Human muscular system
There are more than 600 skeletal muscles in the human body, which make up 30 to 40% of body weight. Muscles are not just “engines” for bones. They support posture, provide breathing, protect internal organs and even participate in thermoregulation.
Structure of skeletal muscle
Each muscle consists of thousands of muscle fibers - multinucleated cells up to 30 cm long. Inside the fiber are myofibrils - contractile filaments made from the proteins actin and myosin. Their ordered arrangement creates a characteristic transverse striation, visible under a microscope.
The muscle is surrounded by several membranes:
- Endomysium - wraps each individual fiber
- Perimysium - groups fibers into bundles
- Epimysium - covers the entire muscle from the outside
These sheaths pass into the tendon, which attaches the muscle to the bone. The tendons are incredibly strong: the Achilles tendon can withstand loads of up to 400 kg.
Muscle classification
According to function, muscles are divided into:
- Agonists - perform the main movement
- Antagonists - perform the opposite movement
- Synergists - help the agonist
- Fixators - stabilize joints
The muscles of the head, neck, torso (back, chest, abdomen) and limbs are distinguished by location. In shape - fusiform, feathery, wide, circular and many others.
How muscles work
Muscle contraction is triggered by a nerve impulse. At the neuromuscular synapse, acetylcholine is released, which causes the actin filaments to slide along the myosin filaments—the muscle shortens. The energy for this process is supplied by ATP.
It is important to understand: a muscle can only pull, but not push. Therefore, muscles always work in pairs. The biceps flexes the arm at the elbow, and the triceps extends it. Disruption of this balance leads to poor posture and chronic pain.
Why study muscles
Knowledge of muscle anatomy is necessary for doctors, physiotherapists, trainers and massage therapists. Understanding the attachment points helps you select the right exercises, diagnose the source of pain, and plan rehabilitation. In 3D atlas Humio you can “undress” the body layer by layer: remove the skin, then the superficial muscles and examine the deep layers.