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Questions and Answers
The PIP joint allows for no joint play in semiflexed position.
The PIP joint allows for no joint play in semiflexed position.
False (B)
The DIP joint can be passively hyperextended 30° beyond the neutral position.
The DIP joint can be passively hyperextended 30° beyond the neutral position.
True (A)
The close-packed position of the PIP and DIP joints is considered to be full flexion.
The close-packed position of the PIP and DIP joints is considered to be full flexion.
False (B)
Intrinsic muscles of the hand have both their proximal and distal attachments outside the hand.
Intrinsic muscles of the hand have both their proximal and distal attachments outside the hand.
Active movements of the hand require no cooperation between intrinsic and extrinsic muscles.
Active movements of the hand require no cooperation between intrinsic and extrinsic muscles.
Flexor digitorum superficialis (FDS) is located in the posterior forearm.
Flexor digitorum superficialis (FDS) is located in the posterior forearm.
The primary role of the FDS is to flex the PIP joints.
The primary role of the FDS is to flex the PIP joints.
The FDS can effectively flex the MCP joint when the PIP joint is fully flexed.
The FDS can effectively flex the MCP joint when the PIP joint is fully flexed.
The tendons of the FDS cross the wrist and enter the dorsal aspect of the hand.
The tendons of the FDS cross the wrist and enter the dorsal aspect of the hand.
The extensor digitorum muscle is not involved in the maximal efficiency of the FDS on the PIP joint.
The extensor digitorum muscle is not involved in the maximal efficiency of the FDS on the PIP joint.
The extensor digitorum is primarily responsible for flexing the fingers.
The extensor digitorum is primarily responsible for flexing the fingers.
The moment arm of the extensor digitorum improves its effectiveness as a wrist extension when the wrist is flexed.
The moment arm of the extensor digitorum improves its effectiveness as a wrist extension when the wrist is flexed.
The extensor expansion originates from the superficial surface of the extensor digitorum tendon.
The extensor expansion originates from the superficial surface of the extensor digitorum tendon.
The action of the extensor digitorum on P2 and P3 is strongest when the wrist is extended.
The action of the extensor digitorum on P2 and P3 is strongest when the wrist is extended.
If the digital flexors are relaxed, the extensor digitorum can effectively extend the distal phalanges.
If the digital flexors are relaxed, the extensor digitorum can effectively extend the distal phalanges.
The extensor indicis and extensor digiti minimi function in exactly the same manner as the extensor digitorum.
The extensor indicis and extensor digiti minimi function in exactly the same manner as the extensor digitorum.
Flexion of the wrist increases the tension in the digital flexors.
Flexion of the wrist increases the tension in the digital flexors.
The median band of the extensor digitorum acts on P1 exclusively.
The median band of the extensor digitorum acts on P1 exclusively.
The accessory movements of the EDC include abduction when the interossei are activated.
The accessory movements of the EDC include abduction when the interossei are activated.
The predominant finger extensor originates from the medial epicondyle of the humerus.
The predominant finger extensor originates from the medial epicondyle of the humerus.
The human hand contains 8 metacarpals in total.
The human hand contains 8 metacarpals in total.
Each of the fingers II to V has two interphalangeal joints.
Each of the fingers II to V has two interphalangeal joints.
The thumb has three phalanges and two interphalangeal joints.
The thumb has three phalanges and two interphalangeal joints.
The carpometacarpal joints are between the metacarpals and the proximal phalanges.
The carpometacarpal joints are between the metacarpals and the proximal phalanges.
The extrinsic muscles include the Extensor pollicis longus and the Adductor pollicis.
The extrinsic muscles include the Extensor pollicis longus and the Adductor pollicis.
The dorsal interossei muscles are responsible for abduction and adduction of the fingers.
The dorsal interossei muscles are responsible for abduction and adduction of the fingers.
The flexor pollicis brevis originates from the thenar muscles of the hand.
The flexor pollicis brevis originates from the thenar muscles of the hand.
Carpal bones form articulations only with the metacarpals.
Carpal bones form articulations only with the metacarpals.
The hypothenar muscles include the Opponens pollicis.
The hypothenar muscles include the Opponens pollicis.
During extension of the CMC joint, the metacarpal rolls and slides in a medial direction.
During extension of the CMC joint, the metacarpal rolls and slides in a medial direction.
Phase 1 of opposition involves the thumb metacarpal rotating medially across the palm.
Phase 1 of opposition involves the thumb metacarpal rotating medially across the palm.
The CMC joint achieves maximal congruity in full abduction.
The CMC joint achieves maximal congruity in full abduction.
The I.MCP joint allows for significant active and passive motions compared to the finger MCP joints.
The I.MCP joint allows for significant active and passive motions compared to the finger MCP joints.
The I.MCP joint primarily allows for flexion and extension movements.
The I.MCP joint primarily allows for flexion and extension movements.
The proximal phalanx of the thumb can actively flex about 80° across the palm.
The proximal phalanx of the thumb can actively flex about 80° across the palm.
Reposition of the CMC joint involves movements of adduction and flexion.
Reposition of the CMC joint involves movements of adduction and flexion.
The posterior oblique ligament is stretched during the medial rotation phase of opposition.
The posterior oblique ligament is stretched during the medial rotation phase of opposition.
Lateral rotation of the thumb metacarpal can occur independently from the other motions.
Lateral rotation of the thumb metacarpal can occur independently from the other motions.
The thumb’s CMC joint has a close-packed position during opposition.
The thumb’s CMC joint has a close-packed position during opposition.
Active wrist extensors are unnecessary for pad-to-side prehension.
Active wrist extensors are unnecessary for pad-to-side prehension.
The tenodesis phenomenon involves both active wrist extension to close the fingers and passive wrist flexion to open the fingers.
The tenodesis phenomenon involves both active wrist extension to close the fingers and passive wrist flexion to open the fingers.
The primary extensors of the fingers include only the EDC muscle.
The primary extensors of the fingers include only the EDC muscle.
Flexors must be contracted to allow partially flexed fingers to surround an object during wrist flexion in individuals with paralysis.
Flexors must be contracted to allow partially flexed fingers to surround an object during wrist flexion in individuals with paralysis.
The EDC's primary role is to prevent hyperextension of the MCP joint during finger extension.
The EDC's primary role is to prevent hyperextension of the MCP joint during finger extension.
Passive tension in finger extensors in a dropped wrist contributes to flexion of both MCP and IP joints.
Passive tension in finger extensors in a dropped wrist contributes to flexion of both MCP and IP joints.
Study Notes
Hand Anatomy
- The hand consists of metacarpals, phalanges, and carpal bones.
- Each finger (except the thumb) has three phalanges: proximal (P1), middle (P2), and distal (P3).
- The thumb has two phalanges: proximal and distal
- The carpometacarpal (CMC) joints are formed by the articulation of the proximal end of the metacarpals and the distal row of carpal bones
- Metacarpophalangeal (MCP) joints are formed by the articulation between the metacarpals and the proximal phalanges.
- Interphalangeal (IP): Proximal (PIP) and Distal (DIP). The thumb has only a single IP joint.
Hand Muscles
- Extrinsic muscles: Originate in the forearm, and insert in the hand, causing a wide range of movements.
- Extensor muscles:
- Extensor carpi radialis longus (ECRL)
- Extensor carpi radialis brevis (ECRB)
- Extensor carpi ulnaris (ECU)
- Extensor pollicis brevis (EPB)
- Extensor pollicis longus (EPL)
- Extensor digitorum (ED)
- Extensor indicis (EI)
- Extensor digiti minimi (EDM)
- Flexor muscles:
- Flexor digitorum superficialis (FDS)
- Flexor digitorum profundus (FDP)
- Extensor muscles:
- Intrinsic muscles: Originate and insert within the hand, responsible for fine motor control and adjustments.
- Thenar muscles: Located on the thumb side of the hand.
- Abductor pollicis brevis (APB)
- Flexor pollicis brevis (FPB)
- Opponens pollicis (OP)
- Adductor pollicis (AP)
- Hypothenar muscles: Located on the little finger side of the hand.
- Abductor digiti minimi (ADM)
- Flexor digiti minimi (FDM)
- Opponens digiti minimi (ODM)
- Dorsal interossei (I-IV)
- Palmar interossei (I-IV)
- Thenar muscles: Located on the thumb side of the hand.
Hand Joint Movements
- PIP and DIP Joints:
- Stable in full extension and flexion.
- Allow some joint play only in semiflexed position.
- Can be passively hyperextended 30 degrees beyond neutral.
- Allow some passive ab- and adduction.
- Close-packed Position: Full extension, due to the stretch placed on the palmar plates.
Intrinsic and Extrinsic Muscle Collaboration
- Most hand movements (opening and closing fingers) require precise cooperation between extrinsic and intrinsic muscles and wrist muscles.
Flexion of Fingers II-V
- Flexor Digitorum Superficialis (FDS):
- Located in the anterior forearm, deep to wrist flexors and pronator teres.
- Four tendons cross the wrist and enter the palmar aspect of the hand.
- Each tendon splits at the proximal phalanx, allowing passage of the FDP tendon.
- Split parts of each tendon partially reunite, cross the PIP joint, and attach to the sides of the palmar aspect of the middle phalanx.
- Primary action: Flexion of the PIP joints.
- Secondary actions: Flexes all the joints it crosses (radiocarpal, MCP, PIP).
- Weak flexor of the MCP joint when the PIP joint is fully flexed.
- Efficiency at PIP is maximal when the MCP joint is extended by contraction of the extensor digitorum (Synergistic action).
- Plays a role in preventing bowstringing of the tendons.
Extension of Fingers II-V
- Extensor Digitorum (ED):
- Predominant finger extensor.
- Originates from a common tendon off the lateral epicondyle of the humerus.
- The terminal tendon inserts into the base of the distal phalanx.
- Excellent moment arm as a wrist extensor.
- Primarily acts on the MCP joint, extending it.
- Extensor Mechanism (1): Arises from the deep surface of the ED tendon, crosses the MCP joint, inserts at the base of P1.
- Median Band (2): Contributes to extension of the middle phalanx (P2).
- Lateral Bands (3): Contributes to extensionof the distal panlax (P3).
- Action on P2 and P3 depends on the degree of tension in the tendon, which is influenced by the position of the wrist and flexion at the MP joint.
- Wrist flexion: Facilitates extension of P2 and P3.
- Wrist extension: Dampens extension of P2 and P3.
- Extensor Indicis (EI) and Extensor Digiti Minimi (EDM): Behave similarly to the ED. Allow for individual extension of the index and little fingers.
- Accessory Movements:
- ED: Abduction of the fingers.
- EI: Adduction of the fingers.
- These actions occur only when the interossei are inactivated.
CMC Joint Opposition
- Opposition: Full arc of thumb movement into the palm, divided into two phases:
- Phase 1: Thumb metacarpal abduction.
- Phase 2: Abducted metacarpal flexes and medially rotates across the palm towards the little finger.
- Stretches the posterior oblique ligament.
- Close-packed Position: Full opposition, due to forces from muscles and stretched ligaments.
I.MCP Joint
- Structure: Articulation between the convex head of the 1st metacarpal and the concave proximal surface of the proximal phalanx of the thumb.
- Arthrokinematics: Similar to MCP joints of the fingers, but with different osteokinematics.
- Range of Motion: Less than MCP joints of the fingers.
- Degrees Of Freedom: Primarily 1 DoF: flexion and extension within the frontal plane.
- Active flexion: 60 degrees.
- Passive flexion: 80 degrees.
- Extension: Return motion from neutral back to full extension.
Pad-to-Side Prehension
- Least precise form of precision handling.
- If hand muscles are paralyzed (e.g., spinal cord injury above C7), wrist extensors can create pad-to-side prehension.
Tenodesis Action
- Uses active wrist extension to close the fingers and passive wrist flexion to open the fingers.
- This happens due to the tension in the flexor and extensor tendons.
- Achieves a cylindrical grip.
- Depends on passive insufficiency of the flexors.
Opening the Hand: Finger Extension
- Often performed in preparation for grasp.
- Primary extensors: EDC and intrinsic muscles (L and IO).
- EDC's role: Pulls the MCP joint toward extension.
- Intrinsic muscles' role: Provide proximal pull on the extensor mechanism, prevent hyperextension of the MCP joint.
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Description
Test your knowledge on the anatomy of the hand, including the structure of metacarpals, phalanges, carpal bones, and various muscles. This quiz covers both the intrinsic and extrinsic muscles associated with hand movement. Perfect for anatomy students or anyone interested in human biology.
