Difference Between Contraction and Constriction

The key difference between contraction and constriction is that contraction is the reduction of size or shortening of muscles, while constriction is the act of tightening, narrowing or closure.

Contraction and constriction are two types of processes taking place in muscles. Contraction takes places in skeletal muscles. Constriction takes place in smooth muscles. Both are involuntary processes, but contraction is sometimes voluntary. Contraction is a result of the tension in the skeletal muscle fibres. Constriction is a result of the pressure caused by smooth muscles within the internal organs in the body.

CONTENTS

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

What is Contraction?

Contraction is the process of shortening in length or reducing in size. It is also the process of becoming smaller in size or shape. Muscle contraction takes place with the activation of tension-generating sites in skeletal muscle fibres. It is based on two variable factors. They are length and tension. There are two types of muscle contractions: isometric and isotonic contractions.

Isometric muscle contraction takes place when the length of the muscle remains the same while the tension changes during a contraction. Isotonic muscle contraction takes place when the muscle tensions remain the same during a contraction. But, in this contraction, the length of the muscle fibers changes. If the length of the muscle fibers shortens, it is a concentric contraction. If the length of muscle fibers lengthens, it is an eccentric contraction. Therefore, muscle contractions do not only shorten the length of muscle fibers with the tension of muscles. Contraction occurs with and without one’s knowledge. Thus, it is induced and autonomic.

What is Constriction?

Constriction is the process of tightening or narrowing to cause an obstruction. This takes place when materials pass through. Constriction in human physiology is the closing or narrowing of a pathway to stop or limit the passing of materials. This process occurs without one’s knowledge. Therefore, it is an autonomic process.

Constriction regulates or controls the passing of fluids or materials within the body. Constriction mostly takes place in smooth muscles. Smooth muscles are found in the internal organs of the human body. They are present in organs such as the eye, stomach, pharynx, intestines, bladder, bronchi and ureter. They are also present in other structures such as muscle sphincters and blood vessels. Constriction in organs and other structures takes place when smooth muscles contract.

There are many types of constrictions, including vasoconstriction, pharyngoesophageal constriction and bronchoconstriction. Vasoconstriction is the constriction of blood vessels to control the flow of blood. Pharyngoesophageal constriction is the constriction in the alimentary canal at the junction of the pharynx and esophagus to control the passing of the bolus after swallowing. Bronchoconstriction is the constriction of the bronchus when air passes through. This causes coughing and wheezing since the airways are disturbed due to constriction.

What are the Similarities Between Contraction and Constriction?

• Contraction and constriction take place in muscles.
• Both have an involuntary function.

What is the Difference Between Contraction and Constriction?

Contraction is the process of shortening or reducing the size, whereas constriction is the process of narrowing or tightening. So, this is the key difference between contraction and constriction. Moreover, contraction usually takes place in skeletal muscle fibres, while constriction usually takes place in smooth muscles. Thus, this is another difference between contraction and constriction.

Furthermore, contraction causes the muscles to make a movement. However, constriction prevents or controls the movement of fluids and materials within the body. Also, the constriction takes place in a passageway. In addition to these differences, contraction is either a voluntary or involuntary process while constriction is an involuntary process.

Below is a summary of the difference between contraction and constriction in tabular form.

Summary – Contraction vs Constriction

Contraction is the process of shortening of length or reducing in size. Muscle contractions usually take place with the activation of skeletal muscle fibres. There are two types as isometric contraction and isotonic contraction. Contractions are both voluntary and involuntary. Constriction is the process of tightening or narrowing to cause an obstruction. It is an involuntary process. This controls or prevents the passing of materials and fluids in a passageway within the body. Constriction mainly involves smooth muscles. Thus, this is the summary of the difference between contraction and constriction.

Reference:

1.  “Muscle Contractions.” Learn Muscular Anatomy, Available here.

Image Courtesy:

1. “1015 Types of Contraction new” By OpenStax –  (CC BY 4.0) via Commons Wikimedia

2. “Blausen 0620 Lungs NormalvsInflamedAirway” By Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014” WikiJournal of Medicine 1 (2). DOI:10.15347/wjm/2014.010. ISSN 2002-4436. – Own work (CC BY 3.0) via Commons Wikimedia