1. Long bones: Each long bone has an elongated shaft (diaphysis) and two expanded ends (epiphyses) which are smooth and articular. The shaft typically has 3 surfaces separated by 3 borders, a central medullary cavity, and a nutrient foramen directed away from the growing end. Examples: (a) typical long bones like humerus, radius, ulna, femur, tibia and fibula; (b) miniature long bones have only one epiphysis like metacarpals, metatarsals and phalanges; and (c) modified long bones have no medullary cavity like clavicle
2. Short bones: Their shape is usually cuboid, cuneiform, trapezoid, or scaphoid. Examples: tarsal and carpal bones
3. Flat bones resemble shallow plates and form boundaries of certain body cavities. Examples: bones in the vault of the skull, ribs, sternum and scapula
4. Irregular bones: Examples: vertebra, hip bone, and bones in the base of the skull
5. Pneumatic bones: Certain irregular bones contain large air spaces lined by epithelium Examples: maxilla, sphenoid, ethmoid, etc. They make the skull light in weight, help in resonance of voice, and act as air conditioning chambers for the inspired air
6. Sesamoid bones: These are bony nodules found embedded in the tendons or joint capsules. They have no periosteum and ossify after birth. They are related to an articular or nonarticular bony surface, and the surfaces of contact are covered with hyaline cartilage and lubricated by a bursa or synovial membrane. Examples: patella, pisiform, fabella, etc. Functions of the sesamoid bones are: (a) to resist pressure; (b) to minimise friction; (c) to alter the direction of pull of the muscle; and (d) to maintain the local circulation.
No comments