Questions and Answers
The extensor expansions are formed by the tendons of what?
the tendons of extensor digitorum longus & brevis muscles
The ___ ___ __ tendons of digits 2, 3, 4 & 5 divide into (3) slips.
extensor digitorum longus
Where does the central slip of the tendons insert?
base of middle phalanx
Where do the 2 lateral slips of the extensor tendons converge?
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What passes distally to insert on the base of the distal phalanx?
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At what level do the tendons of extensor digitorum brevis join extensor digitorum longus?
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What tendons contribute to the lateral aspect of the expansion for the 5th digit?
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How many fibrous sheaths hold the long & short extensor tendons in place?
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What is the name of the strong fibrous structure formed by the fibrous sheaths?
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What is the more proximal part of the extensor hoods called?
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The distal part of the extensor hood is formed mostly from expansions of what?
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What do interosseous muscles contribute to the formation of?
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What is the function of extensor digitorum longus when acting alone?
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When the muscle contracts, the ___ ___ is pulled against the metatarsal head, resulting in extension of MPJs.
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Which joints cannot be extended by the wing portion of extensor hood?
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What do lumbrical muscles do upon contraction?
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Name another muscle that contributes to the function of the extensor hood.
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What is the function of interosseous muscles?
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What is a controversial function of the interosseous muscles?
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On the 1st digit, only the tendon of which muscle is attached to the extensor expansion?
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What is attached to the deep transverse ligament on the lateral side of the 1st digit?
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Extensor expansion of the hallux has a wing & sling present, but lumbricals & interossei do not contribute to them.
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On the medial side of the extensor expansion of hallux, the wing & sling are formed by ___ ___.
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On the lateral side of the extensor expansion of hallux, which muscles are involved?
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Study Notes
Extensor Expansions Overview
- Extensor expansions are formed by tendons of the extensor digitorum longus and brevis muscles, analogous to those in fingers.
Extensor Digitorum Longus Functionality
- Tendons of extensor digitorum longus for digits 2-5 split into three slips; the central slip attaches to the base of the middle phalanx.
- Lateral slips converge over the distal end of the middle phalanx, reforming into the terminal slip that inserts on the base of the distal phalanx.
Tendon Interactions
- Tendons of extensor digitorum brevis merge with extensor digitorum longus near the metatarsophalangeal joints, with the 5th digit receiving contributions from abductor digiti minimi and flexor digiti minimi.
Fibrous Sheaths and Structure
- Long and short extensor tendons are secured by two fibrous sheaths, creating an extensor hood, with the more proximal section termed the extensor sling.
- The extensor sling attaches to the plantar plate via fibers encircling the digit.
Components of Extensor Hood
- The distal portion of the extensor hood is the extensor wing, mainly derived from lumbrical muscle tendon expansions.
- Interosseous muscles aid in forming the sling but not the wing.
Muscle Functions
- Extensor digitorum longus tightens the sling and loosens the wing upon contraction, allowing plantar plate tension and extension at metatarsophalangeal joints; however, it does not extend interphalangeal joints.
- Lumbrical muscles tighten the wing and loosen the sling, facilitating proximal flexion at metatarsophalangeal joints while keeping distal joints extended. Flexor digitorum longus also supports this function due to its link with lumbricals.
Interosseous Muscles
- Interosseous muscles are agreed to function in abduction and adduction.
- Controversy exists regarding their role in extending interphalangeal joints and flexing metatarsophalangeal joints, with some considering their effectiveness only post-lumbrical action.
First Digit Specifics
- Only the tendon of extensor hallucis longus attaches to the extensor expansion of the first digit, while the plantar plate connects to the deep transverse ligament on the lateral side.
Hallux Characteristics
- The extensor expansion of the hallux features a wing and sling, with no contribution from lumbricals or interossei.
- The medial side's wing and sling arise from the abductor hallucis; the lateral side's structure is formed by the adductor hallucis and flexor hallucis brevis.
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Description
Test your knowledge of extensor expansions with this set of flashcards. Each card focuses on important details regarding the tendons involved, including their structure and function. Perfect for students studying human anatomy.
