What systems of mammalian organs provide a high level of vital processes and warm-bloodedness?

Due to the presence of a four-chambered heart in mammals, all organs and tissues of their body are supplied with oxygen-rich arterial blood. Oxygen is used in cells to oxidize organic matter in food brought in by the blood from the intestines. Part of the generated energy is converted into heat, which is stored in the body of mammals due to the developed layer of subcutaneous fatty tissue and the hair coat of their body. Consequently, the joint coordinated activity of the digestive, respiratory, circulatory systems, as well as the perfection of the body integument, provide a high level of vital activity and warm-bloodedness in mammals.