BLOOD COMPONENTS
Blood is the fluid of life because it transports important substances throughout the body and contains living cells. Blood is made up of a liquid medium called plasma
red and white blood cells
Plasma
The clear
yellowish fluid portion of blood is the plasma. Over fifty percent of blood is plasma. Ninety percent of plasma is water and nearly ten percent is dissolved materials. Plasma carries the breakdown products of digested food
There are three groups of plasma proteins that give plasma its yellow color. One group helps to regulate the amount of water in blood. The second group
produced by white blood cells
Red blood cells
The red blood cells carry oxygen to all of the body’s cells. Red blood cells resemble discs with pinched-in centers
as shown in Figure 34.7. Recall that red blood cells develop in the marrow—the center portion of large bones. Red blood cells have no nuclei and only live for about 120 days.
Red blood cells mostly consist of an iron-containing protein called hemoglobin. Hemoglobin chemically binds with oxygen molecules and carries oxygen to the body’s cells. Some carbon dioxide is carried by the hemoglobin
but most carbon dioxide is carried in plasma.
Platelets
Have you ever cut your finger? You probably have noticed that in a short while
the blood flowing from the cut slows and then stops as a blood clot forms a scab. Platelets are cell fragments that play an important part in forming blood clots.
When a blood vessel is cut
platelets collect and stick to the vessel at the site of the wound. The platelets then release chemicals that produce a protein called fibrin. Fibrin is a protein
White blood cells
The body’s disease fighters are the white blood cells. Like red blood cells
white blood cells are produced in bone marrow. Some white blood cells recognize disease-causing organisms
blood cells surround and kill the invaders.
White blood cells are different from red blood cells in important ways. First
many white blood cells move from the marrow to other sites in the body to mature. Unlike red blood cells
plasma
red blood cells (dimpled discs)
