Blood Composition

The blood in the human body is a mixture of fluid and cells. Five times thicker than water, blood has a salty taste and is slightly alkaline with a pH of about 7.4. In the living body, the portion of the blood that is fluid is called plasma. The portion of the blood that contains the cellular components is referred to as the formed elements. An average adult has about 5 liters of blood. Approximately 55% of the blood is plasma and the other 45% is formed elements. This means that when observing a blood specimen about half of a specimen will be serum or plasma and the other half will consist of blood cells.

Plasma is a clear, pale-yellow fluid that is made up almost completely of water. Only about 10% are dissolved substances such as:

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-Gases, like oxygen, carbon dioxide and nitrogen.

-Minerals such as sodium, potassium, calcium, and magnesium.

-Nutrients, like lipids, glucose, triglycerides and cholesterol.

-Proteins, such as albumin. This protein helps to regulate the osmotic pressure of the blood.

-Waste products of metabolism like creatinine and uric acid.

-Other substances such as vitamins, hormones and drugs.

The formed elements in blood are important cells. The formed elements of blood consist of many different cells that provide several different and important functions. There are five different formed elements- erythrocytes, leukocytes, granulocytes, agranulocytes, and thrombocytes. Each of these types of cells has different functions and life spans. A lot about a person's health can be determined by observing the formed elements in a blood sample.