What is the Difference Between Epimysium and Fascia

The main difference between epimysium and fascia is that epimysium is a type of specialized deep fasciae in muscles at the outer most fibrous layer. But, fascia is a sheet of connective tissue beneath the skin. Furthermore, epimysium is made up of dense irregular connective tissue while deep fascia refers to a type of fascia, which covers the muscles. Moreover, the other types of fascia include superficial fascia and visceral and parietal fascia.  

Epimysium and fascia are two types of connective tissue sheets, which attach, stabilize, enclose, and separate muscles and other internal organs. Generally, they serve as passive structures, which reduce the friction of muscular force.  

Key Areas Covered 

1. What is Epimysium
     – Definition, Anatomy, Function
2. What is Fascia
     – Definition, Anatomy, Function
3. What are the Similarities Between Epimysium and Fascia
     – Outline of Common Features
4. What is the Difference between Epimysium and Fascia
     – Comparison of Key Differences

Key Terms 

Connective Tissue, Deep Fascia, Epimysium, Fascia, Parietal Fascia, Superficial Fascia, Visceral Fascia

What is Epimysium  

The skeletal muscles compose of many parallel fascicles made up of bundles of muscle fibers. Of these, epimysium, endomysium, and perimysium are the three types of deep fasciae that occurs in muscles. These three fascia  interpenetrate and surrounds the muscles, bones, nerves, and blood vessels of the body. Furthermore, their function is to reduce the friction generated by muscular forces as well as external forces.  

Moreover, epimysium is the outermost fibrous layer of the skeletal muscle and is made up of dense irregular connective tissues. But, endomysium is an areolar connective tissue, enclosing individual muscle fiber. And, perimysium is the connective tissue sheath with thick and highly wavy collagen fibers. Also, it separates individual fascicles. 

Figure 1: Structure of the Skeletal Muscle

What is Fascia 

Fascia is a sheet of connective tissue, occurring beneath the skin. It covers all the collagenous soft tissues, which enclose bones, muscles, blood vessels, nerves, and other organs. Also, it includes tendons and ligaments, as well. Concerning its functions, the main functions of fascia are to attach, stabilize, impart strength, maintain vessel patency, separate muscles, and enclose different organs. Besides, there are three types of fasciae, occurring in the body. They are the superficial fasciae, deep fasciae, and visceral and parietal fasciae.  

Superficial Fascia 

Superficial fasciae occur directly under the skin. It composes of membranous layers with loosely packed interwoven collagen and elastic fibers. Also, it is thicker in the trunk but, peripherally, it is thinner in the limbs. Some examples of superficial fascia include the platysma muscle in the neck, the external anal sphincter, fascia of the Scarpa, and the dartos fascia in the scrotum.

Figure 2: The Superficial Layer of the Face  

Deep Fascia 

Deep fascia is the type of fascia, which surrounds bones, muscles, nerves, and blood vessels. It has a more fibrous consistency and rich in hyaluronan. Also, it is highly vascularized and contains well-developed lymphatic vessels. Apart from that, Ruffini and Pacinian corpuscles are the types of free, encapsulated nerve endings in the deep fascia.

Moreover, aponeurotic fascia and the epimysial fascia are two types of deep fascia. Of these, aponeurotic fascia is the sheets of pearly-white fibrous tissue, which thins to become tendons. The fascia of limbs, thoracolumbar fascia, and rectus sheath are examples of such fascia. Epimysial fascia or the epimysium, on the other hand, is the connective tissue layer, which surrounds the skeletal muscles. The main muscles surrounded by such fascia include the trunk, pectoralis major, trapezius, deltoid, and gluteus maximus.  

Visceral and Parietal Fascia 

Visceral fascia is the type of fascia, surrounding the organs in cavities like the abdomen, lung (pleura), and heart (pericardium).

Figure 3: Pleura

Meanwhile, parietal fascia lines the wall of a body cavity just outside of the parietal layer of serosa; as an example in the pelvis. 

Similarities Between Epimysium and Fascia  

• Epimysium and fascia are connective tissue layers that enclose different structures of the body.  
• Functionally, they attach, stabilize, enclose, and separate muscles and other internal organs.    
• Also, they are made up of fibrous connective tissue with closely packed bundles of collagen fibers oriented in a wavy pattern parallel to the direction of pull.    
• Thus, they are flexible and able to resist great unidirectional tension forces until their wavy pattern of fibers has been straightened out by the pulling force.    
• Importantly, they reduce the friction of muscle forces or external forces in the body. 

Difference between Epimysium and Fascia 

Definition 

Epimysium refers to the sheath of external connective tissue of a skeletal muscle. Fascia refers to a flat band of tissue below the skin, covering the underlying tissues and separates different layers of tissue. 

Correspondence 

Epimysium is a type of deep fasciae, while the three types of fascia include the superficial fasciae, deep fasciae, and visceral and parietal fasciae. 

Made up of 

Epimysium is made up of dense irregular connective tissue, while fascia is made up of connective tissue primarily containing collagen. 

Occurrence 

Epimysium serves as the outermost fibrous tissue layer in skeletal muscles, while fascia envelops bones, cartilages, muscles, blood vessels, and nerves. 

Function 

Epimysium reduces the friction produced by muscular forces, while fascia stabilizes internal organs, blood vessels, and nerves. 

Conclusion 

Epimysium is the dense irregular connective tissue layer, which encloses the entire muscle. Also, it is a type of deep fasciae that occur in muscles. Importantly, it is responsible for reducing the friction generated by muscular forces. Fascia, on the other hand, is a sheet of connective tissue that occurs below the skin. The three types of fasciae are superficial fasciae, deep fasciae, and visceral and parietal fasciae. Whatever the type, the main function of fascia is to stabilize internal structures. Therefore, in conclusion, the main difference between epimysium and fascia is their occurrence and function. 

References:

1. Gatt A, Agarwal S, Zito PM. Anatomy, Fascia Layers. [Updated 2019 Jul 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available Here.
2. “Epimysium.” Epimysium : Anatomy of Muscle Structure, IvyRose Holistic, Available Here.

Image Courtesy:

1. “Illu muscle structure” (Public Domain) via Commons Wikimedia   
2. “Sobo 1909 260” By Dr. Johannes Sobotta Illustration: K. Hajek and A. Schmitson – Sobotta’s Atlas and Text-book of Human Anatomy 1909 (Public Domain) via Commons Wikimedia   
3. “2313 The Lung Pleurea” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia