Final answer:
Flexion and extension describe movements at synovial joints where flexion decreases the angle between the bones and extension increases it. This terminology applies to movements in the limbs and vertebral column. These movements are facilitated by flexor and extensor muscles working in opposition.
Step-by-step explanation:
Flexion and Extension in Limbs. Flexion and extension are terms used to describe movements at synovial joints in the limbs. Flexion is the movement that decreases the angle between the bones at a joint, effectively bending the joint. In the upper limb, this includes movements like bringing the forearm up towards the shoulder. Extension refers to the opposite movement, where the angle between the bones at a joint is increased, essentially straightening the joint. An example would be straightening the arm at the elbow.
The terms also apply to different ranges of motion in the vertebral column, with flexion being an anterior (forward) bending and extension being a straightening or posterior-directed movement. These concepts are crucial when studying the anatomy and physiology of movement, with particular relevance to the actions of the flexor and extensor muscles. The flexor muscle is responsible for causing flexion at a joint, while the extensor muscle facilitates extension. Muscles work in tandem to permit the range of motion necessary for daily activities. In the limbs, flexion decreases the angle between the bones (bending of the joint), while extension increases the angle and straightens the joint. For the upper limb, all anterior-going motions are flexion, and all posterior-going motions are extension.