Sunday, 15 July 2012

Joints And Their Function

Types of joints
Any point in the body where two or more bones meet is classed as a joint.

Fixed joints
Fixed or fibrous joints allow no movement at all. Fixed joints are held together by a tough fibre that permits no movement and these joints also have no joint cavity. An example of a fixed joint is the skull because it can’t be moved which allows it to protect the brain. An example of fixed joint used in sport is football because you header the ball with your head.

Slightly movable joints
Slightly movable or cartilaginous joints allow very limited movement. Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Ligaments or cartilage stops them from moving the joints too far. The joints have a cushion of cartilage in between the bones with bones vesting on these beds of cartilage. The cushion of cartilage stops the bones from rubbing together. An example of slightly movable joints is the joint between two vertebrae only a small amount of movement is permitted, and indeed necessary between the bones, but excessive movement would cause damage to the spinal cord. An example of when you use slightly movable joints in sport is in gymnastics. When you do stretch and do flips. 

Synovial joints
Synovial joints are freely movable and the most common type of joint. The Synovial joint has existence of capsules surrounding the articulating surfaces of a Synovial joint and the presence of lubricating Synovial fluid within that capsule. Examples of Synovial joints are hinge, ball and socket, pivot, condyloid, saddle and gliding.

Differences and similarities of the types of joints
The similarities of synovial joints and slightly movable joints are that they both can move in different directions, but fixed joints cannot move at all because they are fused together and have no joint cavity. Differences between synovial and slightly movable joints are that synovial joints are freely movable and slightly movable joints allow very limited movement, synovial joints are also more common in the body than slightly movable joints and fixed joints. Ligaments or cartilage stops slightly movable joints from moving too far, this is different to fixed joints because they are held together by tough fibre and different to synovial joints because they have capsules surrounding the articulating surfaces. Slightly movable joints also have a cushion of cartilage in between the bones, which stops them from rubbing. Fixed joints are fused together so they cannot rub together and synovial joints have a lubricating synovial fluid. A similarity of these joints is that they achieve movement at the point of contact of the articulating bones.

The hinge joint allows movement similar to a hinge. It has a convex and concave surface and allows movement in one plane about a single axis. It allows flexion and extension movements. Examples of a hinge joint are the elbow, knee and wrist joints. An example of when the hinge joint is used in sport is football. When a player kicks a ball they use their knee joint, which flexes and then extends.   

Ball and socket
The ball and socket joint allow the greatest range of movement. It moves three planes and three axis. It allows flexion, extension, rotation, abduction, adduction and circumduction. Examples of ball and socket joints are the hip and shoulder. An example of when the ball and socket joint is used in sport is cricket. When a player is bowling they use their shoulder which goes all they way round.

The pivot joint allows rotation of one bone around another. Pivot joints are found in humans in the neck, forearms, knees, and other parts of the skeletal system that are able to rotate. The pivot joint in the neck allows the head to move side to side. Example of a pivot joint in sport is when you are stretching and you turn your head side to side.

The condyloid joint allows movement in two planes and can produce flexion, extension, abduction and adduction movements. Examples of a condyloid joint are your wrists. Example of a condyloid joint used in sport could be basketball. When the players are dribbling with the ball they are using their wrist.

This joint allows movement in one plane and one axis. The bones in a saddle joint can rock back and forth and from side to side, but they have limited rotation. The thumb is an example is a saddle joint. Example of a saddle joint used in sport is in a thumb war. The thumb is moving side to side an back and forth in a thumb war.

The gliding joint allows one bone to slide over another. These occur between the surfaces of two flat bones that are held together by ligaments. Some of the bones in your wrists and ankles move by gliding against each other. Examples are the vertebrae and joints between the carpals and tarsals.

Differences and similarities of synovial joints
Hinge, pivot, ball and socket, saddle, conyloid and gliding joint all have similarities and differences. A similarity of all these synovial joints are that they all can move and a difference between all these joints are that they have a different range of movement and move in different directions.

Hinge – Flexion and Extension
Pivot - Rotation of one bone around another
Ball and socket – Flexion, Extension, Adduction, Abduction, Internal and External Rotation
Saddle – Flexion, Extension, Adduction, Abduction and Circumduction
Conyloid – Flexion, Extension, Adduction, Abduction and Circumduction
Gliding - Gliding movements

Another similarity is that all the joints are in the human body. A difference is that they are all in different places.

Movement at joints

Flexion is the bending movement that decreases the angle between two parts. The angle is 180 degrees and gets decreased in size. Bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed.

Extension is the opposite of flexion and is where a straightening movement that increases the angle between body parts. In a conventional handshake, the fingers are fully extended.

Hyper-extension is the movement or extension of joints, tendons, or muscles beyond the normal limit or range of motion which is 180 degrees.  

Plantar flexion
Plantar flexion is flexion of the entire foot and pointing your toes. This occurs from the ankle. Pressing a car pedal down is an example of plantar flexion.

Dorsiflexion is extension of the entire foot and brining your toes up. Taking your foot off a car pedal is an example of dorsiflexion.  

Pronation is when you rotate your palms to a face down position and when your arms rotate inwards. This can only be done if your arms are half flexed.  

Supination is the opposite of pronation. It’s when your palms are facing upwards and when your arms bones rotate outwards.

Abduction is when a limb in your body is taken away from midline of your body. Raising the arms laterally, to the sides, is an example of abduction.

Adduction is when you bring a limb towards the centre line in of your body. Dropping the arms to the sides, or bringing the knees together, are examples of adduction. The fingers or toes, adduction is closing the digits together.

Sporting examples

Bicep curls
When doing bicep curls your hinge joint in your elbow allows your arms to flex and extend. Your hinge joint is attached to the humerus, radius and ulna. When you are bringing the weights up towards you, your hinge joint is allowing your elbow to flex, decreasing a 180 degrees angle and making your forearm come up towards you. When you bring the weights down, your hinge joint is allowing your elbow to extend, bringing back the arm to 180 degrees

When doing a squat your hinge joint in your knee allows your legs to flex and extend. Your hinge joint is attached to the tibia and femur. When doing a squat you go down like you’re sitting in a chair, your hinge joint is allowing your knees to flex, decreasing a 180 degrees angle.  When you are going back up your hinge joint is allowing your knees to extend, bringing back your legs to 180 degrees.

When you header a ball in football you are using your pivot joint in the top of your neck, this allows your head to move side to side. This means you can get a better movement of the head to header the ball where you want it.  

Bowling in cricket
When you bowl in cricket you’re using your ball and socket joint in your shoulder. The ball and socket joint in your shoulder allows you to rotate your arm all the way round, so it extends, hyper-extends and flexes all in one. This allows the bowler to bowl faster. Bowlers also can put spin on the ball, they can do this by twisting their wrist which has a conydloid joint. 

 Arm raises
When performing an arm raise laterally you are using your ball and socket joint in your shoulder. When performing lateral arm raises you are bringing your arms away from the midline of your body which is abduction. Doing lateral arm raises also makes you do adduction because you’re bringing your arms back to the centre line of your body.   

Calf raises
When doing calf raises you are using a hinge joint in your ankle. When doing calf raises you are doing flexion and extension with your foot. When you do a calf raise you push the weight up by using plantar flexion and when you go down its dorsiflexion.

Baseball Catch  
When catching in baseball you are using your saddle joint and you condlyoid joint in your hand. You are using these joints when you catch the ball. You do all types of movement to catch the ball, but when it’s in your hand and you clench your fist you are doing flexion 


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  3. Thank you for this article, it helped me a lot with one of my Anatomy assignments