The digestive system is a body system that takes solid foods an organism eats and processes it to remove essential nutrients used to energize the organism's body.  The circulatory system is a body system that pumps blood through a network of blood vessels throughout the organism's body.  It is the "superhighway" for delivery to every cell in the organism's body, used to get essential nutrients and fuel in and waste products out.  The digestive system takes solid food and reduces it to a soupy, liquid mixture, called chyme.  The chyme is introduced into the small intestine, which has lots of finger-like projections called villi .  It is here in the small intestine where the villi absorb the glucose, a simple sugar used for energy manufacture in cells, and deliver it to the blood vessels of the circulatory system.  The blood of the circulatory system takes the glucose to every cell in the body, along with necessary oxygen supplied by the lungs of the respiratory system.  The glucose is combined with the oxygen in a chemical process within the mitochondria of the cell.  This process is called cellular respiration and provides energy formation for the cell in the form of an ATP molecule (adenosine triphosphate).  Carbon dioxide and water are formed as waste products, which is then delivered back to the blood, which then takes it to the appropriate excretory system organs for disposal.

How is the digestive system linked with circulatory system and respiratory system?

The products of the digestive system are actually tied directly to the circulatory system in that the organs of the digestive system are used to turn ingested food into products that can be absorbed by the blood and then carried to other organs for use as energy or other functions.

There are also several links between the digestive system and the respiratory system in that there are organs and muscles that serve both, for example the diaphragm which works to force air into and out of the lungs as well as to force waste products out of the digestive system.

All of the systems have to work together as well, without the intake of oxygen and exhalation of carbon dioxide, the function of the digestive system would grind to a halt.  Without the production of glycogen and other things necessary for muscular function, produced by the digestive system and then distributed by the circulatory system, all three functions would cease.

What is the relationship between the circulatory system and the digestive system?

There are six important functions that take place in the digestive system as food turns from nutrients into waste. The six include:

• Ingestion
• Secretion
• Mixing and movement
• Digestion
• Absorption
• Excretion

It is during absorption that the digestive system interacts with the circulatory system.

The small intestine is where much of digestion and absorption occurs. The small intestine contains the plicae circulars and villi. The plicae circular slows down the movement of food through the intestines for absorption. The villi are connected to blood vessels responsible for the absorption of food nutrients directly into the bloodstream.

The circulatory system refers to the channel followed by the blood as it moves throughout the body. The circulatory system is also connected to the digestive system through its function. It provides energy and nutrients necessary for the organs of the digestive system and other body organs to do their work. In addition to its role of absorbing and distributing the nutrients taken in during digestion, the circulatory system provides the energy for the digestive system itself to work. 

How is the respiratory system linked with the circulatory system?

The respiratory system is the system responsible for gaseous exchange in animals.  In humans, this is the mouth, trachea, bronchial tubes, which lead into the lungs, which contain the alveoli, where oxygen is exchanged for carbon dioxide.  The circulatory system is the system in the body that is responsible for pumping blood to every cell in the body.  This would include the heart, all the blood vessels, which are the arteries, veins, and capillaries, and the blood.  Consider the blood the "super-highway" for transportation in the body.  If it has to get there, it will be transported by the blood.  The oxygen breathed into the lungs attaches to a red blood cells heme molecule and is transported to a cell, where it is used in the process known as cellular respiration to create energy for that cell.  Carbon dioxide is a waste product formed as a result of this process, and is taken back to the lungs to be exhaled by the blood.  Oxygen in, carbon dioxide out, courtesy of the respiratory system.  The respiratory and circulatory systems work in tandem to provide gaseous exchange for the body.

How is the digestive system linked to the circulatory system?

The digestive system is made up of various organs that are all supplied blood by the circulatory system; however, I don't think that is the intended connection that the question implies.  Food enters the digestive system through the mouth, and a combination of mechanical and chemical digestion begins assaulting the food there.  After swallowing, the food travels down the esophagus to the stomach.  Chemical digestion occurs there over the next few hours, and then the food (known as chyme) moves from the stomach into the small intestine.  Chemical digestion continues to occur in the first section of the small intestine (duodenum).  Once the food is fully broken down, it needs to be absorbed into the blood stream in order for those nutrients to be transported to cells all around the body.  This is where the digestive system and circulatory system are linked.  The middle section of the small intestine (jejunum) is covered in tiny folds called villi.  These folds increase the surface area and absorption space of the small intestine.  Each villi contains specialized cells that transport different nutrients into the blood.  Once in the blood, the circulatory system delivers the nutrients to the cells. 

What are the connections between the circulatory, respiratory and digestive system?

In a multicellular organism the levels of organization are: cells, tissues, organ, organ system, and organism (from smallest to largest). All parts are specialized (hold a particular structure to complete a particular function). However, all organ systems work together for the good of the whole. 

The respiratory system is composed of the lungs. Its main function is the intaking of oxygen and exhaling of carbon dioxide. 

The oxygen that is inhaled by the respiratory system is delivered to the rest of the body via the circulatory system. The hemoglobin in the red blood cells attaches to the oxygen. As the blood travels through the veins and arteries, it drops off the oxygen from the lungs to the cells and picks up the carbon dioxide from the cells and delivers it to the lungs to be exhaled. 

Some of the oxygen that is inhaled by the respiratory system and delivered by the circulatory system is used during the digestive processes of cellular respiration in the digestive system.  In this process, food (glucose) combines with oxygen to produce carbon dioxide, water, and energy. Hence, some of the carbon dioxide that the blood carries to the lungs is produced during the breakdown of organic materials in the digestive system. 

Describe how the digestive system in humans is linked to the circulatory system?

The digestive system is important because it breaks down foods to their simplest components--fatty acids and glycerol, amino acids and glucose. The amino acids and glucose can be absorbed in the villi(tiny hair-like projections in the small intestine) and enter the circulating blood via capillaries. The fatty acids however, take a different pathway. Inside the vill, are lacteals which absorb the fatty acids and these travel in the circulating lymph fluid. Eventually, in the neck region, the lymph re-enters the bloodstream once again. Therefore, there is a close connection in the small intestine with the circulatory system. Also, the blood travels through the aorta which has smaller branches to supply all the organs of the body, including the digestive system, with necessary substances including oxygen, nutrients and to remove wastes.