If there is bacteria in our blood and there is only 1% of white blood cells, wouldn't that take a long time to dispose of the bacteria?

Most bacteria is good and makes our body function better. If we didn't have any bacteria in our body, we would die. A lot of the bacteria which gets into your body will actually help fight off bad bacteria, viruses, etc! A very small percentage of the bacteria in our body is bad, so when there is one, the white blood cells in addition to some of the good bacteria will help fight it off. 1% is actually plenty, because if the body can get to it before it multiplies constantly, then it can get rid of the bad thing quickly and we won't even know we were sick.

Are erythrocytes (after maturation) still considered cells of the body? (No nucleus, etc)

Yes they are still considered cells if they stared of with a nucleus in which they did. so still have the functions of a cell. if it wasn't a cell how could it die?

how have we evolved if we have such a complicatid biology?

Think of single-celled organisms. They are among the first of all life-forms, and they are incredibly simplistic. Evolution is the process of becoming better and adapting, therefore advanced beings have advanced biology. It would definitely be hard for an amoeba to formulate the answer to a differential equation with simple flagellate motions. However, our brains are capable of doing so thanks to the multiple support systems, which are complicated biology. Hope this helped!

I thought red blood cells are already larger in diameter than the smallest capillaries, so that they have to squeeze through. but now white blood cells are even larger? Don't they also have to travel through the same capillaries?

Firstly, there are three types of capillaries in our body - continuous, fenestrated and sinusoid. The major difference n these three types are that continuous capillaries are less permeable than fenestrated, having sinusoid to be the most permeable and big-sized capillaries in our body. Apparently, the main functions of these types vary accordingly with the permeablity of the vessels and for sinusoid, as it is the largest capillary, allows larger molecules to flow through it, including white blood cells of any kind. Another idea unrelated to this also explains that the role of leukocytes are to fend off external breaches by activating immune system, phagocytosis, releasing substances, etc. Thus, leukocytes are able to escape through any vessel walls to arrive at the needed regions of the body ASAP. So they do not have to pass through the capillaries. I've checked some biology sites and these are all informations I could gather, hope it helps :).

What is the amount of time platelets use to clot where a person injured his or herself?

The normal value of clotting time is 8 to 15 minutes https://en.wikipedia.org/wiki/Clotting_time I do not recommend testing it by cutting yourself on purpose.

The text says: ''Red blood cells, white blood cells, and platelet-producing cells are all descended from a common precursor: a hematopoietic stem cell.'' My question is: Where are hematopoietic stem cells produced? I'm referring to the section: Stem cells and blood cell production.

Hematopoietic stem cells reside in the bone marrow.

How many red blood cells are produced every day? And how come our bodies don't OVERproduce? Can you have too many red blood cells?

I got this from the Internet, but I think it will help. Approximately 2.4 million new erythrocytes are produced per second in human adults. In a normal adult about half a liter are produced by the bone marrow every week. High red blood cell count - high red cells count is caused by a disorder called Polycythemia Vera. This is a genetic condition that causes the bone marrow to produce too many blood cells. People with polycythemia have an increase in hematocrit, hemoglobin, or red blood cell count above the normal limits. for more information visit : - http://www.medicinenet.com/polycythemia_high_red_blood_cell_count/article.htm I know this page has a lot of ads and Spam, but it also has some valuable information

would the components of blood be effected by your blood type?

Yes. Platelets and especially plasma have their own traits that are influenced by one's blood type. Plasma, for instance, can carry anti-A antibodies, anti-B antibodies, both antibodies, or none depending on blood type. This is why blood type still must be considered for plasma and platelet transfusions. Does that help?

Why is a stem cell an ethical issue?

While everybody has stem cells, the cells used for research primarily come from human embryos. Here's the problem: when you harvest stem cells from an embryo, you destroy it. Killing a human being is typically viewed as murder; however, this being an unborn child raises several questions. Would it still be classified as murder if the child was never born? Can it even be classified as murder if the human being was very early in development, to the point where it was still only a mass of cells? Does it feel anything at that point? Is it part of the woman's body, or is it its own being? Much of the questions asked about the matter tie closely to the issue of abortion. It is an ethical issue because when exactly something becomes its own being is unclear, and there is a clear and significant pro (forwarding science for the better) and a clear and significant con (the death of a potential child) to be seen. There is no definite answer to this question, and it is ultimately up to your morals and views to give you the answer. Does this help?

The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in the cell. The nucleus is surrounded by a structure called the nuclear envelope. This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus. Chromosomes contain DNA which provides the genetic information necessary for the production of other cell components and for the reproduction of life.

Main content

Course: Biology library > Unit 33

Lesson 1: Circulatory and pulmonary systems

Components of blood

Google Classroom

The different components that make up blood. Plasma, white blood cells, red blood cells, platelets.

Introduction

If you prick your finger or scrape your knee, you'll see some droplets of blood form. Just by eye, these droplets may seem to be made of uniform red liquid, similar to food coloring or paint. However, if you were to look under a microscope, you would see that your blood is actually a mixture of liquid and cells. And if you could zoom in even further, you would see that there are also many macromolecules (such as proteins) and ions (such as sodium) floating in the liquid. All of these components are important to the roles blood plays in the body.

What is blood?

Blood, by definition, is a fluid that moves through the vessels of a circulatory system. In humans, it includes plasma (the liquid portion), blood cells (which come in both red and white varieties), and cell fragments called platelets.

Plasma is the main component of blood and consists mostly of water, with proteins, ions, nutrients, and wastes mixed in.
Red blood cells are responsible for carrying oxygen and carbon dioxide.
Platelets are responsible for blood clotting.
White blood cells are part of the immune system and function in immune response.

Cells and platelets make up about

45

%

percent of human blood, while plasma makes up the other

55

%

percent. The diagram below shows red blood cells, white blood cells of different types (large, purple cells), and platelets.

Plasma

Plasma, the liquid component of blood, can be isolated by spinning a tube of whole blood at high speeds in a centrifuge. The denser cells and platelets move to the bottom of the tube, forming red and white layers, while the plasma remains at the top, forming a yellow layer.

The plasma is about

90 %

water, with the remaining

10 %

made up of ions, proteins, nutrients, wastes, and dissolved gases. The ions, proteins, and other molecules found in plasma are important for maintaining blood pH and osmotic balance, with albumin (the main protein in human plasma) playing a particularly important role.

Some of the molecules found in the plasma have more specialized functions. For example, hormones act as long-distance signals, antibodies recognize and neutralize pathogens, and clotting factors promote blood clot formation at the site of wounds. (Plasma that’s been stripped of its clotting factors is called serum.) Lipids, such as cholesterol, are also carried in plasma, but must travel with escort proteins because they don’t dissolve in water.

Red blood cells

Red blood cells, or erythrocytes, are specialized cells that circulate through the body and deliver oxygen to tissues. In humans, red blood cells are small and biconcave (thinnest in the center, just

7

-

8

μm

in size), and do not contain mitochondria or a nucleus when mature.

These characteristics allow red blood cells to effectively perform their task of oxygen transport. Small size and biconcave shape increase the surface area-to-volume ratio, improving gas exchange, while lack of a nucleus makes additional space for hemoglobin, a key protein used in oxygen transport. Lack of mitochondria keeps red blood cells from using any of the oxygen they’re carrying, maximizing the amount delivered to tissues of the body.

_Image modified from "Modified sickle cell," by NHLBI (public domain)._

In the lungs, red blood cells take up oxygen, and as they circulate through the rest the body, they release the oxygen to the surrounding tissues. Red blood cells also play an important role in transport of carbon dioxide, a waste product, from the tissues back to the lungs. Some of the carbon dioxide binds directly to hemoglobin, and red blood cells also carry an enzyme that converts carbon dioxide into bicarbonate. The bicarbonate dissolves in plasma and is transported to the lungs, where it's converted back into carbon dioxide and released.

Red blood cells have an average life span of

120

days. Old or damaged red blood cells are broken down in the liver and spleen, and new ones are produced in the bone marrow. Red blood cell production is controlled by the hormone erythropoietin, which is released by the kidneys in response to low oxygen levels. This negative feedback loop ensures that the number of red blood cells in the body remains relatively constant over time.

Platelets and clotting

Platelets, also called thrombocytes, are cell fragments involved in blood clotting. They are produced when large cells called megakaryocytes break into pieces, each one making

2000

-

3000

platelets as it comes apart. Platelets are roughly disc-shaped and small, about

2

-

4

μm

in diameter.

When the lining of a blood vessel is damaged (for instance, if you cut your finger deeply enough for it to bleed), platelets are attracted to the wound site, where they form a sticky plug. The platelets release signals, which not only attract other platelets and make them become sticky, but also activate a signaling cascade that ultimately converts fibrinogen, a water-soluble protein present in blood plasma, into fibrin (a non-water soluble protein). The fibrin forms threads that reinforce the platelet plug, making a clot that prevents further loss of blood.

_Image modified from Components of the blood: Figure 4, by OpenStax College, Biology (CC BY 4.0)._

White blood cells

White blood cells, also called leukocytes, are much less common than red blood cells and make up less than

1 %

of the cells in blood. Their role is also very different from that of red blood cells: they are primarily involved in immune responses, recognizing and neutralizing invaders such as bacteria and viruses.

White blood cells are larger than red blood cells, and unlike red blood cells, they have a normal nucleus and mitochondria. White blood cells come in five major types, and these are divided into two different groups, named for their appearance under a microscope.

One group, the granulocytes, includes neutrophils, eosinophils, and basophils, all of which have granules in their cytoplasm when stained and viewed on a microscope.
The other group, the agranulocytes, includes monocytes and lymphocytes, which do not have granules in the cytoplasm.
A diagram of 5 different white blood cells, shown in 2 different columns. There are sketches of 3 different cells in the first column labeled neutrophil, eosinophil, and basophil. Underneath the cells in column 1 is the label granulocytes. There are sketches of 2 different cells in the second column, labeled monocyte and lymphocyte. Underneath the cells in column 2 is the label agranulocytes.
_Image modified from "Components of the blood: Figure 3," by OpenStax College, Biology (CC BY 4.0)._

Each type of white blood cell plays a specific role in defense. For example, some white blood cells are involved in engulfing and breaking down pathogens, while others recognize specific microorganisms and launch immune responses against them. Different types of white blood cells have different lifetimes, ranging from hours to years, and new cells are produced primarily in the bone marrow (although some are made or mature in the thymus, lymph nodes, and spleen).

Stem cells and blood cell production

Red blood cells, white blood cells, and platelet-producing cells are all descended from a common precursor: a hematopoietic stem cell.

A hallmark of stem cells is that they divide asymmetrically. That is, one daughter cell remains a stem cell of the same type, while the other daughter cell acquires a new identity. For hematopoietic stem cells, which are found in the bone marrow, one daughter cell remains a hematopoietic stem cell, while the other goes on to become a different type of stem cell: either a myeloid stem cell or a lymphoid stem cell.

Image modified from "Hematopoietic system of bone marrow," by OpenStax College, Anatomy & Physiology (CC BY 3.0).

The myeloid stem cells and lymphoid stem cells also divide asymmetrically, with their non-stem cell daughters generating the mature cell types of the blood. Myeloid stem cells give rise to red blood cells, platelets, and some types of white blood cells, while lymphoid stem cells give rise to the types of white blood cells classified as lymphocytes.

Image modified from "Hematopoietic system of bone marrow," by OpenStax College, Anatomy & Physiology (CC BY 3.0).

Hematopoietic, myeloid, and lymphoid stem cells divide throughout a person's lifetime, generating new blood cells to replace old and worn-out ones.

Attribution:

This article is a modified derivative of the following articles:

"Components of the blood," by OpenStax College, Biology (CC BY 4.0).
"Production of the formed elements," by OpenStax College, Anatomy & Physiology (CC BY 3.0).

The modified article is licensed under a CC BY-NC-SA 4.0 license.

Additional references:

Hematopoietic stem cell. (2016, February 16). Retrieved March 16, 2016 from Wikipedia: https://en.wikipedia.org/wiki/Hematopoietic_stem_cell.

Purves, W. K., Sadava, D. E., Orians, G. H., and Heller, H.C. (2003). Blood: A fluid tissue. In Life: The science of biology (7th ed., pp. 954-956). Sunderland, MA: Sinauer Associates.

Purves, W. K., Sadava, D. E., Orians, G. H., and Heller, H.C. (2003).

{CO}_{2}

is transported as bicarbonate ions in the blood. In Life: The science of biology (7th ed., pp. 935-936). Sunderland, MA: Sinauer Associates.

Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J. B., and Singer, S. R. (2014). The components of blood. In Biology (10th ed., AP ed., pp. 1018-1021). New York, NY: McGraw-Hill.

Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., and Jackson, R. B. (2011). Blood composition and function. In Campbell biology (10th ed., pp. 928-931). San Francisco, CA: Pearson.

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Kelly
Posted 8 years ago. Direct link to Kelly's post “If there is bacteria in o...”
If there is bacteria in our blood and there is only 1% of white blood cells, wouldn't that take a long time to dispose of the bacteria?
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(9 votes)
Answer
- Ian Cox
  Posted 8 years ago. Direct link to Ian Cox's post “Most bacteria is good and...”
  Most bacteria is good and makes our body function better. If we didn't have any bacteria in our body, we would die. A lot of the bacteria which gets into your body will actually help fight off bad bacteria, viruses, etc! A very small percentage of the bacteria in our body is bad, so when there is one, the white blood cells in addition to some of the good bacteria will help fight it off. 1% is actually plenty, because if the body can get to it before it multiplies constantly, then it can get rid of the bad thing quickly and we won't even know we were sick.
  Comment on Ian Cox's post “Most bacteria is good and...”
  (15 votes)
😊
Posted 8 years ago. Direct link to 😊's post “what is nucleus”
what is nucleus
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Answer
- SpinosaurusRex
  Posted 8 years ago. Direct link to SpinosaurusRex's post “The nucleus is a membrane...”
  The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in the cell.
  
  The nucleus is surrounded by a structure called the nuclear envelope. This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus. Chromosomes contain DNA which provides the genetic information necessary for the production of other cell components and for the reproduction of life.
  Comment on SpinosaurusRex's post “The nucleus is a membrane...”
  (25 votes)
Rosse
Posted 8 years ago. Direct link to Rosse's post “how have we evolved if we...”
how have we evolved if we have such a complicatid biology?
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(5 votes)
Answer
- Wugee
  Posted 8 years ago. Direct link to Wugee's post “Think of single-celled or...”
  Think of single-celled organisms. They are among the first of all life-forms, and they are incredibly simplistic. Evolution is the process of becoming better and adapting, therefore advanced beings have advanced biology. It would definitely be hard for an amoeba to formulate the answer to a differential equation with simple flagellate motions. However, our brains are capable of doing so thanks to the multiple support systems, which are complicated biology.
  
  Hope this helped!
  Button navigates to signup page
  (12 votes)
Seye.Solabomi
Posted 7 years ago. Direct link to Seye.Solabomi's post “What is the amount of tim...”
What is the amount of time platelets use to clot where a person injured his or herself?
Button navigates to signup pageComment on Seye.Solabomi's post “What is the amount of tim...”
(4 votes)
Answer
- Ivana - Science trainee
  Posted 4 years ago. Direct link to Ivana - Science trainee's post “The normal value of clott...”
  The normal value of clotting time is 8 to 15 minutes
  
  https://en.wikipedia.org/wiki/Clotting_time
  
  I do not recommend testing it by cutting yourself on purpose.
  Button navigates to signup page
  (13 votes)
Ev
Posted 8 years ago. Direct link to Ev's post “I thought red blood cells...”
I thought red blood cells are already larger in diameter than the smallest capillaries, so that they have to squeeze through. but now white blood cells are even larger? Don't they also have to travel through the same capillaries?
Button navigates to signup pageButton navigates to signup page
(5 votes)
Answer
- Jonathan Widarsa
  Posted 8 years ago. Direct link to Jonathan Widarsa's post “Firstly, there are three ...”
  Firstly, there are three types of capillaries in our body - continuous, fenestrated and sinusoid. The major difference n these three types are that continuous capillaries are less permeable than fenestrated, having sinusoid to be the most permeable and big-sized capillaries in our body. Apparently, the main functions of these types vary accordingly with the permeablity of the vessels and for sinusoid, as it is the largest capillary, allows larger molecules to flow through it, including white blood cells of any kind.
  
  Another idea unrelated to this also explains that the role of leukocytes are to fend off external breaches by activating immune system, phagocytosis, releasing substances, etc. Thus, leukocytes are able to escape through any vessel walls to arrive at the needed regions of the body ASAP. So they do not have to pass through the capillaries.
  
  I've checked some biology sites and these are all informations I could gather, hope it helps :).
  Button navigates to signup page
  (8 votes)
YEBrandy
Posted 8 years ago. Direct link to YEBrandy's post “Are erythrocytes (after m...”
Are erythrocytes (after maturation) still considered cells of the body? (No nucleus, etc)
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(6 votes)
Answer
- Ariadne
  Posted 8 years ago. Direct link to Ariadne's post “Yes they are still consid...”
  Yes they are still considered cells if they stared of with a nucleus in which they did. so still have the functions of a cell. if it wasn't a cell how could it die?
  Comment on Ariadne's post “Yes they are still consid...”
  (4 votes)
Silvana
Posted 8 years ago. Direct link to Silvana's post “The text says: ''Red bloo...”
The text says: ''Red blood cells, white blood cells, and platelet-producing cells are all descended from a common precursor: a hematopoietic stem cell.''
My question is: Where are hematopoietic stem cells produced?
I'm referring to the section: Stem cells and blood cell production.
Button navigates to signup pageButton navigates to signup page
(3 votes)
Answer
- Kevin D. Fettel
  Posted 8 years ago. Direct link to Kevin D. Fettel's post “Hematopoietic stem cells ...”
  Hematopoietic stem cells reside in the bone marrow.
  Comment on Kevin D. Fettel's post “Hematopoietic stem cells ...”
  (3 votes)
keilahvillasana
Posted 8 years ago. Direct link to keilahvillasana's post “How many red blood cells ...”
How many red blood cells are produced every day? And how come our bodies don't OVERproduce? Can you have too many red blood cells?
Button navigates to signup pageComment on keilahvillasana's post “How many red blood cells ...”
(2 votes)
Answer
- rune
  Posted 7 years ago. Direct link to rune's post “I got this from the Inter...”
  I got this from the Internet, but I think it will help.
  Approximately 2.4 million new erythrocytes are produced per second in human adults. In a normal adult about half a liter are produced by the bone marrow every week.
  High red blood cell count -
  high red cells count is caused by a disorder called Polycythemia Vera. This is a genetic condition that causes the bone marrow to produce too many blood cells. People with polycythemia have an increase in hematocrit, hemoglobin, or red blood cell count above the normal limits.
  for more information visit : -
  http://www.medicinenet.com/polycythemia_high_red_blood_cell_count/article.htm
  I know this page has a lot of ads and Spam, but it also has some valuable information
  Button navigates to signup page
  (4 votes)
Madina Roshan
Posted 4 years ago. Direct link to Madina Roshan's post “would the components of b...”
would the components of blood be effected by your blood type?
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(2 votes)
Answer
- Tybalt
  Posted 4 years ago. Direct link to Tybalt's post “Yes. Platelets and especi...”
  Yes. Platelets and especially plasma have their own traits that are influenced by one's blood type. Plasma, for instance, can carry anti-A antibodies, anti-B antibodies, both antibodies, or none depending on blood type. This is why blood type still must be considered for plasma and platelet transfusions.
  
  Does that help?
  Button navigates to signup page
  (3 votes)
gianina carletti
Posted 4 years ago. Direct link to gianina carletti's post “Why is a stem cell an eth...”
Why is a stem cell an ethical issue?
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(2 votes)
Answer
- Tybalt
  Posted 4 years ago. Direct link to Tybalt's post “While everybody has stem ...”
  While everybody has stem cells, the cells used for research primarily come from human embryos. Here's the problem: when you harvest stem cells from an embryo, you destroy it. Killing a human being is typically viewed as murder; however, this being an unborn child raises several questions. Would it still be classified as murder if the child was never born? Can it even be classified as murder if the human being was very early in development, to the point where it was still only a mass of cells? Does it feel anything at that point? Is it part of the woman's body, or is it its own being?
  
  Much of the questions asked about the matter tie closely to the issue of abortion. It is an ethical issue because when exactly something becomes its own being is unclear, and there is a clear and significant pro (forwarding science for the better) and a clear and significant con (the death of a potential child) to be seen. There is no definite answer to this question, and it is ultimately up to your morals and views to give you the answer.
  
  Does this help?
  Comment on Tybalt's post “While everybody has stem ...”
  (3 votes)