Muscles allow a person to move, speak, and chew. They control heartbeat, breathing, and digestion. Other seemingly unrelated functions, including temperature regulation and vision, also rely on the muscular system.
Keep reading to discover much more about the muscular system and how it controls the body.
How the muscular system works
The muscles account for around 40 percent of a person's weight with the largest muscle in the body being the gluteus maximus in the buttocks.
The muscular system contains more than 600 muscles that work together to enable the full functioning of the body.
There are 3 types of muscles in the body:
Skeletal muscles are the only muscles that can be consciously controlled. They are attached to bones, and contracting the muscles causes movement of those bones.
Any action that a person consciously undertakes involves the use of skeletal muscles. Examples of such activities include running, chewing, and writing.
Smooth muscle lines the inside of blood vessels and organs, such as the stomach, and is also known as visceral muscle.
It is the weakest type of muscle but has an essential role in moving food along the digestive tract and maintaining blood circulation through the blood vessels.
Smooth muscle acts involuntarily and cannot be consciously controlled.
Located only in the heart, cardiac muscle pumps blood around the body. Cardiac muscle stimulates its own contractions that form our heartbeat. Signals from the nervous system control the rate of contraction. This type of muscle is strong and acts involuntarily.
Eleven main functions of the muscular system
The main functions of the muscular system are as follows:
The muscular system's main function is to allow movement. When muscles contract, they contribute to gross and fine movement.
Gross movement refers to large, coordinated motions and includes:
Fine movement involves smaller movements, such as:
- facial expressions
The smaller skeletal muscles are usually responsible for this type of action.
Most muscle movement of the body is under conscious control. However, some movements are reflexive, such as withdrawing a hand from a source of heat.
Muscle tendons stretch over joints and contribute to joint stability. Muscle tendons in the knee joint and the shoulder joint are crucial in stabilization.
The core muscles are those in the abdomen, back, and pelvis, and they also stabilize the body and assist in tasks, such as lifting weights.
Skeletal muscles help keep the body in the correct position when someone is sitting or standing. This is known as posture.
Good posture relies on strong, flexible muscles. Stiff, weak, or tight muscles contribute to poor posture and misalignment of the body.
Long-term, bad posture leads to joint and muscle pain in the shoulders, back, neck, and elsewhere.
The heart is a muscle that pumps blood throughout the body. The movement of the heart is outside of conscious control, and it contracts automatically when stimulated by electrical signals.
Smooth muscle in the arteries and veins plays a further role in the circulation of blood around the body. These muscles maintain blood pressure and circulation in the event of blood loss or dehydration.
They expand to increase blood flow during times of intense exercise when the body requires more oxygen.
Breathing involves the use of the diaphragm muscle.
The diaphragm is a dome-shaped muscle located below the lungs. When the diaphragm contracts, it pushes downward, causing the chest cavity to get bigger. The lungs then fill with air. When the diaphragm muscle relaxes, it pushes air out of the lungs.
When someone wants to breath more deeply, it requires help from other muscles, including those in the abdomen, back, and neck.
The muscular system allows for movement within the body, for example, during digestion or urination.
Smooth muscles in the gastrointestinal or GI tract control digestion. The GI tract stretches from the mouth to the anus.
Food moves through the digestive system with a wave-like motion called peristalsis. Muscles in the walls of the hollow organs contract and relax to cause this movement, which pushes food through the esophagus into the stomach.
The upper muscle in the stomach relaxes to allow food to enter, while the lower muscles mix food particles with stomach acid and enzymes.
The digested food moves from the stomach to the intestines by peristalsis. From here, more muscles contract to pass the food out of the body as stool.
The urinary system comprises both smooth and skeletal muscles, including those in the:
- penis or vagina
The muscles and nerves must work together to hold and release urine from the bladder.
Urinary problems, such as poor bladder control or retention of urine, are caused by damage to the nerves that carry signals to the muscles.
Smooth muscles in the uterus expand and contract during childbirth. These movements push the baby through the vagina. Also, the pelvic floor muscles help to guide the baby's head down the birth canal.
Six skeletal muscles around the eye control its movements. These muscles work quickly and precisely, and allow the eye to:
- maintain a stable image
- scan the surrounding area
- track moving objects
If someone experiences damage to their eye muscles, it can impair their vision.
10. Organ protection
Muscles in the torso protect the internal organs at the front, sides, and back of the body. The bones of the spine and the ribs provide further protection.
Muscles also protect the bones and organs by absorbing shock and reducing friction in the joints.
11. Temperature regulation
Maintaining normal body temperature is an important function of the muscular system. Almost 85 percent of the heat a person generates in their body comes from contracting muscles.
When body heat falls below optimal levels, the skeletal muscles increase their activity to make heat. Shivering is one example of this mechanism. Muscles in the blood vessels also contract to maintain body heat.
Body temperature can be brought back within normal range through the relaxation of smooth muscle in the blood vessels. This action increases blood flow and releases excess heat through the skin.
Five fun facts about the muscular system
- Muscles make up approximately 40 percent of total weight.
- The heart is the hardest-working muscle in the body. It pumps 5 quarts of blood per minute and 2,000 gallons daily.
- The gluteus maximus is the body's largest muscle. It is in the buttocks and helps humans maintain an upright posture.
- The ear contains the smallest muscles in the body alongside the smallest bones. These muscles hold the inner ear together and are connected to the eardrum.
- A muscle called the masseter in the jaw is the strongest muscle by weight. It allows the teeth to close with a force of up to 55 pounds on the incisors or 200 pounds on the molars.
Below is a 3-D model of the muscular system, which is fully interactive.
Explore the model, using your mouse pad or touchscreen, to understand more about the muscular system.
Muscles play a part in all functions of the body, from heartbeat and breathing to running and jumping. When muscles become damaged, it can impact movement, speech, and much more.
A person should see a doctor if they notice signs of muscular weakness or pain that they cannot explain. A doctor can decide the problem and come up with an appropriate treatment plan.