THE STRUCTURE OF OUR BODY

1. INTRODUCTION

This chapter will describe the basic anatomy of the human body, explaining the

most important elements of the muscular and skeletal system.

2. THE MUSCULOSKELETAL SYSTEM

Every time you sprint through the halls because you're late for class, score

against your opponents during a game, you’re using your bones, muscles and joints.

Without these important body parts, you would be unable to sit, stand, walk, or do any of the activities you do every day.

Movement is only possible thanks to the interaction of Bones, Joints, and

Muscles

From our head to our toes, our bones provide support for our bodies and help form

our shape.

- The skull protects the brain and forms the shape of our face.

- The spinal cord protected by the backbone, or vertebral column.

- The ribs form a cage that shelters the heart, lungs, etc.

- The pelvis helps protect the intestines, and in girls, the reproductive

organs.

Joints occur where two bones meet. They make the skeleton flexible — without

them, movement would be impossible. Muscles are also necessary for movement: They're the masses of elastic tissue that pull our bones when we move.

Together, our bones, muscles, and joints — along with tendons, ligaments, and

cartilage — form our musculoskeletal system and enable us to do every day physical activities.

2.1 THE SKELETON

The skeleton has the following parts:

- Skul l

- Thorax

- Spine, vertebral column or backbone

- Lower limbs

- Upper limbs.

Now we are going to learn some of the major bones of the body:

The skull

It is composed by a large group

o f bones wh i ch f o rm a cav i t y

w h e r e t h e b r a i n l i e s a n d i s

protected.

The thorax

The ribs are elastic arches of bone.

They are twelve in number on either

side and are connected behind with

the vertebral column, and in front

with the sternum.

The sternum is a flattened bone in

the anterior wall of the thorax.

The spine

The spine, vertebral co lumn o r

backbone is a column usually consisting of 24

articulating vertebrae and 9 or 8 fused

vertebrae in the sacrum and the coccyx.

It houses and protects the spinal cord (a

very important group of nerves) in its spinal

canal.

The upper limbs

The lower limbs

The Hip bone consists o f

three bones: Ilium, ischium

and pub is. The r ight and

the left hip bones form the

pelvis.

The pelvis helps protect the

intestines, and in girls the

reproductive organs.

The upper leg is a strong, long and

thick bone called the femur.

The lower leg has 2 bones: the tibia

and the fibula. The tibia is larger

and stronger.

The foot bones are: the tarsal, the

metatarsals and the phalanges.

The skeleton

Movements

There are different types of movement available at different joints (for example the

shoulder moves in far more ways than the knee). Here are the main types of movement:

J o i n t s o c c u r w h e r e two or more bones meet.

They make the skeleton flexible, without

them, movement would be impossible.

J o i n t s allow our bodies to move in many ways. Some joints open and close like a hinge (such as knees and elbows); others allow for more

complicated movement — a shoulder or hip joint,

for example, allows for backward, forward, sideways, and rotating movement; and finally

there are joints that don’t move, like the ones we

can find in the skull, joints made of bones that

must be immovable to protect the brain.

2.2 JOINTS

2.3.- THE MUSCULAR SYSTEM

The Muscular System takes up 40% of our complete body mass and are an

extremely important part of the human body. As it is known that bones are an important and complex structure built for movement, (one of many functions) our bodies would not be able to execute these movements without the specialised functioning of the muscular system.

Types of muscles can be classified as:

1. Cardiac 2. Skeletal 3. Smooth

Cardiac The cardiac muscle tissue is the special, continuous muscle in the heart. We cannot consciously control this muscle, therefore it is involuntary, meaning we cannot contract or move this muscle at our own desire. The muscle fibres consist of a special striated tissue, which are light and dark bands of tissue with its own blood supply. Striated muscle. –

Actin and myosin filaments are found in the cardiac muscle. The cardiac muscle is highly resistant to fatigue and can withstand strain (from exercise etc).

Skeletal Muscle Aka: Striated, Striped. (Due to striped appearance under microscope) The muscles are attached to the bone by tendons and pull on your bones to move them. Unlike the cardiac muscle, you can control the movement of these muscles, which is called voluntary muscle movement. Diagram below is a cross section of skeletal muscle fibre.

Smooth This type of muscle is another involuntary muscle fibre, meaning that conscious control is not permitted. It is controlled through the nervous system and functions in the walls of the digestive system and blood vessels which assist good digestion and blood pressure.

Each muscle fibre can be classified into a certain type. The efficiency of these muscle fibres can be inherited or improved during training.

Type 1: (Slow twitch)

Contract slowly with less force.

Red in colour

Suited to aerobic activities (Sports requiring endurance such as cycling, swimming, jogging.)

Rich blood supply

Contain mitochondria (Aid energy production)

Contract Repeatedly

Exerts minimal force

Type 2a: (Fast twitch)

Known as fast oxidative fibres

Fast contracting (not as fast as 2b)

Quite resistant to fatigue

Produce great force (not as great as 2b)

Red in colour

Suited to aerobic middle distance events (800m and 1500m running)

Exert medium force

Type 2b

Known as fast glycolytic fibres

White in colour

Rapid contracting

Produce large force

Fatigue easily and quickly

Suited to anaerobic activity (such as sprinting, weight lifting, throwing, anything with explosive movements.)

Change of pace and stop and go activities

Major Muscle Groups

Muscles creating movement

Muscle has to come across the joint it is moving.

When muscle contracts, it pulls on the bone, and causes the muscles to pull together around joint.

Strength of contraction depends on muscle fibres in use.

For contraction to occur there must be oxygen and fat or glucose present. Antagonistic muscle pairs Muscles always work in groups to execute movement, by contracting and pulling. Agonist

This muscle shortens to move a joint

Mainly in control for the movement to take place

Contracting muscle Antagonist

Muscle that relaxes when other opposing muscle contracts

If it did not relax, movement would not occur Synergist

Muscles that work together to enable efficient contraction for the agonists

Work with the agonist muscle to direct movement.

Modify direction that the agonist will pull Fixator

Stops unwanted movement

Stabilising joints involved

Maintains posture

Contractions can be classified into different types: Isometric

No change in muscle length

Muscle in static position (static pressup position)

No movement at joint

Quickly leads to fatigue

Concentric

Shortens against a resistance (bicep curl – forearm brought up to upper arm, bicep shortens.)

Otherwise known as ‘positive phase of muscle contraction’ Eccentric

When muscle returns to normal length after contraction (after bicep curl, returning forearm back to starting position)

Muscles working against gravity

Otherwise known as ‘negative phase of muscle contraction’

Sliding filament theory of muscular contraction

This theory refers to the movement of thick and thin fibres which lead to contractions and relaxing of the muscles. When a muscle contracts, the amount of overlap between the thick (myosin) and thin (actin) fibres increases which causes the tiny filaments to pass along each other due to the bridge like myosin fibres. When the thin fibres slide along, it causes a reduction in length of the fibres which causes the shortening of the muscle. This process occurs due to signals being sent from the nervous system to activate these tissues.

Responses to Exercise

Short Term:

Increase in temperature and metabolic activity (build up and break down of substances within the body, eg energy from food)

Greater demand for oxygen to muscles

Increase in blood supply through dilated capillaries Muscle Damage When muscles increase in temperature and become warm, they are more flexible (pliable) and this reduces and prevents muscle damage (pulling a muscle). However is muscle damage occurs, it is not a very serious problem as almost immediately after injury, the muscle starts to repair itself naturally and efficiently. However, as we age, muscle repair slows down and so if a muscle is pulled at a young age, it would repair faster than that of a middle aged person and older. However after a muscle damage is repaired, and the muscle is not exercised or strengthened, then the muscle will remain fairly weak and liable to damage. During muscle repair, fibres are reinforced and this is said to happen during rest and sleep.

Long Term: These responses in the long term depend on intensity and type of activity.

Hypertrophy

This is the development of the muscle through thickening of the muscle fibres, which can be a result of exercise, specifically resistance training (working against a force, eg, weight lifting). The muscle fibres thicken as a result of an increase in the thick (myosin) and thin (actin) fibres. Resistance training also increases muscular endurance allowing it to gradually contract for longer and resist fatigue more. The muscles need to be training regularly in order to maintain shape and bulk otherwise they become weak. When you lift weights, for example, tiny tears occur within the muscle and then they are repaired, stronger, to adapt to the weight training you endure in the future. Fibres are reinforced after tearing, but at a microscopic level which explains why it takes a while to see noticeable hypertrophy. Most sports will benefit from hypertrophy of the muscle, especially rough and physical sports such as rugby or ice hockey where bulk is favoured to push off players and stand ground. Hypertrophy would not favour diving as diving requires a slim physique that streamlines and makes minimal splash on impact with water. Weight lifting is especially in favour of hypertrophy as it increases muscular endurance and resists fatigue longer so heavier weights can be lifted each time hypertrophy increases to a certain level.

Increased strength of tendons Tendons are thick bands of tissue that connect muscle to bone. They are designed to withstand tension and adapt to regular exercise. The strength of the tendons increase in different ways depending on different types of training. When tendons are stronger, they are able to withstand more pressure and tension from muscles and exerted forces. You will be able to endure activity longer, especially that of which puts a lot of tension on your tendons. A tendon not only connects muscle to bone but also moves a certain length when there is movement at the joint. Increase tendon strength would then aid flexibility increasingly. Having weak tendons means that, for example, if you were running a middle distance then your legs, it would seem, would not be able to endure the run with ease but with pain and struggle.