What is the Difference Between Elastic and Muscular Arteries

The main difference between elastic and muscular arteries is that elastic arteries occur closest to the heart, experiencing a great pressure while the heart forces blood into them whereas muscular arteries are responsible for transporting blood to different types of organs in the body. Furthermore, the tunica media of elastic arteries is mainly composed of elastin while the tunica media of muscular arteries is mainly composed of smooth muscle.

Elastic arteries, muscular arteries, and arterioles are the three groups of arteries classified based on their size and function. The main function of arteries is to supply oxygenated blood to the tissues and organs of the body. 

Key Areas Covered

1. What are Elastic Arteries
     – Definition, Structure, Role
2. What are Muscular Arteries
     – Definition, Structure, Role
3. What are the Similarities Between Elastic and Muscular Arteries
     – Outline of Common Features
4. What is the Difference Between Elastic and Muscular Arteries
     – Comparison of Key Differences

Key Terms

Elastic Arteries, Elastin, Muscular Arteries, Smooth Muscle, Tunica Media, Vasoconstriction

What are Elastic Arteries

Elastic arteries or conducting arteries are the arteries closest to the heart. They are characterized by the presence of a large number of collagen and elastin filaments in the tunica media, the middle layer of a typical artery wall. The examples of elastic arteries include the aorta along with its three major branches: left brachiocephalic, right common carotid, right subclavian arteries and pulmonary arteries. In the case of the aorta, the tunica media is the thickest and it contains 50 layers of alternating elastic and smooth muscle fibers.

Figure 1: Structure of Three Types of Arteries

However, the main function of elastic arteries is to receive blood from the heart under high pressure and to gently pass the blood through arteries. Inside elastic arteries, the blood pressure comes to its normal caliber. Generally, the systolic blood pressure between the aortic root and brachial artery can be 14 mm Hg. Significantly, the high resistance of elastic arteries prevents the turbulence of high-pressure blood while the heart reaches its diastolic phase in a process known as Windkessel effect.

Furthermore, the walls of the carotid sinus and the arch of aorta contains both baroreceptors and chemoreceptors. Here, baroreceptors are responsible for sensing the pressure changes while chemoreceptors monitor the oxygen and carbon dioxide concentration of blood along with blood pH.

What are Muscular Arteries

Muscular arteries are a type of arteries that arise from elastic arteries and give rise to arterioles. The main function of these arteries is to supply blood to the organs. Generally, the tunica media of muscular arteries is not thick as elastic arteries and it is composed of 3-10 layers of alternative smooth muscles and elastic fiber layers. Significantly, muscular arteries consist of a less dense subendothelial layer, reducing the risk of atherosclerosis, which increases with the increasing density of the subendothelial layer.

Figure 2: Systemic Blood Pressure

Moreover, muscular arteries are also known as resistance vessels as they exhibit vasoconstriction in response to sympathetic stimulation. That means; they can change the diameter of arteries, controlling the flow of blood as well as blood pressure. Alpha 1 and beta 2 adrenergic receptors are responsible for the sympathetic innervation in muscular arteries.

Similarities Between Elastic and Muscular Arteries

• Elastic and muscular arteries are two types of arteries in the circulatory system of the body.
• Their main function is to transport oxygenated blood from the heart to the organs.
• The wall of both these arteries is composed of three layers: tunica externa, tunica media, and tunica intima.
• Thus, both arteries can be classified based on the composition of the tunica media.
• Also, the lumen of both arteries are smaller in contrast to the size of the lumen of a vein.
• And, they do not contain valves.
• Besides, both undergo a spurty movement of blood. Therefore, their pulses are detectable.
• Moreover, both undergo muscular contractions.
• However, the driving force of blood inside both types of arteries is the pumping pressure of the heart.

Difference Between Elastic and Muscular Arteries

Definition

Elastic arteries refer to an artery with a large number of collagen and elastin filaments in the tunica media, which gives it the ability to stretch in response to each pulse, while muscular arteries refer to a medium-sized artery that draws blood from an elastic artery and branch into “resistance vessels” including small arteries and arterioles. Thus, this is the main difference between elastic and muscular arteries.

Occurrence

While elastic arteries occur closest to the heart, muscular arteries occur in between elastic arteries and arterioles.

Size

Size is another difference between elastic and muscular arteries. Elastic arteries are large, >10 mm in diameter, while muscular arteries are comparatively small, 0.1–10 mm in diameter. 

Examples

Moreover, elastic arteries include aorta, its three major branches, and pulmonary arteries while muscular arteries include external carotid artery, radial and ulnar arteries, popliteal artery, femoral artery, etc.

Function

Elastic arteries receive high-pressure blood from the heart and gently push the blood forward while muscular arteries supply blood to various organs. Hence, this is the functional difference between elastic and muscular arteries.

Blood Pressure

The blood pressure of elastic arteries is high while the blood pressure of muscular arteries is comparatively low.

Tunica Media

Tunica media is also a major difference between elastic and muscular arteries. Elastic arteries contain thick tunica media while muscular arteries contain comparatively thin tunica media.

Tunica Media Composition

The tunica media of elastic arteries mainly contains elastic fibers while the tunica media of muscular arteries mainly contains smooth muscles.

Subendothelial Layer

The density of the elastic fibers and smooth muscle in the subendothelial layer of elastic arteries is high while the density of the elastic fibers and smooth muscle in the subendothelial layer of muscular arteries is comparatively low.

Risk of Atherosclerosis

Elastic arteries are more prone to the formation of atherosclerosis while muscular arteries have a low risk of atherosclerosis due to the presence of a less subendothelial layer. Thus, this is also a difference between elastic and muscular arteries.

Innervation

Baroreceptors and chemoreceptors occur in elastic arteries while alpha 1 and beta 2 receptors occur in muscular arteries.

Vasoconstriction

Elastic arteries do not undergo vasoconstriction while muscular arteries undergo vasoconstriction to control the flow and the pressure of blood. This is another difference between elastic and muscular arteries.

Basal NO production

The basal NO production is high in elastic arteries while the basal NO production is low in muscular arteries.

Conclusion

Elastic arteries are the large arteries that start from the heart. They include aorta and its major branches and pulmonary arteries. Their diameter is high and they conduct blood under high pressure. Significantly, the tunica media of elastic arteries contain a higher amount of elastin. However, these arteries supply blood to the muscular arteries, which have a low diameter in contrast to elastic arteries. The main function of muscular arteries is to supply blood to organs. Their tunica media is comparatively thin. Also, they undergo vasoconstriction. However, the main difference between elastic and muscular arteries is their structure and function.

References:

1. “Arteries|Boundless Anatomy and Physiology.” Lumen Learning, Lumen, Available Here.
2. Leloup, Arthur J A et al. “Elastic and Muscular Arteries Differ in Structure, Basal NO Production and Voltage-Gated Ca(2+)-Channels” Frontiers in physiology vol. 6 375. 15 Dec. 2015, doi:10.3389/fphys.2015.00375

Image Courtesy:

1. “2103 Muscular and Elastic Artery Arteriole” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia  
2. “2109 Systemic Blood Pressure” By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia