Final answer:
The term for stretching of a structure is dilation, which often pertains to the widening or expansion of hollow organs or blood vessels in the medical field.
Step-by-step explanation:
The term that means stretching of a structure is dilation. Dilation refers to the widening or expansion of an organ or a part of the body. In the context of muscles, stretching could lead to an increase in muscle length temporarily, which can be commonly experienced during flexibility exercises or when muscles are subjected to a force that exceeds their resting length. However, in the medical sense, dilation often pertains to hollow structures like blood vessels or the pupils of the eye.
Regarding the other options: 'Ptosis' is the drooping of a body part, typically the eyelids; 'Prolapse' means the slipping forward or down of a part of the body, like an organ; 'Spasm' refers to a sudden involuntary contraction of a muscle or group of muscles.