How do Venous and Arterial blood differ?

How do Venous and Arterial blood differ?
September 09 11:14 2021 Print This Article

The heart is a pump that is constantly delivering purified or oxygenated blood from the left chambers of the heart (left side from the person’s perspective), to millions of cells all over the body, through a large network of blood vessels called arteries. At the same time, impure blood created by the metabolism happening in these cells is collected through a large network of blood vessels called veins and sent to the right chambers of heart, and in turn to the lungs, for purification or oxygenation. Such a mechanism is called a double circulation system.

The only exception to this rule, are the pulmonary artery and pulmonary vein. The pulmonary artery delivers impure blood to the lungs for purification while the purified blood from the lungs is sent to the heart through the pulmonary vein.

Interestingly, there are several differences between arterial and venous blood. These differences matter to pathologists who conduct diagnostic tests and other types of doctors too, during various treatments meted out to patients. It’s also useful for the common man to be aware of these differences.

Differences between arterial and venous blood

Difference Arterial Blood Venous Blood
Location As explained above, arterial blood is oxygenated or purified blood that flows in lungs, pulmonary vein, left chambers of the heart, and vast network of arteries all over the body. In contrast, venous blood is the deoxygenated or impure blood that has passed through all parts of the body except lungs, and is found in the vast network of veins all over the body, right chambers of the heart, and pulmonary artery.
Direction of Flow Arterial blood always flows away from the heart While venous blood flows towards the heart.
Driving Force While the pumping action or pumping pressure of the heart is what delivers or drives flow of arterial blood The pressure of the venous blood is generally 5-8 mm Hg at the right atrium, and rarely needs to be measured.
Blood Pressure

 

 Both arterial and venous blood has pressure in them which is required to sustain the flow. BP in the arterial blood in healthy conditions is 120/80 mm Hg, and this is what a doctor measures using a sphygmomanometer or BP-measuring instrument. The pressure of the venous blood is generally 5-8 mm Hg at the right atrium, and rarely needs to be measured.
Partial Pressure of Oxygen The partial pressure of oxygen, denoted as PaO2, is a measure of oxygen pressure in the blood. It indicates how efficiently oxygen is able to move from the lungs to the arterial blood. Illness of any kind tends to alter this factor. At sea level and with good health of the person, partial pressure of oxygen in the arteries is good enough to satisfy the oxygen requirements of the entire body. This value is generally 100 mm Hg. Venous blood in contrast has lesser PaO2 as most of the oxygen has been delivered to the body cells. This value is generally 30-40 mm Hg. A person with very good health and fitness has better oxygen intake, at sea levels, so this figure can be higher in him/her.
Color of the blood

 

 This is the only physical marker that differentiates these 2 types of blood. Arterial blood is a bright-red color as the hemoglobin present in it has received plenty of oxygen. In contrast, hemoglobin in the venous blood has lost a lot of oxygen, so venous blood is dark-red, almost blackish in colour. Good health and ill-health can also alter these colours slightly.
Constitution Other than oxygen, arterial blood is rich in vitamins, amino acids, minerals and glucose, absorbed from food or medication being given for one or more conditions. In contrast, the venous blood is low in the above constituents as these have already been delivered to the body cells. Instead, its rich in metabolic wastes collected from the body, such as urea and bicarbonate. In the lungs, the bicarbonate is converted to carbon di-oxide and expelled out of the lungs during exhalation.
pH Value Arterial blood generally has a pH of 7.4 in normal health conditions of the person. In comparison, venous blood has a lower pH.
Temperature Arterial blood is around 37 degrees Celsius or 98.6 degree Fahrenheit in a healthy person. In comparison, venous blood has a lower temperature.
Medicinal utility Arterial blood is collected generally to evaluate arterial blood gases (ABG). This is a measure of oxygen and carbon di-oxide content in them. This can indicate efficiency of lung function and presence of any lung condition. Venous blood is what is generally drawn for all routine, laboratory, diagnostic, blood-tests. The reference ranges shown in blood-test reports are based on venous blood.
Method of extraction Arterial blood samples are obtained directly from the artery, generally the radial artery, by a doctor, nurse or paramedic who is trained to do this and is aware of complications that come from not doing it right. Arterial blood can also be obtained using vascular access devices (VADs) such as a femoral arterial line or catheter that are inserted into an artery. Venous blood is drawn by directly puncturing a vein, most often located in the antecubital area of the arm (near the elbow), or the top posterior portion of the hand. Sometimes, VADs such as a central venous pressure line or an IV start may also be used.

 

Venous or Arterial? Get Your Answers Here

What is venous blood?

Venous blood is the oxygen-poor blood that flows toward the heart after delivering oxygen to the body’s tissues. It carries carbon dioxide and other metabolic wastes and appears darker than oxygen-rich arterial blood.

What is arterial blood?

Arterial blood is the oxygen-rich blood that flows away from the heart to the body’s tissues. It is bright red in color due to its high oxygen content and carries nutrients essential for the body’s cells.

What is deoxygenated blood?

Deoxygenated blood is blood that has given up oxygen to body tissues and is returning to the heart with higher carbon dioxide content. This is the type of blood typically found in veins.

How does arterial blood color differ from venous blood?

The color of the arterial blood is bright red because it is rich in oxygen. Venous blood, being deoxygenated, is darker red. This color difference helps doctors distinguish between the two during medical procedures.

 What is the difference between arterial blood and venous blood?

Arterial blood vs venous blood differs in oxygen content, color, flow direction, pressure, pH, and clinical uses. Arterial blood carries oxygen away from the heart, while venous blood returns oxygen-poor blood to the heart.

How are arterial and venous blood used in medical tests?

Arterial blood is collected for arterial blood gas (ABG) tests to measure oxygen and carbon dioxide levels. Venous blood is usually drawn for routine lab tests like glucose, hemoglobin, and cholesterol levels.

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Updated on 22nd Jan 2024