Blood is a "alphabet soup" of cells, nutrients and waste products.  It contains about 60% water and travels through a system of vessels that supply nearly every cell in our bodies.  The main type of cell in blood is the red blood cell which is shaped like a tiny, red, jelly-filled doughnut.  The purpose of the red blood cell is to deliver oxygen from the lungs to all of the cells of the body.  There are about 30,000,000,000,000 red blood cells in an average adult, and this is what gives blood its red color.  The blood also contains white blood cells, complement, and other chemicals which all play an important role in the body's immune system.

General characteristics

Amount: 4 - 6 liters in an average adult

Water: Plasma is the liquid part of blood.  About 50% - 60% of blood is plasma... and plasma is mostly water.

Color: Blood comes in various shades of red.  Blood is bright red when it contains a lot of oxygen (like the blood found in arteries).  Blood is dark red when it is low in oxygen (like the blood found in veins). 

Temperature: same as body temperature.  98degrees F, if you don't have a fever.

pH: this is the acid level of blood.  pH is closely regulated by the body.  Blood is slightly alkaline, with a pH between 7.35 and 7.45.

Viscosity: viscosity is the resistance of a liquid to flow.  Syrup is highly viscous and water has a very low viscosity.  Blood is about 3 - 5 times thicker than water.

Plasma

Plasma is the liquid part of blood and is over 90% water.  Plasma contains all the nutrients absorbed by the digestive tract including: amino acids, fats, carbohydrates, vitamins, and minerals. Plasma proteins include immunoglobulins (also called "antibodies") which help the body fight infection, clotting factors, and transport proteins (like albumin).  Waste products from the body tissues (such as urea and creatinine) are removed through the blood by the kidneys.  These wastes are excreted from the body through urine.

Plasma contains most of the carbon dioxide products produced by cells in a process called cellular respiration.  Most carbon dioxide is removed in the form of bicarbonate ions.  The bicarbonate is converted to carbon dioxide in the lungs where it can be exhaled.

Red blood cells

Description:  a.k.a. - RBC, erythrocyte.  The most common cell in the human body.  Gives blood its red color.

Mission: Delivers oxygen from the lungs to the tissues of the body.

Location:  Red blood cells live and work in the blood.  They faithfully spend their lives delivering oxygen to the tissues.  Red blood cells have no nucleus and are unable to move on their own.  Like innertubes floating down a river, they require moving water to take them throughout the body.  The heart is able to pump every single blood cell in the body from the lungs to the tissues and back to the lungs in less than one minute.  Old and damaged red blood cells are removed from the bloodstream by the spleen.

Weapons:   None.  Red blood cells are defenseless against germs and rely on human immune cells to protect them.

Appearance:  7-8 micrometers in height, has no nucleus, looks somewhat like a tiny, red, jelly-filled doughnut.

Source: Arise from stem cells in the bone marrow.

Life span:  Around 120 days.

Number: Around 20-40 trillion in an average adult.

White blood cells

Description:  a.k.a. - leukocyte, WBC.  There are several types including: neutrophils, lymphocytes, monocytes, basophils, and eosinophils.  White blood cell are the main component of pus.

Location:  White blood cells patrol the bloodstream and, like a good watchdog, are attracted by the scent of invading germs.  Once the enemy is detected, the WBC's quickly travel through the tissues to attack the microscopic invaders.  WBC's give their lives to protect you - once they have left the bloodstream and eaten their share of germs, the WBC's will die.

Weapons:  

• Internal granules - contain chemicals designed to help digest eaten bacteria. 
• Chemical "grenades" - induce inflammation, blows holes in bacteria, and destroys damaged tissue.

Life span:  Usually less than a few days once released from the bone marrow.

Number: Around 40 billion of these can be found traveling throughout the body by way of the bloodstream, however this number can rise quickly to fight infection.

Appearance:  12-14 micrometers in height, contain a single large nucleus.

Source: Arise from stem cells in the bone marrow.

Platelets

Description:  a.k.a. - thrombocytes.  These are actually not cells, but small pieces of cells which help repair damaged blood vessels and help clot blood.

Location:  Platelets patrol the bloodstream and stick to areas of cell damage.

Weapons:  

• Chemical vasoconstrictors - induce contraction of smooth muscle in damaged blood vessels, reducing the amount of bleeding from damaged blood vessels
• Hole pluggers - like a little wad of bubble gum, platelets stick to damaged areas in order to "plug the leak"
• Fibrin nets - platelets help induce the creation of fibrin nets that hold back blood cells

Life span:  About 1-2 weeks once released from the bone marrow.  If they are used up quickly, they can be produced more quickly.

Number:  About 750,000,000 to 1,500,000,000 in the average adult.

Appearance:  2-4 micrometers in height.

Source:  Arise from megakaryocytes in the bone marrow.

 

Photo  - A three-dimensional ultrastructural image analysis of a T-lymphocyte (right), a platelet (center) and a red blood cell (left), using a Hitachi S-570 scanning electron microscope (SEM) equipped with a GW Backscatter Detector. Electron Microscopy Facility at The National Cancer Institute at Frederick (NCI-Frederick).