Cardiorespiratory System Overview - Anatomy & Physiology
Overview of the Cardiorespiratory System
The mammalian cardiovascular and respiratory systems have evolved primarily for the transport of oxygen from the atmosphere to the tissues and of carbon dioxide from the tissues to the atmosphere but there are a number of other functions, including metabolic and heat exchange mechanisms that are also important.
Air is inhaled and passes through the upper respiratory tract (nostrils / nares, nasal cavity, nasopharynx, larynx, trachea) where it is heated and moistened. It then progresses to the lower respiratory tract (bronchi, bronchioles, alveoli) where oxygen diffuses into the blood forming oxyhaemoglobin. Blood flows through the pulmonary vein to the left atrium and subsequently to the left ventricle from which it is ejected by the heart during ventricular systole. Oxygenated blood is then transferred via the aorta to the different parts of the body. The distribution of blood is controlled by vascular tone which dictates the degree of perfusion of capillary beds and therefore the amount of oxygen available to the various tissues. Carbon dioxide produced from cellular respiration is removed from the tissues and transported either attached to proteins, in solution or as bicarbonate via the venous system to the vena cavae and ultimately to the right atrium. The passage of venous blood is a product of blood flow, vascular valves and muscular and respiratory function. Carbon dioxide rich blood enters the right ventricle and is then pumped to the lungs via the pulmonary artery.
The function of the cardiac and respiratory systems are tightly linked and regulated to maintain blood pressure, tissue oxygen delivery and carbon dioxide removal. Cardiac function is controlled by baroreceptors (pressure receptors) which result in changes to the heart rate, contractility and vascular tone. Respiratory function is controlled centrally by chemoreceptors to maintain rate and both centrally and locally to maintain bronchiolar tone.
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