Question

How are the respiratory and circulatory systems connected?

Answer 1

The circulatory system also termed as cardiovascular system consists of blood and blood vessels by which blood is circulated within the body. Blood is termed as the connective tissue. It interconnects various tissues and supplies them nutrients as well as it removes the waste material from tissues.

Complete answer:
The respiratory system is a biological system that is composed of various organs and mechanisms present in animals and plants for the exchange of gases. There are differences in the anatomy and physiology of these systems based on the size of the organism, the environment in which it remains and its evolutionary history.
The circulatory system often termed as the vascular system, is defined an organ system that helps carbohydrates, oxygen, carbon dioxide, hormones, and blood cells to and from the cells in the body to circulate and carry blood to provide nourishment and help to beat with illnesses, regulate temperature and pH, and sustain homeostasis.

The circulatory system shows interconnection with different organs of the body. The main function of the circulatory systems includes:
Supply of nutrients for instance glucose, amino acids, lipids, vitamins etc.
Supply of oxygen ($\mathop O\nolimits_2$) takes place in the different parts of the body.
So, these two systems are interconnected.

Note: The circulatory and respiratory systems get contacted in the lungs. To pump the blood within the body, the circulatory system requires oxygen from the lungs and the respiratory system gives the oxygen that it takes from the air into your bloodstream. The other parts of the body would serve no purpose without these two systems.