Structure and Function of the Blood in Dogs Page 2


What are the Functions of Blood in Dogs?

Each component of blood has very specialized and important functions.

  • Red blood cells contain hemoglobin, which is a red, iron-rich protein. Hemoglobin enables red blood cells to carry oxygen from the lungs to all parts of the body. Red blood cells give blood its color. When the blood is rich in oxygen it is red, and when there is little oxygen in the blood, the blood is blue. Because blood traveling from the lungs to the body usually contains lots of oxygen, blood in the arteries is normally red. Much of the oxygen is removed from the small capillaries by the body tissues, so blood in the veins tends to be blue in color.
  • The white blood cells defend the body against disease. They destroy bacteria and foreign material, they stimulate inflammation and assist in the healing process, and they produce proteins called antibodies that destroy bacteria, viruses, and other diseases. WBCs move in and out of the blood stream, depending upon where they are needed.
  • Platelets help the blood to clot. They group together to form clumps, plugging any holes that develop in blood vessels. Clumps of platelets form a scaffolding upon which a blood clot may form. Formation of a blood clot is a complicated process called coagulation.
  • Plasma is the watery material that carries all other components of the blood within the blood vessels. If water is lost through dehydration, wounds or burns, then the blood can become thickened, almost like sludge, and circulation will be adversely affected.
  • What are the Common Diseases of Blood in Dogs?

    There are several very important and sometimes life-threatening diseases of the blood. Diseases of the blood generally involve either too many or too few of a particular cell or blood component.

  • Red blood cells. Some disorders involving the red blood cells include anemia and polycythemia:

    With anemia there are fewer circulating RBCs than normal. Because anemia decreases oxygen delivery to cells, affected individuals are often tired or weak. Their gums may be pale as well. There are numerous causes of anemia: Anemia may arise because red blood cells are not produced in adequate numbers, because they are lost from the blood stream, or because they are destroyed.

    Polycythemia is the presence of too many RBCs in the blood. This condition is rare in the dog.

  • White blood cells. The most common disorders involving the white blood cells are generally associated with infections, including bacterial, viral, fungal and parasitic infections. In response to these conditions, the body usually manufactures lots of a particular type of white blood cell, so cell numbers in the blood can become very elevated. White blood cell numbers can also become elevated when cancer in the bone marrow causes the production of cancerous white blood cells. The presence of these abnormal white blood cells in the circulation is called leukemia.
  • Platelets. The most common disorder associated with platelets is thrombocytopenia, which is a decrease in the number of circulating platelets. The number of platelets can fall if there is not enough being produced in the bone marrow, if they are being consumed as quickly as they are produced, or if they are lost from the body through continued bleeding.
  • Plasma. The most common disorder involving plasma is a decrease in the circulating proteins. Protein levels may fall if the liver does not produce enough of the protein, albumin, or if protein is lost from the blood or body. Plasma proteins are partially responsible for holding water in the blood vessels. When protein levels fall below a critical level, water leaves the blood stream and enters the tissues or cavities of the body, causing edema.
  • What Types of Diagnostic Tests are Used to Evaluate Blood?

  • A complete blood count (CBC) measures the size, number and maturity of both the red and white blood cells within a specific blood sample. Alterations in the CBC may indicate the presence of either minor or serious disease processes. A decrease in the red blood cell count indicates anemia. Increases in the red cell count might suggest polycythemia. Increased white blood cells may indicate inflammation, bacterial infections or other infections. Severe elevations in WBCs are seen with leukemia. A decreased WBC count may occur with some viral infections or with overwhelming bacterial infections.
  • A platelet count assesses the number of platelets in the blood.
  • A serum biochemistry profile measures many components of the serum in the blood. Serum is the watery portion of the blood that remains after plasma has been allowed to clot. Biochemistry tests detect various blood proteins, the amount of sodium, potassium and chloride in the blood, blood sugar, and numerous enzymes present in the circulation.
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