Which of the following structures routes blood from the periosteum to the central canal of each osteon?
a. canaliculi
b. endosteum
c. osteocytes
(d) perforating canals
The correct answer and explanation is :
Correct Answer: (d) Perforating canals
Explanation:
Bone is a dynamic tissue that requires a constant supply of nutrients and oxygen, which is delivered through a well-organized system of blood vessels. One of the essential structures that support this vascular system in compact bone is the perforating canals, also known as Volkmann’s canals.
The periosteum is a dense, fibrous membrane covering the outer surface of bones (except at the joints). It contains blood vessels, lymphatic vessels, and nerves that nourish and support bone tissue. However, for the nutrients and oxygen in these vessels to reach the central canals (Haversian canals) located in the middle of each osteon (the functional unit of compact bone), the body uses specialized channels—perforating canals.
Perforating canals run perpendicular (or oblique) to the long axis of the bone and connect the blood and nerve supply from the periosteum to the central canals and medullary cavity. These canals pass through the compact bone matrix, allowing for efficient nutrient and waste exchange between the bone surface and its deeper structures. Once inside the bone, the blood flows into the central canals, which run longitudinally through the osteons, supplying the osteocytes (bone cells) housed in lacunae.
Other choices:
- (a) Canaliculi are tiny channels that connect lacunae to each other and to the central canal, allowing for nutrient and waste exchange between osteocytes, but they do not carry blood from the periosteum.
- (b) Endosteum is a membrane lining the inner surfaces of the bone, including the medullary cavity and central canals, but it does not route blood from the periosteum.
- (c) Osteocytes are mature bone cells responsible for maintaining bone tissue, not for routing blood.
Therefore, perforating canals are the correct answer because they directly route blood from the periosteum to the central canals of osteons.