The Musculoskeletal System

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.


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 fibers 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 fibers and create movement when contracted.

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 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.

Muscles of the body

Muscles have many functions in the body, not just for movement. They also provide the body with its shape and contours as well as providing a supporting cover for the skeleton. Muscle tone can be improved by increasing your exercise.

Muscles of the Face, Neck, Shoulder, Back and Arms

The face has several relevant muscles.

Names, position and function of facial muscles

FrontalisUpper part of the craniumElevates eyebrows Draws the scalp forwards
CorrugatorInner corner of eyebrowsForms vertical wrinkles between the eyebrows
ProcerusTop of nose between eyebrowsDepresses the eyebrows (forms wrinkles over bridge of nose)
Orbicularis OculiSurrounds the eyeCloses the eye (blinking) Remember Oculi rhymes with eye
NasalisOver the front of noseCompresses nose (causing wrinkles)
TemporalisRuns downs the side of face towards jawAids chewing Closes mouth
MasseterRuns down and back to the angle of the jawRetracts the jaw and aids chewing (remember Masseter – eater)
BuccinatorForms most of the cheek and gives it shapePuffs out cheeks when blowing Keeps food in mouth when chewing
RisoriusLower cheekPulls back angles of the mouth(smiling)
ZygomaticusRuns down the cheek towards the corner of the mouthPulls corner of the month upwards and sideways
Quadratus labii superiorusRuns upward from the upper lipLifts the upper lip Helps open the mouth
Orbicularis OrisSurrounds the lip and forms the mouthCloses the mouth Pushes lips forwards
MentalisForms the chinLifts the chin Moves the lower lip outwards
TriangularisCorner of the lower lip, extends over the chinPulls the corner of the chin down
PlatysmaFront of throatDraws the lower lip and jaw down, and forms horizontal wrinkles in the neck
Sternocleido mastoid (SCM)Either side of the neckAllows neck to flex and rotate, and nod the head
OccipitalisBack of the skullDraws the head backwards

Muscles of the Upper Body

TrapeziusUpper back and sides of neckRotation of shoulders Draws back the scapula (retracts) Pulls head back Assists in rotation of head
PectoralisFront of chest, under breastPulls arms forward and assists rotation of the arm
DeltoidsSurrounds shouldersLifts arms sideways, forwards and backwards

Muscles of the Arm and Hand

Many of the muscles in the forearm are termed according to their action. They are grouped as flexors and extensors.

The muscles flex and extend, supinate and pronate the hand and arm and the fingers to spread apart and close together

DeltoidsSurrounds shouldersLifts arms sideways, forwards and backwards
BicepsFront of upper armFlexes elbow Supinates the forearm and hand
TricepsBack of upper armExtends the elbow
Brachio radialisOn the thumb side of the forearmFlexes the elbow
FlexorsMiddle of the forearmFlexes and bends the wrist drawing it towards the forearm
ExtensorsLittle finger side of the forearmExtends and straightens the wrist and hand
Thenar musclePalm of the hand below the thumbFlexes the thumb and moves it outwards and inwards
Hypothenar musclePalm of hand below little fingerFlexes little finger and moves it outwards and inwards

Muscles of the Chest, Abdomen, Hips, Legs and Feet

The pectoralis major is the main muscle that covers the front of the chest. It is a thick, fan shaped muscle which gives the chest its contour. It makes up most of the males chest shape and lies under the breasts on females. The latissimus dorsi covers the back of the chest and abdomen. It adducts, extends and medially rotates the shoulder joint. The serratus anterior runs around the side wall of the chest.

  • The main muscles are at the front of the thigh and are called the quadriceps. They are responsible for extending the knee joint and flexing the hip
  • The Adductors are the group of muscles on the inside of the thigh and moves the leg in towards the body
  • The Abductors are on the outside of the thigh and moves the hip outwards. (Remember that the term abduct means to take away)
  • The hamstrings are located at the rear of the thigh and extends the thigh and flexes the leg
  • The abdominal area consists of the two different types of muscles. The internal and external oblique. These muscles allow you to move your body from left to right.
  • The transversus and rectus abdominus allow us to bend down and pick things up (flexion of the trunk)
  • Dorsiflexion of the foot is performed by the tibialis anterior
  • The glutes are the biggest muscle in the body and are the muscles that give your bottom its shape. They are known to be lazy muscles as they are only used to be sat on.
Pectoralis majorAcross upper chestUsed in throwing ad climbing Adducts and medially rotates the arm
Pectoralis minorUnderneath pectoralis majorDraws shoulders downwards and forwards
GlutealsIn the buttocksUsed in walking and running adduction and rotation of the thigh, and extending the hip
HamstringsBack of the thighFlexes and extends the knee
GastrocnemiusCalf of the legFlexes the knee Plantar-flexes the foot
SoleusCalf of leg, below the gastrocnemiusPlantar-flexes the foot
Quadriceps extensorFront of the thigh Group of four musclesExtends the knee, used in kicking
SartoriusCrosses the front of the thighFlexes the knee and hip Abducts and rotates the femur
AdductorsInner thighAdducts the hip Flexes and rotates the femur
Tibialis anteriorFront of the lower legInverts the foot Dorsiflexes the foot Rotates the foot outwards

Muscles of the Back

TrapezuisThe back of the neck and chestMoves scapula up, down and back (retracts) Raises the clavicle
Latissimus dorsiAcross the backUsed in rowing. Adducts, extends and medially rotates the shoulder joint
Erector spinaeThree groups of muscle which lie either side of the spine form the neck to the pelvisExtends the spine Keeps body in an upright position
RhomboidsBetween the shouldersBraces the shoulders Rotates the scapula

Muscles of Respiration

As previously mentioned, the diaphragm is a vital muscle of the respiratory system. This sheet of muscle divides the chest from the abdomen and expands and contracts to allow inhalation and exhalation to occur. But along with the diagram are two other muscles that are important. These are the external and internal intercostal muscles. These muscles draw the ribs downwards and inwards.

Tendons and Ligaments

Tendons and ligaments are made up of collagenous tissue with ligaments attaching bone to bone and tendons attaching muscle to bone. The place where a muscle attaches to a bone but does not move, is known as the origin. To make movement occur, the muscles contract, which will pull on the tendons, this then pulls on the muscles.

Tendons are tough, yet flexible bands of fibrous tissue, which allows movement. Ligaments are stretchy connective tissue which helps to stabilise the joints. They control the range of movements of a joint to prevent them from bending the wrong way. Injuries to both tendons and ligaments are very common, caused mainly by sporting injuries. It is fairly common for tendons to be stretched or torn which can be extremely painful. If ligaments are stretched, either by injury or excess strain the joint will become weaker, as the ligaments are unable to support it.

Muscle Tone

Muscle tone refers to the amount of tension or resistance to movement in a muscle.

Muscle tone is what enables us to keep our bodies in a certain position or posture. A change in muscle tone is what enables us to move. For example, to bend your arm to brush your teeth, you must shorten (increase the tone of) the bicep muscles on the front of your arm at the same time you are lengthening (reducing the tone of) the tricep muscles on the back of your arm. To complete a movement smoothly, the tone in all muscle groups involved must be balanced. The brain must send messages to each muscle group to actively change its resistance.

Characteristics of a Muscle

Muscle tissue has four main properties which allow it to carry out its function. It is able to respond to stimuli (Excitability). It can contract (Contractibility). It can extend without tearing (Extensibility) and it can return to its normal shape (Elasticity)

Growth and Repair of the Muscles

Muscle hypertrophy is the term used for when a muscle cell grows in size, and the commonest reason for this is due to exercise, where there will be an increase in muscle fibre. When a muscle is damaged (torn) the body has to repair it and will do this by using satellite cells which fuse with the ends of the damaged fibre. If the damage is constant, then the process will repeat itself so that more satellite cells are used which will create growth of the muscle.

Pathologies of the Muscular System

DisorderSigns & SymptomsCause
CrampSudden muscle pain, mostly commonly in the calf muscleThe muscle suddenly shortens, which can be due to exercise, nerves or tendons shortening due to age
SprainsPain, inflammation, lack of movementA stretch, tear or twist of a ligament due to force
StrainsPain, inflammation, lack of movementA stretch, tear or twist of a muscle fibre due to force
FibromyalgiaPain and stiffness in the muscles, ligaments and tendonsNo known cause
Muscular DystrophyCauses muscles weakness which slowly gets worse and loss of muscle tissueinherited
SpasticityAn abnormal increase in muscle tone or stiffness in the muscles which will affect movementMay occur with spinal cord injury, MS, Cerebral palsy, brain damage