Skeleton and Joints

Lacunae are the spaces within the lamellae of an osteon which are occupied by a bone cell (osteocyte).

Canaliculi (little canals) are tubes that collect the bile produced by liver hepatocytes. In compact bone, the term is applied to the minute channels that connect lacunae (which contain bone osteocytes) with the Haversian canal at the centre of an osteon.

All bone marrow in children is red (actively forming blood cells). It gradually changes to “yellow” with age except for the sites in C. The medullary cavities contain yellow marrow. Red marrow is found mainly in the flat bones, such as the pelvis, sternum, cranium, ribs, vertebrae and scapulae and in the cancellous (“spongy”) material at the proximal epiphyseal ends of long bones such as the femur and humerus.

The plate is a sieve-like structure, due to the many foramina which allow neurons from the olfactory bulb to contact the olfactory membrane in the superior nasal concha. Thus inhaled air can stimulate our sense of smell.

The appendages (arms and legs) and the girdles form the appendicular skeleton.

Articulating bone surfaces are covered by hyaline cartilage. Synovial membranes cover all other internal joint surfaces.

The manubrium is the upper part of the sternum. The xiphoid process is the lower part.

The coccyx, occipital, sternum and mandible are parts of the axial skeleton.

It is named after the English physician Clopton Havers, also known as the central canal.

In two dimensions osteons appear as circles or ovals under the microscope, while in three dimensions, they are cylindrical.