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Joints

Joints

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Author: Sophia Tutorial
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This lesson will introduce the three types of joints in the human body and will give examples of each type.

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Tutorial

What's Covered

In this lesson, you will learn about the types and structure of joints in the body:

  1. Types of Joints
  2. Synovial Joints

1. Types of Joints

Joints are areas of contact between bones in the body, and there are many different types. Ligaments, a type of dense connective tissue, connect the bones at those joints and help to stabilize them as well. Tendons are the connective tissue holding your muscles to your bones.

Terms to Know

    • Joint
    • a structure that is formed by two or more bones joining together; are held together by ligaments, cartilage, or dense-fibrous tissue
    • Ligament
    • a structure composed of dense irregular connective tissue that holds bones together within synovial joints
    • Tendon
    • A tough band of fibrous connective tissue that usually connects muscle to bone.

There are three types of joints in the body:

1. Synovial Joints 

Synovial joints are the most common type of joint in the body. They contain a cavity filled with synovial fluid, which separates the bones. Synovial joints allow for a wide range of motion.

ExampleThink of the knee joint. You're able to flex and extend your knee, and this type of joint allows for that range of motion.

2. Fibrous Joints

In a fibrous joint, there is no cavity between the bones. The bones are joined by a connective tissue that doesn't allow for very much movement.

ExampleYour skull is made up of over a dozen type of bones, but those bones are connected by fibrous joints called sutures.

3. Cartilaginous Joints

A cartilaginous joint is a type of joint in which cartilage fills the space between bones. This allows for slight movement.

ExampleThink of the bones in the spine. In between each of those, there are little pads of cartilage. This eliminates some of the friction between the bones, and also allows for a slight bit of movement.

Terms to Know

    • Synovial joint
    • the most common joint in humans and also the most complex; contains two key characteristics: surrounded by a joint capsule and contains synovial fluid; also the most highly moveable joint in humans
    • Synovial fluid
    • fluid found within synovial joints to reduce wear and tear and to nourish the structures inside of the joint capsule
    • Cartilaginous joint
    • a joint where two or more bones are held together by a piece of cartilage (example: vertebrae or pubic bones); these joints are slightly moveable
    • Fibrous joint
    • a joint where two or more bones are fused together by tough, fibrous connective tissue (example: skull sutures); this is the least moveable joint of the body

2. Synovial Joints

Let’s take a more in-depth look at synovial joints. This type of joint allows for a wide range of motion. The different types of motion are:

  • Flexion and extension
  • Rotation
  • Circumduction
  • Supination and Pronation
  • Gliding
  • Abduction and adduction

Flexion and extension are the motions made when bending and straightening. Flexion happens when you flex a muscle to bend a joint. Extension happens when you relax the muscle and let the joint straighten.

Terms to Know

    • Flexion
    • A type of movement allowed primarily by synovial joints in which an appendage is able to bend. For example, flexion of the bicep muscle pulls the forearm upward by allowing it to bend at the elbow.
    • Extension
    • A type of movement allowed primarily by synovial joints in which an appendage is straightened from a flexed position. For example, extension of the arm from a flexed position will return it to its normal resting position.

Rotation can occur at synovial joints. To get an example of this type of movement, hold your arm straight out and twist it around its axis. Circumduction happens when an appendage moves in a circular motion. If you do an arm circle, this is an example of circumduction.

Terms to Know

  • Rotation
  • A type of movement allowed primarily by synovial joints in which an appendage pivots about its axis. Holding the arm straight out and twisting it on its axis is an example of rotation.
  • Circumduction
  • A type of movement allowed primarily by synovial joints in which an appendage moves in a circular motion. Doing arm circles in which the arm moves in a large circular pattern like a windmill is an example of circumduction.

Pronation and supination can be demonstrated by your hands and forearms. When you turn your palm and forearm to face upwards, this is supination. When you turn them to face down, this is pronation. The joints in your wrist also allow for gliding. You can wave your hand back and forth as the joints in your wrist enable this gliding motion.

Terms to Know

    • Pronation
    • A type of movement allowed primarily by synovial joints in which the forearm and palm face downward.
    • Supination
    • A type of movement allowed primarily by synovial joints in which the forearm and palm face upward.

Abduction and adduction are also possible. If you lift your arm straight up away from your center, you are abducting it. If you lower it back down to your side, you are adducting it.

Terms to Know

    • Abduction
    • A type of movement allowed primarily by synovial joints in which an appendage is moved away from the body’s center. Lifting your arm up and away from your side is an example of abduction.
    • Adduction
    • A type of movement allowed primarily by synovial joints in which an appendage moves closer to the body’s center. Lowering your arm closer to your side from a lifted position is an example of adduction.

Summary

The contact points between your bones are called joints. There are three main types of joints in your body: synovial, cartilaginous, and fibrous joints. Synovial joints allow for the widest range of motion.

Keep up the learning and have a great day!

Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

Terms to Know
Abduction

A type of movement allowed primarily by synovial joints in which an appendage is moved away from the body’s center. Lifting your arm up and away from your side is an example of abduction.

Adduction

A type of movement allowed primarily by synovial joints in which an appendage moves closer to the body’s center. Lowering your arm closer to your side from a lifted position is an example of adduction.

Cartilaginous joint

A joint where two or more bones are held together by a piece of cartilage (example: vertebrae or pubic bones); these joints are slightly moveable.

Circumduction

A type of movement allowed primarily by synovial joints in which an appendage moves in a circular motion. Doing arm circles in which the arm moves in a large circular pattern like a windmill is an example of circumduction.

Extension

A type of movement allowed primarily by synovial joints in which an appendage is straightened from a flexed position. For example, extension of the arm from a flexed position will return it to its normal resting position.

Fibrous joint

A joint where two or more bones are fused together by tough, fibrous connective tissue (example: skull sutures); this is the least moveable joint of the body.

Flexion

A type of movement allowed primarily by synovial joints in which an appendage is able to bend. For example, flexion of the bicep muscle pulls the forearm upward by allowing it to bend at the elbow.

Joint

A structure that is formed by two or more bones joining together; are held together by ligaments, cartilage, or dense-fibrous tissue.

Ligament

A structure composed of dense irregular connective tissue that holds bones together within synovial joints.

Pronation

A type of movement allowed primarily by synovial joints in which the forearm and palm face downward.

Rotation

A type of movement allowed primarily by synovial joints in which an appendage pivots about its axis. Holding the arm straight out and twisting it on its axis is an example of rotation.

Supination

A type of movement allowed primarily by synovial joints in which the forearm and palm face upward.

Synovial fluid

Fluid found within synovial joints to reduce wear and tear and to nourish the structures inside of the joint capsule.

Synovial joint

The most common joint in humans and also the most complex; contains two key characteristics: surrounded by a joint capsule and contains synovial fluid; also the most highly moveable joint in humans.

Tendon

A tough band of fibrous connective tissue that usually connects muscle to bone.