Chapter 10 - Section 10.4 - Study Guide - Assess Your Learning Outcomes - Page 372: 10

The midpalmar group of intrinsic hand muscles includes several muscles that are important for controlling finger movements, particularly the interosseous and lumbrical muscles. Here's some information about each of these muscles: **Dorsal Interosseous Muscles (Four Muscles):** 1. **First Dorsal Interosseous Muscle**: - **Location**: Located between the index (2nd) and middle (3rd) metacarpal bones on the back (dorsal) side of the hand. - **Action**: This muscle abducts the index finger, meaning it moves the index finger away from the middle finger. - **Innervation**: Innervated by the ulnar nerve. 2. **Second Dorsal Interosseous Muscle**: - **Location**: Located between the middle (3rd) and ring (4th) metacarpal bones. - **Action**: Similar to the first dorsal interosseous muscle, it abducts the middle finger. - **Innervation**: Innervated by the ulnar nerve. 3. **Third Dorsal Interosseous Muscle**: - **Location**: Found between the ring (4th) and little (5th) metacarpal bones. - **Action**: This muscle abducts the little finger. - **Innervation**: Innervated by the ulnar nerve. 4. **Fourth Dorsal Interosseous Muscle**: - **Location**: Situated between the index (2nd) and ring (4th) metacarpal bones. - **Action**: It abducts both the index and ring fingers. - **Innervation**: Innervated by the ulnar nerve. **Palmar Interosseous Muscles (Three Muscles):** 1. **First Palmar Interosseous Muscle**: - **Location**: Located between the index (2nd) metacarpal bone and the adjacent metacarpal bones. - **Action**: These muscles adduct the index finger, meaning they move the index finger toward the middle finger. - **Innervation**: Innervated by the ulnar nerve. 2. **Second Palmar Interosseous Muscle**: - **Location**: Found between the middle (3rd) metacarpal bone and the adjacent metacarpal bones. - **Action**: Similar to the first palmar interosseous muscle, it adducts the middle finger. - **Innervation**: Innervated by the ulnar nerve. 3. **Third Palmar Interosseous Muscle**: - **Location**: Situated between the ring (4th) and little (5th) metacarpal bones and the adjacent metacarpal bones. - **Action**: This muscle adducts both the ring and little fingers. - **Innervation**: Innervated by the ulnar nerve. **Lumbrical Muscles (Four Muscles):** 1. **First Lumbrical Muscle**: - **Location**: These muscles originate from the tendons of the flexor digitorum profundus and insert into the radial sides of the index finger. - **Action**: Lumbricals primarily flex the metacarpophalangeal (MCP) joints and extend the interphalangeal (IP) joints of the fingers. - **Innervation**: Innervated by the median nerve (first and second lumbricals) and the ulnar nerve (third and fourth lumbricals). These midpalmar muscles are essential for finger abduction, adduction, and fine control of finger movements, allowing for tasks like gripping objects, typing, and precise finger manipulations.

The midpalmar group of intrinsic hand muscles includes several muscles that are important for controlling finger movements, particularly the interosseous and lumbrical muscles. Here's some information about each of these muscles: **Dorsal Interosseous Muscles (Four Muscles):** 1. **First Dorsal Interosseous Muscle**: - **Location**: Located between the index (2nd) and middle (3rd) metacarpal bones on the back (dorsal) side of the hand. - **Action**: This muscle abducts the index finger, meaning it moves the index finger away from the middle finger. - **Innervation**: Innervated by the ulnar nerve. 2. **Second Dorsal Interosseous Muscle**: - **Location**: Located between the middle (3rd) and ring (4th) metacarpal bones. - **Action**: Similar to the first dorsal interosseous muscle, it abducts the middle finger. - **Innervation**: Innervated by the ulnar nerve. 3. **Third Dorsal Interosseous Muscle**: - **Location**: Found between the ring (4th) and little (5th) metacarpal bones. - **Action**: This muscle abducts the little finger. - **Innervation**: Innervated by the ulnar nerve. 4. **Fourth Dorsal Interosseous Muscle**: - **Location**: Situated between the index (2nd) and ring (4th) metacarpal bones. - **Action**: It abducts both the index and ring fingers. - **Innervation**: Innervated by the ulnar nerve. **Palmar Interosseous Muscles (Three Muscles):** 1. **First Palmar Interosseous Muscle**: - **Location**: Located between the index (2nd) metacarpal bone and the adjacent metacarpal bones. - **Action**: These muscles adduct the index finger, meaning they move the index finger toward the middle finger. - **Innervation**: Innervated by the ulnar nerve. 2. **Second Palmar Interosseous Muscle**: - **Location**: Found between the middle (3rd) metacarpal bone and the adjacent metacarpal bones. - **Action**: Similar to the first palmar interosseous muscle, it adducts the middle finger. - **Innervation**: Innervated by the ulnar nerve. 3. **Third Palmar Interosseous Muscle**: - **Location**: Situated between the ring (4th) and little (5th) metacarpal bones and the adjacent metacarpal bones. - **Action**: This muscle adducts both the ring and little fingers. - **Innervation**: Innervated by the ulnar nerve. **Lumbrical Muscles (Four Muscles):** 1. **First Lumbrical Muscle**: - **Location**: These muscles originate from the tendons of the flexor digitorum profundus and insert into the radial sides of the index finger. - **Action**: Lumbricals primarily flex the metacarpophalangeal (MCP) joints and extend the interphalangeal (IP) joints of the fingers. - **Innervation**: Innervated by the median nerve (first and second lumbricals) and the ulnar nerve (third and fourth lumbricals). These midpalmar muscles are essential for finger abduction, adduction, and fine control of finger movements, allowing for tasks like gripping objects, typing, and precise finger manipulations.