white blood cells. It is characterized by the presence of too many white blood cells. These white blood cells, which are immature and unable to fight infection, crowd out the red blood cells, sometimes causing anemia and fatigue. Treatment for leukemia includes blood transfusions—in order to increase the number of red blood cells and healthy white blood cells—and chemotherapy. Another possible treatment is bone marrow transplants, as they provide healthy marrow from which new healthy white blood cells can be reproduced.
Careers in medical technology
Medical technology is a booming industry, thanks to the many advances in technology. Whether you wish to become an X-ray technician, a medical technologist or technician, a cytologist, a hematologist, or a nursing assistant, the medical industry is constantly seeking qualified professionals, and there are many avenues of employment from which to choose. Different careers in medical technology require different certifications. Depending on your skill set and budget, you can find a career that fits your needs. This section describes three types of careers to consider in the field of medical technology.
Medical technologist (MLT)
Medical laboratory technologists perform thousands of medical tests on blood, bodily fluids, and tissues.
The results of these tests provide important information that doctors need, in order to make decisions about their patients’ health. In fact, experts suggest that 70% of all clinical decisions are made on the basis of laboratory testing data. Medical laboratory technologists also work in the field of medical research. Their knowledge and expertise contribute to innovations in the prevention, diagnosis, and treatment of diseases and other medical conditions. The Canadian Society for Medical Laboratory Science (CSMLS) is the national certifying body for medical laboratory technologists and assistants, and is the national professional society for Canada’s medical laboratory professionals. To become a medical technologist, you need to complete a three-year degree in a certified program at the college level.
Medical laboratory technologists work in the fields of:
- Clinical chemistry: the measurement of chemical components of blood and bodily fluids, including hormones and drugs.
- Clinical microbiology: the study of bacteria, fungi, viruses, and parasites that invade the body.
- Diagnostic cytology: the study of cells for the detection of cancer.
- Genetics: the study of chromosomes, DNA, and RNA from cells of bodily fluids and tissues, in order to diagnose genetic diseases.
- Electron microscopy: the preparation of highly magnified photographs of cells in order to capture details that ordinary microscopes cannot detect.
- Hematology: the study of diseases in blood cells and the clotting mechanisms of the blood.
- Immunology: the study of the body’s defence mechanisms against disease.
- Transfusion science: the determination of blood types and cross-matching for transfusion.
- Histology/Pathology: the preparation and study of body tissue for the detection of disease.
Cytologist
A cytologist is a medical professional who specializes in the study of cells. Cytology is the study of the origin, formation, structure, function, and classification of cells. The identification of normal and cancerous cells also falls within this field of study. Cytologists are responsible for specimen preparation and staining, as well as the microscopic evaluation and interpretation of patient samples. One of the roles of the cytologist is to identify cancer of the cervix through the microscopic examination of Pap smears. Cytology results are used in diagnosis, patient management, and follow-up treatment.
Hematologist
A hematologist is a physician who specializes in treating conditions that involve blood. They study the blood and tissues that form blood, such as the spleen and bone marrow. The study of hematology includes the identification, treatment, and management of blood disorders such as hemophilia, leukemia, and sickle-cell anemia. Hematologists are also involved with preventative care. Preventing blood disorders can include everything from the genetic testing of parents believed to be carriers of blood diseases, to the administration of supplements that are designed to prevent anemia in patients who are at risk for the disease. Early diagnosis and treatment also plays a large role in hematology, as doctors want to be able to intervene early on, so that they can address blood conditions before complications develop. Hematologists also deal with issues like blood transfusions, stem cell transplants, and bone marrow transplants. To study to become a hematologist, you would need a university degree.
Safety in medical labs
Safety in a medical lab is important. There are many types of dangerous infectious diseases, such as HIV/AIDS, that can be transmitted through blood, serum, and other bodily fluids. Health professionals and technologists taking blood samples and handling bodily fluids need to learn how to safely handle blood and other hazardous materials found in medical labs. Basic safety precautions must be followed at all times, including:
- Washing your hands frequently.
- Wearing protective equipment, when necessary (for example, gloves, laboratory coats, safety glasses).
- Covering cuts and scrapes on the skin of your hands to lessen the chance of infection.
- Safely disposing of sharp objects like needles and scalpels into a “sharps” container.
To ensure the safety of everyone working with hazardous materials, the Canadian government has created the Workplace Hazardous Materials Information System (WHMIS) to standardize the ways in which hazardous materials are labelled, described, and handled. Training in WHMIS is mandatory for everyone working with hazardous materials, including workers in the health sciences. Next, you can review an online tutorial that explains the WHMIS symbols and safety procedures for handling hazardous materials.
Checkpoint
Complete the following quick self-assessment before continuing.
| I can… | Yes! I’ve made notes on this, understand it and am good to continue. | I will need to review to strengthen my understanding. |
|---|---|---|
| Explain how to calculate a complete blood count | ||
| Describe blood disorders including sickle cell anemia and leukemia | ||
| Compare careers in medical technology |
White blood cell counting activity
One of the instruments most often used in medical technology is the microscope. Medical technologists working in hematology use the microscope to recognize the type and number of white blood cells for a WBC count. In this online activity, you will learn about the procedure that is used in laboratories to produce accurate white blood cell counts.
The following table provides a review of the different types of white blood cells that would be observed in a white blood cell count.
| Type | Appearance (micrograph) | Appearance (illustration) | Main targets | Characteristics |
|---|---|---|---|---|
| Neutrophil |  |
 |
Bacteria Fungi |
Multilobed nucleus |
| Eosinophil |  |
 |
Larger parasites Modulate allergic inflammatory responses |
Bi-lobed nucleus Many red stained granules |
| Basophil |  |
 |
Release histamine for inflammatory responses |
Bi-lobed or tri-lobed nucleus |
| Lymphocyte |  |
  |
B cells: releases antibodies and assists activation of T cells T cells: kills cells as needed |
Large, fills almost whole cell |
| Monocyte |  |
 |
Monocytes migrate from the bloodstream to other tissues and differentiate into tissue resident macrophages, |
Kidney shaped nucleus |
Explore
Explore these blood cell smears to give you an idea of what you would observe under the microscope if you were counting white blood cells. Sample data for an actual white blood cell count is provided next.
White blood cells identification
The five types of white blood cells can be identified by examining the features of a blood smear taken from a healthy patient under a microscope.
Multiple fields of view from the same blood smear slide are examined. In each view, the type(s) of white blood cells present are identified. A count of each type of WBC is recorded in a table like the one shown next:
| Number in field | |||||
|---|---|---|---|---|---|
| Field # | Neutrophils | Lymphocytes | Monocytes | Eosinophils | Basophils |
| 1 | 0 | 0 | 2 | 0 | 0 |
| 2 | 0 | 1 | 0 | 0 | 0 |
| 3 | 1 | 0 | 0 | 0 | 0 |
| 4 | 1 | 0 | 0 | 0 | 0 |
| 5 | 0 | 1 | 0 | 0 | 0 |
| 6 | 1 | 0 | 0 | 0 | 0 |
| 7 | 1 | 0 | 0 | 0 | 0 |
| 8 | 2 | 0 | 0 | 0 | 0 |
| Total | 6 | 2 | 2 | 0 | 0 |
| Percent (total/10) x 100 |
60% | 20% | 20% | 0% | 0% |
The reason for examining multiple fields of view from the same slide is because a blood smear slide is larger than the field of view available under high magnification. In order to observe enough cells to get a valid count, a technologist needs to move the slide around and examine more than one field of view. In the example table you just examined, only 8 separate fields of view are recorded. In a medical lab, the technologist would normally observe through many fields of view in order to count 100 white blood cells.
Analysis
Examine the results from the sample of white blood cells. Can the results from the sample lead to the diagnosis of a specific health condition or multiple possible conditions (it isn’t always possible to get a 100% certain diagnosis). For example, allergies, an infection and/or leukemia.