Blood & Immune System


Perhaps nothing is quite as important in the human body as blood - a collection of specialized cells which are suspended in the tannish-colored liquid known as plasma. As it flows around the body, blood spreads heat, distributes hormones, collects waste and carries oxygen and nutrients.

Each human adult has about 5 litres (or 11 pints) of blood in their body.  Some 50-55 percent of blood is made up of plasma, and 90 percent of plasma is water.  Plasma is also made up of several dissolved substances such as hormones, glucose, enzymes and waste products such as lactic acid and urea.  Proteins are also found in plasma, including fibrinogen, albumins, and globular proteins or globulins.  Alpha and beta globulins help to transport the fatty substances (such as cholesterol) known as lipids.

Gamma globulins comprise the disease-fighting substances which are called antibodies.  The remaining 45-50 percent of the blood is made up of three different types of specialized cells:

  • Red blood cells, also known as erythrocytes, carry H oxygen.
  • White blood cells, or leucocytes, are part of the body's defense system.
  • Platelets or thrombocytes, which are tiny pieces of larger cells and help in the process of clotting.

Blood is also one of the body's connective tissues.  As such, it consists of cells and cell fragments suspended in plasma.  Blood is the body's only liquid tissue.  Blood makes up approximately 8 percent of the body's total weight.  It is slightly alkaline and has a normal pH range between 7.35 and 7.45 and is somewhat heavier than water and four or five times more viscous.

The blood is involved in three activities which can be categorized as transportation, regulation, and protection. The blood helps provide conditions which are suitable for cellular functions.

Transport functions of blood include:

  • Carrying oxygen and nutrients to the cells.
  • Transporting carbon dioxide and nitrogenous wastes from the tissues to the kidneys and lungs, where these wastes can be made ready to exit the body.
  • Carrying endocrine gland hormones to their targeted tissues.

Regulation activities of the blood include:

  • Helping to regulate body temperature through the removal of heat from areas such as skeletal muscles and routing it to other regions or the skin, where the heat can dissipate.
  • Playing an important role in the balance of electrolytes and fluids.  Salts and plasma proteins contribute to the body's osmotic pressure.
  • Functioning in the regulation of pH through the action of buffers in the bloodstream.

The protection category of blood function includes:

  • Clotting mechanisms which prevent the loss of fluid through hemorrhage when the blood vessels become damaged.
  • Helping to protect the body against microorganisms through the phagocytic white blood cells.
  • Protecting against disease by antibodies in the blood reacting against the invading agents.

The Immune System

The main means by which the body protects itself from the invasion of microorganisms is the immune system.  The immune system, which incorporates the lymphatic system, fights off hostile viruses, fungi and bacteria on the skin every second of every day.  The two intrinsic defense systems that provide resistance to these invasions are:

  • Innate (nonspecific) defense system - This system is always on the job and responds within minutes to protect the body from foreign substances.  The body's external body membranes, the intact skin and mucosae, are the first line of defense in the immune system.  The second line of defense, which is put in use when the first line has been penetrated, is the use of phagocytes, antimicrobial proteins and other cells.  The hallmark of this phase is inflammation.
  • Adapative (specific) defense system - This system is equipped with more complex weapons to fight particular substances and serves as the body's third line of defense.  It takes longer to be routed into play.  Although the defense systems are considered separately they do work hand in hand with each other.

Although the lymphoid organs and other organs are important aspects of the body's immune response, the immune system is a functional system rather than a system composed of organs.  The structure of the immune system includes a diverse array of molecules along with trillions of immune cells, including lymphocytes, that are found in lymphoid tissues and which circulate through body fluids.

The immune system was once thought to be comprised of the adaptive defense system only.  Today's medical practitioners know that the adaptive and innate defenses are intertwined.  Many defensive molecules are released by both systems, and the innate responses are now thought to be more specific against some foreign substances than first thought. 

Proteins which are released during innate system responses serve to alert cells of the adaptive immune system that specific foreign molecules have entered the body.

Some people are not aware that their environment plays an active role in immune response by the body.  Air pollution, toxic substances, second-hand cigarette smoke and pesticides can affect the body's defense system.

Lack of sleep can also affect the immune system.  Eight hours of sleep is optimal, and five and under hours of sleep per night can seriously depress immune functions.  Dieting can reduce the number of "killer" cells found in the body, and an excessive amount of lifting weights in the gym can temporarily impair the immune system by the production of cortisol and adrenaline.

Not only does a properly operating immune system protect the body from infectious microorganisms, it also fights cancer cells.

Posted in Blood & Immune System

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Blood & Immune System Disorders


Allergies are abnormal reactions to everyday substances. They are caused by the immune system's overreaction to histamine, a chemical that the body releases to fight microbial invaders. But in allergies, the invaders are not viruses or bacteria. They are harmless substances: pollens, dust, mould spores or harmless microscopic bugs called dust mites that live in carpets, clothing and bedding.

Chronic Fatigue Syndrome

While many people complain of feeling overly tired from time to time, some of those individuals may actually be experiencing Chronic Fatigue Syndrome (CFS). A patient is generally thought to be stricken with CFS when his or her fatigue becomes a prevalent condition which is not alleviated over an extended period of time.


The human body has a "thermostat" in the hypothalamus in the brain. Every person has his or her own standard temperature setting, which is typically around 37⁰C, or 98.6⁰F. When this temperature rises, people are known to be experiencing a fever.


People suffering from anaemia are unable to receive an optimal amount of oxygen carrying capacity in their bloodstreams. A few of the symptoms include feeling tired, appearing pale, and having an elevated heartbeat and shortness of breath.

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