Osteogenic cells are undifferentiated and develop into osteoblasts. Bone MarkingsДЇoramen (holes through which blood vessels can pass through)ДЇour types of cells are found within bone tissue. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points. A hole is an opening or groove in the bone that allows blood vessels and nerves to enter the bone.

In general, their size and shape is an indication of the forces exerted through the attachment to the bone. These are the attachment points for tendons and ligaments. A projection is an area of a bone that projects above the surface of the bone. These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation. As the name implies, an articulation is where two bone surfaces come together (articulus = вЂњjointвЂќ). There are three general classes of bone markings: (1) articulations, (2) projections, and (3) holes. (Figure) describes the bone markings, which are illustrated in ( (Figure)). The surface features of bones vary considerably, depending on the function and location in the body. In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints ( (Figure)).

Tendons and ligaments also attach to bones at the periosteum. The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. The outer surface of the bone is covered with a fibrous membrane called the periosteum (peri вЂ“ = вЂњaroundвЂќ or вЂњsurroundingвЂќ). The medullary cavity has a delicate membranous lining called the endosteum (end- = вЂњinsideвЂќ oste- = вЂњboneвЂќ), where bone growth, repair, and remodeling occur. When the bone stops growing in early adulthood (approximately 18вЂ“21 years), the cartilage is replaced by osseous tissue and the epiphyseal plate becomes an epiphyseal line.

Each epiphysis meets the diaphysis at the metaphysis, the narrow area that contains the epiphyseal plate (growth plate), a layer of hyaline (transparent) cartilage in a growing bone. Red marrow fills the spaces in the spongy bone. The wider section at each end of the bone is called the epiphysis (plural = epiphyses), which is filled with spongy bone. A typical long bone shows the gross anatomical characteristics of bone.

Re elect skull and bones