Which cells have the lifespan of approximately 7.5 days and one-third of their population remains in the spleen (unless needed to fight significant bleeding)?

Platelets

Explanation:

Platelets have a lifespan of approximately 7.5 days. Two-third of their population circulate in the blood and contribute to homeostasis. The remaining one-third is stored in the spleen, where they remain unless needed in cases of severe bleeding.

intimacy, passion and commitment are the components of a interpersonal relationship emphasized in the triangular theory of love by robert sternberg.

the triangular theory of love says love can be comprehend as this componest form the vertices of a triangle.  

intimacy relates to feelings such as of closeness and connection;

passion relates the drives that brings people together, as physical attraction.

commitment relates to the being in a long-term relationship.