Final answer:
A typical dog has between 800 and 1200 olfactory receptors which is much more than the less than 400 in humans. Bloodhounds have an even more advanced sense of smell. Dogs' remarkable olfactory abilities allow them to detect medical conditions, which makes them useful in cancer detection studies.
Step-by-step explanation:
Dogs are known for their remarkable olfactory abilities, which can be attributed to their increased number of functional genes for olfactory receptors. A typical dog has significantly more olfactory receptors than a human - between 800 and 1200, compared to fewer than 400 in humans. Bloodhounds, which were bred specifically for their sense of smell, have even more enhanced olfactory systems.
The extraordinary olfactory abilities of dogs enable them to detect certain medical conditions, such as changes in blood glucose levels and even cancerous tumors in some cases. The hypothesis behind using dogs in cancer detection studies is that they can sniff out cancerous cells due to their advanced sense of smell, making them more effective than humans in identifying lung cancer in urine samples.