Question

question 9

the glenohumeral joint that articulates the humerus to the pectoral girdle is a highly mobile joint. this mobility comes at a cost because ______.

a muscles that span this mobile joint will only provide a reduced amount of power
b these type of joints are harder to control and coordinate
c the blood vessels that lead to the arm and hand can easily be cut off by the free range of motion
d the joint is relatively unstable and can easily dislocate

Explanation:

Identify the core anatomical principle

The question asks about the trade-off of the high mobility of the glenohumeral (shoulder) joint. In human anatomy, there is an inverse relationship between joint mobility and joint stability. This is a fundamental concept in Joint Classification and joint mechanics.

Analyze the trade-off of high mobility

A joint that allows a wide range of motion in multiple planes (like the ball-and-socket glenohumeral joint) must have a loose joint capsule and relatively weak ligamentous support compared to more stable, restricted joints (like the hip joint).

Evaluate the given options

• Option A suggests a reduction in muscle power, which is incorrect because muscle power depends on muscle physiology, not joint mobility.
• Option B suggests control and coordination issues, which is incorrect because motor control is managed by the nervous system.
• Option C suggests blood vessels being cut off, which is anatomically incorrect under normal physiological ranges of motion.
• Option D states that the joint is relatively unstable and can easily dislocate. This directly reflects the trade-off: high mobility results in low stability, making the shoulder joint the most commonly dislocated diarthrotic joint in the body.

Answer:

• A - muscles that span this mobile joint will only provide a reduced amount of power
• B - these type of joints are harder to control and coordinate
• C - the blood vessels that lead to the arm and hand can easily be cut off by the free range of motion
• D - the joint is relatively unstable and can easily dislocate (Correct answer)