Final answer:
Fish myocardium gets its oxygen from the coronary arteries. These arteries supply oxygenated blood to the heart muscle, necessary for its function. Coronary veins, on the other hand, carry deoxygenated blood away from the heart.
Step-by-step explanation:
The myocardium of fish receives its oxygen from the coronary arteries. In fish, as in mammals, the coronary arteries branch off from the aorta and supply oxygenated blood to the heart muscle. Unlike mammals, fish have a single circulatory system where the blood passes through the heart once during each complete circuit of the body. However, the basic principle of coronary circulation remains the same, with coronary arteries providing the necessary oxygen and nutrients to the cardiac muscle.
The correct answer to the question 'How does fish myocardium get its oxygen?' is a. Coronary arteries. Coronary veins are responsible for taking the deoxygenated blood away from the heart muscle to the right atrium, and luminal blood refers to the blood inside the heart chambers.