The Skeleton What does the skeleton do? The skeleton provides the basic framework of the

body. It has five major functions:

SHAPE AND SUPPORT MOVEMENT PROTECTION BLOOD PRODUCTION MINERALS STORAGE

SHAPE AND SUPPORT - The skeleton provides us with our shape; without it, our body would have no framework to support itself on. The skeleton also gives the body its size and, in some cases, can influence overall body weight.

MOVEMENT - Some of the bones of the body are held together by freely moveable joints. This means you are able to bend your body and move about.

PROTECTION - The skeleton also protects the vital soft tissue organs of the body. The most important are:

the rib cage - protects the heart and the lungs the pelvic girdle - protects the abdomen the spinal column - protects the spinal chord the skull - protects the brain

BLOOD PRODUCTION - Blood is made in the bone marrow, particularly in the marrow of the long bones of the body. Blood contains both red and white blood cells. The red blood cells carry oxygen to muscles and the white blood cells fight infection in the body.

MINERALS STORAGE – Bones store calcium and phosphorus that make the bones strong and hard. When the body needs these minerals, the bones release small amounts of them into the blood for use elsewhere.

Types of Bones There are over 200 bones in the body and over 100

joints. Bones are divided into four main types :

FLAT BONES - the scapula, the patella, the sternum, the pelvis and the ribs

SHORT BONES – the phalanges IRREGULAR BONES - the vertebrae and the short

bones of the hands and feet LONG BONES - the bones of the arms and the legs

OTHER BONES

CRANIUM - the brain case made up of EIGHT flat bones

CLAVICLE AND SCAPULA – the collar and shoulder bones that make up the shoulder. The scapula also connects the arm to the central skeleton.

STERNUM - has 10 pairs of ribs attached to it

RIBS – 12 pair of flat bones HUMERUS – long upper arm bone RADUIS AND ULNA - rotate around each

other, letting you turn your palms up and down

PELVIS - where the legs are connected to the skeleton

PHALANGES - make up fingers and toes FEMUR - longest bone in the body; stronger weight-

for-weight than steel PATELLA - kneecap, protects the knee joint. It is

embedded in the tendon of a muscle and not attached to any other bone.

FIBULA – the outer bone of the lower leg TIBIA - shin bone

Male skeletons tend to be bigger overall; female skeletons have a wider pelvis so that is easier to have children.

Joints and Movement There are many types of joint in the body, including

joints that we do not move and joints that only move slightly. The movement of joints is an important factor affecting participation and performance.

JOINT STRUCTURE Most joints are synovial joints. Synovial joints are

enclosed inside a capsule filled with a lubricating fluid, called synovial fluid. This fluid reduces the friction on the joint surfaces as they move against each other. A membrane seals the synovial capsule so that the fluid does not leak out.

CARTILAGE Joint surfaces are also covered by smooth, slippery

cartilage. This aids the production of synovial fluid. Joints often include another kind of cartilage, called

white fibro-cartilage. This is smooth and hard in order to help free movement. Fibro-cartilage is tough and elastic. It acts as a shock absorber, cushioning impact on the synovial joints. For example, the knee contains fibro-cartilage to cushion the joint against the impact of walking, running and jumping.

LIGAMENTS AND TENDONS Ligaments and tendon hold together moving joints. Ligaments are very strong elastic fibers that keep

joints intact (hold bone to bone).

All the major joints rely on ligaments and tendons for stability.

Tendons attach muscles to bones. Both ligaments and tendons can be strained or torn

as a result of violent movement.

TYPES OF MOVEMENT Because movement is so important in sport

and physical activity, special terms describe the different kinds of movement:

» FLEXION» EXTENSION» ROTATION » ABDUCTION

» ADDUCTION

DIFFERENT TYPES OF MOVEMENT:

FLEXION - Flexion is the bending of a joint. For example, flexion occurs at the knee as the foot is drawn back to kick a ball.

EXTENSION - Extension is the straightening of a limb at the joint. For example, when putting the shot, the elbow is straightened during release.

ROTATION - Rotation is the ‘swiveling’ of a joint; for example, moving the head from side to side.

ABDUCTION AND ADDUCTION - Abduction involves moving a limb away from the

central axis of your body. Adduction is the opposite from abduction, moving a

limb back towards the central axis of your body.

The central axis is a straight line travelling from the top of your head straight down to the ground.

Types of Joints The type of joints that are particularly important for

physical activity and sport are:

– BALL AND SOCKET JOINT - allows a full range of movement; for example, the hip and shoulder joints

– HINGE JOINT – allows movement in one plane: flexion and extension.

– GLIDING JOINT - occurs in the many small bones of the hand and feet, allowing allow a slight sliding motion forwards and backwards and from side to side

– PIVOT JOINT - allows rotation; for example, atlas and axis in the neck

Muscles

Every movement of your body depends on muscles. There are three different types of muscles:

INVOLUNTARY MUSCLE (SMOOTH) - is found in the body’s internal organs. It performs its function without any conscious control, but usually quite slowly.

VOLUNTARY OR SKELETAL MUSCLE (also known as ‘striped’ or ‘striated’ muscle) - mainly found attached to the skeleton, capable of rapid contraction that causes skeletal movement. It is under our conscious control.

CARDIAC MUSCLE - is only found in the heart and is also involuntary. It never stops working until we die. It pumps blood from our heart around the body.

Voluntary Muscles - How They Perform, In Detail FRONT DELTOIDS - create abduction at the shoulder when

you raise your arm sideways; for example, swimming arm action

PECTORALS - create adduction at the shoulder, across the chest; for example, push-ups

BICEPS - allows flexion at the elbow; for example, chin-ups

ABDOMINALS - allow you to flex your trunk; for example, sit -ups

QUADRICEPS - make extension of the leg possible at the knee; for example, squats and kicks

BACK TRAPEZIUS - allows rotation of the shoulders; for

example, cricket bowling action LATISSIMUS - adduction at the shoulder behind your

back; for example, climbing a rope TRICEPS - create extension at the elbow; for

example, push-ups and throwing GLUTEALS - allow extension, abduction and

adduction at the hip (gluteus maximus is the biggest gluteal); for example, squats and jumping

HAMSTRINGS - allow flexion of the knee; for example, sprinting (leg action recovery)

GASTROCNEMIUS - allows you to stand on your tiptoes, by creating extension at the ankle; for example, sprinting (start)

TASK: Name all the muscles

Muscle Attachment

Voluntary muscles are attached to your skeleton by TENDONS, usually across a synovial joint. These are fibrous and INELASTIC.

The point where the muscle tendon attaches to the fixed or stationary bone is called the ORIGIN.

The point where the muscle tendon attaches to the moving bone is called the INSERTION.

Muscles shorten as they contract. This makes the joint move.

WHEN A MUSCLE CONTRACTS, THE INSERTION MOVES TOWARDS THE ORIGIN.

HOW MUSCLES WORK

Muscles can only create movement in one direction - by becoming shorter. This means that you need two muscles at every joint to allow movement in two directions.

Therefore, MUSCLES WORK IN PAIRS. For example, when your biceps CONTRACT, they make your elbow flex, pulling your forearm up. To allow your elbow to extend, you need your triceps to CONTRACT and pull your arm back down, meaning the biceps are RELAXING.

Muscles working in opposite directions like the above example are said to be working ANTAGONISTICALLY. The muscle doing the work and creating the movement is called the AGONIST or PRIME MOVER. The muscle that is relaxing and letting the movement take place is called the ANTAGONIST.

When you flex your elbow – for example, during a bicep curl - the bicep is the AGONIST and the tricep is the ANTAGONIST.

When other muscles assist the prime mover in creating a movement, they are called SYNERGISTS. Example: deltoids during a press-up.

All muscles have fast and slow twitch fibers or a mixture of the two. The proportions are inherited.

FAST TWITCH FIBERS produce powerful contractions very quickly

(explosive) these fibers become fatigued in a short time great for sprinting and fast bowling

SLOW TWITCH FIBERS produce less powerful, slower contractions become fatigued less quickly ideal for endurance events like marathon-running