How does blood work, and what problems can occur?

Blood is a combination of plasma and cells that circulate through the body. It supplies essential substances, such as sugars, oxygen, and hormones, to cells and organs, and removes waste from cells.

Hematologists work to identify and prevent blood and bone marrow diseases. They also study and treat the immune system, blood clotting, and blood vessels.

Health conditions that affect the blood can be life threatening, but effective treatment is often available. In the United States, blood diseases accounted for 10,066Trusted Source deaths in 2008, mostly different types of anemia.

Structure

The main components of blood are:

• plasma
• red blood cells
• white blood cells
• platelets

Plasma

Plasma accounts for around 55% of blood fluid in humans. Plasma is 92% water, and the contents of the remaining 8% include:

• glucose
• hormones
• proteins
• mineral salts
• fats
• vitamins

The remaining 45% of blood mainly consists of red and white blood cells and platelets. Each of these has a vital role to play in keeping the blood functioning effectively.

Find out what plasma donation involves.

Red blood cells, or erythrocytes

Red blood cells have a slightly indented, flattened disk shape. They transport oxygen to and from the lungs. Hemoglobin is a protein that contains iron and carries oxygen to its destination. The life span of a red blood cell is 4 months, and the body replaces them regularly. The human body produces around 2 millionTrusted Source blood cells every second.

The expected number of red blood cells in a single drop (microliter) of blood is 4.5–6.2 million in males and 4.0–5.2 million in females.

What percentage of red blood cells should people have in their body?

White blood cells, or leukocytes

White blood cells make up less than 1% of blood content, forming vital defenses against disease and infection. The number of white blood cells in a microliter of blood usually ranges from 3,700–10,500. Higher or lower levels of white blood cells can indicate disease.

What does it mean if a person has a high white blood cell count?

Platelets, or thrombocytes

Platelets interact with clotting proteins to prevent or stop bleeding. There should be between 150,000 and 400,000 platelets per microliter of blood.

Bone marrow produces red blood cells, white blood cells, and platelets, and from there they enter the bloodstream. Plasma is mostly water that is absorbed from ingested food and fluid by the intestines. The heart pumps them around the body as blood by way of the blood vessels.

Functions

Blood has various functions that are central to survival. They include:

• supplying oxygen to cells and tissues
• providing essential nutrients to cells, such as amino acids, fatty acids, and glucose
• removing waste materials, such as carbon dioxide, urea, and lactic acid
• protecting the body from diseases, infections, and foreign bodies through the action of white blood cells
• regulating body temperature

The platelets in blood enable the clotting, or coagulation, of blood. When bleeding occurs, the platelets group together to create a clot. The clot forms a scab, which stops the bleeding and helps protect the wound from infection.

Blood groups

A person’s blood type is determined by the antigens on the red blood cells. Antigens are protein molecules on the surface of these cells.

Antibodies are proteins in plasma that alert the immune system to the presence of potentially harmful foreign substances. The immune system protects the body from the threat of disease or infection.

Knowing a person’s blood type is essential if they are receiving an organ donation or blood transfusion. Antibodies will attack new blood cells if the blood is the wrong type, leading to life threatening complications. For example, anti-A antibodies will attack cells that have A antigens.

Red blood cells sometimes contain another antigen called RhD. Doctors also note this as part of the blood group. A positive blood group means that RhD is present.

Humans can have one of four main blood groups. Each of these groups can be Rhd-positive or -negative, forming eight main categories.

• Group A positive or A negative: A antigens are present on the surfaces of blood cells. Anti-B antibodies are present in the plasma.
• Group B positive or B negative: B antigens are present on the surfaces of blood cells. Anti-A antibodies are present in the plasma.
• Group AB positive or AB negative: A and B antigens are present on the surfaces of blood cells. There are no antibodies in the plasma.
• Group O positive and O negative: There are no antigens on the surfaces of blood cells. Both anti-B and anti-A antibodies are present in the plasma.

People with group O blood can donate to virtually any blood type, and people with group AB+ blood can usually receive blood from any group.

People can talk with their doctor to find out their blood type or find out by donating blood.

Blood groups are important during pregnancy. If a pregnant person has RhD-negative blood, for example, but the fetus inherits RhD-positive blood, treatment will be necessary to preventTrusted Source a condition known as hemolytic disease of the newborn.

Disorders

Disorders and diseases of the blood can impair the many functions that blood performs.

Some common blood disorders are:

• Anemia: This happens when low red blood cell or hemoglobin levelsTrusted Source mean the cells do not transport oxygen effectively, leading to fatigue, pale skin, and other symptoms.
• Blood clotting: Clotting helps wounds and injuries heal, but blood clots that form inside a blood vessel can create a blockage, which can be life threatening. If clots become dislodged and move through the heart to the lungs, a pulmonary embolism can form.
• Blood cancers: Cancers such as leukemia, myeloma, and lymphoma occur when blood cells start to divide uncontrollably without dying off at the end of their life cycle.
• Hemophilia: If a person has low levels of clotting factors in the blood, they can bruise or bleedTrusted Source very easily. They may bleed for too long after a minor injury or surgery, or during menstruation. It affects around 18,000 peopleTrusted Source in the U.S.
• Sickle cell disease: An inherited trait causes red blood cells to take on a crescent shape. It affects over 100,000Trusted Source people in the U.S., mostly Black Americans. It can severely impact how blood functions and can be life threatening.
• Thalassemia: This is also a type of inherited anemia in which the body produces an unusual form of hemoglobin. It affected around 1,000Trusted Source people in the U.S. in 2008 and is most common in people from around the Mediterranean and parts of Asia.

If symptoms suggest a person may have a blood disorder, they should seek medical advice. A doctor may refer them to a specialist in blood disorders, known as a hematologist.

Learn more here about different blood disorders.

Summary

Blood is essential for maintaining the health and life of the human body. It has many functions, including delivering nutrients and oxygen. The four main components of blood are red blood cells, white blood cells, plasma, and platelets.

Problems that arise due to illness or blood loss can be life threatening, but effective treatment is available for many blood-related disorders.

Source - Medical News Today

All about hematopoietic stem cell transplantation.

Hematopoietic stem cell transplantation (HSCT) is a treatment for some types of cancer and other diseases. Stem cells can come from blood or bone marrow.

Stem cells are non-differentiated cells. They can develop into various “specialist” cells in the body.

Doctors are already using stem cells in some treatments. With further research, expertsTrusted Source hope that stem cell transplantation will have more uses and lead to new treatments.

In this article, learn about the uses of stem cell transplantation and how it works.

What can stem cell transplants treat?

The Food and Drug Administration (FDA)Trusted Source has approved the use of stem cell transplants to treat:

• some types of cancer
• some blood disorders
• some immune system disorders

Some specific examples includeTrusted Source:

• multiple myeloma
• leukemia
• some lymphomas
• aplastic anemia
• thalassemia
• sickle cell disease
• severe combined immune deficiency syndrome, which affects some newborns

Stem cell transplantation has also shown promiseTrusted Source as a treatment for some neurological diseases, such as multiple sclerosis (MS).

However, the FDA has not yet approved this as an MS treatment, and it warnsTrusted Source against undergoing any unapproved procedures due to safety concerns.

Where do stem cells come from?

Stem cells can come from:

• blood
• the umbilical blood
• bone marrow

Who donates stem cells?

A person can receiveTrusted Source stem cells from a donor or their own body.

In allogeneic HSCT, a donor supplies stem cells. Their tissue and blood types need to match those of the recipient, so donors are often close relatives.

Clinicians check for proteins called human leukocyte antigens to compare types of blood and tissue and check whether two people are a match.

In autologous HSCT, stem cells are harvested from the person who needs the treatment. Then, the cells are reintroduced into their body in a targeted way.

Peripheral blood

Circulating blood contains stem cells, and a person with cancer may receive stem cells from their own blood after chemotherapy. There must be no cancer cells left in the body when the person has stem cell treatment.

Chemotherapy and radiation that targets bone marrow can remove stem cells from the area. So after treatment, it can help to reintroduce stem cells into the body. These new stem cells can take root without competition from cancer cells and help produce healthy blood.

This process, called autologous HSCT or “conditioning,” involves the following steps:

• The person takes medication to stimulate stem cell production for around 4 days.
• They have a blood test to check whether there are enough stem cells to harvest.
• If there are, the person undergoes a process that involves drawing blood, which passes through a machine and reenters the body through the other arm.
• This process takes about 3 hours, and the person remains awake.
• The person may need to repeat the process the next day if too few cells were collected the first time.

Umbilical cord blood

Umbilical cord blood contains more stem cells than circulating blood, which makes it particularly suitable. The stem cells can be transplanted into the same person or someone with matching blood and tissue types.

To harvest umbilical stem cells, a healthcare professional collects 40–70 millilitersTrusted Source of blood from the fetal cord immediately after clamping it at both ends. They draw the sample from the area between the two clamps, freeze the sample, and store it in a cord blood bank, in case the person ever needs it.

Bone marrow

If a person donates bone marrow, whether for their own needs or someone else’s, they can expect the following:

• They will have a general anesthetic.
• The doctor will use a needle and syringe to remove around 2 pintsTrusted Source of bone marrow from the hip bone, possibly from several locations. This takes 1–2 hours.
• Afterward, there may be some pain and marks on each side of the hips where the doctor inserted the needle.

Risks and complications

• There is a risk of infectionTrusted Source, especially for people who receive stem cells from a donor.
  
  Someone with cancer may have chemotherapy before the transplant. This stops the body from rejecting the transplanted cells, but it also suppresses the ability to fight infections.

  Some people develop hepatic veno-occlusive disease with additional kidney or lung abnormalities after having HSCT. Doctors can treatTrusted Source this using a medication called defibrotide sodium (Defitelio).

  Another risk associated with allogeneic stem cell transplant is graft-versus-host disease. This happens when donated cells attack a person’s tissues. The less exact the match between the donor and recipient, the higher the risk of this issue. Doctors may use drugs to reduce the risk.

Complications for donors

• Bone marrow donors may experience:

  • tiredness
  • discomfort
  • aching in and around the lower back and hips

  These usually pass after a few days. Over-the-counter acetaminophen (Tylenol) and nonsteroidal anti-inflammatory drugs, or NSAIDs, such as ibuprofen (Advil), can help.

  A doctor may also recommend taking an iron supplement until the red blood cell count returns to normal. Many donors can return to their daily routines after resting for a few days, but it may take 2–3 weeksTrusted Source to recover fully. The bone marrow usually replenishes itself in 4–6 weeks.

HSCT for immune and neurological diseases

• Researchers are looking into other uses of stem cell transplants. Because these cells have regenerative properties, they may help repair damaged tissues and treat diseases that involve nerve damage, for example.

  In one 2016 studyTrusted Source, people with severe MS experienced significant improvements after undergoing HSCT. Inflammation decreased, symptoms stopped worsening, and some people had better mobility.

  A 2017 review also supported the use of HSCT as an MS treatment and suggested that it might help treat other neurological and neuroinflammatory diseases, such as:

  • stiff person syndrome, which involves muscles stiffness and spasms
  • various peripheral neuropathies
  • myasthenia gravis

  Meanwhile, a 2019 reviewTrusted Source suggested that stem cells might help treat neurodegenerative diseases, such as Parkinson’s and Alzheimer’s, and might also support the healing of wounds, including those in dental tissue.

  The researchers note that while many obstacles remain, HSCT and other stem cell therapies might one day provide cures for a range of diseases.

Summary

• Doctors sometimes use stem cell therapy to help treat some types of cancer, some blood disorders, and some immune conditions.

  Stem cell transplantation also shows promise as a treatment for certain neurological and autoimmune diseases, such as MS, but more research is needed before the FDA can approve it for these purposes.

How much blood is in the human body?

The amount of blood in a person’s body will depend on their age and size. Losing a certain amount of blood will not cause any harm to the body.

According to an older review article in Critical CareTrusted Source, blood accounts for:

• approximately 7–8% of an adult’s body weight
• approximately 8–9% of a child’s body weight
• approximately 9–10% of an infant’s body weight

In this article, learn more about the average volume of blood in adults and children. Learn, too, what causes blood loss, how it affects the body, and what to do if it happens.

Blood volume

According to a 2020 articleTrusted Source, there are around 10.5 pints (5 liters) of blood in the average human adult body, although this will vary depending on various factors. During pregnancy, a woman may have up to 50% more blood.

The average quantities of blood are::

• about 9 pints (4.3 liters) of blood in an average-sized female (5 feet 5 inches tall and weighing 165 pounds)
• about 12.2 pints (5.7 l) in an average-sized male (6 feet in height and weighing 200 pounds)
• in an infant, about 1.2 fluid ounces (fl oz) for every pound of body weight (75 – 80 milliliters (ml) of blood per kilogram).
• in a child, about 1–1.2 fl oz for every pound of body weight (70–75 ml of blood per kg)

For clarity, Medical News Today has converted these figures from the formula given in Open Anesthesia.

Blood volume test

According to an older article in the Journal of Nuclear Medicine Technology, a blood volume test can measure the amount of blood in a person’s body.

A doctor may use this test to assess a variety of conditions, such as:

• congestive heart failure
• kidney failure
• shock

There are different ways of testing, but a blood volume test usually involves injecting a small amount of a tracer substance into the body. A healthcare professional will then use imaging technology to track blood moving around the body.

How much blood can you lose or donate?

According to the American Red Cross, the standard amount of blood a person will give during a blood donation is 1 pint. This is around 10% of the blood in the body and a safe amount of blood to lose.

A person may feel a little faint after donating blood, and so donation centers ask donors to rest for 10–15 minutes and take some refreshments before leaving.

If a person has an illness or accident, they may lose more blood. This can lead to shock, and it can be life threatening.

Shock and blood loss

Severe bleeding can be dangerous. In medical terms, shock means that not enough oxygen is reaching tissues in the body. Low oxygen levels can cause damage to the brain and other organs.

If someone is losing blood, the body will start to direct blood toward the vital organs and away from the skin, fingers, and toes. A person may begin to look pale or feel numbness in their extremities.

According to a 2019 articleTrusted Source, when a person loses around 15% of their blood volume, they can start to experience shock, although their blood pressure and other signs will likely be normal at this point.

After losing 20–40%, the person’s blood pressure will start to fall, and they will begin to feel anxious. If they lose more blood, they will start to feel confused. Their heart rate may rise to around 120 beats per minute (bpm), as the body tries to maintain blood supply to the vital organs.

When blood loss is 40% or more, the person will be in severe shock. Their pulse rate will rise over 120 bpm. They will feel lethargic and may lose consciousness.

Causes of bleeding and shock

Bleeding can be external or internal, but both types can lead to shock.

External bleeding: Head wounds or a deep wound or a cut on or near a vein, such as on the wrist or neck, can result in severe blood loss.

Internal bleeding: An internal injury, such as a blow to the abdomen, can lead to a sudden and significant loss of blood, but this may not be visible from the outside. The clinical review in Critical CareTrusted Source indicates that medical conditions, such as a perforated ulcer, lung cancer, or a ruptured ovarian cyst, can also cause internal bleeding.

Depending on where internal bleeding occurs, bruising may start to appear. There may be a loss of blood through the mouth, nose, or other orifices.

Getting help

A person with severe bleeding will need medical attention.

For external bleeding, the person should:

• sit or lie down
• raise the injured part, if possible
• apply pressure to the wound to slow the bleeding or ask someone else to do this

Someone should call 911 if:

• bleeding is severe
• bleeding does not stop or slow down on applying pressure
• severe bruising appears on the body or the head
• there is a change in consciousness or difficulty breathing

Transfusions

A blood transfusion is a medical procedure to donate blood to someone who needs it.

Possible reasons include:

• losing a lot of blood
• having an illness that affects the blood, such as cancer or anemia

Blood transfusions can be a life-saving procedure. People can also receive other parts of blood, such as plasma and platelets, for various treatment purposes.

How much blood do we produce a day?

The body makes around 2 million red blood cells per second. Blood cells develop from stem cells in the bone marrow. Stem cells are a type of cell that can create other cells. This process happens continually throughout a person’s life.

Blood consists of different parts:

• Red blood cells carry oxygen and carbon dioxide.
• White blood cells help defend the body against disease and infection.
• Platelets help stop bleeding.
• Plasma carries blood cells, platelets, and other components and supports the immune system. The American Red Cross state that it makes up 55% of blood and is 92% water.

The Red Cross also state that body takes around 24 hours to replace lost plasma, but 4–6 weeks to replace red blood cells.

Red blood cells get their color from hemoglobin, which contains iron. It can take several months for iron levels to return to normal after losing or donating blood. The Office of Dietary SupplementsTrusted Source note that frequent donors may have low levels of iron in their blood.

People who have experienced blood loss due to donation or another reason may benefit from:

• drinking plenty of fluids, especially water
• consuming iron-rich foods, such as beef liver and fortified foods

Many people now donate plasma. Are there any risks?

How the body maintains blood levels

The circulatory or cardiovascular system is responsible for moving blood around the body. Within this system, the heart pumps the blood to the blood vessels, which deliver blood to the body’s organs. There, the blood delivers oxygen and other nutrients.

Others systems and organs that play a crucial role are:

• the kidneys, which regulate the fluid balance in the body
• the skeletal system, as bone marrow produces blood cells
• the nervous system, which enables the other systems to fulfill their tasks

A problem with any of these systems can affect blood flow and blood volume, the delivery of oxygen, and a person’s ability to survive.

Takeaway

Around 7–8% of an adult’s body weight is blood. The body can easily replace a small amount of lost blood, which makes blood donation possible.

If a person loses around 15% or more of their blood, there may be a risk of shock. Anyone who has signs of significant internal or external bleeding should seek immediate medical help.

Source - Medical News Today

 

The