muscular system
The 5 main functions of the muscular system are movement, support, protection, heat generation and blood circulation

The muscular system is like a machine that converts chemical energy from food into mechanical energy. The 5 main functions of the muscular system are movement, support, protection, heat generation, and blood circulation.

1. Movement

  • Skeletal muscles pull on the bones causing movements at the joints.
  • Skeletal muscles pull on the soft tissues of the face causing facial expressions.
  • Movement caused by the respiratory muscles enables breathing.

2. Support

  • Muscles of the body wall support the internal organs.
  • As these muscles lose their tone, the internal organs of the abdominal-pelvic cavity may bulge outward as seen in some individuals as they age.

3. Protection

  • Skeletal muscles, particularly of the body wall, cushion the body's internal organs (abdominal cavity) from force applied to the exterior of the body. 

4. Heat generation

  • Heat is a waste product of muscle metabolism, which helps maintain an internal body temperature of 98.6 F.
  • Shivering is a mechanism of the muscular system that generates heat to warm an overly cooled body.

5. Blood circulation

  • Cardiac muscles aid pumping action of the heart by aiding blood circulation.

What are the types of muscles in the muscular system?

The muscular system consists of skeletal, smooth and cardiac muscles:

  1. Skeletal muscles: These create movement in the body. There are nearly 700 skeletal muscles and make up about 40% of a person’s body weight.
  2. Smooth muscles: These are involuntary muscles that line the walls of the blood vessels and viscera (organs in the abdominal cavity).
  3. Cardiac muscles: These cause the heart to contract and expand properly.

What are the functions of skeletal muscle fibers?

Skeletal muscle fibers are categorized into two types, slow-twitch fiber and fast-twitch fiber. These perform different functions:

Slow-twitch fibers

  • Contract at a slow rate. 
  • Play a vital role in endurance or aerobic activities such as cross-country or long-distance races.

Fast-twitch fibers

  • Contract at a fast rate. 
  • Produce explosive power and perform fast repetitive contractions.
  • Mainly used in 100-meter races or sprints, high jumps, weightlifting, basketball and football.
  • Play a vital role in performing anaerobic activities.

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What foods are good for the muscular system?

Nutrient-rich food is important for the muscular system to function properly. Foods that contribute to a strong muscular system include:

  • Meat, poultry, milk, eggs and seafood all contain amino acids essential for the body. Dairy products help strengthen the bones and muscles with nutrients such as calcium, vitamin D, phosphorus and potassium.
  • Whole grains, fruits and vegetables contribute to a healthy muscular and skeletal system. 
    • As carbohydrates are broken down into glucose, they increase insulin levels in the blood, which causes adenosine triphosphate (ATP) to be carried to the muscles around the body. These nutrients give the muscles the ability to function properly.
    • Infused with tons of antioxidants, fruits like grapes form nitric oxide in the body and help to maintain heart health. Citrus fruit, blueberries, oatmeal, soy, potatoes, legumes and avocado are also beneficial for muscles and contribute to overall health. 
    • Vegetables drastically reduce the risk of cardiovascular disease, lower cholesterol and eliminate free radicals that lead to aging and cancer.
  • Unsaturated fats such as omega-3 in fish oil, olive oil, peanut oil and soy oil (to name a few) keep the cells nourished.
    • Healthy fats prevent or reduce inflammation and function as a reserve fuel source when carbohydrates are depleted.
    • Omega-3 fatty acids lower the risk of arrhythmia (irregular heartbeats) and prevent plaque accumulation in the arteries. The American Heart Association advises eating fish twice a week.
  • Chocolate with 60%-70% cocoa reduces the risk of nonfatal heart attacks and stroke. Dark chocolate components include flavonoids called polyphenols which can reduce blood pressure, clotting and inflammation.

What is an oblique muscle?

The oblique muscles consist of external oblique muscle and internal oblique muscle.
The oblique muscles consist of external oblique muscle and internal oblique muscle.

The oblique muscles consist of external oblique muscle and internal oblique muscle. They are a group of muscles of the abdomen (belly) acting together forming a firm wall. This wall supports muscles of the spine and internal organs help maintain an erect posture and protects the organs from getting injured by keeping them in their anatomical (expected) position.

Abdominal muscles work together to produce movements of the spine as well as to compress the abdominal viscera. The oblique muscles make up two of the three muscle layers that surround the abdominal wall with the third layer of transversus abdominis muscle.

In vertebrates, the abdomen is a large body cavity enclosed by layers of the muscular wall at the front and sides. The vertebral column at the back houses and protects major elements of the gut, such as part of the esophagus, stomach, small intestine, large intestine, liver, pancreas, gall bladder, and spleen, as well as parts of the urinary system, such as kidneys and ureters.

The contraction of the abdominal muscles helps the body breathe out and increases the intra-abdominal pressure, such as during sneezing, coughing, passing stools, urinating, and childbirth.

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What is the external oblique muscle?

The external oblique muscle is the outermost muscle located on both sides of the trunk. The muscle fibers lie beneath the thoracic (chest) and abdominal skin originating from the lower ribs to the pelvis (hip bone). The muscular part makes up the lateral part of the abdominal wall. The muscle contributes to the variety of trunk movements and is mainly responsible for performing functions, such as twisting the sides of the trunk, pulling the chest downwards, rotating the spine. Any form of strain, injury, or trauma to the muscle can be debilitating.

The external abdominal oblique muscle has a variety of functions depending on whether it contracts unilaterally (one side) or bilaterally (both sides):

  • When acting unilaterally and in synergy with the internal oblique muscle, it rotates the trunk to the opposite side.
  • When working together with back muscles, it contributes to bending of the trunk sideways.
  • When contracting on both sides, it leads to the forward flexion (forward bending) of the trunk. This activity also increases the tone of the abdominal wall and positive intra-abdominal pressure, which is part of various physiological processes, such as forced exhalation, defecation (passing stools), micturition (urinating), and labor (childbirth).

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What is the internal oblique muscle?

It is a broad, thin muscular sheet found on the sides of the abdomen arranged perpendicular (at right angles) and deep to the external oblique muscle. It has multiple sites of origin and is divided into anterior (front) fibers, posterior (hind) fibers, and lateral (sideways) fibers according to its origin sites. This muscle is an opposing force to the diaphragm reducing upper chest cavity volume during exhalation. The contraction of this muscle also rotates and bends the trunk sideways. The muscle is also called the “same side rotator.”

Along with other muscles of the abdominal wall, internal abdominal oblique muscle is important for maintaining normal abdominal wall tension:

  • The contraction of these muscles has a protective and supportive role.
  • The bilateral (both sides) contraction of this muscle also increases the intra-abdominal pressure and aids in functions, such as forced expiration (exhalation), micturition (urination), defecation (passing stools).
  • Weakness of these muscles increases the risk of abdominal hernias.

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Medically Reviewed on 3/8/2022
References
The Muscular System: https://www.shsu.edu/~bio_mlt/Chapter10.html Muscular and Skeletal Systems:

https://www2.estrellamountain.edu/faculty/farabee/biobk/biobookmusskel.html

Biology Dictionary. Oblique Muscle. https://biologydictionary.net/oblique-muscle/

Science Direct. Abdominal External Oblique Muscle. https://www.sciencedirect.com/topics/neuroscience/abdominal-external-oblique-muscle