The sequence of events that produces growth at the epiphyseal plate is
A) Hypertrophy, calcification, proliferation, cell death, ossification, remodeling
B) Proliferation, hypertrophy, cell death, calcification, ossification, remodeling
C) Proliferation, hypertrophy, calcification, cell death, ossification, remodeling
D) Hypertrophy, proliferation, calcification, ossification, remodeling
The correct answer and explanation is:
The correct answer is C) Proliferation, hypertrophy, calcification, cell death, ossification, remodeling.
Explanation:
The epiphyseal plate, also known as the growth plate, plays a crucial role in the lengthening of bones during childhood and adolescence. This process involves a series of events that occur sequentially. Below is the breakdown of the correct sequence:
- Proliferation: The first stage involves the rapid division of chondrocytes (cartilage cells) in the zone of proliferation. These newly formed chondrocytes stack into columns and help increase the size of the epiphyseal plate.
- Hypertrophy: Following proliferation, the chondrocytes in the next zone undergo hypertrophy (growth in size). These hypertrophied chondrocytes enlarge and signal the next stages of growth.
- Calcification: As the chondrocytes enlarge, the surrounding extracellular matrix begins to calcify. The matrix becomes hardened due to the deposition of calcium salts, which is a precursor to bone formation. This calcification process leads to the death of the hypertrophied chondrocytes as they are unable to receive nutrients through diffusion in the calcified matrix.
- Cell Death: As a result of the calcification, the chondrocytes in the hypertrophic zone die. This cell death creates cavities that will eventually be filled by bone-forming cells.
- Ossification: In the zone of ossification, osteoblasts (bone-forming cells) invade the spaces left by the dead chondrocytes. The osteoblasts begin to lay down bone matrix, replacing the cartilage with bone tissue.
- Remodeling: Finally, the bone is remodeled to strengthen it and shape it to its final structure. Osteoclasts (bone-resorbing cells) break down the unneeded parts of the bone, while osteoblasts continue to deposit new bone tissue.
This entire process contributes to the elongation of long bones, which is essential for overall skeletal growth. As an individual matures, the epiphyseal plate gradually narrows and eventually ossifies completely, signaling the end of bone lengthening.