Morphofunctional characteristics of the оs penis of mammals

The study analyzed the morphofunctional organization of the mammalian baculum (os penis). In many mammals, bone tissue caused the penis to harden, which forms the bone of the penis (os penis or baculum). This structure appeared later in evolution than others, and it is present only in representatives of the most evolutionarily young class of vertebrates, i.e., mammals. The baculum is present in the penis of marsupials and placental mammals (rodents, some bats, pinnipeds, cetaceans, individual predators, semi-monkeys, and some monkeys). The bone tissue is usually located in the anterior region of the penis between the cavernous and spongy bodies. The baculum is an unpaired bone. On the cross-section of representatives of different species, the baculum can be rounded, square, triangular, or flat. Most often, the baculum is a cylindrical rod, expanded in the proximal and distal parts, and it has outgrowths of various shapes. Histogenesis of the bone tissue during os penis formation in embryogenesis occurs by indirect osteogenesis. In the area of the future os penis, a cartilaginous model is formed from the mesenchyme, in place of which the bone tissue then develops. The base of the baculum is formed by lamellar bone tissue, in which osteones are well expressed. Coarse fibrous (reticulofibrous) bone tissue and fibrous cartilage tissue are found on the surface of the baculum. The baculum was found to increase the overall hardness of the penis when bending during copulation.