Final answer:
The minor horizontal tracings on the eyelids that fan from each corner of the eye are known as crow's feet. These lines emerge due to repetitive facial expressions, age-related skin changes, and decreased skin elasticity and collagen production.
Step-by-step explanation:
The minor horizontal tracings found on both upper and lower eyelids that fan from each corner of the eye are known as crow's feet or laugh lines. These are small wrinkles or lines that emerge at the outer corners of the eyes. They develop over time due to various factors including repetitive muscle movement (such as squinting or smiling), the loss of skin elasticity, and reduced collagen production as a person ages. Crow’s feet can be more apparent when a person smiles or squints, because the skin bunches together due to the muscle movements beneath. In the context of anatomy and physiology, understanding features like crow's feet involves studying the skin’s structure and the muscles of facial expression, as well as the impact of aging on the integumentary system.
Proper functioning of the eye muscles is essential for movement and vision, with the medial and lateral rectus muscles contributing to the horizontal component of eye movement. Rapid eye movements, or saccades, play a pivotal role in redirecting the fovea onto different visual stimuli, which is crucial for sharp central vision. However, crow’s feet are more associated with the skin and muscles around the eye, not the eye movement control muscles like the medial and lateral rectus muscles.