Group of people with dumbbells and steppers

Human Muscular System

The human muscular system is composed of smooth muscles, skeletal muscles, and the cardiac muscles. This Buzzle write-up provides some information about this organ system.
The human muscular system comprises more than 600 muscles, which act in groups. Muscles are contractile organs or tissues that facilitate all types of movements involving the body parts (legs, arms, appendages, etc.), and even subtle movements (smiling, frowning, etc.). Muscles are distinguished as either involuntary or voluntary. Involuntary muscles function within the body automatically, without you being able to control them. Voluntary muscles are the ones that are under your control. Besides facilitating movement, muscles also play a vital role in pumping blood, maintaining posture and stability, digestion, etc. Muscles are made up of a type of elastic tissue, and each muscle comprises thousands of tiny fibers. Each fiber is composed of long thin cells that are packed in bundles, which in turn are wrapped in perimysium. Myosin and actin are proteins that are present in the fibers. There are three kinds of muscles in the human muscular system: the skeletal muscle; the cardiac muscle; and the smooth muscle. Besides these, the facial muscles and the tongue are of a unique kind.

Types of Muscles

Skeletal Muscles
Accounting for most of the body weight, skeletal muscles are voluntary muscles, which means that are under our control. These are mostly found attached to the skeleton, and are responsible for moving different parts of the skeleton. Generally, these are attached to the ends of bones, stretching all across the joint and then attached to another bone. Tendons, which are cords or bands of inelastic tissue, attach these muscles to the bones. Skeletal muscles are of different shapes and sizes, which enable them to perform a variety of tasks. The gluteus maximus, or the muscle that occurs in the buttocks, is the largest skeletal muscle. Some of the other major skeletal muscles include the deltoid muscle in the shoulders, the biceps and triceps in the arm, the pectoralis in the chest, the rectus abdominus in the abdomen, and the quadriceps and hamstring muscles in the legs.

Movements that we consciously perform involve these muscles. For example, you cannot pick up an object with your hand unless you want your hand to do so. These muscles are sometimes referred to as striated muscles, because the dark and light fibrous material make them seem striped. Along with bones, these muscles form the musculoskeletal system of the human body.

Cardiac Muscle
The heart is made up of the cardiac muscle, which is also referred to as the myocardium. These muscles are thick and contract in order to pump out the blood and then relax in order to allow more blood in. The cardiac muscle is an involuntary muscle, which means that it is not under our control. Special type of cells in the cardiac muscle, called the pacemaker, help in controlling the heartbeat.

Smooth Muscles
These are the involuntary muscles of the human muscular system. These generally occur in layers or sheets, with one muscle layer behind another. These muscles are not under our control. The brain and the body control these muscles in performing their functions without any conscious volition from your part. These don't have the striped or banded appearance of the skeletal muscles, which is why these are called smooth muscles. These are found inside organs such as the stomach, intestines, bladder, uterus, and blood vessels. These muscles play a vital role in digestion. For instance, peristalsis (wavelike muscle contractions of the alimentary tract) moves the food along the digestive tract. Smooth muscles also occur in the eyes, which help to keep the eyes focused. According to scientists, the eyes can move over 100,000 times in a day, making them the busiest muscles.

Facial Muscles
There are more than 30 muscles in the face. Not all facial muscles are attached to bones. Many of these muscles are attached to the underside of facial skin. These are involved in facial expressions such as frowning, laughter, surprise, sadness, etc.

And another unique muscle is the tongue, which is free at one end and only attached on the other end. The tongue actually comprises a group of muscles, which work in unison, enabling you to chew and swallow food, and talk.

On a concluding note, muscles are essential for the healthy functioning of the human body. If any of these muscles get damaged due to medical conditions, it can have an adverse impact on the quality of life of an individual.
Little girl sticking out her tongue
Facial muscles
Peristalsis. involuntary wavelike muscular contraction
Cardiac muscle
skeletal muscle