Why do calves have muscles

Our body is covered with many muscles, which provide certain power when the body moves. Muscles are relatively hard and can also protect bones. 639 muscles evenly cover the bones. So, why do calves have muscles? This is a difficult question to answer because muscles have existed in the body since the early days of human evolution.

There are approximately 639 muscles in the human body. It is composed of about 6 billion muscle fibers, the longest of which is 60 cm long and the shortest is only about 1 mm. Large muscles weigh about two kilograms, while small muscles weigh only a few grams. The average person's muscles make up about 35 to 45 percent of their body weight.

According to the structure and function, it can be divided into three types: smooth muscle, cardiac muscle and skeletal muscle. According to the morphology, it can be divided into long muscle, short muscle, broad muscle and orbicularis muscle. Smooth muscle mainly constitutes the internal organs and blood vessels, and has the characteristics of slow contraction, durability, and low fatigue. Myocardial muscle constitutes the heart wall. Neither of them contracts according to human will, so they are called involuntary muscles. Skeletal muscle is distributed in the head, neck, trunk and limbs and is usually attached to bones. Skeletal muscle contracts quickly and forcefully, fatigues easily, and can expand and contract at will, so it is called voluntary muscle. Skeletal muscle appears striated when observed under a microscope, so it is also called striated muscle.

Skeletal muscle is the power part of the motor system and is divided into white and red muscle fibers. White muscle relies on rapid chemical reactions to contract or stretch quickly, while red muscle relies on continuous oxygen supply to move. Under the control of the nervous system, skeletal muscles contract, pulling bones to produce movement. There are more than 600 skeletal muscles in the human body, which are widely distributed and account for about 40% of body weight. Regardless of the size, each skeletal muscle has a certain shape, structure, position and auxiliary devices, and is richly distributed with blood vessels and lymphatic vessels, and is innervated by certain nerves. Therefore, each skeletal muscle can be considered an organ.

The head muscles can be divided into two parts: facial muscles (expression muscles) and chewing muscles. The trunk muscles can be divided into back muscles, chest muscles, abdominal muscles and diaphragm. The lower limb muscles are divided into hip muscles, thigh muscles, calf muscles and foot muscles according to their location. They are all thicker than the upper limb muscles, which is related to supporting body weight, maintaining upright posture and walking.