Anatomy and Pathophysiology of Anemia

 ANATOMY AND PHYSIOLOGY PHYSIOLOGY

Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood "thicker" than pure water. The average person has about 5 liters (more than a gallon) of blood.  A liquid called plasma makes up about about half of the content of blood. Plasma contains contains proteins that help blood to clot, transport substances through the blood. Blood plasma also contains glucose and other dissolved nutrients. About half of blood volume is composed of blood cells:

Anatomy •

Red blood cells,

Physiology *scientific name for red blood cells is erythrocytes.

*they are formed in the bone marrow and are created by a stem cell. *Red cells are the most numerous of all blood cells in the blood. They are produced at a rate of  4-5 billion every hour in an adult human!

It looks like a doughnut, but without a hole in the middle. Red cells are 7-8 microns in diameter. Yet, they are the heaviest particles in the blood. *After they deliver the oxygen, the red  blood cells pick up a waste product called  carbon dioxide, known as CO 2. Then they  make the return trip back to the lungs through the veins where the CO 2 can finally be released. The body eliminates carbon dioxide every time we breathe out! Then, the red blood cells start the trip all over again.

Red blood cells contain hemoglobin, a protein that carries oxygen. Oxygen is known as O2. Each time we take a breath in, we are inhaling oxygen in the air.

The role of red cells is to absorb oxygen through the little alveoli in your lungs and deliver it to all the muscles, tissues and organs in your body.

To do this, they travel through large arteries and tiny capillaries. Sometimes the capillaries are so small, the red cells have to squeeze and bend themselves in half to get through in order to release their load of oxygen!

• White blood

cells

White Blood Cells, Platelets (stained purple), a T-Lymphocyte white cell (stained green), and a Monocyte white cell (stained gold) as seen through a scanning electron microscope. ©2000 Dennis Kunkel, Ph.D.

scientific name for white blood cells is Leukocytes.

White blood cells are an important part of our body's immune system. Their role is to defend the body against infection by germs.

White blood cells are capable of  passing through the walls of  capillaries (tiny blood vessels) in order to attack, kill and consume intruder germs.

There are many different kinds of white blood cells and each one has a very specific job to do. There are lymphocyte T cells and lymphocyte B cells, monocytes, and granulocytes. Granulocytes contain little granules in their cytoplasm, or cell matter. Granulocytes can be identified even further as neutrophils, basophils and eosinophils. Granulocytes recognize signals that enemy germs send out when they invade the body.

Monocytes and lymphocytes do not contain any granules. But when granulocytes detect an enemy germ, they and the monocytes find it and eat it! Then the monocyte examines the bits of protein the germ was made of  to see how it was put together.

Next, the monocyte calls on the lymphocyte T cell (or Helper T cell) which learns to recognize what the germ looks like.

The lymphocyte T cell then engages the help of the lymphocyte B cell which makes a special weapon called an antibody to use against the germ. The lymphocyte B cell produces copy after copy of these antibody weapons.

When the antibody weapon finds its target, the germ is stunned, wounded and killed.

Then the granulocyte and monocyte move in to finish it off! There are between 7,000 to 25,000 white cells in a single drop of blood!

• Platelets

Inactivated (smooth) platelet (stained blue) among spiky, activated platelets as seen through a scanning electron microscope. ©2000 Dennis Kunkel, Ph.D.

Platelets are sticky little pieces that help prevent bleeding and make the blood clot when a cut is made.

When a stem cell decides to make platelets, it turns into a factory cell called a megakaryocyte. This is a very large cell with several nuclei. The megakaryocyte never leaves the bone marrow, but it does produce many, many tiny fragments. These fragments are actually the platelets, small pieces of cell material or cytoplasm.

Platelets do leave the bone marrow and circulate freely in the bloodstream. Normally, platelets look round and smooth, but when they get busy plugging up cuts and wounds they become spiky and ragged around the edges. When an injury occurs to a blood vessel wall, the platelets respond by literally throwing themselves over the cut to form a temporary plug within minutes slowing the loss of blood.

The platelets also attract a protein found in plasma called fibrin and use it to form a dense netting that traps red blood cells and quickly becomes a clot.

All of the blood cells in your body are mixed together in a slightly yellowish liquid called Plasma. Plasma is mostly made up of water, but also contains proteins, sugars and salt. In addition to carrying blood cells throughout the body, plasma also carries hormones, nutrients and chemicals, such as iron. Plasma has the important function of maintaining the pH of  the blood at approximately 7.4.