Question

Which of the following statements is correct about the circulatory system in animals?

• A. Blood circulation occurs in closed vessels in arthropods
• B. In annelids, the tissues are not in direct contact with the circulating fluid
• C. In fishes, the heart pumps deoxygenated blood only
• D. The circulatory system transports excretory substances to the excretory organs

Answer 1

The correct option is A

Blood circulation occurs in closed vessels in arthropods

The correct option is A.

Explanation for the correct option:

1. The arteries, veins, and capillaries of the circulatory system, which is basically just a network of cylindrical vessels, branch off from the heart, which functions as a pump. This closed-loop device, found in all vertebrate creatures as well as certain invertebrates, stops the blood from spilling out of a hole.
2. Arthropods, which include insects, crustaceans, and most mollusks, have "open" circulatory systems as opposed to closed ones.
3. Blood is pumped into a hemocoel, an open cavity, as opposed to being contained by blood arteries. Since the blood mixes with the interstitial fluid in the hemocoel, it is frequently referred to as hemolymph.
4. The hemolymph circulates through the organs inside the body cavity as the animal moves, and it subsequently returns to the heart through holes known as Ostia.
5. This movement enables the exchange of nutrients and, in some species without direct gas exchange sites, serves as a fundamental mechanism to transfer gases away from the exchange site.
6. The main mechanism for moving nutrients and gases throughout the body is the circulatory system.
7. In creatures that are only a few cell layers thick, simple diffusion permits some water, nutrient, waste, and gas exchange; nevertheless, bulk flow is the only way to reach the full body of bigger, more sophisticated species.

Final answer: The correct statement about the circulatory system in animals is blood circulation occurs in closed vessels in arthropods.