anaphysio blood

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ANATOMY AND PHYSIOLOGY OF THE BLOOD

Bone marrow is the soft, flexible, vasculartissue found in the hollow interior

cavities and cancellous bone spaces in the center of many bones and which is the

source oferythrocytes (red blood cells) and leukocytes (white blood cells).

There are two main types of bone marrow. Red bone marrowis the center of

production of all blood cells except one type of lymphocyte, which matures in the

thymus.Yellow bone marrowstores fats.

As the source of blood cells, the bone marrow is critical to the health of people.

The disruption of the intricate harmony, such as the production of too many, too few, or

abnormal blood cells, results in diseases, such as leukemia, that can be life-threatening.

Fig. 1a Fig. 2b

Fig. 1a Illustration of a section through long bone, with spongy bone in its center.Fig. 2b Long Bone
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Marrow types

Fig. 2c Section through the femur head, showing the cortex, the red bone marrowand a spot ofyellow bone marrow. The white bar

represents 1 centimeter.

There are two types of bone marrow: red marrow (consisting mainly of myeloid tissue)

and yellow marrow (consisting mainly of fat cells). Red blood cells, platelets, and most

white blood cells arise in red marrow; some white blood cells develop in yellow marrow.

Both types of bone marrow contain numerous blood vessels and capillaries.

At birth, all bone marrow in children is red. With age, more and more of it is converted to

the yellow type.

Red marrow is found mainly in the flat bones, such as the hip bone, breast bone, skull,

ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the

proximal ends of the long bones femur and humerus. Yellow marrow is found in the

hollow interior of the middle portion of long bones.

In cases of severe blood loss, the body can convert yellow marrow back to red marrow

in order to increase blood cell production.

Stroma

The stroma of the bone marrowis all tissue that is not directly involved in the primary

function of hematopoiesis. The yellow bone marrow belongs here, and makes the

majority of the bone marrow stroma, in addition to stromal cells located in the red bone

marrow.
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Still, the stroma is indirectly involved in hematopoiesis, since it provides the

hematopoietic microenvironmentthat facilitates hematopoiesis by the parenchymal

cells. For instance, they generate colony stimulating factors, affecting hematopoiesis.

Macrophages contribute especially to red blood cell production. They deliver iron for

hemoglobin-production.

The blood vessels constitute a barrier, inhibiting immature blood cells from leaving the

bone marrow. Only mature blood cells contain the membrane proteins required to attach

to and pass the blood vessel endothelium. Hematopoietic stem cells may also cross the

bone marrow barrier and may thus be harvested from blood.

Blood and its Components

Medical men categorize blood as connective tissue. This precious liquid contains

erythrocytes, leukocytes, and platelets which are also known as thrombocytes. The

blood cells mentioned above are responsible for transport, immunity, and clotting

functions.

Our blood makes up about 8% of an average adults body weight that is about 5

liters. Arterial blood departs from the heart carrying oxygen with the help of

erythrocytes, that is why it is bright red. Venous blood on its way back to the heart has

less oxygen and is darker in color. Blood is 4 or 5 thicker than water. Blood

temperatures within the body are about 100.4 degrees Fahrenheit, or 38 degrees

Celsius.

Blood is segregated into two basic divisions - the cellular components and the

plasma. About 45% of the total blood volume of the human body is made up the cellular

elements.
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The major elements of blood are the red blood cells, the white blood cells and the

platelets, i.e the erythrocytes, the leukocytes, and the thrombocytes. The red blood cells

outnumber other cells. A cubic millimeter of blood contains 4.3-5.8 million erythrocytes.

To compare the figures, a cubic milliliter of blood contains 5,000 - 10,000 white blood

cells and 250,000 - 450,000 platelets only.

Fig. 1a

Erythrocytes are special biconcave disks. This shape is designed for the diffusion

of gas. Erythrocytes live for approximately 120 days, that is why our body keeps

producing young red blood cells.

Leukocytes are white blood cells that help fight off infection and illness. White

blood cells are larger than red cells and can move independently in an amebic fashion.

When the body creates additional white blood cells, it runs a fever. White cells are

completely transparent and can be watched in the microscope by staining only.

Platelets are the smallest blood cells. Some scientists consider them to be

forming elements instead of cells. There are about 250,000 - 450,000 platelets in one

cubic millimeter of blood. The platelets are the only blood cells lacking nuclei and they

are able to move on their own just like leukocytes do. As a rule platelets survive in the

blood for 5 - 9 days. It is important to notice that platelets are vital to the blood clotting


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process. This phenomenon helps human organism prevent excessive blood loss in case

of injury. When the string of platelets joins together a certain amount of serotonin is

released into the blood stream to restrict the flow of blood through the blood vessels.

Hemopoiesis is a vitally important process of creating of new blood cells. Bone

marrow located in bones of the skull, the humerus, ribs, femora, pelvis, and sternum is

responsible for forming platelets, erythrocytes, and granular leukocytes. Agranular

leukocytes are created in the spleen, lymph nodes, tonsils and thymus. As soon as the

blood cell life comes to an end, the liverand the spleen destroy them.

General Composition of the Blood.

Blood consists of a faintly yellow fluid, the plasma orliquor sanguinis, in which are

suspended numerous minute particles, the blood corpuscles, the majority of which are

colored and give to the blood its red tint. If a drop of blood be placed in a thin layer on a

glass slide and examined under the microscope, a number of these corpuscles will be

seen floating in the plasma. Blood also contains hormones, fats, carbohydrates,

proteins, and gases.

We know that blood is made mostly of plasma. But there are 3 main types of blood cells

that circulate with the plasma:

Platelets, which help the blood to clot.

Clotting stops the blood from flowing out

of the body when a vein or artery is

broken. Platelets are also called

thrombocytes.

Red blood cells, which carry oxygen. Of

the 3 types of blood cells, red blood cells

are the most plentiful. In fact, a healthy

adult has about 35 trillion of them. The
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body creates these cells at a rate of about 2.4 million a second, and they each

have a life span of about 120 days. Red blood cells are also called erythrocytes.

White blood cells, which ward off infection. These cells, which come in many

shapes and sizes, are vital to the immune system. When the body is fighting off

infection, it makes them in ever-increasing numbers. Still, compared to the

number of red blood cells in the body, the number of white blood cells is low.

Most healthy adults have about 700 times as many red blood cells as white ones.

White blood cells are also called leukocytes.

What does blood do?

Blood carries oxygen from the lungs and nutrients from the digestive tract to the bodys

cells. It also carries away carbon dioxide and all of the waste products that the body

does not need. (The kidneys filter and clean the blood.) Blood also

Helps keep your body at the right temperature

Carries hormones to the bodys cells

Sends antibodies to fight infection

Contains clotting factors to help the blood to clot and the bodys tissues to heal

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