Question

Describe the postnatal growth of long bones. How do bones lengthen? How do they widen? Describe the microscopic anatomy of the epiphyseal plate.

A) Bones lengthen by addition of bone tissue at the diaphysis.
B) Widening of bones primarily occurs at the epiphyseal plate.
C) The epiphyseal plate is primarily composed of compact bone.
D) The epiphyseal plate remains unchanged throughout adulthood.

Answer 1

Option (B), Long bones lengthen through new bone tissue added at the epiphyseal plate, and widen due to appositional growth.

Step-by-step explanation:

The postnatal growth of long bones pertains to how these bones lengthen and widen as a human develops. Bones lengthen through the process happening at the epiphyseal plate, where new bone tissue is added. Chondrocytes (cartilage cells) divide on the epiphyseal side of the epiphyseal plate; one stays near the epiphysis to maintain the growth process, while the other moves toward the diaphysis and eventually undergoes calcification, replacing cartilage with bone, thus elongating the bone.

Bones widen through a process known as appositional growth. This involves osteoclasts resorbing old bone within the medullary cavity, and osteoblasts depositing new bone tissue beneath the periosteum. As a result, both the diameter of the diaphysis and the size of the medullary cavity increase.

The microscopic anatomy of the epiphyseal plate is critical for the understanding of bone growth. It is composed of layers of hyaline cartilage where, on the diaphyseal side, the cartilage gets ossified, allowing for the lengthening of the bone. This plate converts into an epiphyseal line as bone growth stops in early adulthood, marking the end of longitudinal growth.