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Home > Anatomy & Physiology > Shapes of Muscles

Shapes of Muscles

 

What are the different shapes of muscle?

There are 5 different muscle shapes within the human body:

  • Circular
  • Convergent
  • Parallel
  • Pennate
  • Fusiform

Circular Muscles

These muscles appear circular in shape and are normally sphincter muscles which surround an opening such as the mouth, surrounded by Obicularis Oris and Obicularis Oculi surrounding the eyes

Convergent Muscles

These are muscles where the origin (the attachment to a fixed bone, usually the proximal attachment) is wider than the point of insertion. This fibre arrangement allows for maximum force production. An example is Pectoralis Major. Convergent muscles are also sometimes known as triangular muscles.

Parallel Muscles

Parallel muscles have fibres which, as the name suggests, run parallel to each other and are sometimes called strap muscles.

They are normally long muscles which cause large movements, are not very strong but have good endurance. Examples include Sartorius and Sternocleidomastoid. Some textbooks include Fusiform muscles in the parallel group.

Pennate Muscles

Pennate muscles have a large number of muscle fibres per unit and so are very strong, but tire easily. They can be divided into:

  • Unipennate: These muscles have their fibres arranged to insert in a diagonal direction onto the tendon, which allows great strength. Examples include the Lumbricals (deep hand muscles) and Extensor Digitorum Longus (wrist and finger extensor)
  • Bipennate: Bipennate muscles have two rows of muscle fibres, facing in opposite diagonal directions,with a central tendon, like a feather. This allows even greater power but less range of motion. An example is the Rectus Femoris
  • Multipennate: As the name suggests Multipennate muscles have multiple rows of diagonal fibres, with a central tendon which branches into two or more tendons. An example is the Deltoid muscle which has three sections, anterior, posterior and middle.

Fusiform Muscles

Sometimes included in the parallel muscle group, these muscles are more spindle shaped, with the muscle belly being wider than the origin and insertion. Examples are Biceps Brachii and Psoas major

 

Now Test Yourself

1. What does the fibre arrangement of convergent muscles allow?










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1. What does the fibre arrangement of convergent muscles allow?



  • Strength







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2. Name the three types of pennate muscles












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2. Name the three types of pennate muscles



  • Unipennate
  • Bipennate
  • Multipennate





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3. Give an example of a fusiform muscle











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3. Give an example of a fusiform muscle



  • Biceps Brachii







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4. Parallel muscles are usually long and have good what?










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4. Parallel muscles are usually long and have good what?



  • Endurance






Start again with first card >

 


Next - Types of muscle contraction >>

 

Resources:


Learn More About:

 

Pectroralis major

Pectoralis Major - a convergent muscle

Sternocleidomastoid

Sternocleidomastoid - A parallel muscle

Rectus Femoris

Rectus Femoris - a bipennate muscle

Biceps Brachii

Biceps Brachii - a fusiform muscle

   
 




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