Flexor Pollicis Longus Origin, Insertion, Action, Innervation

Muscle Anatomy of the Flexor Pollicis Longus

Origin: Middle anterior surface of the radius and the interosseous membrane
Insertion: Palmar aspect of the base of the distal phalanx of thumb
Actions: Flexion of the thumb
Innervation: Anterior interosseous branch of the median nerve (C8, T1)
Blood Supply: Muscular branches from the radial artery and the anterior interosseous artery from the ulnar artery

Muscle Anatomy: Flexor Pollicis Longus Actions

Primary Actions of the Flexor Pollicis Longus

1.  Flexion of the thumb at the interphalangeal joint


  • None


  • Extensor pollicis longus

2. Flexion of the thumb at the carpometacarpal joint


  • Flexor Pollicis Brevis
  • Adductor Pollicis
  • Opponens Pollicis


  • Extensor Pollicis Brevis
  • Abductor Pollicis Longus

Secondary Actions of the Flexor Pollicis Longus:

1. Assists with flexion of the thumb at the metacarpophalangeal joint


  • Flexor Pollicis Brevis


  • Extensor Pollicis Brevis
  • Extensor Pollicis Longus
  • Abductor Pollicis Longus

2. Assists with flexion of wrist


  • Flexor Carpi Radialis Longus
  • Palmaris Longus
  • Flexor Carpi Ulnaris


  • Extensor Carpi Radialis Longus
  • Extensor Carpi Radialis Brevis
  • Extensor Carpi Ulnaris

Note: Flexor digitorum superficialis and flexor digitorum profundus also assist with flexion of the wrist

Information about cause and effect of Flexor Pollicis Longus pain:

Flexor Pollicis Longus Muscle: Thumb Pain

Recommended Anatomy Books:

Anatomy Coloring Book

The Anatomy Coloring Book is one of the best study and reference books for beginning anatomy students. The diagrams are clearly labeled and allow you to see the relationship and placement of the various structures of the body. You will also be surprised how the act of coloring will help with recall. But this is not just a beginners book, it is also great for practitioners and therapists to have on hand to use with clients and patients to use as a visual reference.

Human Muscle Anatomy

The Trail Guide To The Body is another excellent book to help you learn the musculature of the human body. Though the book is geared toward massage therapists and physical therapist assistants, the book with its illustrations and text helps anyone gain a thorough understanding of the human musculoskeletal system and movement. I highly recommend this book for anyone studying anatomy and believe that MTs, PTAs, and teachers of body movements should have this book in their possession. I also highly recommend this book for the lay person who wants to gain understanding of the muscle, skeletal system and how our bodies move. This book will not disappoint!

Basic Clinical Massage Therapy

Out of the scores of books in my office Basic Clinical Massage Therapy is by far the most referenced book in my library. The musculoskeletal system is overlaid on human models allowing you to learn the precise location, origin and insertions of each muscle. The models are pictured in various poses throughout the book which also helps you visualize muscles in motion and their actions relationship with the skeletal structure and other muscles. Though it is written for massage therapists, it is an excellent book for anyone who wants to learn about the muscular system. MT's will benefit from recommended treatments for each muscle.

Muscle Anatomy Flashcards

Musculoskeletal Anatomy Flashcards Are you a student or professional therapist who needs to brush up on the musculoskeletal system? Dr. Joseph E. Muscolino DC has developed a comprehensive set of flashcards that will help develop a mind's picture of exactly where the muscles lie under the skin. A highly recommended study aid for students. Great for non students who want an easy comprehensive anatomy guide.

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