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Thenar muscles: want to learn more about it?

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Thenar muscles

Thenar muscles

The thenar musculature consists of four short muscles located on the lateral (radial) aspect of the hand. These muscles include the adductor pollicis, abductor pollicis brevis, flexor pollicis brevis and opponens pollicis.

Together, the thenar muscles form a fleshy prominence on the lateral (radial) aspect of the palm called the thenar eminence. These muscles originate from different carpal bones and distally attach to the thumb.
The majority of the thenar muscles are innervated by the median nerve (T1). The exceptions are the deep head of flexor pollicis brevis and adductor pollicis muscle that receive their innervation via the ulnar nerve (C8, T1).

The main function of the thenar muscles is to produce the movements of the thumb. More specifically, these muscles are responsible for the adduction, abduction and flexion of the thumb at the metacarpophalangeal (MCP) and carpometacarpal (CMC) joints. Their combined actions can produce the opposition of the thumb, which is the combination of flexion, adduction and medial rotation.

This article will introduce you to the anatomy and function of the thenar muscles.

Key facts about the thenar muscles
Definition

Thenars are a group of four short muscles responsible for the movements of the thumb
Muscles Adductor pollicis, abductor pollicis brevis, flexor pollicis brevis and opponens pollicis
Innervation Median nerve (T1), ulnar nerve (C8, T1)
Function Adduction, abduction, flexion, medial rotation and opposition of thumb

Flexor pollicis brevis muscle

The flexor pollicis brevis is the most medial of the thenar muscles. It arises by two muscle heads (superficial and deep) which are separated by the tendon of flexor pollicis longus. The superficial head originates from the flexor retinaculum and the tubercle of the trapezium bone, while the deep head originates from the trapezoid and capitate bones. From here, the heads run side by side in lateral direction to insert onto the base of proximal phalanx 1.

The two heads of the flexor pollicis brevis muscle differ in innervation. The superficial head receives its innervation via the recurrent branch of the median nerve (T1), while the deep head is innervated by the deep branch of the ulnar nerve (C8, T1). The blood supply for this muscle is derived from the radial artery.

The prime function of the flexor pollicis brevis muscle is to produce flexion of the thumb at the metacarpophalangeal and carpometacarpal joints. It also contributes to the medial rotation of the thumb.

Start with the anatomy of the thenar muscles by exploring our videos, quizzes, labelled diagrams and articles.

Abductor pollicis brevis muscle

The abductor pollicis brevis is the most superficial muscle of the thenar group. It originates from the tubercles of the scaphoid and trapezium bones as well as the flexor retinaculum. From here, the muscle fibers extend laterally and distally, ending in a tendon that inserts onto the lateral aspect of the base of proximal phalanx 1.

The abductor pollicis brevis muscle receives its innervation via the recurrent (thenar) branch of the median nerve. Its blood supply is provided mainly by the superficial palmar branch of the radial artery.

The prime function of this muscle is the abduction of the thumb at the first carpometacarpal joint along with its long counterpart, the abductor pollicis longus muscle. Abductor pollicis brevis also takes part in the flexion and opposition of the thumb.

Feeling a bit overwhelmed? Learn the attachments, innervation and functions of the thenar muscles faster and easier with our upper extremity muscle charts!

Adductor pollicis muscle

The adductor pollicis is a short and broad, fan-shaped muscle of the palm. It arises by the two muscular heads: oblique and transverse. The transverse head originates from the palmar base of metacarpal bone 3, while the oblique head arises from the capitate bone and palmar bases of metacarpal bones 2 and 3. From their origins, the muscle heads run laterally, converging into a single muscle belly that inserts onto the medial base of proximal phalanx 1.

The adductor pollicis muscle receives its innervation via the deep branch of ulnar nerve (C8, T1). The blood supply for this muscle is provided by the deep palmar arch.

As its name suggests, the prime function of adductor pollicis muscle is to produce strong adduction of the thumb at the first carpometacarpal joint. This action pulls the abducted thumb towards the index finger. Additionally, this muscle works with other thenar muscles and contributes to the opposition of the thumb.

Opponens pollicis muscle

The opponens pollicis is a short muscle located deep to the abductor pollicis brevis muscle. It originates from the tubercle of trapezium bone and flexor retinaculum. The muscle fibers then run distally to insert onto the lateral aspect of the first metacarpal bone.

The opponens pollicis muscle receives its innervation via the recurrent branch of median nerve (T1) and its blood supply via the superficial palmar branch of the radial artery.

The prime function of opponens pollicis is to produce the opposition of the thumb in the first carpometacarpal joint. The opposition is a complex movement in which the flexion, adduction, and medial rotation occur together. This movement is of key importance for fine motor skills and precise movements of the hand (e.g. writing or pinching).

Thenar muscles: want to learn more about it?

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“I would honestly say that Kenhub cut my study time in half.” – Read more. Kim Bengochea Kim Bengochea, Regis University, Denver

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