Which of these is a Multipennate Muscle?

Appeared in: Bihar CHO - 2021

Explanation

A multipennate muscle is characterized by fascicles that attach obliquely from many directions to several intramuscular tendons.
The deltoid muscle, specifically its acromial (intermediate) part, is a classic example of this architecture.
This arrangement allows for a high density of muscle fibers, making the deltoid a very powerful abductor of the arm despite a limited range of motion for individual fibers.

Option B: The gluteal muscles, particularly the large gluteus maximus, have a coarse, quadrilateral, or convergent fiber arrangement, which is structurally different from the multipennate pattern.
Option C: The biceps brachii is a classic example of a fusiform muscle, where the fibers run parallel to the muscle's long axis, forming a spindle shape.
Option D: While the triceps brachii has three heads, its fibers are generally arranged in a parallel or convergent manner, inserting into a common tendon. It is not a multipennate muscle.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of skeletal muscles based on fiber arrangement as background academic context rather than a clinical decision trigger.
The deltoid muscle is a common site for administering intramuscular (IM) injections, such as vaccines, for volumes typically up to 1 mL.
Nurses must accurately locate the injection site (2-3 fingerbreadths below the acromion process) to avoid injuring the underlying axillary nerve and posterior circumflex humeral artery.
Understanding that the deltoid is multipennate helps explain why it's chosen for injections: its dense structure allows for good absorption of medication.

How to Approach the Question

First, identify the key term in the question: 'Multipennate Muscle'.
Recall the definition of a multipennate muscle: it has multiple tendons with muscle fibers (fascicles) attaching to them obliquely, resembling several feathers side-by-side.
Systematically evaluate each option based on your knowledge of muscle anatomy.
Consider the Biceps and Triceps muscles. These are long muscles in the arm, and their structure is typically fusiform or parallel, not multipennate. Eliminate these options.
Consider the Gluteoid muscle. While large and powerful, its fiber arrangement is generally coarse and convergent, not multipennate.
Recall the structure of the Deltoid muscle. It covers the shoulder and has distinct anterior, middle (acromial), and posterior parts. Its middle part is known for its multipennate structure, which provides great strength for arm abduction. This makes it the correct answer.

Concept Tested & Keywords

Q53K4Wrzl5zR_Q5ffAeBWE

E6 Anatomy BDChaurasia V1 10e p. 74-76

E6 Anatomy Grays 43e Vol 2 Part 2 p. 101-103

Practise the full Bihar CHO - 2021

Attempt every question from this paper in a timed mock, then review the full solution for each one.