Question

Which of the following statements about circulatory systems is true?

• A. Hormones are transported in the blood.
• B. All invertebrates have an open circulatory system.
• C. Capillaries have thicker walls than veins do.
• D. The systemic circulation carries blood to and from the lungs

Answer 1

Answer: (A)

Most vertebrates and some invertebrates, such as this annelid earthworm, have a closed circulatory system.

The thin walls of the capillaries allow oxygen and nutrients to pass from the blood into tissues and allow waste products to pass from tissues into the blood.

Systemic circulation moves blood between the heart and the rest of the body. It sends the oxygenated blood out to cells and returns deoxygenated blood to the heart.

Hormones are transported in the blood.

Endocrine glands release hormones directly into the blood