There are more than 600 muscles in the body, and together they account for about 40 percent of a person's weight (National Cancer Institute, SEER training modules). The body on screen carries 422 muscle parts laid over its skeleton. Tap any of them for its name, where it starts and ends, and what it moves.
Muscle parts by region
| Region | Parts | Different names | Examples |
|---|---|---|---|
| Head and neck | 100 | 51 | Sternocleidomastoid, digastric, the six muscles that turn each eye |
| Trunk | 78 | 41 | Diaphragm, external oblique, psoas major, the muscles between the ribs |
| Shoulder, arm and hand | 124 | 49 | Deltoid, biceps brachii, triceps brachii, supinator |
| Hip, leg and foot | 120 | 56 | Gluteus maximus, sartorius, gastrocnemius, soleus |
A part is one separate piece of the model. Left and right are separate parts, and so are the heads of a muscle: the triceps brachii has three on each arm. Counting each name once gives 197 names across the body.
Several large muscles come in pieces that can be told apart. The deltoid, the pectoralis major and the trapezius are each in three parts. The triceps has its long, lateral and medial heads, and the biceps brachii, the biceps femoris and the gastrocnemius have two heads each. A few tendons and bands sit with the muscles too, among them the calcaneal tendon at the heel and the iliotibial tract down the outside of the thigh.
The shoulder, one part at a time
Tap the cap of the shoulder. The card names one of the three parts of the deltoid: the clavicular part at the front, the acromial part over the point of the shoulder or the spinal part behind. All three share one description, taken from Gray's Anatomy: the fibers start from the clavicle, the acromion and the spine of the scapula, and converge on the outer side of the humerus.
Press Fade the rest and the chosen part stands alone in a glass body. Press Hide it and the part is gone, which uncovers what lies beneath. Do the same with the other two parts and the muscles under the deltoid show, around the top of the humerus. Reset brings every part back.
Whole regions come and go the same way. Under Muscular system, the switch for Shoulder, arm and hand removes all 124 parts at once and leaves the arm bones.
What the names say
| Word | Meaning | In the model |
|---|---|---|
| Vastus | Huge | Vastus lateralis, vastus medialis, vastus intermedius |
| Maximus | Large | Gluteus maximus |
| Longus | Long | Adductor longus, fibularis longus, palmaris longus |
| Brevis | Short | Adductor brevis, fibularis brevis |
| Deltoid | Triangular | Deltoid |
| Teres | Round | Teres major, teres minor |
| Rectus | Straight | Rectus femoris |
| Oblique | Diagonal | External oblique |
| Brachii | Of the arm | Biceps brachii, triceps brachii |
| Gluteus | Of the buttock | Gluteus maximus, gluteus medius, gluteus minimus |
The meanings are those given in the National Cancer Institute's training module on muscle groups. Type any of the words into the search box and every muscle that carries it is listed, left and right.
Long muscles and short ones
The sartorius measures 62.6 cm from top to bottom on this body. Gray's Anatomy calls it the longest muscle in the body. The rectus femoris, on the front of the thigh, comes to 55.6 cm and the gracilis, on the inner side, to 51.3 cm. Along the back, the longissimus thoracis runs for 52.0 cm beside the spine.
Small muscles are here too, in the larynx and around the eye. Switch off the skeleton and zoom in on an eye socket: six muscles turn each eyeball and a seventh, the levator palpebrae superioris, raises the upper eyelid.
Ten questions on 66 muscles
Start the quiz and a muscle lights up on one side while the rest of the body turns to glass. Where a muscle has several heads, all of them light together, so the question is about the biceps and not about one head of it. Four names are offered, drawn from the same region where possible.
The view closes in on the muscle, and the body still turns. A side or back view often settles the answer, since some muscles show only from behind. The bone quiz on the 3D skeleton follows the same pattern.
Gaps in the muscle layer
The data behind the body has no muscles of the face or of chewing. Four trunk muscles are missing: latissimus dorsi, rectus abdominis, internal oblique and transversus abdominis. The front of the abdomen is therefore partly open, and the back shows deeper muscles than a real back would.
Of the 422 parts, 417 have a written description. The body is one adult man, and the size and shape of muscles differ widely between people. The full 3D anatomy view adds the organs, vessels and brain to the same body, and the 3D body visualizer shows how build changes a figure's outline.