Tag: our skeletal system and the skin

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.

Each scapula or pectoral girdle has a concave, articular surface called the glenoid cavity which articulates with the head of the humerus. The ball like the head of the humerus articulates with the glenoid cavity which creates a ball and socket joint that allows the upper limb great motility. So, the correct answer is 'Ball and socket'.

A hinge joint is a common class of synovial joint that includes the ankle, elbow and knee joints. Hinge joints are formed between two or more bones where the bones can only move along one axis to flex or extend. The elbow is a hinged joint made up of three bones which are the humerus, ulna and radius. So, the correct answer is 'Humerus and ulna/radio-ulna'.

• Joints are points of contact between bones, or between bones and cartilages.
• Synovial joints are characterized by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements. 
• The humerus is the long bone in the upper arm. It is located between the elbow joint and the shoulder. At the elbow, it connects primarily to the ulna. The type of joint between humerus and ulna is synovial joint.
• So, the correct answer is 'Humerus and ulna'.

• Joints are points of contact between bones, or between bones and cartilages.
  
• Synovial joints are characterized by the presence of a fluid-filled synovial cavity between the articulating surfaces of the two bones. These joints help in locomotion and many other movements.
  
• Gliding joint is a type of synovial joint formed between bones that meet at flat or nearly flat articular surfaces. Gliding joints allow the bones to glide past one another in any direction along the plane of the joint - up and down, left and right, and diagonally.
  
• An example of the gliding joint is zygapophyses of adjacent vertebrae.
  
• So, the correct answer is 'Zygapophyses of adjacent vertebrae'.