Difference Between Nerve and Vein

Main Difference – Nerve vs Vein

Nerve and vein are two components involved in the transportation of different elements in the animal body. Nerves belong to the nervous system, but, veins are a component of the circulation system. The main difference between nerve and vein is that nerve is an axon bundle of neurons in the peripheral nervous system, which carries nerve impulses whereas veins are blood vessels, which return deoxygenated blood towards the heart. Both nerves and veins vary in size. Ideally, both nerve and vein carry corresponding things in one direction excluding the mixed nerve. The constriction and dilation of veins are coordinated by autonomic nervous system.

Key Areas Covered

1. What is a Nerve
      – Definition, Composition, Types, Function
2. What is a Vein
      – Definition, Composition, Types, Function
3. What are the Similarities Between Nerve and Vein
      – Outline of Common Features
4. What is the Difference Between Nerve and Vein
      – Comparison of Key Differences

Key terms: Cranial Nerves, Deep Veins, Mixed Nerves, Motor Nerves, Pulmonary Veins, Sensory Nerves, Spinal Nerves, Superficial Veins, Systemic Veins

What is a Nerve

Nerve refers to any cordlike bundles, which are made up of neurons through which both sensory and motor impulses pass between the central nervous system and the body. A nerve consists of axon bundles in the peripheral nervous system. Each axon in a nerve is wrapped by a connective tissue layer. The transmission of nerve impulses through a nerve can occur either as an electric impulse or chemical signal. The nerves contained by the nervous system of humans are shown in figure 1.

Figure 1: Nerves in the Body

Sensory nerves, motor nerves, and mixed nerves are three types of nerves in the peripheral nervous system. Sensory nerves, which are also called afferent nerves, carry nerve impulses from the sensory organs to the central nervous system. Motor nerves or efferent nerves carry nerve impulses from the central nervous system to the effector organs. Mixed nerves contain both sensory and motor nerves within the same nerve. These nerves can be divided into two as cranial nerves and spinal nerves based on their evolvement from the central nervous system. Cranial nerves are evolved from the brain, and spinal nerves are evolved from the spinal cord. However, nerves play a key role in coordinating the functions of the body.

What is a Vein

Vein refers to any tube forming part of the circulation system, which mainly carries deoxygenated blood towards the heart. The deoxygenated blood is drained from the microcirculation of blood capillaries. This blood is collected into the venules, which are connected to the blood capillaries. Venules are the smallest type of veins. Venules drain blood into veins. Different veins originate from different tissues and organs of the body. Ultimately, all the veins drain blood into two large veins known as superior vena cava and inferior vena cava. The human venous system is shown in figure 2.

Figure 2: Human Venous System

The wall of a vein is made up of three types of tissue layers: tunica adventitia, tunica media, and tunica intima. Tunica adventitia is the outermost layer of the vein, and it is made up of connective tissues. Tunica media is the middle layer of the vein, which is made up of smooth muscles. Tunica intima is the inner layer of a vein. It is made up of a smooth endothelial layer. Each vein is composed of valves in the lumen to prevent the backward movement of blood. The major driving force of the blood inside a vein is the contraction of muscles near to a vein. The structure of a vein is shown in figure 3.

Difference Between Nerve and Vein_Figure 3

Figure 3: Vein Structure

Systemic, pulmonary, Superficial, and deep veins are the four types of veins in the body. Systemic veins drain deoxygenated blood from the body to the heart. Superficial veins occur near the skin. Deep veins occur within muscles and tissues. Pulmonary veins drain oxygenated blood from the lungs to the heart.

Similarities Between Nerve and Vein

Both nerve and vein are involved in transporting things in the body.
Both nerve and vein carry things in the same direction excluding mixed nerve.
Both nerve and vein vary in size.

Definition

Nerve: Nerve refers to any of the cordlike bundles that are made up of neurons through which both sensory and motor impulses pass between the central nervous system and the body.

Vein: Vein refers to any tube forming part of the circulation system, which mainly carries deoxygenated blood towards the heart.

Function

Nerve: Nerves carry nerve impulses.

Vein: Veins carry deoxygenated blood.

Belong to

Nerve: Nerves belong to the nervous system.

Vein: Veins belong to the circulation system.

Color

Nerve: Most nerves are white in color, and the other nerves are yellow in color.

Vein: Veins exhibit a green color through the skin.

Composition

Nerve: Nerves are made up of axons of the neurons in the peripheral nervous system.

Vein: Veins are made up of connective tissue, muscle tissue, and epithelial tissue.

Types

Nerve: Cranial nerves, spinal nerves, afferent nerves, efferent nerves, and mixed nerves are the types of nerves.

Vein: Systemic, pulmonary, superficial, and deep veins are four types of veins.

Branching

Nerve: Nerves are not branched structures.

Vein: Veins are branched structures.

Conclusion

Nerve and vein are two components of the body, which aid transportation. Nerve belongs to the nervous system, and it carries nerve impulses between central nervous system and the body. Vein belongs to the circulation system, and it carries deoxygenated blood towards the heart. The main difference between nerve and vein is the type of material carried by each component in the body.

Reference:

1.“ Nerves – Brain, Spinal Cord, and Nerve Disorders.” Merck Manuals Consumer Version, Available here.
2. Bailey, Regina. “Types of Veins That Keep Your Heart Ticking.” ThoughtCo, Available here.

Image Courtesy:

1.” TE-Nervous system diagram” By Own work (CC BY 3.0) via Commons Wikimedia
2. “Venous system en” By LadyofHats, Mariana Ruiz Villarreal – own work (Public Domain) via Commons Wikimedia
3. “Illu vein” (Public Domain) via Commons Wikimedia