Cardiovascular System
The cardiovascular system is a closed system in which blood flows throughout the body in a circular fashion. Each of the organs is supplied with oxygen and nutrients for use by the organ’s cells. In turn, the same vessels remove carbon dioxide and wastes for elimination through organs such as the lungs, kidneys and liver. The molecules of nutrients and waste diffuse across cell and vascular membranes in opposite directions simultaneously due to a gradient of concentration.
The heart is the organ that serves as a pump and keeps the blood flowing through the vessels, which then delivers nutrients and oxygen to the tissue. The heart is composed of striated muscle that alternately contracts and relaxes, taking deoxygenated blood from the body and pumping it through the lungs where oxygen is taken up by the hemoglobin of red blood cells and carbon dioxide is released into the atmosphere. The oxygenated blood is then pumped back to the heart where it is then pumped throughout the body including the heart itself. The heart is composed of four chambers -- one atrium and ventricle for the right side and one atrium and ventricle for the left side -- separated by four one-way valves: tricuspid, pulmonary, mitral and aortic. This arrangement permits blood to flow in only one direction, right to left. Contraction is regulated by two collections of specialized heart cells called nodes, and a system of specialized nerve fibers called bundles.
Once blood leaves the heart, it flows through progressively smaller blood vessels (arteries) until it reaches the end-organs where the smallest blood vessels (capillaries) reside. The capillaries are so small (5 to 10 millionths of a meter) and their walls so thin (about 1 millionth of a meter or less) that water, oxygen, carbon dioxide, nutrients and waste can diffuse across them. Vessels carrying carbon dioxide and waste to the heart from the periphery are called veins. For each artery in the body, there is a corresponding vein.
Various techniques are used to measure the integrity and function of the cardiovascular system. These include:
- Electrocardiogram
- Blood Pressure
- Pulse
- Various Types of Heart Monitors
- Various Blood Tests
- The ileum, begins the absorption process by taking up small soluble particles as the remaining food moves towards the large intestine.
- In the large intestine, additional water and nutrients are absorbed and transported to various tissues throughout the body where they are used for energy and cellular metabolism.
- Non-useable waste products of digestion are stored in the colon until they are excreted from the body.
In healthy individuals, the entire digestive process typically takes between 30 and 40 hours from ingestion through waste removal.
Diseases and conditions such as inflammatory bowel disease, Crohn’s disease, ulcerative colitis, cancers, Celiac disease and pancreatitis, among others can all affect the digestive system, as well as some bacterial, viral and parasitic infectious diseases.