Joints - SS1 Biology Lesson Note

Skeletal joints, also known as articulations, are the points where two or more bones come together in the body. Joints allow for movement and flexibility while providing stability and support to the skeletal system. There are various types of joints, classified based on their structure and the degree of movement they allow. Joints are one of two kinds:

1.     Movable Joints: Movable joints, also known as synovial joints, are the most common type of joint in the human body. These joints allow for a wide range of movements and are found in various parts of the body. Here are some examples of movable joints:

·        Hinge Joint: Hinge joints allow movement in only one plane, like a hinge on a door. They enable flexion (bending) and extension (straightening) movements. Examples include the elbow joint and the knee joint.

Figure 64 image from shuttershock.com 

·        Ball-and-Socket Joint: Ball-and-socket joints are characterized by a rounded end of one bone fitting into a cup-like socket of another bone. This structure allows for a wide range of movements, including flexion, extension, abduction (movement away from the body), adduction (movement toward the body), and rotation. The shoulder joint and the hip joint are examples of ball-and-socket joints.

Figure 65 image from diva-portal.org

·        Pivot Joint: Pivot joints allow for rotational movements around a central axis. They involve one bone rotating around another bone. An example is the joint between the first and second vertebrae of the neck, which allows for rotation of the head.

·        Condyloid Joint: Condyloid joints enable movement in two planes, allowing flexion, extension, abduction, adduction, and circumduction (a circular movement). The joint at the base of the fingers and the joint between the radius bone and the wrist (radiocarpal joint) are examples of condyloid joints.

·        Saddle Joint: Saddle joints have a shape resembling a rider's saddle, allowing for movements like condyloid joints but with a greater range of motion. The joint at the base of the thumb (carpometacarpal joint) is an example of a saddle joint.

·        Gliding Joint: Gliding joints enable sliding or gliding movements between flat or slightly curved surfaces of bones. They allow for limited movements in multiple directions. Examples include the joints between the vertebrae in the spine and the joints between the carpal bones of the wrist.

Figure 66 image from shuttershock.ocm

2.     Immovable Joints: Immovable joints, also known as fibrous joints, are joints where the bones are tightly connected by dense fibrous connective tissue, allowing little to no movement between them. These joints provide stability and support to the skeletal system