>>307 It's a bit weird to use 領域 for a body area, no?

領域【 りょういき 】
1 [region] region of land (region of land of a particular district)
area / domain / territory
2 area / field / domain
3 the area over which a matter or a person has influence
scope / area / spectrum / extent / field / range / domain / territory / line
4 a territory of one country
domain / territory / province

None of these definitions relate to human bodies.
Unless it's a study like in 研究領域... Then it should be "area".