The difference between tendons and muscles is: muscles are a general term, while tendons specifically refer to the muscles on the upper thighs and arms. Both tendons and muscles can be used to describe a person's strength, such as: This person is covered in tendons/muscles.

The human body has 639 muscles. It is composed of approximately 6 billion muscle fibers, with the longest muscle fiber reaching 60 cm and the shortest only about 1 mm. Large muscles weigh about two kilograms, while small muscles weigh only a few grams. The average person's muscles account for about 35 to 45 percent of their body weight.

Extended information:

There are many principles for naming muscles, the main ones are:

1. According to shape, such as trapezius muscle and deltoid muscle;

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2. Press the location, such as supraspinatus muscles, infraspinatus muscles, tibialis anterior muscles, intercostal muscles, etc.;

3. Press the starting and ending points, such as sternocleidomastoid muscles, sternotongue Bone muscles, etc.;

4. According to location and size, pectoralis major muscles, pectoralis minor muscles, psoas major muscles, etc.;

5. According to functions, such as supination muscles, adductor magnus muscles, etc. Muscles, flexor muscles, extensor muscles, etc.;

6. According to the structure, such as semitendinosus muscles, semimembranous muscles, etc.;

7. According to the structure and location, the biceps brachii muscle, Quadriceps muscles, etc.;

8. According to location and fiber direction, such as external oblique muscles, transverse abdominal muscles, etc.

Reference material: Baidu Encyclopedia_Tondon Baidu Encyclopedia_Muscle