Final answer:
Olfaction operates through the interaction of odor molecules with olfactory receptors. Dogs, particularly bloodhounds, have a more acute sense of smell than humans because they possess a significantly larger number of olfactory receptors and a greater olfactory epithelium area.
Step-by-step explanation:
Olfaction, or the sense of smell, involves the detection of odor molecules by olfactory receptors. In people, this process occurs in the olfactory epithelium located in the back of the nasal cavity. Humans have around 350 olfactory receptor subtypes that enable us to sense approximately 10,000 different odors. This capacity is dwarfed when we consider dogs, specifically bloodhounds. Bloodhounds have been selectively bred for their sense of smell and possess about 4 billion olfactory receptors and proportionally larger olfactory epithelia, giving them a far more acute sense of smell.
When odorant molecules bind to receptors in the olfactory epithelium, this interaction triggers nerve impulses that travel to the olfactory bulb of the brain. The disparity in olfactory sensitivity between species is partly due to differences in the number of functional genes for olfactory receptors and the overall size of the olfactory epithelium. Dogs have between 800 and 1200 olfactory receptor genes, compared to fewer than 400 in humans and other primates.