Introduction To Blood - Online Tutor, Practice Problems & Exam Prep

Blood is a specialized liquid connective tissue essential for life, comprising erythrocytes (red blood cells), leukocytes (white blood cells), platelets, and plasma. It performs vital functions including transport of oxygen (O₂), nutrients, and waste products; regulation of body temperature and pH; and protection against blood loss and infection. The hematocrit, indicating the percentage of blood volume made up of red blood cells, is crucial for assessing health. Plasma, the liquid extracellular matrix, contains proteins like albumin and electrolytes, maintaining fluid balance and supporting various physiological processes.

Functions of Blood

In this video, we're going to talk about blood and the functions of blood. And so, we already know from some of our past life experiences of getting injured and from some of our previous lesson videos that blood is a red, viscous, or thick, specialized liquid connective tissue of the cardiovascular system, which, recall, includes the heart, the blood itself, and the blood vessels that project throughout the body. In fact, technically, blood is the only liquid tissue in the body, which is pretty interesting to note. And again, we know that blood is a reddish color, but the shading of red can actually vary depending on the oxygen content of the blood. And so, blood tends to be a bright red color with high oxygen content, and it tends to be a darker red color with lower oxygen content. And again, blood is quite viscous or thick, and so it tends to be more dense than water and also stickier than water as well. Now, blood is also slightly alkaline or slightly basic in terms of its pH, and it has a pH that is slightly above 7. More specifically, the pH tends to be in this specific range of 7.35 to 7.45, and it's critical for the blood to be able to maintain this specific pH range for all of its components to function properly. Now, there is quite a lot of blood in a typical human body. In fact, adults tend to have somewhere between 4 to 6 liters of blood in the body, which is equivalent to about one to one and a half gallons of blood. And that makes up about 8% of the total body mass, and so again, that's a pretty significant amount of blood in the human body. And, once again, we already know that blood is crucial in supporting life. We know this from a young age. Losing blood is not something that's good. And this is because blood actually carries out many different functions, including these three functions that are essential that we have listed down below in our table, which are transport, regulation, and protection.

So in terms of transport, the blood can actually serve as a vehicle to help deliver oxygen gas or O₂, nutrients such as glucose, for example, and several different types of hormones to the body cells. And so, notice in this image, we've got a picture of the lungs, which allows us to inhale oxygen gas. And again, the blood can help to serve as a vehicle to deliver that oxygen gas to tissues and cells throughout the body. Blood can also help to transport waste products as well, such as, for example, carbon dioxide gas, and it will transport those waste products to elimination sites. And so again, the tissues and cells throughout our body will produce carbon dioxide gas as a waste, and the blood can transport that waste to the elimination site, which in this case is the lungs, and that allows us to exhale the carbon dioxide gas into the environment.

Now, the next function that we have here is regulation, and the blood can help regulate the body in several different ways. It can help to maintain body temperature since the blood is a source of heat. And recall from our previous lesson videos on the integumentary system that the blood vessels near the surface of the skin can actually vasoconstrict or narrow down when it's really cold outside. When it does that, it reduces blood flow toward the surface of the skin, and that helps our bodies maintain heat during cold conditions since it is going to prevent heat loss from the blood to the environment. In the opposite conditions, when it's really hot outside, the blood vessels near the surface of the skin dilate, and that increases blood flow to the surface of the skin, and so that is going to help facilitate heat loss from the blood to the environment, helping cool us down under hot conditions. Now, the blood also has buffers in it that help maintain the optimal pH range, which recall blood is slightly alkaline with a pH range of about 7.35 to 7.45, and it's critical that the blood is able to maintain that specific range. Again, it uses buffers in order to do that. Lastly, the blood has proteins that allow it to maintain fluid volume in the cardiovascular system, and so this helps to ensure that not too much fluid is lost from the blood into the surrounding tissues.

Now, the final function that we have here is protection. The blood can help protect our bodies by helping to prevent blood loss after an injury since blood has proteins in it that allow it to form blood clots that block and reduce blood loss after an injury. And so, notice here in this image, you can see that there's a cut in this person's hand. But notice that shortly after the cut is made, there's a blood clot that forms, and that reduces blood loss and ultimately helps to protect our body. Also, the blood can help to prevent infection since it has immune cells that help defend against invaders and pathogens. So, this here concludes our brief lesson on blood and the functions of blood, and as we move forward in our course, we'll be able to learn a lot more. So I'll see you all in our next video.

Introduction to Blood Example 1

So here we have an example problem that asks, which of the following functions is not primarily associated with blood? And we've got these 4 potential answer options down below. Now, option A says transport of hormones from endocrine glands to target organs. And, of course, recall from our previous lesson videos that endocrine glands will secrete their products, which are hormones, into the bloodstream. And we know that the bloodstream essentially serves as a highway that reaches almost every part of our body. And so we know that the blood is able to transport these hormones to their specific target organs. And so, again, option A is a function associated with blood. So for that reason, we can cross it off because again, we're looking for the function that is not primarily associated with blood. Now option B says regulation of pH balance by buffering acidic and alkaline substances. And so recall from our last lesson video that the pH of blood is maintained at a slightly basic range of 7.35 to 7.45. And so in order to maintain that very specific pH range, it does utilize buffers. And so it does regulate pH through the use of buffers, and it is able to buffer acidic and alkaline substances. So option B, again, is a function associated with blood. We can cross it off because we're looking for the function that is not associated with blood. Now option C says production of digestive enzymes for breaking down food in the stomach. Now this is something that we have not talked about in our previous lesson videos being associated with blood. In fact, this is not a function of blood, and it is more so the function of epithelial cells that are lining the stomach. And so for that reason, we can indicate that C here is the function that is not primarily associated with blood. So C here is the correct answer to this problem. Now just to be short, let's check option D, which says removal of metabolic waste products such as carbon dioxide and urea. And again, we know that the blood is able to transport these metabolic wastes and transport them to their elimination sites. So carbon dioxide elimination site would be our lungs, and urea, the elimination site would be the kidneys, through the urine. And so, option D again is associated with blood, and so we can cross it off. And again, option C is the correct answer, so that concludes this problem, and I'll see you all in our next video.

Composition of Blood

In this video, we're going to talk about the composition of blood. Blood can actually be separated out into three components that we have numbered down below in the text, 1, 2, and 3. Now before we cover each of these three components of blood, let's first recall from our previous lesson videos that blood is a type of specialized liquid connective tissue. And like all tissues, it consists of living cells and a nonliving extracellular matrix. Notice, this is exactly what we're indicating on the right side, that these three components of blood are either considered living cells or cell fragments that we call formed elements, or they are considered part of the nonliving extracellular matrix.

The very first component of blood listed in our lesson is the erythrocytes, commonly known as red blood cells and abbreviated as RBCs. Erythrocytes are the most numerous type of cell in the blood, making them the main cell type. As their name implies, their components give them a reddish color. Because they are the most numerous cell type in the blood, this is what gives our blood that reddish color. Functionally, these erythrocytes are adapted for gas transport, specifically oxygen (O2 gas) and carbon dioxide (CO2 gas) transport.

The term hematocrit is highly linked to erythrocytes. The hematocrit represents the percentage of the total blood volume that is composed of red blood cells. It is an important value because it can give medical professionals insight into the overall health of their patients. If the value falls outside of the normal range, that could indicate a problem with the patient. The normal range for the hematocrit is somewhere between 36-50, and males tend to have a higher hematocrit than females. Let's say that the hematocrit value for a specific patient is about 45. This means that 45% of the total blood volume is made up of red blood cells.

The second component of blood is the buffy coat, named after its color since it has this light buff type of color. The buffy coat consists of white blood cells, also known as leukocytes, which are important for providing immunity, and platelets, also known as thrombocytes. These are cell fragments that are important for the blood clotting process, which helps to reduce blood loss during an injury.

Lastly, the third and final component of the blood is the plasma, the nonliving extracellular matrix. Plasma is a liquid extracellular matrix, consisting of 90% water, with electrolytes such as sodium ions and chloride ions, and various proteins dissolved in it, such as albumin, globulins, and fibrinogen, which are plasma proteins that we'll talk more about later in our course.

Notice that initially, the blood is pretty homogeneous, meaning that the components of the blood are evenly distributed throughout the tube. After being inserted into a centrifuge, which spins the sample very fast, it can separate the blood components based on their densities, where more dense components end up closer toward the bottom of the vial. Now, visually distinguishable, we can see the erythrocytes at the bottom in red. The hematocrit, represented here as 45%, indicates the volume percentage of red blood cells for this particular patient. Above it, the thin layer represents the buffy coat, making up less than 1% of the total blood volume. At the top, we see the plasma in yellow, making up about 55% of the total blood volume. This concludes our brief lesson on the composition of blood, and I'll see you all in our next video.

Introduction to Blood Example 2

So here we have a pretty straightforward example problem that says label the pie chart representing the components of blood. And so notice down below we've got this pie chart, and we've got these three interactive blanks that we need to fill in. Now we are going to start with this red portion over here, and of course, we know from our last lesson video that this must represent the red blood cells or the erythrocytes. And so here in this blank, you can fill in either erythrocytes, red blood cells, or you could put RBCs as the abbreviation for red blood cells. Now the red blood cells can make up anywhere between about 36 to about 50% of the total blood volume under normal circumstances. And so notice over here, we're indicating that it's taking up about 45% of the total blood volume or 45% of the pie chart. And recall that this percentage of the total blood volume made up specifically by red blood cells is referred to as the hematocrit. Now the next region that we're going to look at is this tiny sliver that you can see here, and this is going to be the buffy coat. And recall that the buffy coat is going to consist of white blood cells or leukocytes and platelets as well. And then last but not least, we have this yellow region over here. This is going to represent the blood plasma, which recall is the liquid extracellular matrix. It's made up of 90% water with dissolved electrolytes and dissolved proteins. And the plasma can make up the vast majority of the total blood volume. Here, we're indicating that it's making up about 55% of the total blood volume. And you can see those ions, those electrolytes dissolved here in the plasma. And so this here concludes our example problem, and I'll see you all on our next video.

Plasma accounts for _____% of all blood, and water accounts for _____% of plasma.

• A. 55;90
• B. 90;55
• C. 45;55
• D. 55;45

The most numerous formed element in blood are the ____________, and their function is ____________.

• A. Platelets; to prevent bleeding from open wounds.
• B. White blood cells; to carry oxygen.
• C. White blood cells; to fight infection.
• D. Erythrocytes; to carry oxygen and CO₂

Here’s what students ask on this topic:

What are the main functions of blood in the human body?

Blood performs several vital functions in the human body, including transport, regulation, and protection. It transports oxygen (O₂), nutrients, and hormones to cells, and removes waste products like carbon dioxide (CO₂). Blood also helps regulate body temperature and pH levels, maintaining a slightly alkaline pH range of 7.35 to 7.45. Additionally, blood protects the body by forming clots to prevent blood loss after injuries and by using immune cells to defend against infections.

What is the composition of blood?

Blood is composed of three main components: erythrocytes (red blood cells), leukocytes (white blood cells), and platelets, collectively known as formed elements, and plasma. Erythrocytes are the most numerous and are responsible for gas transport. Leukocytes provide immunity, and platelets are crucial for blood clotting. Plasma, the liquid extracellular matrix, makes up about 55% of blood volume and consists of 90% water, electrolytes, and proteins like albumin, globulins, and fibrinogen.

What is hematocrit and why is it important?

Hematocrit is the percentage of the total blood volume that is composed of red blood cells (erythrocytes). It is an important measure because it provides insight into a patient's overall health. Normal hematocrit values range from 36% to 50%, with males typically having higher values than females. Deviations from the normal range can indicate various health issues, such as anemia or polycythemia.

How does blood help regulate body temperature?

Blood helps regulate body temperature through its heat distribution properties. When it's cold, blood vessels near the skin's surface constrict (vasoconstriction) to reduce blood flow and heat loss. Conversely, when it's hot, these vessels dilate (vasodilation) to increase blood flow and facilitate heat loss, cooling the body. This thermoregulatory function is crucial for maintaining a stable internal environment.

What role do buffers in blood play in maintaining pH levels?

Buffers in blood help maintain its slightly alkaline pH range of 7.35 to 7.45. These buffers, such as bicarbonate ions (HCO₃^-), neutralize excess acids or bases, preventing significant pH fluctuations. This stability is essential for the proper functioning of enzymes and other biochemical processes in the body.