Difference Between Arterial and Venous Blood

Main Difference – Arterial vs Venous Blood

Arteries and veins are the two types of blood vessels found in a closed circulatory system in animals. Typically, in a double circulation system, arteries of the systemic circulation carry blood away from the heart and veins carry blood towards the heart. The main difference between arterial and venous blood is that arterial blood is oxygenated whereas venous blood is deoxygenated. The arterial blood is bright red in color and the venous blood is blackish red in color. However, pulmonary artery and pulmonary vein are two exceptions to this; pulmonary artery carries deoxygenated blood away from the heart while pulmonary vein carries oxygenated blood towards the heart.

Key Areas Covered

1. What is Arterial Blood
      – Definition, Characteristics, Function
2. What is Venous Blood
      – Definition, Characteristics, Function
3. What are the Similarities Between Arterial and Venous Blood
      – Outline of Common Features
4. What is the Difference Between Arterial and Venous Blood
      – Comparison of Key Differences

Key Terms: Artery, Arterial Blood, Deoxygenated Blood, Double Circulation, Oxygenated Blood, Systemic Circulation, Vein, Venous Blood

Difference Between Arterial Blood and Venous Blood - Comparison Summary

What is Arterial Blood

Arterial blood is the oxygenated blood that flows in the arteries of the body. Arterial blood also flows into the lungs and the left chamber of the heart. Since the majority of hemoglobins in the arterial blood is oxygenated, arterial blood is bright red in color. It exhibits a purple color through the skin. The arterial blood is rich in oxygen and other nutrients such as glucose, amino acids, and vitamins. It flows from the heart to the metabolizing tissues throughout the body to supply oxygen and nutrients to the cells.

Difference Between Arterial Blood and Venous Blood

Figure 1: Oxygenated (left) and deoxygenated (right) blood drops

Arterial blood is mainly used to measure the acidity (pH), oxygen concentration, and carbon dioxide concentration in the blood. The test method is called the arterial blood gas (ABG) test. It is used to check the efficiency of the lungs to remove carbon dioxide from the blood as well as to take oxygen into the blood. Oxygenated and deoxygenated blood drops are shown in figure 1. 

What is Venous Blood

Venous blood is the deoxygenated blood found in the veins, the right chambers of the heart, and the pulmonary artery. The oxygenated blood that comes through the arteries passes through the blood capillaries, exchanging the materials of blood with the extracellular matrix of the tissue. Oxygen, glucose, amino acids, and vitamins move into the extracellular fluid from the blood. In Meanwhile, the metabolic wastes of the tissue such as carbon dioxide and urea move into the blood. The whole exchanging process of materials between the blood and the extracellular fluid is called microcirculation.

Main Difference -  Arterial Blood vs Venous Blood

Figure 2: Formation of Venous Blood

Since blood in the venous end is deoxygenated, the color of the blood is blackish red. This deoxygenated blood moves through the venules to the veins. Ultimately, all deoxygenated blood from the body comes to the right atrium of the heart through superior and inferior vena cava. The superior vena cava drains blood from the upper part of the body above the diaphragm. The inferior vena cava drains blood from the lower parts of the body. The formation of the venous blood at blood capillaries is shown in figure 2. 

Similarities Between Arterial and Venous Blood

  • Arterial blood and venous blood flow within blood vessels.
  • Both arterial blood and venous blood contains the same amounts of hemoglobin.

Difference Between Arterial and Venous Blood

Definition

Arterial Blood: Arterial blood is the oxygenated blood that is found in the lungs, pulmonary vein, left chambers of the heart, and arteries.

Venous Blood: Venous blood is the blood that has passed through various blood capillaries of various organs except for the lungs, and is found in veins, right chambers of the heart, and pulmonary artery.

Flow

Arterial Blood: Arterial blood flows in lungs, left chambers of the heart and in arteries.

Venous Blood: Venous blood flows in the right chamber of the heart and in veins.

Direction of the flow

Arterial Blood: The arterial blood flows away from the heart.

Venous Blood: The venous blood flows towards the heart.

Driving Force

Arterial Blood: The driving force of the arterial blood is the pumping pressure of the heart.

Venous Blood: The driving force of the venous blood is the muscular contractions.

Blood Pressure

Arterial Blood: The normal pressure of the arterial blood is 120/80 mm Hg.

Venous Blood: The normal pressure of the venous blood is 5-8 mm Hg at the atrium.

Partial Pressure of Oxygen

Arterial Blood: The PaO2 in the arterial blood is around 100 mm Hg.

Venous Blood: The PaO2 in the venous blood is around 30-40 mm Hg.

Color of the Blood

Arterial Blood: The arterial blood is bright red in color.

Venous Blood: The venous blood is blackish red in color.

Rich in

Arterial Blood: The arterial blood is rich in oxygen and nutrients such as glucose, amino acids, and vitamins.

Venous Blood: The venous blood is rich in HCO3 and metabolic wastes such as urea.

pH

Arterial Blood: The pH of the arterial blood is 7.40.

Venous Blood: The venous blood consists of a lower pH than the arterial blood.

Temperature

Arterial Blood: The temperature of the arterial blood is 37 ºC.

Venous Blood: The temperature of the venous blood is lower than that of the venous blood.

Method of Collection

Arterial Blood: The arterial blood is collected by the direct puncture of an artery.

Venous Blood: The venous blood is collected by the direct puncture of a vein by a venipuncture.

Medical Uses

Arterial Blood: The Arterial blood is used to test arterial blood gases.

Venous Blood: The venous blood is used for routine blood tests.

Conclusion

Arterial blood and venous blood are two types of blood found in the blood vessels of a closed circulation system. Arterial blood is rich in oxygen and nutrients. But, venous blood is rich in metabolic wastes such as carbon dioxide and urea. Since arterial blood is rich in oxygen, the color of the blood is bright red. The color of the deoxygenated venous blood is blackish red. The main difference between arterial and venous blood is the amounts of oxygen dissolved in each type of blood. 

Reference:

1.“Arterial blood.” Wikipedia, Wikimedia Foundation, 20 Aug. 2017, Available here. Accessed 29 Aug. 2017.
2.“Arterial Blood Gases.” WebMD, WebMD, Available here. Accessed 29 Aug. 2017.
3.“Venous blood.” Wikipedia, Wikimedia Foundation, 9 July 2017, Available here. Accessed 29 Aug. 2017.

Image Courtesy:

1. “NIK 3232-Drops of blood medium” By Unknown – (CC BY 3.0) via Commons Wikimedia
2. “Anatomy and physiology of animals Capillary bed with lymphatic capilaries” By The original uploader was Sunshineconnelly at English Wikibooks – Transferred from en.wikibooks to Commons by Adrignola using CommonsHelper. (CC BY 3.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things

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