Anatomical position and attachment sites
The flexor digitorum longus (m. flexor digitorum longus) is located in the deep layer of the posterior leg muscles. Precise knowledge of the attachment sites of this muscle is essential for understanding its biomechanics.
- Muscle origin: the muscle fibers originate directly from the posterior surface of the tibia. Neither the fibula nor the anterior surface of the tibia participates in the origin of this muscle.
- Insertion site: the tendon descends onto the foot and divides, attaching to the distal (phalangeal) phalanges of four toes — from the second to the fifth (II–V).
Biomechanic functions
Due to its location and attachment sites, the muscle performs several crucial tasks simultaneously:
- Toe flexion: specifically flexes the distal phalanges of digits II, III, IV, and V.
- Foot flexion: participates in general plantar flexion of the entire foot.
- Arch support: actively supports the medial arch, preventing its flattening under loads.
Innervation and Blood Supply
Neural regulation and blood supply to the muscle are provided by major neurovascular structures of the posterior leg:
- Innervation: provided by branches of the tibial nerve — n. tibialis. Spinal roots from the fourth lumbar to the second sacral segments (L₄–S₂) are involved in innervation.
- Blood supply: arterial blood inflow comes from the posterior tibial artery — a. tibialis posterior.
Briefly: answers to topical questions
Through which osteofibrous canal does the tendon of the flexor digitorum longus pass onto the foot?
The tendon of the flexor digitorum longus passes from the leg to the foot through the medial malleolar canal (canalis malleolaris medialis). From this canal, it proceeds into the calcaneal canal (canalis calcaneus), which ensures the transition of contents into the plantar region.
With the tendon of which muscle does m. flexor digitorum longus cross on the sole?
On the sole of the foot, the tendon of the flexor digitorum longus crosses with the tendon of the flexor hallucis longus (m. flexor hallucis longus). In the area of this crossing, called chiasma plantare, the tendon of m. flexor hallucis longus passes beneath the tendons of the flexor digitorum longus.
Which muscles of the foot originate from the tendons of the flexor digitorum longus?
The lumbrical muscles (mm. lumbricales) originate from the tendons of the flexor digitorum longus of the foot. Each of them departs from the slips of the tendon dividing to individual digits and extends to the dorsum of the toes toward the dorsal aponeurosis of the proximal phalanges of digits II–V.
Which muscle attaches to the tendon of the flexor digitorum longus to correct the direction of its pull?
The quadratus plantae muscle (m. quadratus plantae, also known as m. flexor accessorius) attaches to the lateral margin of the flexor digitorum longus tendon. This muscle straightens the pull of the flexor digitorum longus toward digits II–V and enhances their flexion.
Remembering the attachment sites is easy: the muscle works for 4 toes (from the 2nd to the 5th), reaching all the way to the tips (distal phalanges) to ensure a secure grip of the foot.
Class and exam questions
On which bone does the flexor digitorum longus originate?
The muscle originates strictly on the posterior surface of the tibia.
Which toes does this muscle flex?
It is responsible for flexing the second through the fifth (II–V) toes of the foot. The big toe has its own flexor.
Which nerve innervates the m. flexor digitorum longus?
Innervation is provided by the n. tibialis (tibial nerve, segments L₄–S₂).
What else to study on this topic
- Interspinal muscles (mm. interspinales): location and functions
- Blood supply to the anterolateral abdominal wall
- Anastomoses between the superior and inferior epigastric arteries
- Omohyoid muscle (m. omohyoideus) and its intermediate tendon
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