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💀anatomy and physiology i review

Externus

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

Externus is a term used in the context of naming skeletal muscles, specifically referring to muscles that are located on the outer or external side of the body. These muscles are responsible for various movements and functions that are essential for the proper functioning of the musculoskeletal system.

5 Must Know Facts For Your Next Test

  1. Externus muscles are often named using the term 'externus' to indicate their external or outer location, such as the 'Obliquus Externus Abdominis' muscle.
  2. These muscles play a crucial role in movements like rotation, abduction, and extension of the limbs and trunk.
  3. The location of externus muscles can help differentiate them from internus muscles, which are located on the inner side of the body.
  4. Externus muscles are often involved in complex movements that require coordination between multiple muscle groups.
  5. Understanding the location and function of externus muscles is essential for accurately assessing and treating musculoskeletal injuries or imbalances.

Review Questions

  • Explain the significance of the term 'externus' in the context of naming skeletal muscles.
    • The term 'externus' in the context of naming skeletal muscles refers to muscles that are located on the outer or external side of the body. This distinction is important because it helps differentiate these muscles from 'internus' muscles, which are located on the inner or internal side. Knowing the location of externus muscles is crucial for understanding their specific functions and roles in various movements and actions of the musculoskeletal system.
  • Describe the primary functions and movements associated with externus skeletal muscles.
    • Externus skeletal muscles are typically responsible for movements that involve rotation, abduction, and extension of the limbs and trunk. These muscles play a vital role in complex movements that require coordination between multiple muscle groups. For example, the 'Obliquus Externus Abdominis' muscle is an externus muscle that contributes to the rotation and flexion of the trunk. Understanding the specific functions and locations of externus muscles is essential for assessing and treating musculoskeletal injuries or imbalances.
  • Analyze the relationship between the location of externus muscles and their role in the overall functioning of the musculoskeletal system.
    • The location of externus muscles on the outer or external side of the body is directly linked to their functional roles within the musculoskeletal system. Muscles positioned on the exterior of the body are often responsible for movements that require greater range of motion, power, and coordination, such as rotation, abduction, and extension. This strategic placement allows externus muscles to generate the necessary force and leverage to perform these complex actions. Furthermore, the distinction between externus and internus muscles helps healthcare professionals accurately assess and treat musculoskeletal issues by understanding the specific roles and relationships of these muscle groups within the body's integrated system of movement and support.