Difference Between Valve and Sphincter

The key difference between valve and sphincter is that valve is a flap-like structure of a hollow organ that allows one-way fluid flow through it while sphincter is a ring-like muscle which is able to contract or close a bodily passage or opening.

Valve and sphincter are two structures that carry out similar functions in our body. Both structures facilitate the flow of fluids in one direction and prevent backflow. A valve is like a door which opens only in one direction. It is a flap-like structure of a hollow organ. On the other hand, the sphincter muscle is a ring-like muscle that can relax or contract.

1. Overview and Key Difference
2. What is a Valve
3. What is a Sphincter
4. Similarities Between Valve and Sphincter
5. Side by Side Comparison – Valve vs Sphincter in Tabular Form
6. Summary

What is a Valve?

A valve is a flap-like structure of a hollow organ. It ensures the one-way fluid flow through it. There are four valves in our heart. They regulate the flow of blood in the correct direction and prevent backflow and mixing of oxygenated blood with deoxygenated blood.

Figure 01: Heart Valves

Mitral valve and tricuspid valve control blood flow from atria to ventricles while aortic valve and pulmonary valve control blood flow out of the ventricles. Heart valves are thin membranes. They open and close properly.

What is a Sphincter?

Sphincter muscles are the ring-like muscles located in hollow organs. These muscles surround bodily passages or openings. Sphincters can contract or relax. A sphincter actively assists flow in one direction by relaxing and actively resists flow in the opposite direction by contracting. In our anal canal, there are sphincter muscles as internal anal sphincter and external anal sphincter in order to prevent unwanted bowel leakages. Damages in sphincter muscles cause faecal incontinence. Another important sphincter in our body is the sphincter pylori that holds food in the stomach until it mixes with gastric juices. Moreover, sphincter urethrae is another important sphincter that controls urination.

Figure 02: Urinary Sphincter

In our eyes, there is a sphincter called sphincter papillae that is important for the contraction of pupil in the presence of bright light. Likewise, the human body has over 60 types of sphincters.

What are the Similarities Between Valve and Sphincter?

We have valves and sphincters in our body.
Both valve and sphincter facilitate the flow of fluids in one direction.
Both prevent backflow.
They are located in hollow organs of our body.

What is the Difference Between Valve and Sphincter?

Valve and sphincter are two structures that allow one-way fluid flow in hollow organs. However, the valve is a flap-like structure, while sphincter is a ring-like muscle. So, this is the key difference between valve and sphincter. Mitral valve, tricuspid valve, aortic valve and pulmonary valve are some examples of valves present in our body while internal anal sphincter, external anal sphincter, sphincter pylori, sphincter urethrae and sphincter papillae are some examples of sphincters located in our body.

The below infographic summarizes the difference between valve and sphincter.

Summary – Valve vs Sphincter

A valve is a membrane, commonly present in the circulatory system or digestive system, and it allows the passage of fluid only in one direction. Meanwhile, the sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice. Therefore, this is the key difference between valve and sphincter. Mitral valve, tricuspid valve, aortic valve and pulmonary valve are some examples of valves present in our body while internal anal sphincter, external anal sphincter, sphincter pylori, sphincter urethrae and sphincter papillae are some examples of sphincters located in our body.

Reference:

1. “Sphincter Muscle.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 18 Aug. 2017, Available here.
2. “Heart Valves.” YourHeartValve, Available here.

Image Courtesy:

1. “2011 Heart Valves” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
2. “Urinary Sphincter” By BruceBlaus – Own work (CC BY-SA 4.0) via Commons Wikimedia