The term [muscle] arises from the Latin word [musculus] which derives from the Latin term [mus] meaning "mouse". We can only guess that, just as today, Roman fathers would show their biceps and forearm muscles to their children and tried to make them believe a mouse had gotten under their skin!. The root term for muscle is [-my-]. The corresponding combining form is [-myo-]. 

There are three types of muscle in the human body:

• Skeletal muscle: it is typical of muscles related to bones (skeletal) and they are voluntary.
• Smooth muscle: found in organs that act without volition (involuntary), such as the digestive system and glands.
• Cardiac muscle: found exclusively in the heart.

Muscles are formed by subunits, each one surrounded by a named membrane. One of the suffixes that means layer or membrane is [-sium]:

• Epimysium: Epi=outer; my=muscle; sium=membrane. The outer or external membrane (layer) of a muscle
• Perimysium: Peri=around; my=muscle; sium=membrane. A membrane around a muscle
• Endomysium: Endo= inner or internal; my=muscle; sium=membrane. The inner or internal membrane of a muscle- 

Original image courtesy of Wikipedia. Click on the image for a larger version.