Bones grow in diameter due to bone formation __. a. in the medullary cavity b. beneath the periosteum c. in the epiphyseal plate d. within the metaphysis
The Correct Answer and Explanation is:
The correct answer is b. beneath the periosteum.
Bones grow in diameter through a process called appositional growth, which occurs beneath the periosteum, a dense layer of connective tissue that covers the surface of bones. This type of growth is responsible for increasing the thickness and strength of bones as an individual matures.
How does appositional growth work?
Appositional growth involves the addition of new bone tissue on the outer surface of the bone. This occurs in two key steps:
- Osteoblasts beneath the periosteum (the outer layer of the bone) lay down new bone matrix. Osteoblasts are specialized cells responsible for synthesizing and mineralizing bone tissue. They deposit new bone layers on the surface, leading to an increase in the diameter of the bone.
- As new bone is formed on the surface, osteoclasts (bone-resorbing cells) work in the inner part of the bone, specifically in the medullary cavity, to remove old bone. This ensures that the bone remains light enough for the body to move effectively while increasing in strength. The removal of bone tissue inside the shaft allows for the bone to expand in diameter without becoming too heavy.
Bone Formation Mechanism:
- Osteoblasts create new bone matrix by secreting collagen and mineral salts, which eventually harden and form compact bone.
- The new bone layers add to the outer surface, making the bone wider, while osteoclasts break down old bone from the inside.
- This process is regulated by various hormones such as growth hormone and sex hormones, especially during growth periods in childhood and adolescence.
This type of bone growth is crucial for adapting the bone structure to the increasing mechanical stresses placed on it, especially as an individual grows and becomes more active.
