The Composition of Blood

Have you ever wondered what blood is made up of?

With the average adult possessing five to six liters of blood in the body, this fluid is vital to our lives, circulating oxygen through the body and serving many different functions.

Despite its simple, deep-red appearance, blood is comprised of many tiny chemical components. This infographic visualizes the composition of blood and the microscopic contents in it.

What is Blood Made Up Of?

There are two main components that comprise blood:

• Plasma – 55%
  Plasma is the fluid or aqueous part of blood, making up more than half of blood content.
• Formed elements – 45%
  Formed elements refer to the cells, platelets, and cell fragments that are suspended in the plasma.

Plasma

Plasma is primarily made up of water (91%), salts, and enzymes, but it also carries important proteins and components that serve many bodily functions.

Plasma proteins make up 7% of plasma contents and are created in the liver. These include:

• Albumins
  These proteins keep fluids from leaking out of blood vessels into other parts of the body. They also transport important molecules like calcium and help neutralize toxins.
• Globulins
  These play an important role in clotting blood and fighting infections and are also transporters of hormones, minerals, and fats.
• Fibrinogen and Prothrombin
  Both of these proteins help stop bleeding by facilitating the creation of blood clots during wound-healing.

Water and proteins make up 98% of plasma in blood. The other 2% is made up of small traces of chemical byproducts and cellular waste, including electrolytes, glucose, and other nutrients.

Formed Elements

There are three categories of formed elements in blood: platelets, white blood cells, and red blood cells. Red blood cells make up 99% of formed elements, with the other 1% comprised of platelets and white blood cells.

• Platelets (Thrombocytes)
  Platelets are cells from the immune system with the primary function of forming clots to reduce bleeding from wounds. This makes them critical not only for small wounds like cuts but also for surgeries and traumatic injuries.
• White blood cells (Leukocytes)
  White blood cells protect our bodies from infection. There are five types of white blood cells with different roles in fighting infections: some attack foreign cells and viruses, some produce antibodies, some clean up dead cells, and some respond to allergens.
• Red blood cells (Erythrocytes)
  Red blood cells deliver fresh oxygen and nutrients all over the body. They contain a special protein called hemoglobin, which carries oxygen and gives blood its bright red color.

The lifespan of a typical red blood cell is around 120 days, after which it dies and is replaced by a new cell. Our bodies are constantly producing red blood cells in the bone marrow, at a rate of millions of cells per second.

Abnormal Red Blood Cells

Normal red blood cells are round, flattened disks that are thinner in the middle. However, certain diseases and medical therapies can change the shape of red blood cells in different ways.

Here are the types of abnormal red blood cells and their associated diseases:

Sickle cell anemia is a well-known disease that affects the shape of red blood cells. Unlike normal, round red blood cells, cells associated with sickle cell disease are crescent- or sickle-shaped, which can slow and block blood flow.

Other common causes of abnormally shaped red blood cells are thalassemia, hereditary blood disorders, iron deficiency anemia, and liver disease. Identifying abnormal blood cells plays an important role in diagnosing the underlying causes and in finding treatments.

The Functions of Blood

We know that blood is vital, but what does it actually do in the body?

For starters, here are some of the functions of blood:

• Blood transports oxygen to different parts of the body, providing an energy source. It also delivers carbon dioxide to the lungs for exhalation.
• The platelets, white blood cells, and plasma proteins in blood play an important role in fighting infections and clotting.
• Blood transports the body’s waste products to the kidneys and liver, which filter it and recirculate clean blood.
• Blood helps regulate the body’s internal temperature by absorbing and distributing heat throughout the body.

While we all know that we can’t live without blood, it serves many different functions in the body that we often don’t notice. For humans and many other organisms alike, blood is an integral component that keeps us alive and going.

A Newfound Link Between Cancer and Aging?

A new study in 2022 reveals a thought-provoking relationship between how long animals live and how quickly their genetic codes mutate.

Cancer is a product of time and mutations, and so researchers investigated its onset and impact within 16 unique mammals. A new perspective on DNA mutation broadens our understanding of aging and cancer development—and how we might be able to control it.

Mutations, Aging, and Cancer: A Primer

Cancer is the uncontrolled growth of cells. It is not a pathogen that infects the body, but a normal body process gone wrong.

Cells divide and multiply in our bodies all the time. Sometimes, during DNA replication, tiny mistakes (called mutations) appear randomly within the genetic code. Our bodies have mechanisms to correct these errors, and for much of our youth we remain strong and healthy as a result of these corrective measures.

However, these protections weaken as we age. Developing cancer becomes more likely as mutations slip past our defenses and continue to multiply. The longer we live, the more mutations we carry, and the likelihood of them manifesting into cancer increases.

A Biological Conundrum

Since mutations can occur randomly, biologists expect larger lifeforms (those with more cells) to have greater chances of developing cancer than smaller lifeforms.

Strangely, no association exists.

It is one of biology’s biggest mysteries as to why massive creatures like whales or elephants rarely seem to experience cancer. This is called Peto’s Paradox. Even stranger: some smaller creatures, like the naked mole rat, are completely resistant to cancer.

This phenomenon motivates researchers to look into the genetics of naked mole rats and whales. And while we’ve discovered that special genetic bonuses (like extra tumor-suppressing genes) benefit these creatures, a pattern for cancer rates across all other species is still poorly understood.

Cancer May Be Closely Associated with Lifespan

Researchers at the Wellcome Sanger Institute report the first study to look at how mutation rates compare with animal lifespans.

Mutation rates are simply the speed at which species beget mutations. Mammals with shorter lifespans have average mutation rates that are very fast. A mouse undergoes nearly 800 mutations in each of its four short years on Earth. Mammals with longer lifespans have average mutation rates that are much slower. In humans (average lifespan of roughly 84 years), it comes to fewer than 50 mutations per year.

The study also compares the number of mutations at time of death with other traits, like body mass and lifespan. For example, a giraffe has roughly 40,000 times more cells than a mouse. Or a human lives 90 times longer than a mouse. What surprised researchers was that the number of mutations at time of death differed only by a factor of three.

Such small differentiation suggests there may be a total number of mutations a species can collect before it dies. Since the mammals reached this number at different speeds, finding ways to control the rate of mutations may help stall cancer development, set back aging, and prolong life.

The Future of Cancer Research

The findings in this study ignite new questions for understanding cancer.

Confirming that mutation rate and lifespan are strongly correlated needs comparison to lifeforms beyond mammals, like fishes, birds, and even plants.

It will also be necessary to understand what factors control mutation rates. The answer to this likely lies within the complexities of DNA. Geneticists and oncologists are continuing to investigate genetic curiosities like tumor-suppressing genes and how they might impact mutation rates.

Aging is likely to be a confluence of many issues, like epigenetic changes or telomere shortening, but if mutations are involved then there may be hopes of slowing genetic damage—or even reversing it.

While just a first step, linking mutation rates to lifespan is a reframing of our understanding of cancer development, and it may open doors to new strategies and therapies for treating cancer or taming the number of health-related concerns that come with aging.