Where human muscles get their names
Human body muscles are divided into groups named for the gross movement they cause at bone joints. Names of human muscle groups characterize the direction in which they position, or move about, the bones of the human skeleton. Group names, by design, represent clear opposite directions because of how human joints are engineered.
An individual muscle within a group may, or may not, carry the name of the group as part of its full name. Some muscles are named to match the name of the bone to which it attaches. Other muscles are named with a word that describes its shape.
Hint: If you spend time necessary to learn the names of human bones well, it will make your study of human muscles much easier.
The complex arrangement of bone attachments for individual human muscles permits a wide range of controlled elegant movement of the human skeleton. Bone attachment patterns compensate for the fact that muscles work in a straight line. Each individual muscle has a narrow range of motion because it can do no more than shorten and lengthen.
In human anatomy all descriptions of body motion are based upon the assumption that the starting place is the body in the anatomical position. Review the picture of the the male figure in the anatomical position and notice the position of his hands, arms, legs, and head.
Muscle groups that cause bending movement that decreases the angle between two body parts – starting from the anatomical position – are called flexors. Bending at the elbow, clenching a hand into a fist, and sitting down are movements achieved by contraction – shortening – of the flexor muscles. The movement itself is called flexion, and the word ‘flexor’ will sometimes be found as part of the name of an individual muscle in one of these groups.
The opposite movement is extension. Extensor muscles cause movement that increases the angle between body parts. To stand up from a sitting position the knee joints must be ‘extended’ – the angle between the leg and thigh increasing in size. Muscles that move the leg or arm posterior to the anatomical position also fall into the class called extensors. Muscles that cause extension often contain the term ‘extensor’ as part of their name.
Another set of descriptive terms, abduction and adduction, were devised to group muscles that pull body structures away from, or toward, the midline of the body, or the midline of the hand, or the midline of the foot. Raising the arms laterally is an example of abduction.
Dropping the arms back to the sides of the body is an example of adduction. Again some of the muscles, but not all, responsible for such movement will include in their full name the word ‘abductor’ or ‘adductor’.
Rotational motion at the shoulder, and hip joint may be toward the median of the body, medial rotation, or away from the median of the body, lateral rotation. Click this link for a 3 minute video that demonstrates anatomical motions that you will want to remember before you begin to learn names of muscles.
As discussed in another article on this website, Orientation in Anatomy, it is important not to blow off learning these simple opposite terms describing human body movement. This is because one of the 3 major characteristics of each human muscle you will need to learn will be the action taken by that muscle – flexion, extension, rotation, abduction, etc. The other 2 characteristics you will need to know are each muscle’s major points of attachment to its bone – the origin (end of the bone that does not move much when the muscle shortens) and the insertion (end of the bone that moves a lot when the muscle shortens).
This video by the famous Mr. Ford uses these anatomic terms as he walks you through the muscles of the most complex joint arrangement in the human body, the muscles that control full rotation of the arm.
Other articles on this site that you may find helpful are:
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Margaret Thompson Reece PhD, physiologist, former Senior Scientist and Laboratory Director at academic medical centers in California, New York and Massachusetts and CSO at Serometrix LLC is now CEO at Reece Biomedical Consulting LLC.
Dr. Reece is passionate about helping students, online and in person, pursue careers in life sciences. Her books “Physiology: Custom-Designed Chemistry” (2012), “Inside the Closed World of the Brain” (2015) and the workbook (2017) companion to her online course “30-Day Challenge: Craft Your Plan for Learning Physiology” are written for those new to life science. More about her books can be found at amazon.com/author/margaretreece
Dr. Reece offers a free 30 minute “how-to-get-started” phone conference for students struggling with human anatomy and physiology. Schedule an appointment by email at DrReece@MedicalScienceNavigator.com.