Back to A&P I Syllabus (updated 10/17/05)
Bone Tissue Lab
Be able to identify all the parts of a bone as shown below. In addition, know the layers of the periosteum, and be able to identify the types and functions of the cells in each. The articular cartilages are covered by perichondrium.
Proximal epiphysis (head and neck) of the femur. Note differences between spongy and compact bone in the illustrations below.
The spongy bone tissue of the flat bones of the skull as seen below is known as diploe.
Examine slides of bone tissue under the microscope, and be able to identify all structures shown below. Osteons are also known as Haversian systems (named after their discoverer, Havers), and osteonic canals are also known as central canals and Haversian canals. Perforating canals are also known as Volkmann canals.
Be able to describe, in detail, the two methods of bone formation shown in the fetus below.
Stages in endochondral bone formation. Know and be able to describe which cells and tissues are involved in each step.
There are four layers or zones of transformation from cartilage to bone in the epiphyses, where hyaline cartilage is replaced by bone during bone growth and maturation. This process is normally completed by age 25: 1) zone of resting cartilage; 2) zone of proliferating cartilage; 3) zone of hypertrophic cartilage; 4) zone of calcification (calcified matrix). Beyond this is a zone of bone deposition (performed by osteoblasts).
Below are shown osteoclasts, bone-resorbing cells formed from the fusion of several nuclei, in monocytes, a type of white blood cell.
Epiphyseal plates, as seen in a radiograph.
There are numerous ways of classifying fractures. All fractures are either incomplete or complete, nondisplaced or displaced, simple (closed) or compound (open). The greenstick fracture is found in children, where the break is incomplete, due to more collagen tissue, and less ossification.
A complete fracture will also be one of the following types, depending upon the angle of the break. Two fractures are named for the person who first described them, so the names must be memorized: 1) Pott's * fracture occurs when the foot is everted (turned outward), breaking the fibula above the lateral malleolus, and usually also breaking a portion of the medial malleolus (the lower projection of the tibia, shown below). This is a very dangerous break, sometimes causing death from a pulmonary embolism (clot in the lung), due to placing too much weight on the ankle too soon and dislodging a blood clot or droplets of fat from the medullary cavity. This fracture is sometimes also called a trimalleolar fracture, since a small portion of the fibula fits posterior to the talus; 2) Colles ** fracture is a break in the distal end of the ulna (and usually the radius) in which the distal end is displaced in a posterior direction. In an impacted (compression) fracture one bone fragment is driven into the medullary space or spongy bone of the other. This can occur easily with the head and neck of the humerus and femur.
* Sir Percivall Pott (1713-88), British surgeon; ** Abraham Colles (1773-1843), Irish surgeon
Fracture repair is somewhat like endochondral ossification. Be able to compare and contrast these two processes, as shown in the next two illustrations. Osteoclasts are more numerous in the endosteum, while osteoblasts are more common in the inner osteogenic layer of the periosteum.
The final stage involves bone remodeling from spongy to compact bone.
