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Anatomy & Physiology - Body Systems

The Cardiovascular System

The branches of science that will help you understand the body parts and functions are anatomy and physiology. Anatomy deals with the study of the human body (the components, structure and position) and physiology is the study of how the body functions.

Body Systems

The body comprises several systems: The Cardiovascular system, Digestive system, Endocrine system, Muscular system, Neurological system, Respiratory system and Skeletal system.

The Cardiovascular System

The cardiovascular system comprises the heart, blood, blood vessels and lymphatic system.


The function of the heart is to pump blood around the body. The heart is a hollow, muscular organ divided by a vertical wall called the septum. These two chambers are divided into a thin-walled atrium above and a thick-walled ventricle below, making four chambers. Between each pair of chambers are valves preventing any backflow of blood. Blood vessels leaving the heart generally carry oxygenated blood through vessels known as arteries. These are large, hollow elastic tubes with thick muscular walls designed to withstand high pressure with the blood leaving the heart. Their size gradually diminishes as they spread throughout the body, reaching fine, hair-like vessels known as capillaries. Blood vessels that return blood to the heart are veins that generally carry de-oxygenated blood. They are elastic tubes containing valves to help prevent the backflow of blood. Blood is forced through arteries by the heart's pressure, whereas venous flow is aided by muscular contraction.

The two exceptions to the above are the pulmonary artery, which carries deoxygenated blood from the heart to the lungs, and the pulmonary vein, which carries oxygenated blood from the lungs to the heart. The circulation is divided into two principal systems known as general or systemic circulation: the circulation around the body and the pulmonary circulation to and from the lungs.


The fluid surrounding tissue cells throughout the body is called interstitial fluid and is serviced by blood transporting oxygen and nutrients to it while┬ž lymph removes toxins and waste products. Blood forms about 79% of the bodyweight consisting of Plasma, Corpuscles and Platelets. Erythrocyte (red blood cells) transport oxygen and carbon dioxide, leucocytes (white blood cells), produced in red bone marrow (myeloid tissue), and lymphocytes fight infection and thrombocyte (platelet) are essential to blood clotting at the site of an injury. Plasma is a clear slightly alkaline yellow fluid in which the following are dissolved - blood, proteins, salts, waste materials, gases, enzymes, hormones and vitamins. The blood has three main functions, transport, regulation, and protection.


  • oxygen from the lungs to the cells
  • carbon dioxide from the cells to the lungs
  • nutrients from the intestines to the cells
  • waste material from the cells
  • hormones from the endocrine glands to the cells
  • the heat from various cells


  • pH (concentration of hydrogen ions)
  • body temperature
  • salts
  • the water content in the cells


  • Blood prevents loss by clotting and combats toxins


The lymphatic system is the protective system that picks up materials, cleanses them of waste products and toxins, and returns them to the blood. Although it is described as a separate system, it is part of the vascular system and is intertwined with blood circulation. As blood is the primary transport system to the body, it may also bring bacteria to the tissues.

Effect of exercise on the cardiovascular system

The effects of regular exercise on the vascular system:

  • The supply of blood vessels to the heart will increase, lowering blood pressure and improving the functioning of the heart
  • Lowers the cholesterol levels in the blood, helping to reduce the risk of arteries "furring up" and possible heart disease
  • The period needed for the heart rate to return to normal after exercise is reduced
  • The network of capillaries in a muscle will increase, thereby increasing the supply of blood, oxygen and nutrients to the working muscle

The Bohr Shift

This is a microbiological phenomenon first described in 1904 by the Danish physiologist Christian Bohr: a decrease in blood pH or an increase in blood CO2 concentration will result in haemoglobin proteins releasing oxygen and a decrease in carbon dioxide or increase in blood pH will result in haemoglobin picking up more oxygen.

Page Reference

If you quote information from this page in your work, then the reference for this page is:

  • MACKENZIE, B. (2001) Physiology - [WWW] Available from: [Accessed

Additional Resources

Study Guide to the Systems of the Body provides links to web-based resources on how each part of the body works.