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The extensor digitorum longus (EDL) muscle is a fast-contracting muscle located in the anterior (extensor) compartment of the leg. It is responsible for dorsiflexion of the foot and extension of the toes. The EDL muscle has been widely studied in contractile research and is often used as an example of a 'fast' muscle. Its contractile and passive properties can be measured ex vivo, providing valuable insights into muscle function and various medical conditions, such as Duchenne muscular dystrophy and postpolio syndrome.
| Characteristics | Values |
|---|---|
| Full Form | Extensor Digitorum Longus |
| Type | Feather-like muscle, Fast contracting muscle, Fast muscle, Unipennate muscle |
| Location | Lateral part of the front of the leg, Anterior (extensor) compartment of the leg |
| Origin | Inferior part of the lateral tibial condyle, Proximal half of the medial surface of fibula, Anterior surface of the interosseus membrane, Deep surface of the fascia, Intermuscular septa between it and the tibialis anterior on the medial, Intermuscular septa between it and the peroneal muscles on the lateral side |
| Insertion | Middle and distal phalanges of digits 2 to 5 |
| Innervation | Deep fibular nerve (L5, S1), a branch of the common fibular nerve |
| Blood Supply | Two arteries of the leg: the proximal part is supplied by the anterior tibial artery, and the distal part receives blood from the fibular artery |
| Function | Dorsiflexion of the foot, Extension of the toes, Everses the foot |
| Related Conditions | Duchenne muscular dystrophy (DMD), Charcot-Marie-Tooth disease, Postpolio syndrome, Diabetes, Rheumatoid arthritis |
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What You'll Learn
EDL Muscle Contraction Studies
The extensor digitorum longus (EDL) is a feather-like muscle in the anterior (extensor) compartment of the leg. It is the most lateral muscle in the extensor compartment and is classified as an unipennate muscle. The EDL muscle is one of the most commonly used muscles in physiology studies, particularly in the study of muscle contraction.
To study the contractile properties of the EDL muscle, researchers may use an in vitro system, such as the Aurora Scientific in vitro muscle test system. This system allows for the manipulation of ion and chemical concentrations necessary for optimal muscle force generation. The contractile properties measured may include specific twitch force, specific maximal tetanic force, time to peak tension (TPT), and half relaxation time (½ RT).
For example, one study compared the contractile properties of EDL muscles from adult (2-6 months old) and aged (12-22 months old) mice. They found that the EDL muscles of aged mice had significantly lower specific force, longer tetanus relaxation times, and lower fatiguability compared to adult mice.
Another study investigated the impact of dystrophin deficiency on the contractile and passive properties of EDL muscles in mice. They found that the absence of dystrophin reduced specific twitch and tetanic forces, increased stiffness, and increased resistance force in the mdx EDL muscle.
In addition to these studies, researchers have also examined the contractile properties of isolated fast-twitch EDL muscles from male and female mice to understand the effects of ageing and gender. They found that ageing caused a greater decrease in muscle mass and cross-sectional area in females compared to males, and that females were more affected by ageing in terms of absolute force and muscle relaxation times.
In summary, EDL muscle contraction studies involve evaluating the contractile and passive properties of the muscle using in vitro or in situ approaches. These studies have provided valuable insights into the effects of ageing, gender, and genetic factors on muscle function and have important implications for understanding muscle diseases and developing therapeutic interventions.
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EDL Muscle Attachments
The extensor digitorum longus (EDL) muscle is a feather-like muscle in the anterior (extensor) compartment of the leg. It is the most lateral of all the muscles in the extensor compartment and lies laterally to the tibialis anterior and extensor hallucis longus. The anterior tibial artery and vein pass between the EDL muscle and the tibialis anterior.
The EDL muscle originates from the inferior part of the lateral tibial condyle, the proximal half of the medial surface of the fibula, and the anterior surface of the interosseus membrane. The part of its origin at the tibial condyle is fused with the originating fibres of the fibularis longus muscle. After its origin, the muscle descends inferiorly and, just above the ankle, gives off a tendon that passes under the superior extensor retinaculum and through the inferior extensor retinaculum.
Within the inferior extensor retinaculum, the tendon splits into four smaller tendons that are wrapped together in a synovial sheath. After exiting the retinaculum, these four tendons diverge towards the toes. Superficially, to the proximal phalanges, each tendon widens and forms the triangular dorsal digital expansions (or extensor hoods). The medial portion of each extensor hood blends with the respective tendons of the lumbrical muscles, while the lateral parts related to digits 2-4 are joined by the tendons of the extensor digitorum brevis muscle.
The EDL muscle participates in dorsiflexion of the foot when its proximal attachments are fixed. When the distal attachments are fixed and the body is in the anatomical position, the EDL muscle, along with the tibialis anterior, extensor hallucis longus, and fibularis tertius, brings the trunk and lower limb to the front. This action moves the body's weight-bearing point from the proximal to the distal part of the foot.
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EDL Muscle and Tendon Injuries
The extensor digitorum longus (EDL) muscle is a feather-like muscle in the anterior (extensor) compartment of the leg. It is the most lateral of all the muscles in the extensor compartment. The EDL muscle is involved in the dorsiflexion of the foot, as well as the eversion of the foot and extension of the toes.
The EDL muscle is susceptible to various injuries, including tendon tears and muscle hernias, often as a result of sports injuries or ankle sprains. High-resolution musculoskeletal ultrasound and MRI scans can be used to detect and evaluate these injuries. For example, an MRI scan can reveal partial tears near the myo-tendinous junction, as well as heterogenicity and hematomas within the tendon.
In the case of a tendon tear, the patient may experience anterior ankle tenderness, oedema, and deformity of the interphalangeal joint, with an inability to actively dorsiflex the hallux. Treatment options may include conservative treatment, primary repairs, reconstructions, or tendon transfer surgery, as observed in the case of a 52-year-old female patient who underwent a tendinous transfer of the EDL to the EHL using a Pulvertaft technique following an EHL tendon rupture.
To prevent injuries, it is important to understand the optimal length at which the EDL muscle develops maximum twitch tension. This can be determined by stimulating the muscle at different resting tensions. Additionally, the muscle's response to eccentric contractions can be assessed by applying cycles of eccentric contractions with rest between cycles.
The contractile and passive properties of the EDL muscle can be measured ex vivo using systems like the Aurora Scientific in vitro muscle test system. This involves assembling a tissue-organ bath and adjusting the temperature to 30°C, among other technical specifications.
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EDL Muscle Fibre Types
The Extensor Digitorum Longus (EDL) muscle is a fast-contracting muscle with 60% of Type IIB fibres at the surface. It is a pennate muscle, situated at the lateral part of the front of the leg. It is also the most lateral of all the muscles in the extensor compartment. The EDL is a feather-like muscle of the anterior (extensor) compartment of the leg.
The EDL muscle originates on the anterior tibia, runs down the front of the tibia anterior to the ankle joint and deep to the extensor retinaculum. It inserts on the middle and distal phalanges of digits 2 to 5. The distal portion of the EDL muscle subdivides into four tendons that insert onto the distal phalanx of digits 2–5. The four tendons are all wrapped together by a synovial sheath. After exiting the retinaculum, the four tendons diverge towards the toes.
The EDL muscle is widely used as an example of a 'fast' muscle in many contractile studies. The rat EDL contains approximately 5% type I, 53% type IIa and 42% type IIb fibres, whereas in mice, the proportions are 46% type IIa and 54% type IIb. In both these species, the fibre type is predominantly fast, with a similar number of both oxidative and glycolytic phenotypes. The fibre-type distribution within the EDL is non-uniform, with a decrease in the proportion of fatigue-resistant fibre phenotype across the medial-to-lateral axis.
The EDL muscle has been studied in the context of various medical conditions, such as Duchenne muscular dystrophy (DMD), Charcot-Marie-Tooth disease, and post-polio syndrome. The contractile and passive properties of the EDL muscle can be measured ex vivo using the Aurora Scientific in vitro muscle test system. This involves assembling a tissue-organ bath and adjusting various parameters, such as temperature and gas flow.
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EDL Muscle and Muscular Dystrophy
The extensor digitorum longus (EDL) is a feather-like muscle in the anterior (extensor) compartment of the leg. It is the most lateral of all the muscles in the extensor compartment. The EDL muscle, along with the tibialis anterior, extensor hallucis longus, and fibularis (peroneus) tertius muscles, are all part of the anterior compartment of the leg. These muscles share a common function: the dorsiflexion of the foot.
The EDL muscle originates from the inferior part of the lateral tibial condyle, the proximal half of the medial surface of the fibula, and the anterior surface of the interosseus membrane. The muscle then descends inferiorly and, just above the ankle, gives off a tendon that passes under the superior extensor retinaculum and through the inferior extensor retinaculum. Within the inferior extensor retinaculum, the tendon splits into four smaller tendons, which are all wrapped together by a synovial sheath. After exiting the retinaculum, these four tendons diverge towards the toes.
The contractile and passive properties of the EDL muscle can be measured ex vivo using the Aurora Scientific in vitro muscle test system. This involves assembling a tissue-organ bath and attaching it to a muscle mounting apparatus. The gas line is then connected to the oxytube, and the water circulation lines are fastened to the water-jacket tissue bath. The temperature is adjusted to 30°C, and 5 PSI of 95% O2-5% CO2 is allowed to flow through the oxytube.
Muscular dystrophy refers to a group of over 30 genetic conditions that cause muscle weakness and other related symptoms. The symptoms of muscular dystrophy worsen over time and can be present at birth, develop in childhood, or manifest in adulthood, depending on the specific type. One example of muscular dystrophy is Duchenne muscular dystrophy (DMD), a severe muscle-wasting disease caused by dystrophin deficiency. Dystrophin is a protein that stabilizes the muscle cell membrane during contraction. In DMD, the absence of dystrophin leads to membrane tearing, initiating a chain reaction that results in muscle cell death and a reduction in muscle force.
The EDL muscle has been studied in the context of muscular dystrophy, particularly in mdx mice. Light microscopic histomorphometry has been used to quantify the developmental histopathological changes induced by muscular dystrophy in the EDL muscle. The absence of dystrophin has been shown to significantly impact the contractile and passive properties of the EDL muscle in these studies.
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Frequently asked questions
The extensor digitorum longus (EDL) muscle is a feather-like muscle of the anterior (extensor) compartment of the leg. It is involved in dorsiflexion of the foot and extension of the toes.
The EDL muscle is involved in the dorsiflexion of the foot and extension of the toes. It is also involved in eversion of the foot as it crosses the subtalar, metatarsophalangeal, and interphalangeal joints.
The EDL muscle is commonly associated with conditions such as Charcot-Marie-Tooth disease, postpolio syndrome, diabetes, and rheumatoid arthritis.
The function of the EDL muscle can be evaluated using techniques such as the Aurora Scientific in vitro muscle test system, stimulation at different resting tensions, and subjecting it to a six-step stretching protocol.
