Muscular system anatomy and physiology

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Muscular system anatomy and physiology


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Muscular system anatomy and physiology

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The muscular system is made up of three types of muscle tissue: skeletal, smooth, and cardiac muscle tissue.

They differ in terms of their location, cell structure, and innervation. But they also share some characteristics: they’re all excitable, meaning that the cells react to a stimulus, they all contract--meaning that the cells will shorten, they all have extensibility--meaning that the cells can be stretched, and they’re all elastic--meaning that they can recoil or bounce back to their original length.

Let’s start with skeletal muscles. Skeletal muscles usually attach to bones, but in some cases, they attach to the skin, like the muscles in our face that control facial expression.

Skeletal muscles are voluntary muscles, meaning that they can be controlled consciously, but some skeletal muscles are also controlled subconsciously.

Your diaphragm, for example, you can contract consciously when you take a big breath, but it also continues to contract and relax without conscious effort when you’re fast asleep or thinking about other things.

Skeletal muscles help you maintain your posture and stabilize joints, and because skeletal muscles use up a lot of energy as they contract and relax, they also generate a lot of heat as a byproduct. That’s why we shiver to stay warm when it’s really cold.

Now let’s take a look at the biceps brachii, a skeletal muscle in your upper arm. Like most muscles there’s the belly of the muscle and the muscle tendons.

The muscle belly is the part that contracts and it’s wrapped in a layer of connective tissue called the epimysium.

Now let’s take a look at the cross-section of the muscle belly, there are thin layers of connective tissue called the perimysium that separate the muscle into fascicles.

Each muscle fascicle consists of a bundle of muscle fibers, and each muscle fiber is a muscle cell, or myocyte.


The muscular system is composed of specialized cells called muscle fibers, which contain contractile proteins that enable them to contract and relax. The main types of muscle tissue are: skeletal, cardiac and smooth muscles.

Skeletal muscles are voluntary muscles attached to bones, which enable movement of the skeleton, and maintain body temperature by generating heat. The cardiac muscle is present only in the heart and is responsible for cardiac contraction that pumps blood throughout the body. Smooth muscles lie mainly in the walls of hollow viscera, such as the stomach and intestines, where they help to propel substances through these organs.


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  2. "Physiology" Elsevier (2017)
  3. "Human Anatomy & Physiology" Pearson (2018)
  4. "Principles of Anatomy and Physiology" Wiley (2014)
  5. "MHC composition and enzyme-histochemical and physiological properties of a novel fast-twitch motor unit type" American Journal of Physiology-Cell Physiology (1991)
  6. "Exercise induced increases in muscle fiber number" European Journal of Applied Physiology and Occupational Physiology (1986)
  7. "Enzyme activity and fiber composition in skeletal muscle of untrained and trained men" J Appl Physiol (1972)

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