Circulatory System

Major function, major organs, major tissues


A group of organs that work together to perform related function's. Organs never work alone. Two or more organs working together to perform a relatated function are known as an organ system. In human, the digestive system is an organ system made up of several organs : the mouth, esophagus, stomach, liver, Pancreas, small and large intestine, and anus


  • Respiration - delivers oxygen to the cells and removing carbon dioxide from them
  • Nutrition - carries digested food substances to the cells of the body
  • Waste Removal - disposes of waste products and poisons that would harm the body if they accumulated
  • Immunity - helps protect the body from disease
  • Cellular Communication - the circulatory system provides a mode of transport for hormones
  • Thermoregulation - the circulatory system transports heat (can both warm and cool body)

The circulatory system functions in the delivery of oxygen, nutrient molecules, and hormones and the removal of carbon dioxide, ammonia and other metabolic wastes. Capillaries are the points of exchange between the blood and surrounding tissues


The heart and circulatory system (also called the cardiovascular system) make up the network that delivers blood to the body's tissues. With each heartbeat, blood is sent throughout our bodies, carrying oxygen and nutrients to all of our cells.

The circulatory system is composed of the heart andblood vessels, including arteries, veins, and capillaries.Every day, the approximately 10 pints (5 liters) of blood in your body travel many times through about 60,000 miles (96,560 kilometers) of blood vessels that branch and cross, linking the cells of our organs and body parts. From the hard-working heart, to our thickest arteries, to capillaries so thin that they can only be seen through a microscope, the cardiovascular system is our body's lifeline.

The circulatory system is composed of the heart and blood vessels, including arteries, veins, and capillaries. Our bodies actually have two circulatory systems: The pulmonary circulation is a short loop from the heart to the lungs and back again, and the systemic circulation (the system we usually think of as our circulatory system) sends blood from the heart to all the other parts of our bodies and back again.


The term tissue is used to describe a group of cells found together in the body. The cells within a tissue share a common embryonic origin. Microscopic observation reveals that the cells in a tissue share morphological features and are arranged in an orderly pattern that achieves the tissue’s functions. From the evolutionary perspective, tissues appear in more complex organisms. For example, multicellular protists, ancient eukaryotes, do not have cells organized into tissues.

Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Connective tissue, as its name implies, binds the cells and organs of the body together and functions in the protection, support, and integration of all parts of the body. Muscle tissue is excitable, responding to stimulation and contracting to provide movement, and occurs as three major types: skeletal (voluntary) muscle, smooth muscle, and cardiac muscle in the heart

The Heart and Circulatory System - How They Work