Answer :
Final answer:
The fifth zone in the epiphyseal plate, as it directly relates to the four primary zones, is the zone of calcification, where chondrocytes die and the matrix calcifies, allowing for the transformation into bone tissue. Option d is correct.
Explanation:
The epiphyseal plate is essential for longitudinal bone growth and is composed of four distinct zones: the reserve (or resting) zone, the proliferative zone, the zone of maturation and hypertrophy, and the zone of calcified matrix. In the context of the question, although there is no 'fifth zone' explicitly named, we could consider the adjacent zone of ossification, part of the metaphysis, as the next region following the four primary zones.
However, if by 'fifth zone' the question is referring to the last of the four primary zones, it would be the zone of calcification, which is where the chondrocytes die due to the calcification of the matrix around them, and the area where capillaries and osteoblasts from the diaphysis start to transform the calcified cartilage into osseous tissue.
Therefore, the correct answer is d. Zone of calcification.
