Structure and Function of the Blood in Dogs

Below is information about the structure and function of canine blood. We will tell you about the general structure of blood, how blood works, common diseases that affect the blood and common diagnostic tests performed in dogs to evaluate blood.

What is Blood?

Blood is the life-maintaining transport fluid that circulates oxygen and nutrients throughout a dog’s body, carries away waste products, and helps defend against disease. Blood consists of numerous components, such as cells and proteins, that circulate in a fluid called plasma. The millions of cells that circulate in blood include erythrocytes (red blood cells), leukocytes (white blood cells) and thrombocytes (platelets). Besides transporting vital components, the blood plays an important role in the immune functions of the body and is vitally important to coagulation (ability of blood to clot properly).

Various components of blood are produced in several tissues and organs. Red blood cells, platelets and some white blood cells are manufactured in the bone marrow, which is present in the central cavity of the long bones of the body. Other white blood cells are formed in the lymph nodes. Proteins that circulate in the blood are manufactured in the liver and by circulating white blood cells. At times the spleen is also a site of the production of some blood components.

Where Is Blood Located in Dogs?

Blood is located in almost every part of the body, because it circulates through the body’s heart, arteries, veins and capillaries (the tiny vessels that connect arteries and veins). Any tissue containing blood vessels normally contains blood.

What Is the General Structure of Canine Blood?

Blood consists of four main parts: red blood cells, white blood cells, platelets and plasma.

Red blood cells (RBCs). These are the most numerous cells found in the blood. In the normal dog, there may be 5.5 to 8.5 million RBCs in a microliter of blood. RBCs are disc-shaped cells that contain hemoglobin, an important protein that transports oxygen. Mature red blood cells are unique in that they do not contain a nucleus. (The nucleus is the small, oval area in the cell that contains DNA genetic material.)

White blood cells. Several classes of white blood cells (WBCs) circulate in the blood. At any given time, in the normal dog, there are roughly 6,000 to 17,000 of these cells per microliter of blood. The types of white blood cells are as follows:

Platelets. Platelets are not cells; they are very tiny disks that look like flat plates and are produced primarily in the bone marrow. Their major function is to plug any leak that develops in the walls of blood vessels and to start the process of blood clotting. In normal dogs, there are often 175,000 to 500,000 platelets per microliter of blood.

Plasma. Plasma is the fluid portion of blood. It is a watery mixture of proteins, minerals and other chemicals vital to the body. It contains substances such as sodium, potassium, chloride, magnesium, glucose (blood sugar), and various enzymes that are produced in the liver, pancreas, kidneys, and muscles. Plasma also contains important clotting factors and many body waste products.

What are the Functions of Blood in Dogs?

Each component of blood has very specialized and important functions.

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.

What Types of Diagnostic Tests are Used to Evaluate Blood?