Muscles of the Human Body: Types, Major Groups and Their Functions
written by: Leigh A. Zaykoski•edited by: Leigh A. Zaykoski•updated: 3/28/2011
The human body has more than 600 muscles, which control several critical functions and make it possible to bend, lift objects and perform other functions. Learn more about the muscles of the human body to better understand how they work.
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Types of Muscle
Muscles come in three types: smooth, cardiac or skeletal. The smooth muscles of the digestive system contract and relax to push food through the body. The smooth muscles of the bladder contract during urination and relax when it is time to hold urine in the bladder. Pregnant women also use their smooth muscles to give birth. Because you cannot control these muscles, they are also called involuntary muscles. The heart consists of cardiac muscle, which allows the hard to contract and relax as it pumps blood throughout the body. Cardiac muscle is also voluntary, as you cannot control its functions. Skeletal muscles work with the bones of the body to control movement. These muscles are voluntary, as you can control their movements. Muscles connect to the bones with tendons, which are pieces of tough tissue.
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Major Muscles of the Human Body
Each major muscle group has specific functions. The abdominal muscle group, located in the stomach area, helps you sit up and maintain proper posture. The deltoids are located at the top of the shoulder. This muscle group helps you lift objects over your head. The deltoids consist of anterior, medial and posterior parts. The biceps, located at the front of the upper arm, allow you to lift and pull objects. The gastrocnemius and soleus allow humans to stand on their toes and push off while walking. These muscles are in the back of the lower leg.
The erector spinae helps you maintain proper posture and runs up your entire back. Some people refer to this muscle as the “low back muscle." The hamstrings, located at the back of the thigh, allow you to walk. This group consists of three different muscles. The gluteus, located in the buttocks, has several functions. This muscle group allows you to stand up, walk and climb stairs. The gluteus maximus, a part of the gluteus muscle group, is the largest muscle in the human body.
The latissimus dorsi and rhomboids are located in the back. The latissimus dorsi – also called lats – are located in the midback. The rhomboids are located between the shoulder blades. These muscle groups help you maintain good posture and perform actions like pulling open doors. The pectoralis muscles are located at the front of the upper chest. These muscles make it possible to push open doors and push up from a lying position.
The obliques, located on the sides of the body, make it possible to rotate your body. Strengthening these muscles helps prevent back pain. The trapezius muscle is a large muscle located in the midback and upper back. These muscles make it possible to move your head sideways. Because of their location, problems with the trapezius muscles can also cause knots in the neck. The triceps are at the back of the upper arm and allow you to make pushing movements. The quadriceps – referred to as the quads – are located at the front of the thigh. These muscles allow you to walk, stand up and climb stairs. This muscle group consists of four muscles.