Blood

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Blood Objectives

Describe the composition of blood, including the relative amounts and roles of red blood cells (RBCs), white blood cells (WBCs), and platelets.
Identify RBCs, platelets, and the five different types of WBCs under the microscope.
Distinguish between A, B, AB and O blood types as well as Rh positive and negative blood, and explain why individuals can only accept certain donor blood.

Humans have been aware of the significance of blood for thousands of years. In the time of Aristotle in Ancient Greece approximately 2300 years ago, all body fluids were considered to be a type of “blood,” even tears, urine, and mucus. The names may have changed, but we understand blood is essential to human life, and loss of blood is life-threatening.

Many animals, including some humans, have a strong physiological response to the sight, smell, or taste of blood. This would make evolutionary sense, avoiding blood loss could be critical for survival.

Unfortunately, this makes thinking about blood challenging for many people. We’ll do our best to limit potentially disturbing imagery and topics while introducing this amazing substance.

We’ll start with an overview of basic blood components.

You can select the closed captioning “cc” option if you would like to see the text.

Neither Mark or I were keen on providing a test tube of blood to show the components; so Mark came up with a handmade solution.

If you have kids at home, they may literally eat this up while learning a bit of biology.

Blood cells are tiny, so we use models, posters, and microscopic specimens to study normal blood characteristics.

As you go through the next three videos, list in your notes the five types of white blood cells and characteristics (like frequency, shape, and color) that you can use to tell them apart.

In this guide we are learning what the five WBCs are; we will focus on what they specifically do in an upcoming guide on Defense Systems. At that point you will be using the notes you take today on WBC features.

Most of human blood is the plasma fluid and red blood cells. That doesn’t mean the white blood cells and platelets are insignificant. This video demonstrates how a patient’s slide can be scanned to view white blood cells. Note the most frequently found white blood cells in this specimen.

Views of an eosinophil and monocyte at 400x magnification.

A (one) basophil on the entire slide, at 600x.

Here is a gallery of blood components to supplement your notes. There are hints of white blood cell functions; there is more information on this in an upcoming guide.

Blood Components

Erythrocyte

Also known at a red blood cell, or RBC. It’s primary function is to carry oxygen and it may also carry some carbon dioxide (the rest of the CO2 may be dissolved in blood plasma).

Platelet

Once part of a larger cell in the bone marrow, each platelet has the potential to form part of a fibrin clot.

Neutrophil

This cell is one of the three granulocytes, along with eosinophils and basophils. Neutrophils have vesicles that do not pick up much stain. Their role is to eat up debris in a wound, including pathogens.

Lymphocyte

Smaller than the other WBCs, this cell is mostly nucleus with very little visible cytoplasm. When activated, these cells have a variety of methods for destroying pathogens.

Monocyte

This is the largest of the WBCs with a large nucleus that sometimes looks like it has a dent in it. Monocytes can eat debris, including pathogens and play a critical role in activating other WBCs to attack pathogens.

Eosinophil

A type of granulocyte with pink-staining vesicles. The chemicals in these vesicles can destroy parasites like tiny worms.

Basophil

A type of granulocyte with blue-staining vesicles. The chemicals in these vesicles can activate a large inflammation response against parasites.

Plasma

Blood plasma is mostly water, with a wide variety of other substances including: nutrients, hormones, chemical wastes, and more.

You may have had your blood “typed” at some point in your life. Now we’ll examine what blood type indicates and why it is important.

Now, check your understanding of blood type by answering the questions in the next video.

The plasma membrane that surrounds cells has to let some things into the cell, move some substances out of the cell, and block other substances completely. This video introduces the process of diffusion.

Sometimes coming at the same concept from different directions helps solidify the memory. On a cellular level, different representations (visual, audio, tactile) may result in more synaptic connections between neurons in the cerebral cortex of the brain. In case you would like one more look at blood typing, there is an additional video on this guide’s resource page.

Resources

The next section introduces the impact of aerobic exercise on the cardiovascular system.

Check your knowledge. Can you:

describe the composition of blood, including the relative amounts and roles of red blood cells (RBCs), white blood cells (WBCs), and platelets?
identify RBCs, platelets, and the five different types of WBCs under the microscope?
distinguish between A, B, AB and O blood types as well as Rh positive and negative blood, and explain why individuals can only accept certain donor blood?