Final answer:
The retromammary space is the loose areolar tissue that separates the breast from the pectoralis major muscle, and is made of loose connective tissue containing various cells and fibers.
Step-by-step explanation:
The loose areolar tissue that separates the breast from the pectoralis major muscle is known as the retromammary space. This space is comprised of loose connective tissue, also referred to as areolar connective tissue. Areolar tissue contains a mix of cells and fibers, including fibroblasts, macrophages, collagen, and elastic fibers, dispersed in a matrix.
The flexible and tough nature of this tissue provides essential structural support and maintains the positions of organs and vessels within the body.