Tag: joints in the human body

Saddle joint is a type of synovial joint in humans in which opposing articular surfaces with both concave and convex surfaces fit into one another. Example of saddle joint is carpometacarpal joint of thumb.

Synovial joints are characterised by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other movements. Common examples of synovial joints are ball and socket joint (between the humerus and pectoral girdle) and hinge joint (knee and elbow joints).

The fabella is a fibrocartilaginous or ossified sesamoid bone of the knee, classically located within the tendon of the lateral head of the gastrocnemius muscle, behind the lateral condyle of the femur.

Joint between atlas and axis vertebrae is an example of pivot joint. It is a type of synovial joint. This joint is characterised with central bony pivot surrounded by collar of bone and ligament. This type of joint permits supination, rotation and pronation types of movements. Examples are proximal radioulnar joint and atlanto-axial joints.

According to functional classification, joints may be immovable (synarthroses), slightly movable (amphiarthroses) and freely movable (diarthrosis). According to structure, joints can be classified into fibrous, cartilaginous and synovial.
The pivot joint is a synovial joint, which permits the movement of bone about one axis of rotation. In pivot, the joint central bony pivot of one bone is surrounded by a collar of bone and ligaments. The types of movement possible are rotation, pronation, supination. An example of pivot joints is proximal radioulnar and atlantoaxial joints.

Ball and socket is a type of synovial joint in which globe-like the head of one bone fits into the cup-like concavity of another bone. It permits flexion, extension, internal rotation, lateral rotation, abduction, adduction and circumduction type of movements. 

Head of the humerus is articulated with the cup-shaped socket of pectoral girdle by a joint, called as ball and socket joint. It is movable in all planes and also exhibits rotation. Pivot joint exhibits rotation only while hinge joint shows up and down motion in one plane only. The correct answer is B.

The hinge joint is a synovial joint, which permits uni-axial movement of bone about one axis of rotation. In a hinge joint, the convex surface of one bone fits into the concave surface of another. The movements possible are flexion and extension. Examples of hinge joints are elbow (radio-ulna with upper arm), interphalangeal joint, knee and ankle joints.

Locomotion is the movement of organisms from one place to another. The femur and the acetabulum form the hip joint. Hence, the rotation of head of femur in acetabulum will lead to the movement of the legs and thereby, be help in locomotion. Bending of arm at elbow will only cause movement of hands and hence no locomotion. Peristalsis is the movement of the oesophagus as food pases through it and so, it can also not be considered as locomotion. Contraction of the heart will only cause pumping of blood and will not be responsible for actual locomotion.