Normally a sperm can easily penetrate the egg, but if another sperm has already entered, or the sperm and/or egg is defective. Ignore the other answer because it merely restates your question. So a sperm can always penetrate an egg unless it is too late or either it or the egg is defected.
Hope this helps!
Answer:
Esophagoscopy
Explanation:
According to my research on different veterinary procedures, I can say that based on the information provided within the question the veterinary is most likely to perform an Esophagoscopy. This is a procedure where the veterinary inserts a flexible endoscope in the mouth of the dog and guides it down to the esophagus. This device then takes enhanced images and displays it on a screen for the veterinary to see. This allows them to investigate and hopefully find the ulcer that is causing this problem.
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Pathogens : A bacterium, virus, or other microorganism that can cause disease.
Examples of pathogens: bacteria which include salmonella, listeria and viruses such as Cryptosporidium.
The human body contains many natural defenses against some common pathogens as well as “helpful” bacteria that helps fight off diseases
