Deep head of flexor pollicis brevis
Caput profundum flexoris brevis pollicis
- Related terms: Deep head; Flexor pollicis brevis: Deep head
Definition
Deep head of flexor pollicis brevis | |||
Origin | Trapezoid, capitate bones. | ||
Insertion | Base of the proximal phalanx (radial side). | ||
Innervation | Deep branch of ulnar nerve C8, T1 | ||
Action | Flexes the thumb | ||
Antagonist | Extensor pollicis longus muscle, Extensor pollicis brevis muscle | ||
The deep head of flexor pollicis brevis is the more medial and deeper portion of this thenar muscle, contributing to thumb flexion. This head is often smaller and may be variably present.
Origin
It arises from the trapezoid bone and the capitate bone.
Course & Insertion
The deep head courses obliquely to converge with the superficial head. Together, both heads insert via a common tendon onto the radial side of the base of the proximal phalanx of the thumb.
Innervation
When present, the deep head of flexor pollicis brevis receives its nerve supply from the ulnar nerve.
References
Okwumabua E, Sinkler MA, Bordoni B. Anatomy, Shoulder and Upper Limb, Hand Muscles. [Updated 2023 Jul 24]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537229/
Loss J, Li ZM. Biometry of thenar muscle origins on the flexor retinaculum. Clin Anat. 2020 Nov;33(8):1176-1180.
