Chapter 10 - Section 10.4 - Study Guide - Assess Your Learning Outcomes - Page 371: 8

The thenar group of intrinsic hand muscles consists of four muscles located at the base of the thumb. These muscles play a crucial role in controlling the movements and positioning of the thumb. Here's some information about each of these muscles: 1. **Adductor Pollicis**: - **Location**: This muscle is located on the palm side of the hand and forms part of the thenar eminence (the fleshy part at the base of the thumb). - **Action**: The primary function of the adductor pollicis is to adduct the thumb, which means it moves the thumb toward the palm, allowing the thumb to approach the other fingers. - **Innervation**: It is innervated by the ulnar nerve. 2. **Abductor Pollicis Brevis**: - **Location**: This muscle is also part of the thenar eminence. - **Action**: The abductor pollicis brevis primarily abducts the thumb, meaning it moves the thumb away from the palm, allowing it to move away from the other fingers. - **Innervation**: It is innervated by the median nerve. 3. **Flexor Pollicis Brevis**: - **Location**: Found in the thenar eminence. - **Action**: The main function of the flexor pollicis brevis is to flex the thumb at the metacarpophalangeal joint, allowing the thumb to bend at the base. - **Innervation**: It is innervated by the median nerve. 4. **Opponens Pollicis**: - **Location**: This muscle is also located within the thenar eminence. - **Action**: The opponens pollicis muscle is responsible for opposing the thumb, which means it allows the thumb to move across the palm and make contact with the other fingers, facilitating grasping and pinching movements. - **Innervation**: It is innervated by the median nerve. The thenar muscles are essential for the precise and coordinated movements of the thumb, which are critical for activities that require fine motor skills and grip strength. These muscles enable actions like gripping objects, writing, holding utensils, and performing tasks that require dexterity and precision in the hand.

The thenar group of intrinsic hand muscles consists of four muscles located at the base of the thumb. These muscles play a crucial role in controlling the movements and positioning of the thumb. Here's some information about each of these muscles: 1. **Adductor Pollicis**: - **Location**: This muscle is located on the palm side of the hand and forms part of the thenar eminence (the fleshy part at the base of the thumb). - **Action**: The primary function of the adductor pollicis is to adduct the thumb, which means it moves the thumb toward the palm, allowing the thumb to approach the other fingers. - **Innervation**: It is innervated by the ulnar nerve. 2. **Abductor Pollicis Brevis**: - **Location**: This muscle is also part of the thenar eminence. - **Action**: The abductor pollicis brevis primarily abducts the thumb, meaning it moves the thumb away from the palm, allowing it to move away from the other fingers. - **Innervation**: It is innervated by the median nerve. 3. **Flexor Pollicis Brevis**: - **Location**: Found in the thenar eminence. - **Action**: The main function of the flexor pollicis brevis is to flex the thumb at the metacarpophalangeal joint, allowing the thumb to bend at the base. - **Innervation**: It is innervated by the median nerve. 4. **Opponens Pollicis**: - **Location**: This muscle is also located within the thenar eminence. - **Action**: The opponens pollicis muscle is responsible for opposing the thumb, which means it allows the thumb to move across the palm and make contact with the other fingers, facilitating grasping and pinching movements. - **Innervation**: It is innervated by the median nerve. The thenar muscles are essential for the precise and coordinated movements of the thumb, which are critical for activities that require fine motor skills and grip strength. These muscles enable actions like gripping objects, writing, holding utensils, and performing tasks that require dexterity and precision in the hand.