The Human Respiratory System
Before delving into the computational methods of reconstructing the respiratory models, we first discuss the respiratory system from a functional point of view. In addition, descriptions, locations, geometry, and naming conventions for the anatomical part
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The Human Respiratory System
2.1
Introduction
Before delving into the computational methods of reconstructing the respiratory models, we first discuss the respiratory system from a functional point of view. In addition, descriptions, locations, geometry, and naming conventions for the anatomical parts are discussed in order to establish a basis for decision-making when reconstructing the model. This chapter provides the fundamentals of the anatomy and physiology of the respiratory system and may be skipped if the reader has an established background in this field. The primary function of the respiratory system is gas exchange. Oxygen (which we need for our cells to function) from the external environment is transferred into our bloodstream while carbon dioxide (a waste product of cellular function) is expelled into the outside air. The billions of tissue cells in our body lie too far from the inhaled air to exchange gases directly, and instead blood circulates the oxygen to the cells. This occurs during each breath we take where oxygen first enters the nose or mouth during inhalation. The air passes through the larynx and the trachea which then splits into two bronchi. Each bronchus bifurcates into two smaller branches forming bronchial tubes. These tubes form a multitude of pathways within the lung and terminating at the end with a connection to tiny sacs called alveoli. The exchange of gases takes place at the alveoli, where oxygen (O2 ) diffuses into the lung capillaries in exchange for carbon dioxide (CO2 ). Exhalation begins after the gas exchange and the air containing CO2 begins the return journey through the bronchial pathways and back out to the external environment through the nose or mouth. Secondary functions of the respiratory system include filtering, warming, and humidifying the inhaled air. This includes the vocal cords in the larynx for sound production, lungs for control (or homeostasis) of body pH levels, and the olfactory bulbs in the nose for smell. The respiratory system can be separated into regions based on function or anatomy (Fig. 2.1). Functionally there is the conducting zone (nose to bronchioles), which consists of the respiratory organs that form a path to conduct the inhaled air into the deep lung region. The respiratory zone (alveolar duct to alveoli) consists of the alveoli and the tiny passageways that open into them where the gas exchange takes J. Tu et al., Computational Fluid and Particle Dynamics in the Human Respiratory System, Biological and Medical Physics, Biomedical Engineering, DOI 10.1007/978-94-007-4488-2_2, © Springer Science+Business Media Dordrecht 2013
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2 The Human Respiratory System
Fig. 2.1 Schematic of the respiratory system displayed by the upper and lower respiratory tract region
place. Anatomically, the respiratory system can be divided into the upper and lower respiratory tract. The upper respiratory tract includes the organs located outside of the chest cavity (thorax) area (i.e. nose, pharynx, larynx), whereas the lower respiratory tract inclu
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