Skeletal Muscles are also known as the striated muscles and are controlled voluntarily. Skeleton muscle functions to facilitate voluntary movements and stability in the body. The skeletal muscles are mostly attached to the bones. The skeletal muscle structure consists of bundles of muscle fibers surrounded by connective tissue. The flexible muscle fibers that compose skeletal muscles can have a diameter that can vary from less than half an inch to slightly over three inches.

When these fibers contract, the muscles can move the bones, allowing humans to perform many kinds of movements. In this article, we will study the skeletal muscles structure, function, types, examples, and properties.

What are Skeletal Muscles?

The muscles are mostly attached to bones and are responsible for the body’s voluntary actions, such as walking, lifting, and running, are referred to as skeletal muscles or voluntary muscles. The skeleton muscles are multinucleated. They have a striated appearance under a microscope because of the alignment of contractile proteins. They are made up of elongated muscle fibers arranged into bundles.

Skeletal muscles work in coordination with the nervous system to perform precise and coordinated movements, providing stability and support to the skeletal structure. They are also necessary for maintaining posture and producing heat through metabolic processes.

Skeletal Muscles Definition

Skeletal muscles are a particular type of voluntary muscle tissue that are connected by tendons to the bones and are responsible for posture maintenance and movement of the body. The arrangement of actin and myosin filaments within their fibers gives them a striated appearance.

Skeletal Muscles Diagram

The following is a labeled diagram of skeletal muscles:

Skeletal Muscles Structure

Skeletal muscle histology examines the microscopic structure and organization of skeletal muscle tissue, highlighting its cellular composition and arrangement. Muscle fibers, the basic building blocks of skeletal muscles, are arranged in a structured manner. Long, multinucleated cells known as muscle fibers include myofibrils, which are made up of repeating units known as sarcomeres.

Skeletal muscle tissue has a uniquely striated appearance due to these sarcomeres, which are made up of overlapping actin and myosin filaments. The perimysium, a type of connective tissue, envelops the bundles of muscle fibers known as fascicles.

A full muscle is formed by the enclosure of these fascicles in an epimysium-like sheath of connective tissue. Collagen fibers from the endomysium, perimysium, and epimysium combine at the ends of muscles to produce tendons, which attach muscles to bones. The structural foundation required for force production and transmission during muscle contraction is provided by this hierarchical arrangement, allowing the body to function properly and move around.

Also Read: Mechanism of Muscle Contraction

Skeletal Muscles Functions

The below are the functions of skeletal muscles:

• Movement: Skeletal muscles enable voluntary movements such as walking, running, and lifting objects.
• Posture and Stability: They maintain body posture and stabilize joints to support the skeletal system.
• Joint Stability: Skeletal muscles surround joints to prevent excessive movement and reduce injury risk.
• Heat Generation: Muscles produce heat during activity, helping regulate body temperature.
• Breathing: Some skeletal muscles help in breathing by expanding and contracting the rib cage.

Skeletal Muscles Tissue

The term “skeletal muscle tissue” describes a specific type of muscle tissue that is found in humans. It is attached to the skeleton and is responsible for controlling voluntary movements. It is made up of multinucleated, long, cylindrical muscle fibers arranged into bundles known as fascicles. The arrangement of contractile proteins within the muscle fibers gives skeletal muscle tissue a striped appearance under a microscope, which is known as striating.

Skeletal Muscles Location

Skeletal muscles are located throughout the body, attached to bones and covering joints. These muscles are located in the limbs, torso, head, and neck, and are responsible for several movements and functions. The force required for activities like walking, holding objects, and maintaining posture is provided by these muscles. Skeletal muscle relaxants are used to help with skeletal muscle relaxation when there is skeletal muscular stiffness or damage.

Skeletal Muscles Example

Some of the examples of skeletal muscles include:

• Biceps Brachii: The muscles in the upper arm that flex the elbow joint and supinate the forearm are called the biceps brachii.
• Quadriceps Femoris: This set of four muscles, which is situated in the front of the thigh, is responsible for flexing the hip joint and extending the knee joint.
• Gastrocnemius: Located in the leg’s calf area, the gastrocnemius is responsible for flexing the knee joint and plantar flexion of the foot.
• Rectus Abdominis: This muscle, which is located in the anterior abdominal wall, is responsible for compressing the internal organs of the abdomen and flexing the trunk.
• Trapezius: The trapezius, which is found in the neck and upper back, controls the scapula’s rotation, retraction, elevation, and depression.

Skeletal Muscles Properties

The following are the properties of skeletal muscles:

• Voluntary Control: Skeletal muscles can be activated and regulated based on an individual’s purposes and needs.
• Striated Appearance: Under a microscope, the structured arrangement of actin and myosin filaments within muscle fibers gives skeletal muscle tissue a striped or striated appearance.
• Attachment to Bones: Tendons attach skeletal muscles to bones, allowing them to push against the skeleton and cause movement at joints.
• Excitability: Skeletal muscles can respond to stimuli from the nervous system or other muscle fibers by generating electrical impulses known as action potentials.
• Contractility: Skeletal muscles have the ability to shorten forcibly when stimulated, enabling them to produce movement by pulling on bones and other structures.
• Elasticity: After contraction, skeletal muscles can return to their original length due to their elastic properties, allowing for controlled movement and preventing overextension.
• Extensibility: Skeletal muscles can lengthen passively beyond their resting length when an external force is applied.
• Multinucleated Fibers: The skeleton mucles are multiplenucleated. This means it has multiple nuclei in the muscular fibers of skeletal muscle tissue promote the production and repair of proteins.

Skeletal Muscle Types

Skeletal muscles can be divided into two types:

Red Muscles

The red pigment known as myoglobin, which is present in large quantities in the human body, is responsible for the appearance of red muscles. These muscles have a greater number of mitochondria and a smaller diameter. The oxygen that the mitochondria require to synthesize ATP is stored in the myoglobin. There are a lot of blood capillaries in red muscles.

White Muscles

The white muscles have a larger diameter and contain less myoglobin than the red muscles. Also, there are fewer mitochondria in them.

Also Read: Difference Between Red Muscle and White Muscle

Cardiac Muscle

Cardiac muscle is specific to the heart and contracts automatically, triggered by signals from the autonomic nervous system and pacemaker cells. Under a microscope, it shows striations much like skeletal muscle, but its unique characteristic is the presence of intercalated discs, which allow for quick electrical conduction and strong mechanical contraction. Constant contraction of cardiac muscle successfully circulates blood, supported by intrinsic pacemaker activity and its endurance. Overall, cardiac muscle maintains circulation and controls heart rate and rhythm, ensuring the essential functioning of the cardiovascular system.

Smooth Muscle

Smooth muscle is a type of muscular tissue present in various organs, including the blood vessels, digestive tract, and airways. It contracts involuntarily due to the influence of hormones and the autonomic nervous system, in contrast to skeletal muscle. Smooth muscle is made up of spindle-shaped cells arranged in layers and does not have the striated look of other muscle types.

It helps with processes like controlling blood pressure and transferring food through the digestive system since it contracts slowly and can hold its contractions for long periods. Also, smooth muscle has great adaptability, since it can expand and contract to meet variations in organ volume or vessel diameter. Overall, smooth muscle is necessary for controlling blood flow, gastrointestinal motility, and respiratory function.

Also Read: Difference Between Voluntary and Involuntary Muscles

Difference Between Smooth Muscle and Skeletal Muscle

The below table lists the differences between smooth muscle and skeletal muscle: