Introduction to the muscular system

00:00 / 00:00


The human body consists of hundreds of muscles, which come in all different shapes and sizes. Each muscle’s particular structure allows it to perform a specific function.

The muscles are attached to bones or other tissues, to help us maintain position, perform movements and even protect some organs.

Ok, now muscle tissue is made up of contractile cells, often called muscle fibers. Muscle tissue can be grouped into 3 types; skeletal, cardiac and smooth muscle.

Skeletal muscles connect to the skeleton and other structures like the eyes to help with movement and stability of the body.

These muscles are voluntary, meaning that we have active control of them to perform movements, like flexing your elbow.

Cardiac muscle is the muscle tissue that makes up the walls of the heart. These muscles contract in a rhythmic way to pump blood to the whole body and they are involuntary meaning that we can’t consciously control this type of muscle.

Lastly, is smooth muscle, which mainly lies in the walls of blood vessels and hollow organs. In blood vessels, smooth muscle helps contract the vessel walls to alter their diameter, which helps control blood flow.

In hollow organs, smooth muscles perform rhythmic contractions called peristaltic contractions, which moves the contents of these organs in one direction, like food in the stomach or small intestine.

Smooth muscle is also under involuntary control. Alright, now muscles come in a variety of shapes that help serve their specific functions.

For example, a flat muscle has parallel fibers, and often has a flat sheet-like tendon called an aponeurosis - as is the case for the external oblique muscle covering the abdomen.

Next is a quadrate muscle, which describes a square muscle with four equal sides. An example of a quadrate muscle is the famous six pack, anatomically called the rectus abdominis, which is a long paired muscle that is divided into square-like portions by bands of connective tissue.


Humans' muscular system consists of hundreds of muscles that carry out many different functions. It is made up of skeletal muscles, which are voluntary muscles that we can control, and smooth muscles, which are involuntary muscles that we cannot control. Skeletal muscles are attached to bones by tendons, and when they contract, they pull on the bones and move the body. Smooth muscles line the walls of blood vessels and organs such as the stomach and intestines, and they contract to move substances through these vessels or organs.


  1. "Clinically Oriented Anatomy" Lippincott Williams & Wilkins (2013)
  2. "Atlas of Human Anatomy" Saunders/Elsevier (2014)
  3. "Anatomy, Bone Markings" undefined (2020 Jan)

Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

Cookies are used by this site.

USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.