(b) Any of the following persons, in order of priority stated, when persons in prior classes are not available at the time of death, and in the absence of actual notice of contrary indications by the decedent or actual notice of opposition by a member of the same or a prior class, may give all or any part of the decedent's body for any purposes specified in Section 44-43-340:

1. (1) a health care agent or other attorney in fact authorized to make such gifts by a health care power of attorney or by a durable power of attorney executed pursuant to law;
2. (2) the spouse;
3. (3) a son or daughter eighteen years of age or older;
4. (4) either parent;
5. (5) a brother or sister eighteen years of age or older;
6. (6) a guardian of the person of the decedent at the time of his death;
7. (7) any other person authorized or under obligation to dispose of the body.