Final answer:
Nutrients reach osteocytes in compact bone via canaliculi connected to the central Haversian canal, whereas in spongy bone, they diffuse through blood vessels that penetrate the less dense trabecular network.
Step-by-step explanation:
Comparing how nutrients reach individual osteocytes in compact bone and in spongy bone, we find two different structures adapted to facilitate nutrient transfer. In compact bone, nutrients reach osteocytes through a well-organized structure called an osteon. Each osteon has a central Haversian canal that contains blood vessels and nerves. The osteocytes reside in spaces called lacunae, and the nutrients diffuse to these osteocytes through tiny channels called canaliculi. In contrast, spongy bone lacks osteons. Instead, it is made up of a lattice-like network structure with trabeculae. The osteocytes in spongy bone still reside in lacunae and receive their nutrients from blood vessels of the periosteum that penetrate the spongy bone and blood that circulates in the marrow cavities.
The correct answer to the question is option 'a)': Nutrients diffuse through canaliculi in compact bone, and through canals in spongy bone. This is because the dense nature of compact bone necessitates a network of canaliculi for nutrient delivery, while the less dense spongy bone allows for direct penetration by blood vessels through the trabecular network.