Download Blood ppt from class.

As it circulates throughout the body, red blood cells carry oxygen to all parts of
your body and they remove carbon dioxide. However, did you know that the
blood has more than just one type of cell? The most abundant are red blood
cells that carry oxygen. There are also little cell-like pieces called platelets that
are essential in blood clotting. One of the most fascinating components of
blood, are the white blood cells. These can be further divided into five types of
cells which defend the body against bacteria, viruses and parasites. The blood
cells are suspended in plasma, which consists mostly of water with clotting
factors, cell nutrients, sugar, and hormones.
Marrow is a yellow-white tissue in the center of many bones. It's
the location of a type of stem cell (specifically, the pluripotential
hemopoietic stem cell), from which come the many types of blood
cells. It's a marvelous biological feat that all the cells in our blood -red, white and the platelets -- come from one type of cell that
develops into such a variety of results.
Here are drawings of the cells in your blood. The familiar red
blood cell, pictured in the lower right, is the erythrocyte. It was
once a living cell, but by the time it gets to your bloodstream it's
only a "biological box" that can carry large amounts of oxygen. On
the lower left are the platelets. When you have a cut, the platelets
bind together and form a blood clot that stops the bleeding.
The white blood cells are a collection of five types of cells that patrol the
blood stream and tissues of the body looking for bacteria, viruses and
parasites. Together they are known as white blood cells or leukocytes. The
most common type of leukocyte is the neutrophil and is the body's front line
of defense against harmful bacteria. You have probably seen evidence of
neutrophils if you've ever had a cut that got infected. Surrounding the
infection is usually a fluid called "pus" which mostly contains the remains of
dead neutrophils.
Monocytes will patrol the bloodstream for a little while, but soon develop into
macrophages that can actually "eat" bacteria in the body that isn't supposed to be
there. Because of this, macrophages are large and able to engulf the invader.
Basophils are the least common white blood cell. In addition to fighting
bacteria, they are involved in releasing histamine, a biochemical that
ultimately leads to an increase in swelling.
Not pictured are lymphocytes, which are the second most common type
of leukocytes. Lymphocytes are commonly found in the blood, but also in
the lymphatic system. They develop into either B-lymphocytes or Tlymphocytes and have many functions in fighting bacteria and viral
infections.
Eosinophils are especially valuable as fighters of
parasites. Because of this association, doctors
may suspect a parasitic infection if you have a
blood test that shows a higher number of
eosinophils in the blood than normal.
Remember the white blood cell called the monocyte? At some point in its development, it becomes
a macrophage, which is Greek for "Large Eater." It's kind of like a powerful garbage disposal that is
useful to our immune system because it can actually eat (the process of phagocytosis) foreign
invaders, whether microbial or not. Once the phagocyte surrounds the bacterium, it will destroy it by
"digesting" it. Macrophages patrol the body looking for anything it can "eat." However,
macrophages are particularly on the lookout for anything marked with a "special sign." Other white
blood cells, especially the lymphocytes, attach antibodies to foreign microbes which effectively
identifies the germ as something bad that needs to be destroyed.
Maybe less familiar is the distribution of another network of
vessels that are similar to veins, but not as extensive. Instead
of transporting blood, they carry a clear fluid called lymph.
As nutrients seep from the blood into the tissues, the
lymphatic system collects this fluid along with any
associated wastes and returns it to the blood. Lymph is a
great place to fight microbes and it's filled with lymphocytes
and other white blood cells. Before the lymph gets recycled
into the bloodstream, lymphocytes work to identify any
harmful microbes so they can be destroyed.
Along the lymphatic system are collections of
specialized tissue called lymph nodes. These are
places where large amounts of lymphocytes stay,
which can attack any microbes found in the lymph as
it filters through the lymph node.
The spleen is an oval-shaped organ located in the upper-left side
of your belly, between the stomach and diaphragm. It's where
old, worn-out blood cells go to be recycled. However, since it's
also where bacteria are filtered out of the blood, it's the largest
single organ of the immune system. Oddly enough, the spleen is
a non-essential organ. You can actually live without it, but you'll
be more likely to get certain types of bacterial infections.
The thymus, located between your lungs and behind your
sternum, is where T-lymphocytes develop. Though these white
blood cells begin from stem cells in bone marrow, they further
specialize into T-lymphocytes here. The "T" actually stands for
"thymus" to reflect this origin. The thymus is an interesting organ:
Although it's active in young people and teenagers, it shrinks and
becomes much less active in adults.