Ch. 9 The Muscular System

Amerman - Human Anatomy & Physiology 2nd Edition

Amerman2nd EditionHuman Anatomy & PhysiologyISBN: 9780136873822Not the one you use?Change textbook

Amerman 2nd Edition

Ch. 9 The Muscular System

Problem 12

Chapter 9, Problem 12

Which of the following is not a muscle of the rotator cuff?
a. Teres major muscle
b. Teres minor muscle
c. Subscapularis muscle
d. Infraspinatus muscle
e. Supraspinatus muscle

Verified step by step guidance

Step 1: Understand the anatomy of the rotator cuff. The rotator cuff is a group of four muscles and their associated tendons that stabilize the shoulder joint and allow for a wide range of motion. These muscles are: supraspinatus, infraspinatus, teres minor, and subscapularis.

Step 2: Review the function and location of each rotator cuff muscle. For example, the supraspinatus assists in abduction of the arm, the infraspinatus and teres minor are involved in external rotation, and the subscapularis is responsible for internal rotation.

Step 3: Examine the teres major muscle. The teres major is not part of the rotator cuff. It is located near the teres minor but has a different function, primarily assisting in adduction and internal rotation of the arm.

Step 4: Compare the teres major muscle to the other muscles listed in the question. Note that the teres major does not contribute to the stabilization of the shoulder joint, which is a key function of the rotator cuff muscles.

Step 5: Conclude that the teres major muscle is the correct answer to the question, as it is not part of the rotator cuff group.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Rotator Cuff Muscles

The rotator cuff is a group of four muscles and their associated tendons that stabilize the shoulder joint. These muscles include the supraspinatus, infraspinatus, teres minor, and subscapularis. They play a crucial role in shoulder movement and stability, allowing for a wide range of arm motions.

Teres Major vs. Teres Minor

The teres major is often confused with the teres minor but serves a different function. While the teres minor is one of the rotator cuff muscles, responsible for external rotation of the arm, the teres major is not part of the rotator cuff and primarily aids in internal rotation and adduction of the arm.

Shoulder Joint Anatomy

Understanding the anatomy of the shoulder joint is essential for identifying the muscles involved in its movement. The shoulder is a ball-and-socket joint, allowing for extensive mobility, but this also makes it susceptible to injuries. Knowledge of the surrounding muscles, including the rotator cuff, is vital for comprehending shoulder mechanics.

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Related Practice

Textbook Question

Mark the following statements as true or false. If the statement is false, correct it to make a true statement.

The rhomboid major and minor muscles retract the scapula.

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Textbook Question

Mr. Bell presents with the inability to move certain muscles on one side of his face. You ask him to make various facial expressions and find that on his right side he is unable to purse his lips, pull in his cheeks, elevate his upper lip, and smirk. What muscles is Mr. Bell unable to contract?

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Textbook Question

Which of the following muscle groups is considered muscles of inspiration?

a. External intercostal muscles

b. Internal intercostal muscles

c. External oblique muscles

d. Internal oblique muscles

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Textbook Question

Match the muscle with its main action: