How Many Muscles Are in the Human Body?

Your body has three different types of muscles. They include:

Skeletal muscle

Your skeletal muscles are attached to your bones via tendons. Each muscle is comprised of thousands of muscle fibers that are bundled together.

The organized arrangement of these fibers leads to a striped pattern. Because of this, you may also hear skeletal muscle referred to as striated muscle.

Skeletal muscle is predominantly involved in movement. When one of these muscles contracts, it allows movement of a specific area of the body.

Your skeletal muscles are voluntary. That means that you can control their movement. They’re the only category of muscle for which you can do this.

Smooth muscle

Smooth muscle can be found in many different organ systems of your body, including but not limited to your:

• digestive system
• respiratory system
• cardiovascular system
• renal system
• reproductive system

Smooth muscle cells are often rounded at the center and tapered off at the sides. Unlike skeletal muscle, they aren’t striated. The term “smooth muscle” refers to the more uniform appearance of this type of muscle tissue.

Smooth muscle is involuntary. That means that you can’t control its movement. Each cell contains chains of filaments that can connect it to other neighboring cells, forming a mesh-like network that allows the cells to contract uniformly.

Cardiac muscle

Cardiac muscle is found only in your heart. It’s the type of muscle that allows your heart to beat. You may also see this type of muscle referred to as the myocardium.

The myocardium is one of the three layers of tissue in your heart. It’s located between the inner lining of the heart (endocardium) and the protective sac that surrounds your heart (pericardium).

Similar to skeletal muscle, cardiac muscle is organized into fibers and has a striated appearance. Individual cardiac muscle cells are closely connected to each other, which helps enable your heart to beat in a coordinated fashion.

Like smooth muscle, cardiac muscle is involuntary. It contracts in response to electrical impulses created by a special type of cell in your heart.

Skeletal muscles can be found in all areas of your body. Here is a diagram of some of the most well-known and most used skeletal muscles, and what they do.

Skeletal muscle

The functions of your skeletal muscles include:

• enabling movement of the body
• providing structural support
• maintaining posture
• generating heat, which helps maintain body temperature
• acting as a source of nutrients such as amino acids
• serving as an energy source during starvation

You may also see skeletal muscles divided according to which area of the body they serve, such as:

Muscles of the head and neck

The muscles in this area control movement of the face, head, and neck. Examples include:

• Zygomaticus: This muscle is involved in facial expression and lifts the corners of your mouth, such as when you smile.
• Masseter: The masseter is found in the jaw and is used to close your mouth and to chew food.
• Eye (extraocular) muscles: This is a group of muscles that controls the movements of your eyes as well as the opening and closing of your eyelids.
• Muscles of the tongue: This group of muscles help to elevate and lower the tongue as well as help it move in and out.
• Sternocleidomastoid: This is the major muscle that’s involved when you rotate or tilt your head to the side. It’s also involved in tilting your head forward.

Muscles of the trunk

These muscles are located in the area of your torso and abdomen. Some examples are:

• Erector spinae: These muscles are involved in supporting your spine and enabling movements such as bending, arching, and twisting of the spine.
• Oblique muscles: This group of muscles, which includes the external and internal obliques, helps you to bend to the side or twist your body at the waist.
• Intercostal muscles: The intercostal muscles are located around your ribs and help facilitate inhaling and exhaling.
• Diaphragm: The diaphragm separates your torso from your abdomen. It’s also involved in breathing, contracting when you inhale, and relaxing when you exhale.
• Levator ani: This muscle group supports the organs and tissues around your pelvis. It’s also important for urination and bowel movements.

Muscles of the upper extremities

This includes the muscles that move your shoulders, arms, wrists, and hands. Examples of important muscles in this area include:

• Trapezius: This muscle is used for several movements, including tilting your head back, raising your shoulders, and moving your shoulder blades together.
• Pectoralis major: The pectoralis major is located in your upper chest and is utilized for rotational, vertical, and lateral movements of your arm.
• Deltoid: The deltoid works to lift or rotate your arm at the shoulder.
• Biceps brachii: The biceps brachii flexes the forearm. When this happens, your elbow bends.
• Triceps brachii: The triceps brachii extends the forearm, straightening the elbow.

Muscles of the lower extremities

This area involves the muscles that move your legs and feet. Some examples that you may be familiar with are:

• Gluteus maximus: This muscle is used for movement of your hips and thighs. It’s important for maintaining posture, standing up from a sitting position, or going up stairs.
• Quadriceps: This is actually a group of muscles that are located at the front of your thigh and work together to straighten your leg at the knee.
• Hamstrings: Your hamstrings are located in the back part of your leg. This muscle group helps to extend your thigh and to bend your leg at the knee.
• Tibialis anterior: You use this muscle when you raise the sole of your foot from the ground
• Soleus: The soleus works to lower the sole of your foot to the ground. It’s important for maintaining your posture while you’re walking.

Smooth muscle

The function of smooth muscle can vary depending on where it’s found in the body. Let’s look at some functions of smooth muscle by system:

• Digestive system: The contractions of smooth muscle help to push food through your digestive tract.
• Respiratory system: Smooth muscle tissue can cause your airways to widen or narrow.
• Cardiovascular system: Smooth muscle in the walls of your blood vessels aids in the flow of blood and also helps to regulate your blood pressure.
• Renal system: Smooth muscle helps to regulate the flow of urine from your bladder.
• Reproductive system: In the female reproductive system, smooth muscle is involved in contractions during pregnancy. In the male reproductive system, it helps to propel sperm.

Smooth muscle is also involved in some sensory processes. For example, smooth muscle is what causes your pupils to expand or contract.

Cardiac muscle

Cardiac muscle allows your heart to beat. A heartbeat is generated in response to an electrical impulse.

Cardiac muscle contracts in response to this electrical signal, which is initiated by a special type of cell called a pacemaker cell.

The electrical signal travels from the upper to the lower part of your heart. Because cardiac muscle cells are closely connected to one another, they’re able to contract in a coordinated wave-like fashion that forms the heartbeat.

Still interested in learning more about your muscles? Here are some more fun facts:

• Your skeletal muscles make up between 40 to 50 percent of your total body weight.
• Skeletal muscle mass begins to decline as you get older. This process typically begins after the age of 40.
• Water is important for all living things. In fact, your muscles are made up of about 79 percent water.
• The largest muscle in your body is the gluteus maximus.
• Think about this the next time you cozy up with a good book: Your eye muscles make an estimated 10,000 coordinated movements in just 1 hour of reading.
• Your cardiac muscle tissue works hard! Your heart can pump at least 2,500 gallons of blood in a single day.
• Your cardiac muscle has limited regeneration capabilities. That’s why damage to this tissue through things like heart disease or myocarditis can have serious health implications.
• Smooth muscle tissue is important in moving food through your digestive tract. Did you know that it takes about 44 hours for food you eat to pass through your digestive tract?
• Although we may not think about it often, smooth muscle is vital. In fact, many treatments target this tissue. Examples include medications to treat asthma and high blood pressure.

Muscle tissue is found throughout your body and its structure and function can be very diverse. You have three different types of muscle: skeletal, smooth, and cardiac. Skeletal muscle alone accounts for over 650 different muscles.

Your muscles perform many important functions that are critical to your health. Some examples of processes that muscles are involved in include things like movement, digestion, and the beating of your heart.