Structure of a Typical Long Bone Long bones have a tubular bone shaft, consisting of a bone collar surrounding a hollow medullary cavity, which is filled with yellow bone marrow in adults. Epiphyses are at the ends of the bone, and consist of internal spongy bone covered by an outer layer of compact bone.The epiphyseal line is located between the epiphyses and diaphysis, and is a remnant of the epiphyseal plate. The external surface of the bone is covered by the periosteum.The internal surface of the bone is lined by a connective tissue membrane called the endosteum.he epiphyseal line is located between the epiphyses and diaphysis, and is a remnant of the epiphyseal plate. The external surface of the bone is covered by the periosteum. The internal surface of the bone is lined by a connective tissue membrane called the endosteum.