Why are red blood cells considered to be cells?

Why are red blood cells considered to be cells?

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Wikipedia states that a cell is

the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.

It then goes on to state that

All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.

Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point?

A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact… It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.

Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.

Low Red Blood Cell Count

Red blood cells are one of the most important parts of the body as they carry oxygen between your lungs and the various cells in your body. This is why people with a low red blood cell count will feel it significantly and even show it. They may be weak, tired, and pale or have issues catching their breath. This information should help you better understand what is going on and what you can do.

What Is the Normal Red Blood Cell Count Range?

The most common cell type in your blood is the red blood cell. There are millions and millions of red blood cells, which are disc-shaped. The bone marrow of healthy adults will continuously produce them. Red blood cells contain hemoglobin, a substance responsible for bringing carbon dioxide and oxygen throughout your body.

The red blood cell count, or RBC count, lets you know if you have a low amount of red blood cells, which is known as anemia, or a high amount, which is known as polycythemia. There are many possible causes of low red blood cell count, such as chronic blood loss leading to iron deficiency anemia, acute blood loss, or hereditary disorders. High RBC levels, on the other hand, are fairly uncommon.

The optimal range for an average person will be between 3.95 and 5.35 M/mm3, but it varies by person, gender, and age. These figures from webmd show specific ranges for given groups.

Normal Red Blood Cell (RBC) Count

4.5 to 5.5 million RBCs per microliter (mcL) or 4.5&ndash5.5 x 10 12 /liter (L)

4.0 to 5.0 million RBCs per mcL or 4.0&ndash5.0 x 10 12 /L

Pregnancy values should be slightly lower

3.8 to 6.0 million RBCs per mcL or 3.8&ndash6.0 x 10 12 /L

4.1 to 6.1 million RBCs per mcL or 4.1&ndash6.1 x 10 12 /L

Signs and Symptoms of Low Red Blood Cell Count

Fatigue or tiredness is the most common of all symptoms associated with having a low red blood cell count. This is due to the lack of hemoglobin within the blood since this iron-rich protein is found in your red blood cells and carries oxygen throughout the body.

Other symptoms of a low red blood cell count may include dizziness (particularly when standing), shortness of breath, headaches, pale skin, chest pain, and coldness in the hands or feet.

When there aren&rsquot enough red blood cells in your body to carry hemoglobin, your heart has to work even harder so the lower amount of oxygen in your blood can be moved. This may lead to heart failure in severe cases or less serious issues such as an enlarged heart, a heart murmur, or irregular heartbeats (arrhythmias).

Complications of Low Red Blood Count

When you have a low red blood cell count, your blood has a reduced capacity to carry oxygen and its viscosity is also reduced. Your blood is therefore &ldquothinner&rdquo and can move more quickly because of the lack of resistance among the body&rsquos blood vessels. This in turn causes more blood to flow through your heart in a single minute than typically does, known as increased cardiac output. The blood also carries less oxygen so your blood vessels dilate, further reducing resistance and increasing the speed of blood flow.

During exercise or other times of increased demand, your body can&rsquot cope because of your low red blood cell count. Your heart will try to beat faster and will increase your breathing rate so your tissues get enough oxygen. This is frequently not enough, leading to tissue injury or even acute heart failure.

Causes of Low Red Blood Cell Count

1. Red Blood Cell Loss

Bleeding is a common cause of red blood cell loss. It may happen quickly, such as from surgery, frequent blood draws, or an injury. It may also occur slowly and chronically, such as from heavy menstruation or a lesion in your intestinal system leading to bleeding.

2. Increased Destruction

Bone marrow produces red blood cells which then circulate for around 120 days in the bloodstream with damaged or old cells being removed by your spleen. Various diseases may cause excess damage to blood cells or make the spleen remove them too early. Some possibilities include autoimmune hemolytic anemia and sickle cell anemia.

3. Inadequate Production

There are also diseases, drugs, and infections which can interfere or damage the bone marrow cells responsible for producing mature red blood cells. Some examples include chemotherapy, myelodysplasia, or scarring of the bone marrow.

4. Other Causes

Other potential causes of a low red blood cell count include:

  • Anemia
  • Bone marrow failure
  • Bleeding
  • Erythropoietin deficiency due to kidney disease
  • RBC destruction from blood vessel injuries or transfusions
  • Malnutrition nutritional deficiencies of vitamins B6 or B12, folic acid, copper, or iron
  • Leukemia
  • Multiple myeloma (bone marrow cancer)
  • Pregnancy
  • Overhydration

Treatment for Low Red Blood Count

The treatment for a low red blood cell count will depend on the causes and symptoms. If anemia is the cause and you have cancer, you may need a red blood cell transfusion.

If it is due to anemia, you may receive drugs that stimulate the production of erythropoietin or supplement it. These can be given as injections and take several weeks to start working.

Anemia from malnutrition may require oral or IV supplements. You may also be directed to eat foods with folic acid or iron.

What You Can Do About Low Red Blood Cell Count

You can also do some simple things on your own to improve your red blood cell count.

Why are red blood cells considered alive?

Whether or not something is "alive" is currently under the jurisdiction of philosophy more than science. "Life" is a rather arbitrary notion, since we're all composed of chemicals that are not alive. It has no place in biology, frankly, so decide for yourself how you want to define life.

If you want my personal advice, don't look for a definition. Instead, use "life" and "alive" as general concepts, to express a vague idea that doesn't need further definition. "I'm alive, that cup is not," that sort of stuff.

Well, all due respect, we get degrees called philosophiae doctor for a reason. While science itself does not consider the question "why" so often, the scientist is obliged to. Not only to ensure his/her ethical compass is well calibrated, but because we do science to better understand "life". The debate over whether or not cells not containing genetic material or not having a metabolism being "life" is probably not a very interesting one scientifically, it nevertheless is a philosophical consideration individuals in the life sciences aught to have in the back of their mind. In particular, people who do research in origins of life might find this question very crucial in a research context.

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Blood cells can stay alive for about 120 days. anon299892 October 26, 2012

Why doesn't a red blood cell have a nucleus? anon169575 April 21, 2011

@anon161060: It is (almost) only mammalian RBCs that lack nuclei, and these only lack nuclei as mature RBCs. As a red blood cell matures it expels its nucleus from its body, making room for more hemoglobin. anon161060 March 18, 2011

RBC don't have a nucleus. Why are they called cells? FrameMaker 10 hours ago

@ chicada- There are three main concerns with having to many red blood cells. The first concern is that the blood becomes thicker, making the heart work harder to pump it through your veins. Second, thicker blood is less likely to reach the smaller capillaries in the body. Lastly, blood with a high red cell count is more likely to form clots, which can be very dangerous if they form in major arteries or in the brain. GiraffeEars 10 hours ago

@ Chicada- Your bone marrow produces your red blood cells. In some cases bone marrow will produce too many red blood cells, other times red blood cell count may be high because of overproduction of proteins in the liver. Poor lung and heart function can also be a reason for the increase in your red blood cell count.

Sometimes there are less serious reasons for having a high red blood cell count. Living at high altitudes can lead to a higher blood cell count. This is because the function of red blood cells is to deliver oxygen, and there is less oxygen in the air at high elevation. If you donate plasma, you will also have a high red blood cell count relative to your blood volume. chicada 10 hours ago

What causes a high red blood cell count? What are the consequences of having too many red blood cells?

Problems anemia can cause

The first thing the doctor needs to know is how severe your anemia is. Anemia can affect your quality of life and has been found to shorten survival in people with cancer. It can make you feel very tired because cells in your body can’t get enough oxygen. In some cases, this lack of oxygen may be bad enough to threaten your life. Anemia can also make your heart work harder. So if you already have a heart problem, anemia can make it worse. Anemia can also make it hard for you to breath normally, making it challenging to do your usual activities.

Severe anemia may mean you have to delay your cancer treatment or have your treatment dose reduced. It can also cause some cancer treatments to not work as well as they should.

Your cancer care team may try to figure out your risk of serious problems from the anemia based on any symptoms you are having and your hemoglobin level. If you’re not having symptoms, they will try to figure out how likely you are to have them in the near future. This will be based on a number of things, including:

  • Your hemoglobin level and other lab results
  • The type of cancer treatments you’ve had in the past
  • The chances that any treatments you’re now getting could make the anemia worse
  • Whether you have lung, heart, or blood vessel (circulation) problems
  • Your age

If you don’t seem to be at risk for problems from anemia, your cancer care team will watch your hemoglobin level closely and ask about symptoms each time you visit the office.

What is pus?

Pus is a whitish-yellow, yellow, or brown-yellow protein-rich fluid called liquor puris that accumulates at the site of an infection.

It consists of a buildup of dead, white blood cells that form when the body’s immune system responds to the infection.

When the buildup is on or near the surface of the skin, it is called a pustule or pimple. An accumulation of pus in an enclosed tissue space is called an abscess.

Share on Pinterest Pus consists of macrophages and neutrophils, sent by the body’s immune system to combat infection.

Pus is the result of the body’s natural immune system automatically responding to an infection, usually caused by bacteria or fungi.

Leukocytes, or white blood cells, are produced in the marrow of bones. They attack the organisms that cause infection.

Neutrophils, a type of leukocyte, have the specific task of attacking harmful fungi or bacteria.

For this reason, pus also contains dead bacteria.

Macrophages, another type of leukocyte, detect the foreign bodies and release an alarm system in the form of small, cell-signaling protein molecules called cytokines.

Cytokines alert the neutrophils, and these neutrophils filter from the bloodstream into the affected area.

The rapid accumulation of neutrophils eventually leads to the presence of pus.

Pus is a sign of infection.

Pus after surgery indicates that there is a post-surgical complication in the form of an infection.

People who detect a discharge of pus following surgery should tell their doctor immediately.

In a patient with weakened immunity, the system may not respond correctly. There may be an infection with no pus.

This can occur if the person:

  • is receiving chemotherapy
  • is taking immunosuppressant medications following an organ transplant
  • has HIV
  • has poorly controlled diabetes.

The doctor will likely prescribe an antibiotic, possibly an ointment for topical application.

Antibiotics help the white blood cells attack the infection. This speeds up the healing process and prevents further complications with the infection.

If there is an abscess, it may need draining, and there may be a special incision care program.

The whitish-yellow, yellow, yellow-brown, and greenish color of pus is the result of an accumulation of dead neutrophils.

Pus can sometimes be green because some white blood cells produce a green antibacterial protein called myeloperoxidase.

A bacterium called Pseudomonas aeruginosa (P. aeruginosa) produces a green pigment called pyocyanin.

Pus from infections caused by P. aeruginosa is particularly foul-smelling.

If blood gets into the affected area, the yellowish or greenish color may also have tinges of red.

The underlying reason for the pus is the main target for treatment, and the strategy will depend on the cause.

Home treatments

If pus builds up close to the surface of the skin, such as in pimples, medical intervention is not required. The pus may be drained at home.

Soaking a towel in warm water and holding it against the infected pus for 5 minutes will reduce the swelling and open up the pimple or skin abscess for a faster healing process.

Clinical intervention

Patients who have undergone surgery and who notice a discharge of pus should not apply over-the-counter antibiotic cream, alcohol, or peroxide.

They should contact their doctor or surgeon.

Large abscesses or those that are difficult to access should also be treated by a clinician.

The doctor will attempt to create an opening so that the pus can ooze out, or evacuate. Medications may also be necessary.

Treatment to remove pus may be necessary in the following cases:

Recurring otitis media, or middle ear inflammation: This can lead to recurring excess fluid in the middle ear. A specialist may need to insert a grommet in the eardrum to help evacuate this fluid.

Grommets are small plastic tubes that are inserted into the ear.

As well as draining fluid, grommets also allow air into the space behind the ear drum, reducing the risk of a future buildup of fluid.

Abscesses: Antibiotics may treat smaller abscesses, but sometimes they are not effective .

The doctor may need to insert a drainage-channel to help evacuate the pus rapidly.

A surgical drain may be used to assist with removal of pus.

This is a tube-like structure that may or may not be attached to a suction pump.

Septic arthritis: If an infection develops in a joint, or passes from another part of the body to a joint, pus and general inflammation can occur in the joint.

After identifying which bacterium is causing the infection, the doctor will decide on a course of intravenously administered antibiotics. This may last many weeks.

Joint drainage may be necessary to remove pus.

A flexible tube with a video camera at its tip, called an arthroscope, is placed into the joint through a tiny incision.

This device guides the doctor to insert suction and drainage tubes around the joint to draw out the infected synovial fluid.

Arthrocentesis is a different procedure.

It involves removing the infected fluid with a needle. The extracted fluid is examined for bacteria, and the arthrocentesis repeated every day until there are no more bacteria in the fluid.

How the Antarctic Icefish Lost Its Red Blood Cells But Survived Anyway

In 1928, a biologist named Ditlef Rustad caught an unusual fish off the coast of Bouvet Island in the Antarctic. The "white crocodile fish," as Rustad named it, had large eyes, a long toothed snout and diaphanous fins stretched across fans of slender quills. It was scaleless and eerily pale, as white as snow in some parts, nearly translucent in others. When Rustad cut the fish open, he discovered that its blood, too, was colorless—not a drop of red anywhere. The crocodile fish's gills looked odd as well: they were soft and white, like vanilla yogurt in contrast, a cod's gills are as dark as wine, soaked in oxygenated blood.

Later, Johan Ruud and other researchers confirmed that the Antarctic icefishes, as they are now known, are the only vertebrates that lack both red blood cells and hemoglobin—the iron-rich protein such cells use to bind and ferry oxygen through the circulatory system from heart to lungs to tissues and back again. At first blush, biologists regarded icefishes' pallor blood as a remarkable adaptation to the Antarctic's freezing, oxygen-rich waters. Perhaps icefishes absorbed so much dissolved oxygen from the ocean through their gills and ultra thin skin that they could abandon those big, spongy red blood cells. After all, the biologists reasoned, thinner blood requires less effort to circulate around the body and saving energy is always an advantage, especially when you are trying to survive in an extreme environment.

More recently, however, some biologists have proposed that the loss of hemoglobin was not a beneficial adaptation, but rather a genetic accident with unfortunate consequences. Since icefish blood can only transport 10 percent as much oxygen as typical fish blood, icefishes were forced to dramatically alter their bodies in order to survive. In this scenario, despite an evolutionary blunder that would be lethal to most fish, the icefishes' grit—as well as a little ecological serendipity—rescued them from their own bad blood. Scientists continue to revise icefishes' evolutionary history as new evidence surfaces, but their story is surely one of the most unique and bizarre in the animal kingdom.

Icefishes live in the Southern Ocean, which encircles Antarctica. Rotating currents essentially isolate these waters from the world's warmer seas, keeping temperatures low: temperatures near the Antarctic Peninsula, the northernmost part of the mainland, range from about 1.5 degrees Celsius in the summer to –1.8 degrees Celsius in the winter. Many fish in the Southern Ocean, including icefishes, produce antifreeze proteins to prevent ice crystals from forming in their blood when ocean temperatures drop below the freezing point of fresh water. Sixteen species of Antarctic icefishes comprise the family Channichthyidae, which falls under the larger suborder Notothenioidei. Among the hundreds of red-blooded Notothenioid species, only the icefishes lack hemoglobin. Together, the Notothenioids and icefishes dominate the waters they call home, accounting for approximately 35 percent of fish species and 90 percent of fish biomass in the Southern Ocean.

By comparing icefish DNA to the DNA of red-blooded fish, William Detrich of Northeastern University and his colleagues identified the specific genetic mutations responsible for the loss of hemoglobin. Basically, one of the genes essential for the assembly of the hemoglobin protein is completely garbled in icefishes. Although no other vertebrate completely lacks red blood cells, biologists have observed a diminishing of red blood cells in response to a changing environment. When it gets cold, it's advantageous for fish to make their blood a little thinner and easier to circulate. Fish that live in cold waters usually have a smaller percentage of red blood cells in their blood than fish that live in warmer waters. And fish in temperate regions decrease the percentage of red blood cells in their blood each winter to save energy. Relying on these facts, some biologists assumed that Antarctic icefish evolved incredibly thin blood as an adaptation to the Southern Ocean.

Kristin O'Brien of the University of Alaska Fairbanks and her colleague Bruce Sidell (who is now sadly deceased) decided to test this assumption. In a paper titled "When bad things happen to good fish," O'Brien and Sidell first point out that, compared to their cousins the Notothenioids and other similarly sized fish, icefishes have larger hearts and blood vessels. Although icefishes pump unusually thin blood through their bodies, their circulatory systems handle huge volumes. O'Brien and Sidell calculated that icefishes expend approximately twice as much energy as red-blooded Notothenioids moving all that extra blood. Whereas fish in temperate zones devote no more than five percent of their resting metabolic rate to their hearts, icefishes invest a whopping 22 percent of their body's available energy in their giant tickers.* O'Brien and Sidell also show that icefish have more blood vessels nourishing certain organs than red-blooded fish. If you peel back the outer layers of a typical fish's eye and fill the blood vessels with yellow silicone rubber, you will see a web of neatly segregated vessels tracing the contour of the eye like the ribs of a pumpkin. Do the same to an icefish's eye and you will find a dense, tangled mess like a plate of spaghetti.

Like other biologists in recent years, O'Brien and Sidell view the icefishes' large hearts and capillaries, high blood volume and dense nets of blood vessels as compensations for the loss of hemoglobin. But these adaptations alone might not have been enough to save icefishes from extinction—they likely benefited from fortuitous circumstances as well. Around 25 million years ago, the Southern Ocean flowing around Antarctica—which had broken away from other continents—began to cool. Not only did the colder water offer more oxygen, it also killed many species that did not evolve antifreeze proteins or otherwise adapt to the cold, creating a frigid sanctuary that the icefishes and their relatives have dominated ever since.

Today, however, icefishes face a new threat: manmade climate change. The Southern Ocean is getting warmer and possibly more acidic and less nutritious. O'Brien says researchers have shown that adult icefishes are more sensitive to changes in temperature than red-blooded fish—they cannot stand the heat. If Ruud was right—that "only in the cold water of the polar regions could a fish survive that has lost its pigment"—then the ongoing changes to the Southern Ocean might be the icefishes' undoing. Consider this version of their story: icefishes evolved to survive sub-freezing temperatures in one of the most extreme environments on Earth, only to lose their red blood cells to a genetic accident despite the mishap, they kept swimming, expanding their hearts and growing more blood vessels to get enough oxygen around their bodies now, people are turning the Southern Ocean into a habitat for which icefishes are completely unsuited, forcing them to adapt once again or perish. Personally, I'm clinging to the hope that even if icefishes do not have any hemoglobin in their blood, they have plenty of resilience coursing through their veins.

*Source for cardiac energy investment: Hemmingsen, E. A. and Douglas, E. L. (1977). Respiratory and circulatory adaptations to the absence of hemoglobin in chaenichthyid fishes. In Adaptations within Antarctic Ecosystems (ed. G. A. Llano), pp. 479-487. Washington: Smithsonian Institution.


Ferris Jabr is a contributing writer for Scientific American. He has also written for the New York Times Magazine, the New Yorker and Outside.

Anemia Causes and Treatments (Low Red Blood Cell Counts)

Red blood cells contain hemoglobin, a protein that enables the blood to carry oxygen to every part of the body. Anemia develops when the body does not produce enough red blood cells or red cells are lost due to bleeding or other causes. In people with anemia, the blood is unable to supply enough oxygen to the body. This is also known as "low hemoglobin" or "low hgb."

There are many possible causes of anemia. Symptoms of anemia can include:

  • Fatigue
  • Weakness
  • Dizziness
  • Headache
  • Irritability
  • Shortness of Breath (severe cases)
  • Chest Pains (severe cases)

Anemia can be a temporary problem or a chronic condition. Milder anemia can be treated with dietary changes, iron replacement (oral or IV) and vitamin supplementation.

Patients with more severe anemia may receive various medications to boost red cell production or inhibit red cell destruction. Patients with very low red blood cell counts may require blood transfusion.

Why is hemoglobin bound in red blood cells?

Why isn't hemoglobin directly synthesized and released into the blood plasma? Producing it only contained in red blood cells seems like a lot of wasted energy to me.

To keep it safe and separate from all the other nasty stuff in your blood. Primarily proteases that would chop up hemoglobin. Cell biology is all about compartmentalizing relevant reactions and processes. It's basically the same reason that the cell has organelles like the lysosome or the nucleus, to keep things that need to be separate

To add to this, carbonic anhydrase is another factor in blood chemistry and it is highly active in red blood cells. Carbonic anhydrase maintains the pH balance, which is impacted by CO2/O2 balance (carbon dioxide is more acidic, so carbonic anhydrase generates the buffer H2CO3). Carbonic anhydrase is commonly cited as the fastest working enzyme, but part of the reason for its speed is that it is contained within red blood cells, the area where its reactant (carbon dioxide) is at highest concentration.

A red cell provides a host of services to the hemoglobin it contains. Red cells produce diphosphoglycerate, shunting it off the glycolytic pathway. Without proper DPG levels, oxygen would be too strongly bound for release in the tissues. Red cells also have high levels of glutathione an essential redox buffer necessary that maintains the proper disulfide-sulfhydral balance of the protein portions of hemoglobin among other functions to do with oxidative stress. However, I wouldn't be surprised if the original evolutionary advantage of packaging hemoglobin in erythrocytes were about protecting iron from infective microorganisms.

If we want to jump back some in our evolutionary timeline, lots of more primitive species of arthropods use hemolymph, where the pigments are not bound in cells, but there are hemocytes that function as a rudimentary immune system.

Jumping forward into more complex organisms, the next level you can look at would be Deuterostomes, but they also contain a dissolved pigment, not a cell bound one (and not very much of it, really). Tunicates also don't have cell bound respiratory pigments. I think the first place erythrocytes show up is in Craniata? Hagfishes have them.

I'm inclined to believe it has more to do with immune function and keeping oxygen sequestered away. All blood cells come off of the hematopoietic stem cell, which evolved before red blood cells. Keeping oxygen sequestered has a twofold benefit: First, without the cells, the maximum oxygen carrying capacity of the blood is limited by the amount of oxygen that can be dissolved in it - sequestering that in cells means the blood can essentially always dissolve more. Second, it prevents the hemoglobin from being attacked by rogue adaptive immune cells (which would very quickly prove to be fatal) and keeps it from being available to bacterial infections, for the same reasons.

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