The muscles
Muscles
Muscles are classified into three different types, which are skeletal, smooth and cardiac.
Skeletal muscles, also known as striated due to its appearance or voluntary due to its action, are attached to bones and deal with movement. These muscles are made up of fine, thread-like fibres of muscles containing light and dark bands. Skeletal muscles can be made to contract and relax by voluntary will. They have striations due to the actin and myosin fibres and create movement when contracted.
This system gives individuals the ability to move using muscles and the skeleton. It consists of the body’s bones, muscles, tendons, ligaments, joints, cartilage, and other connective tissue.
Smooth muscles, also called unstriated or involuntary, tend to be found within hollow organs such as blood vessels, the intestines and the respiratory tract. This muscle works automatically with no participant control. This type of muscle does not tire easily, and the contractions are slow, rhythmic and automatic.
Cardiac muscle is what the heart is made up of and only exists in your heart. It is similar in appearance to skeletal muscle in that it is striated. This type of muscle never tires and contracts and relaxes with no participant control. It is made up of short, cylindrical fibres and is purely controlled by the nervous system.
There are over 650 different types of muscles in the human body, making up nearly half of the body weight. The main function is to move joints, to which they are joined, by shortening and pulling one end of the muscle closer to the other end. Each muscle is made up of muscle fibres that are controlled by the brain, sending an impulse to the fibres via the nerves.
When a muscle is damaged, fibres become torn, and the connective tissue around the muscle is also damaged. The fibres are damaged, and fluid seeps out of torn fibres, which causes localised swelling. This fluid tends to stick the fibres together, which causes pain as the muscle is irritated by the slightest contraction. Stretching exercises will increase the length, flexibility and tone of muscles which allows the joint to move further than before.
| Name | Position | Action |
| Frontalis | Upper part of the cranium | Elevates eyebrows; draws the scalp forwards |
| Corrugator | Inner corner of eyebrows | Draws eyebrows together (frowning) |
| Procerus | Top of nose between eyebrows | Depresses the eyebrows (forms wrinkles over the nose) |
| Orbicularis Oculi | Surrounds the eye | Closes the eye (blinking) |
| Nasalis | Over the front of nose | Compresses nose (causing wrinkles) |
| Temporalis | Runs downs the side of face towards jaw | Aids chewing; closes mouth |
| Masseter | Runs down and back to the angle of the jaw | Lifts the jaw; gives strength for biting (clenches the teeth) |
| Buccinator | Forms most of the cheek and gives it shape | Puffs out cheeks when blowing; keeps food in mouth when chewing |
| Risorius | Lower cheek | Pulls back angles of the mouth (smiling) |
| Zygomaticus | Runs down the cheek towards the corner of the mouth | Pulls corner of the month upwards and sideways |
| Quadratus labii superiorus | Runs upward from the upper lip | Lifts the upper lip; helps open the mouth |
| Orbicularis Oris | Surrounds the lip and forms the mouth | Closes the mouth; pushes lips forwards |
| Mentalis | Forms the chin | Lifts the chin; moves the lower lip outwards |
| Triangularis | Corner of the lower lip, extends over the chin | Pulls the corner of the chin down |
| Platysma | Front of throat | Pulls down the lower jaw; angles the mouth |
| Sterno – mastoid | Either side of the neck | Pulls head down to shoulders; rotates head to side; pulls chin onto chest |