The human circulatory system has nearly 60,000 miles of blood vessels. These vessels provide a mode of transport for erythrocytes (red blood cells) leukocytes (white blood cells), platelets and plasma. It is the red blood cells that carry oxygen and nutrients to cells throughout the body. The circulatory system is responsible for delivering these life sustaining products but it can’t do it alone. The digestive and respiratory systems work with the circulatory system to deliver these important necessities.
The respiratory system aids the process with the use of external and internal respirations. External respirations consist of the movement of oxygen into the lungs during inhalation and carbon dioxide is removed from the lungs during exhalation. Internal respiration is the process by which oxygen is transferred from the blood to body cells.
Nutrients for the cells are found in food and are classified as carbohydrates, lipids (fats) and proteins. The main source of carbohydrates are sugars such as sucrose which comes from sugar cane, lactose which comes from dairy and starches which come from grains. Lipids are found in butter, cheese, margarine’s, whole milk, eggs, nuts, olive oils, nuts, fish and other sources. Proteins are found in animal products such as milk, eggs, and meat. They can also be found in soybeans, fruit, and nuts.
It is the digestive system that works with the blood and lymph vessels so the circulatory system can deliver nutrients to the cells of the body. Food is eaten and broken down enabling the nutrients to be absorbed and used by the body. The breaking down of this food actually begins before the first bite is actually taken. As the food mixes with saliva in the mouth the enzymes start to work, beginning the process.
Once the food reaches the stomach, it is broken down further with the aid of stomach muscles and gastric juices. It then passes from the stomach into the small intestines. The small intestines are a large tube approximately 1 1/2-2 inches (3.5-5 cm) around and if stretched out about 22 feet (6.7 m) long. Here, the food mixture is broken down even more so the body can absorb the nutrients. They are absorbed by the body with the aid of the liver, pancreas, and gallbladder.
These three organs release juices into the first part of the small intestines to aid in digestion and increase absorption. The pancreas helps digest fats and proteins. The liver, however has a little more to do. The liver releases bile which helps fats to be absorbed into the bloodstream. The gallbladder stores the excess bile until it is needed. After the red blood cells absorb the nutrients, this nutrient rich blood passes through the liver where harmful substances and wastes are filtered out. The blood then flows through the body where the nutrients and oxygen are absorbed by organs and cells.
The circulatory system is not a stand alone system. It requires the assistance of other systems such as the respiratory, urinary, endocrine, digestive and integumentary (skin) systems in order to function properly. Because the majority of the body’s cells are immobile, they can’t get the basics for their existence without help. With the aid of the digestive system nutrients are absorbed through the walls of the intestines where they are picked up by he blood vessels and carried where they are needed.