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Osteons on cross-section of a bone. In osteology, the osteon or haversian system (/ h ə ˈ v ɜːr. ʒ ən /; named for Clopton Havers) is the fundamental functional unit of much compact bone. Osteons are roughly cylindrical structures that are typically between 0.25 mm and 0.35 mm in diameter. [1]
Diagram of a typical long bone showing both cortical (compact) and cancellous (spongy) bone. Haversian canals [i] (sometimes canals of Havers, osteonic canals or central canals) are a series of microscopic tubes in the outermost region of bone called cortical bone. They allow blood vessels and nerves to travel through them to supply the osteocytes.
An irregular bone is one that does not have an easily classified shape and defies description. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones. [1]
Located in the main shaft of a long bone (consisting mostly of compact bone), the medullary cavity has walls composed of spongy bone (cancellous bone) and is lined with a thin, vascular membrane . [1] [2] This area is involved in the formation of red blood cells and white blood cells, and the calcium supply for bird eggshells. The area has been ...
Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. Short bones provide stability and support as well as some limited motion. [38] The bones of the wrist and ankle are short bones. Flat bones are thin and generally curved, with two parallel layers of compact bone sandwiching a layer of ...
In a disorder known as rachitis fetalis anularis the ends of the long bones (epiphyses) are enlarged. [2] Another disorder, rachitis fetalis micromelica, is a deficiency in the growth (as a shortness) of the bones. [2] There is a surgical procedure called distraction osteogenesis which is used to lengthen long bones. [3]
It is composed of around 270 bones at birth – this total decreases to around 206 bones by adulthood after some bones get fused together. [1] The bone mass in the skeleton makes up about 14% of the total body weight (ca. 10–11 kg for an average person) and reaches maximum mass between the ages of 25 and 30. [2]
There are a total of 64 bones in the arms, 32 in each arm Upper arm bones (6 bones in total; 3 on each side) Humerus (2) Pectoral girdle (shoulder) Scapula (2) Clavicle (2) Lower arm bones (4 bones in total, 2 on each side) left bone Ulna (2) (Lined up with pinky) Radius (2) (Lined up with thumb) Hand (54 bones in total; 27 in each hand) Carpals