14.3 – Physiology (Function) of the Muscular System

The main function of the muscular system is to assist with movement. Muscles work as antagonistic pairs. As one muscle contracts, the other muscle relaxes. This contraction pulls on the bones and assists with movement. Contraction is the shortening of the muscle fibers while relaxation lengthens the fibers. This sequence of relaxation and contraction is influenced by the nervous system.

Muscles also work to keep the posture of the body. This is done through muscle contraction, where the trunk is kept straight either when sitting or standing.

Naming of Muscles

There are many nomenclatures for naming muscles. Some of these include:

• divisions: biceps, triceps, quadriceps
• size: maximus (largest), minimus (smallest)
• shape: deltoid (triangular), trapezious (trapezoid)
• action: flexor (to flex), adductor (towards the midline of the body)

Table 14.1a-b. Understanding a Muscle Name from the Latin. Adapted from Betts et al., 2013. Licensed under CC BY 4.0.

Table 14.1a. Understanding a Muscle Name from the Latin. Example: abductor digiti minimi. Translation: A muscle that moves the little finger or toe away. Adapted from Betts et al., 2013. Licensed under CC BY 4.0.

Word	Latin Root 1	Latin Root 2	Meaning
abductor	ab = away from	duct = to move	a muscle that moves away from
digiti	digitus = digit	n/a	refers to a finger or toe
minimi	minimus = mini, tiny	n/a	little

Table 14.1b. Understanding a Muscle Name from the Latin. Example: adductor digiti minimi. Translation: A muscle that moves the little finger or toe toward. Adapted from Betts et al., 2013. Licensed under CC BY 4.0.

Word	Latin Root 1	Latin Root 2	Meaning
adductor	ad = to, toward	duct = to move	a muscle that moves towards
digiti	digitus = digit	n/a	refers to a finger or toe
minimi	minimus = mini, tiny	n/a	little

Image Descriptions

Figure 14.2 image description: The top panel shows the anterior view of the human body with the major muscles labeled. Labels read (from top, head): occipitofrontalis (frontal belly), sternocleidomastoid, trapezius, deltoid, pectoralis minor, serratus anterior, pectoralis major, arm muscles: biceps brachii, brachialis, brachioradialis, pronator teres, flexor carpi radialis, abdomnial: rectus abdominis, abdominal external oblique, lower body: tensor fasciae latae, illiopsoas, pectineus, adductor longus, sartorius, gracilis, rectus femoris, vastus lateralis, vasus medialis, fibularis longus, tibialis anterior. The bottom panel shows the posterior view of the human body with the major muscles labeled. Labels read (from top, head, left side): epicranial aponeurosis, occipitofrontalis, splenius capitis, levator scapulae, rhombus, trapezius, supraspinatus, teras minor, infraspinatus, teres major, triceps brachii, seratus posterior inferior, external oblique, lower body: gluteus medius, gluteus maximus, semimebranosus, peroneus longus, tibialis posterior, (right side, from top) trapezius, deltpid, latissimus dorsi, arm: brachioradialis, extersor carpi radialis, extensor digitorum, extensor carpi ulnaris, flexor carpi ulnaris, lower body: gluteus minimus, gemellus muscles, biceps femoris, semitendinosus, gracilis, gastrocnemius, soleus. [Return to Figure 14.2].

Attribution

Except where otherwise noted, this chapter is adapted from “Muscular System” in Building a Medical Terminology Foundation by Kimberlee Carter and Marie Rutherford, licensed under CC BY 4.0. / A derivative of Betts et al., which can be accessed for free from Anatomy and Physiology (OpenStax). Adaptations: dividing Muscular System chapter content into sub-chapters.