Veterinary Hematology is more than just blood cells. Blood, highly functional and truly definitive, does much more than provide for the transport of cellular metabolites and waste products. Blood is made up of four major components: Plasma, Red Blood Cells, White Blood Cells, and Platelets.
Each component possesses its own diagnostic significance in the veterinary clinical setting.
Without blood, you have no viable mammal life. Therefore without blood, the clinician has no valid clinical picture of disease-state. To appreciate the value of blood, the clinician should examine each individual component of blood separately to gain an appreciation for the clinical significance and diagnostic value of veterinary hematology in their practice. Anemia will also be discussed.
Plasma
Plasma carries blood and blood proteins. Aside from a high water content, plasma also contains dissolved salts, calcium, sodium, magnesium, and potassium. Plasma contains clotting factors and on exposure to air it will clot. Serum is the clear fluid that separates from clotted whole blood and clotted plasma. Plasma comprises approximately 20% of the animal body's extracellular fluid. Most plasma protein molecules are too large to pass through the capillary walls into the interstitial space. The small amount of protein that can pass through the capillary walls is primarily taken up by the lymph nodes and eventually returned to the circulation.
The Majority of the plasma proteins are produced in the liver. Plasma proteins form three major chemical groups (fractions) and have varying functions:
*albumin - approximately 60%
*fibrinogen - approximately 4%
*globulins - approximatly 36% over three subfractions (IgA, IgB, & IgG)
The relative proportions of plasma proteins can vary in certain diseases and these variations can be clinically useful in determining proper IV therapy. Albumin is the smallest of the plasma proteins and easily passes through capillary walls. In kidney disease, large amounts of albumin are excreted through damaged kidney tubules and can be detected in the urine.
Functions of the plasma proteins include:
Intravascular collid osmotic pressure. Maintains fluid and electrolyte levels.
Transport of insoluble substances allowed by protein binding processes
Contribution towards the plasma viscosity
Inflammatory response via microbe fighting antibodies
Protein storage reserve
Clotting
Protection from infection via plasma gamma globulins
Plasma also contains inorganic ions, which are important in regulating cell function and maintaining Homeostasis. As an example, depletion of potassium may occur following severe diarrhea and vomiting. Potassium is an essential element of cell excitability. Sharp decreases in potassium will cause muscle weakness and cardiac abnormalities. Similar problems may cause sodium depletion. Subtherapeutic sodium levels in the plasma will result in the volume of extracellular fluid to decrease which will lead to a drop in blood pressure causing lethargy, dizziness, weakness and fainting.
Plasma carries a wide range of substances including dissolved gasses left over from the respiratory exchange cycle (mostly CO2). Blood carries oxygen because it does not have an affinity for plasma related to its water solubility.
Nutrients, the most abundant being glucose, are carried in the blood plasma as a source of fuel for cellular metabolism. Amino acids, fatty acids, triglycerides, cholesterol and vitamins are also carried by plasma. Urea, uric acid, creatinine from the kidneys, bilirubin from the gall bladder and other waste materials are also transported by plasma. Plasma proteins carry hormones, such as cortisol and thyroxine. The plasma also carries certain drugs and ETOH.
Platelets
Platelets are the result of cellular fragments shed from the megakaryocyte while in the bone marrow. Platelets considered cell fragments rather than actual cells, play a critical role in blood clotting. When an injury to the body occurs, a chemical substance is released at the site of injury.
Platelets are able to quickly adhere to this chemical and begin to form alliances with other platelets and clotting factors. This alliance is the body's defense against bleeding to death.
Platelets are also significant in forming diagnostic clues to the blood smear and can be useful at guiding the clinician in care planning, treatment and further diagnostic steps. Platelet morphology together objective data can be indicative of bleeding disorders and leukemia.
RBCs
Red Blood Cells, seemingly basic, are created and have the sole purpose of kee
收藏至：
