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Questions and Answers
Which muscle is responsible for abducting the thumb away from the palm?
The deep head of the Flexor Pollicis Brevis is innervated by the median nerve.
False
What is the role of the Opponens Pollicis muscle?
Allows opposition of the thumb
The three muscles at the base of the thumb are known as the ______.
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Which nerve primarily innervates all thenar muscles?
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Match each thenar muscle with its primary function:
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The Flexor Pollicis Brevis has only one head.
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What is the insertion point of the Abductor Pollicis Brevis?
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Which muscle is primarily responsible for the opposition of the thumb?
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What is a unique feature of the deep head of the Flexor Pollicis Brevis regarding its innervation?
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Which of the following statements about the Abductor Pollicis Brevis is true?
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What best describes the primary function of the Flexor Pollicis Brevis muscle?
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Which action is NOT directly facilitated by the thenar muscles?
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Which muscle among the thenar group is primarily involved in pinching movements?
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Study Notes
Muscle Anatomy
-
Thenar Muscles: Group of three muscles located at the base of the thumb.
-
Abductor Pollicis Brevis:
- Origin: Tubercle of the scaphoid and trapezium bones; flexor retinaculum.
- Insertion: Lateral side of the base of the proximal phalanx of the thumb.
-
Flexor Pollicis Brevis:
- Origin: Superficial head - tubercle of trapezium; deep head - floor of the carpal tunnel.
- Insertion: Lateral side of the base of the proximal phalanx of the thumb.
-
Opponens Pollicis:
- Origin: Tubercle of the trapezium bone; flexor retinaculum.
- Insertion: Entire length of the radial side of the 1st metacarpal.
-
Abductor Pollicis Brevis:
Innervation
- All thenar muscles are primarily innervated by the median nerve.
- Specifically, the recurrent branch of the median nerve supplies:
- Abductor Pollicis Brevis
- Flexor Pollicis Brevis (superficial head)
- Opponens Pollicis
- The deep head of the Flexor Pollicis Brevis is innervated by the ulnar nerve.
- Specifically, the recurrent branch of the median nerve supplies:
Functions Of Thenar Muscles
-
Abductor Pollicis Brevis:
- Abducts the thumb away from the palm.
-
Flexor Pollicis Brevis:
- Flexes the thumb at the carpometacarpal and metacarpophalangeal joints.
-
Opponens Pollicis:
- Allows opposition of the thumb, enabling it to touch the other fingers, crucial for grasping and pinching movements.
Muscle Anatomy
- Thenar muscles consist of three key muscles situated at the base of the thumb.
-
Abductor Pollicis Brevis:
- Originates from the tubercle of the scaphoid and trapezium bones, and the flexor retinaculum.
- Inserts on the lateral side of the base of the proximal phalanx of the thumb.
-
Flexor Pollicis Brevis:
- Composed of two heads:
- Superficial head from the tubercle of the trapezium.
- Deep head from the floor of the carpal tunnel.
- Inserts on the lateral side of the base of the proximal phalanx of the thumb.
- Composed of two heads:
-
Opponens Pollicis:
- Originates from the tubercle of the trapezium and the flexor retinaculum.
- Inserts along the entire length of the radial side of the 1st metacarpal.
Innervation
- The median nerve primarily innervates all thenar muscles.
- The recurrent branch of the median nerve supplies:
- Abductor Pollicis Brevis
- Flexor Pollicis Brevis (superficial head)
- Opponens Pollicis
- The deep head of the Flexor Pollicis Brevis receives innervation from the ulnar nerve.
Functions Of Thenar Muscles
-
Abductor Pollicis Brevis:
- Responsible for abducting the thumb away from the palm.
-
Flexor Pollicis Brevis:
- Flexes the thumb at both the carpometacarpal and metacarpophalangeal joints.
-
Opponens Pollicis:
- Facilitates the opposition of the thumb, allowing it to touch other fingers, essential for grasping and pinching actions.
Muscle Anatomy
- Thenar muscles consist of three key muscles at the base of the thumb.
- Abductor Pollicis Brevis: Controls the abduction of the thumb, enhancing thumb mobility.
- Flexor Pollicis Brevis: Responsible for flexion of the thumb at the metacarpophalangeal (MCP) joint, crucial for gripping and pinching actions.
- Opponens Pollicis: Enables opposition by bringing the thumb across the palm, vital for grasping and performing detailed tasks.
Innervation
- All thenar muscles are primarily innervated by the median nerve, facilitating their function.
- The deep head of the Flexor Pollicis Brevis may receive additional innervation from the ulnar nerve, which can influence its actions.
Functions Of Thenar Muscles
- Abductor Pollicis Brevis: Key for thumb mobility and critical for multiple hand functions.
- Flexor Pollicis Brevis: Enhances thumb grip, essential for effective pinching and holding.
- Opponens Pollicis: Plays a crucial role in thumb opposition, allowing for the ability to touch fingertips, important for complex manual tasks.
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Description
This quiz focuses on the thenar muscles, a group of three essential muscles located at the base of the thumb. You'll learn about their origins, insertions, and functions. Test your knowledge on the abductor and flexor pollicis brevis and their roles in thumb movement.
