What is the Difference Between Intrinsic and Extrinsic Muscles

The main difference between intrinsic and extrinsic muscles is that intrinsic muscles are the muscles of the body that occur deep within the structure near the axial and appendicular skeleton, whereas extrinsic muscles do not occur deep within a structure but they occur superficially.

Intrinsic and extrinsic muscles are two types of muscles classified according to the location of the muscles in the body.

Key Areas Covered

1. What are Intrinsic Muscles
   • Definition, Characteristics, Importance
2. What are Extrinsic Muscles
   • Definition, Characteristics, Importance
3. Similarities Between Intrinsic and Extrinsic Muscles
   • Outline of Common Features
4. Difference Between Intrinsic and Extrinsic Muscles
   • Comparison of Key Differences               

Key Terms

Muscles, Extrinsic Muscles, Intrinsic Muscles

What are Intrinsic Muscles

Intrinsic muscles are types of muscles that occur closer to the axial and the appendicular skeleton. For instance, the intrinsic muscles of the hand lay deeper in the hand. Further, the main function of the intrinsic muscles is to control flexion and extension.

Figure 1: Muscles of the Hand

The intrinsic muscle groups of the hand are the thenar (thumb) and hypothenar (little finger) muscles; the interossei muscles (four dorsally and three volarly) originating between the metacarpal bones; the lumbrical muscles arising from the deep flexor (special because they have no bony origin) to insert on the dorsal extensor hood mechanism. Palmaris brevis, which is a superficial muscle, and adductor pollicis are also intrinsic muscles.

What are Extrinsic Muscles

Extrinsic muscles are the other type of muscles that occur superficially in the structure. Therefore, extrinsic muscles occur less close to the axial and appendicular skeleton. The type of muscular movement of the extrinsic muscles is flexion and abduction.

Figure 2: Extrinsic Muscles of the Tongue

Moreover, the extrinsic muscles of the tongue include genioglossus muscle, hyoglossus muscle, styloglossus muscle, and palatoglossus muscle. Since they are extrinsic muscles, they are located on the surface of the tongue and attach the tongue to other structures. Although they are all attached to the tongue, they have differing origins. For example. genioglossus muscle originates from the mandible, the hyoglossus muscle is from the hyoid bone, the styloglossus muscle is from the styloid process, and the palatoglossus muscle is from the palatine aponeurosis.

Similarities Between Intrinsic and Extrinsic Muscles

• Intrinsic and extrinsic muscles are two types of muscles in the body.
• They are classified according to their location.
• Moreover, the main function of these muscles is to carry out muscular movements.

Difference Between Intrinsic and Extrinsic Muscles

Definition

Intrinsic muscles refer to a group of muscles located within or situated deeper in a structure while extrinsic muscles refer to a group of muscles lying superficially on a structure.

Occurrence

Usually, intrinsic muscles occur deeply in the structure while extrinsic muscles occur superficially.

Axial and Appendicular Skeleton

Intrinsic muscles occur closer to the axial and appendicular skeleton while extrinsic muscles occur away from the axial and appendicular skeleton.

Origination

Moreover, intrinsic muscles originate within the structure while extrinsic muscles originate near the structure.  

Muscular Movements

Intrinsic muscles undergo flexion and extension while extrinsic muscles undergo flexion and abduction.

Type of Movements

Intrinsic muscles carry out muscular movements mostly within the structure extrinsic muscles move the whole structure.

Examples

Interossei and lumbrical muscles in the hand are examples of intrinsic muscles while genioglossus muscle, hyoglossus muscle, styloglossus muscle, and palatoglossus muscle are examples of extrinsic muscles in the tongue.

Conclusion

Intrinsic muscles are the type of muscles that occur deep in the structure. Therefore, they occur near the axial and appendicular skeleton. However, the main types of muscular movements of the intrinsic muscles include flexion and extension. Extrinsic muscles, on the other hand, occur superficially and away from the axial and appendicular skeletons. The main types of muscular movements of the extrinsic muscles include flexion and abduction. Hence, the main difference between intrinsic and extrinsic muscles is their location.

References:

1. Intrinsic muscles. Biology Articles, Tutorials & Dictionary Online. (2021, January 21). Retrieved September 13, 2022.
2. (2021, January 19). Extrinsic muscles. Biology Articles, Tutorials & Dictionary Online. Retrieved September 13, 2022.

Image Courtesy:

1. “Wrist and hand deeper palmar dissection-en” By Wilfredor – Own Work (CC BY-SA 3.0) via Commons Wikimedia
2. “Hyoglossus” By Image:Gray1019.png modiefied by Uwe Gille – Own Work (Public Domain) via Commons Wikimedia