Which pair of muscles flexes the neck? Which muscle extends the neck? 8. Which muscles help you smile? Trunk 9. Which muscles bend the waist forward? Which muscle pulls the waist upright? 10. Which muscles laterally flex the vertebral column?
Upper extremity 11. The humerus can be extended or flexed. List two muscles and their action which inse the humerus and either extend or flex the humerus. 12. List one muscle that inserts on the radius and its action. 13. List one muscle that inserts on the ulna and its action.
The Correct Answer and Explanation is :
Here are the answers to the questions about muscles:
Neck Muscles
- Flexion of the Neck:
- Sternocleidomastoid: This muscle flexes the neck when both sides contract. It also helps rotate the head when one side contracts.
- Extension of the Neck:
- Trapezius: The upper portion of the trapezius can help extend the neck by pulling the head back. Additionally, the splenius capitis also assists in neck extension.
Facial Muscles
- Muscles that help you smile:
- Zygomaticus Major and Minor: These muscles lift the corners of the mouth, creating a smile.
Trunk Muscles
- Bending the Waist Forward:
- Rectus Abdominis: This muscle is responsible for flexing the lumbar spine, which leads to forward bending of the waist.
- Pulling the Waist Upright:
- Erector Spinae: These muscles extend the vertebral column and help return the trunk to an upright position from a flexed position.
- Lateral Flexion of the Vertebral Column:
- External Obliques and Internal Obliques: These muscles, when acting unilaterally, laterally flex the vertebral column to the side.
Upper Extremity Muscles
- Muscles that Flex and Extend the Humerus:
- Flexion: Pectoralis Major: This muscle helps flex the humerus by bringing the arm forward and inward.
- Extension: Latissimus Dorsi: This muscle is responsible for extending the humerus, pulling the arm backward.
- Muscle Inserting on the Radius:
- Biceps Brachii: It inserts on the radial tuberosity of the radius and is responsible for elbow flexion and forearm supination.
- Muscle Inserting on the Ulna:
- Triceps Brachii: This muscle inserts on the olecranon process of the ulna and extends the elbow joint.
Explanation:
The muscles of the body work in pairs or groups to produce movements. The muscles responsible for the neck’s movement allow for both flexion and extension, which is vital for head and neck mobility. The action of smiling involves specific facial muscles, while the trunk muscles control movements like bending and straightening. The muscles that control the upper limbs are crucial for various actions like lifting, pulling, and gripping, enabling the wide range of motions necessary for everyday tasks. Each muscle’s insertion point plays a significant role in its action, whether it’s moving a bone or a joint.