The Respiratory System, Third Edition

Susan Whittemore, Donna Bozzone

Description

Praise for the previous edition:

"...well-developed...clear and detailed...useful at the secondary level in health and anatomy classes and for research...Recommended."—Library Media Connection

Breathing is essential to human survival, as it gives us the necessary oxygen we need to live. Yet the act of respiration is an involuntary process, something many people do not think about on a day-to-day basis. The Respiratory System, Third Edition explains how we get air into our lungs, how our bodies use that air, and the fundamental physical and biological principles underlying respiratory function. In addition, this essential title examines several respiratory diseases and how they affect the body as a whole. Packed with full-color photographs and illustrations, this absorbing book provides students with sufficient background information through references, websites, and suggested reading for further study.

Sujets

• Life Sciences
• Respiratory
• Sciences et techniques
• Biology
• Respiratory system
• Lung
• Medicine
• Lungs
• Research
• Discovery
• Science

Informations

• Publié par: Infobase Publishing
• Date de parution: 01 août 2021
• Nombre de lectures: 0
• EAN13: 9781646937240
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

The Respiratory System, Third Edition
Copyright © 2021 by Infobase
All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher. For more information, contact:
Chelsea House An imprint of Infobase 132 West 31st Street New York NY 10001
ISBN 978-1-64693-724-0
You can find Chelsea House on the World Wide Web at http://www.infobase.com
Contents Cover Copyright Chapters Breathing Thin Air The Air We Breathe Why Do We Breathe? Anatomy of the Respiratory System The Diffusion of Gas Molecules How Do We Breathe? Preventing Collapse of the Lungs Adjusting to Changing Oxygen Demands Diseases of the Respiratory System Support Materials Glossary Bibliography Further Resources About the Authors Index
Chapters
Breathing Thin Air
In May 1996, Jon Krakauer was one of eight members of a guided expedition up Mount Everest, the world's tallest mountain. Although Krakauer eventually reached the summit, 12 other climbers who were on the mountain during the same time period died, including four from his own expedition. Krakauer recounted this harrowing tale in his book Into Thin Air .



Figure 1.1 Jon Krakauer speaks with reporters about his ordeal on Mount Everest, where he nearly died after running out of oxygen on his descent from the summit.
Krakauer nearly died on Mount Everest. As he was descending from the summit, he became concerned that his oxygen supply would run out before he could reach the uppermost camp where additional oxygen tanks were stored. He asked a fellow climber to turn off the oxygen valve on his back so he could conserve his remaining oxygen. Unfortunately, the climber inadvertently opened Krakauer's valve completely, and within minutes, his tank was completely out of oxygen. Krakauer described how he began to lose his eyesight and mental faculties immediately. He was fully aware that, in the absence of oxygen, his brain cells were dying at a rapid pace. He struggled to reach the encampment before he completely lost consciousness. It is evident from his ability to write this gripping tale that he suffered no permanent brain damage from his experience. Other climbers in Krakauer's situation were not as lucky.
What is "thin air," and why is it so physiologically challenging for humans? In his book, Krakauer explains that all health risks associated with high-altitude environments are either due to or worsened by the low oxygen levels at those heights. Some climbers have returned from expeditions with permanent brain damage. Others have lost appendages and suffered extensive tissue damage due to hypothermia, a potentially lethal condition in which the body temperature is significantly lower than normal. Hypothermia occurs more rapidly in low-oxygen environments.



Figure 1.2 Climbing Mount Everest is very difficult due to the lack of oxygen as the climber gets higher. Expeditions to the summit must carry adequate supplies of oxygen to aid their members' survival.
High-altitude pulmonary edema, or HAPE, is another dangerous ailment experienced by some high-altitude climbers. With HAPE, dangerously high blood pressure develops in the small blood vessels of the lungs, forcing fluid to leak into the air spaces. A person experiencing HAPE begins to drown in the body fluids that have collected in their lungs. Without immediate treatment, death is a likely possibility.
Krakauer's account of the expedition highlights dramatically the importance of oxygen availability for human survival. Why do we need to breathe oxygen? How do we remove oxygen from the atmosphere and deliver it to all of our cells? 
The Air We Breathe

What is Thin Air?
What is "thin air," and why is it so physiologically challenging for humans? Thin air causes altitude sickness, a series of related symptoms that strikes those who are not acclimated to higher altitudes. Altitude sickness happens because at high altitudes, air pressure decrease and so does the amount of oxygen in that air. The reduced oxygen can affect even the most determined mountaineers, intent on scaling Mount Everest, as well as tourists visiting a high-altitude city for a short vacation.
High-altitude pulmonary edema, or HAPE, is another dangerous ailment experienced by some high-altitude climbers. With HAPE, dangerously high blood pressure develops in the small blood vessels of the lungs, forcing fluid to leak into the air spaces. A person experiencing HAPE begins to drown in the body fluids that have collected in their lungs. Without immediate treatment, death is a likely possibility. 1 Why do we need to breathe oxygen? How do we remove oxygen from the atmosphere and deliver it to all of our cells? 
Earth's Atmosphere
To understand respiration, it is necessary to consider the composition of air. Atmospheric air consists of a mixture of gases and other airborne molecules. The predominant gases are nitrogen (78%), oxygen (21%), argon (less than 1%), and carbon dioxide (0.04%). 2 All these gases are present in consistent concentrations. Small amounts of other gases are present in variable concentrations.
The composition of Earth's atmosphere has changed significantly over the course of the planet's history. When Earth was initially formed, it was too hot to retain an atmosphere. Scientists think that Earth's first atmosphere consisted of helium, hydrogen, ammonia, and methane. Scientists hypothesize that water vapor, carbon dioxide, and nitrogen were the main constituents of Earth's second atmosphere. This second atmosphere was the result of the intense volcanic activity associated with that period of Earth's history.
Volcanic eruptions released huge amounts of water vapor into Earth's atmosphere, resulting in cloud formation and rain. Over time, water collected into reservoirs, forming oceans, lakes, and rivers. Scientists believe that the carbon dioxide in the atmosphere was washed from the sky into these water reservoirs, where it became tied up chemically in the sediments. Because nitrogen is less chemically reactive than carbon dioxide, it did not bind to sediments and therefore remained in the atmosphere. As a result, nitrogen began to accumulate and eventually predominate in the atmosphere.
Scientists also think that the intense solar radiation of that time period was of sufficient intensity to split water vapor into hydrogen and oxygen. Like nitrogen, oxygen also began to accumulate in the atmosphere, while hydrogen gas, which is lighter, escaped Earth's atmosphere. Once there was life on Earth and organisms that were capable of photosynthesis had evolved, oxygen levels in the atmosphere rose significantly. Photosynthesis had this effect because oxygen is one of the products of its reactions.
These shifts in the gaseous composition of Earth's atmosphere occurred over billions of years. Unfortunately, human activity is changing the composition of our atmosphere markedly over a much shorter time frame. For example, the increased atmospheric levels of carbon dioxide and methane, which are greenhouse gases that contribute to the overall trend in global warming, are due to human actions. Along with several other U.S. government agencies, the National Oceanic and Atmospheric Administration (NOAA) is researching where and how these greenhouse gases are being generated, how their increased abundance is affecting the Earth's ecosystems and air quality, and what we can do to prevent further degradation of our environment.
Partial Pressures of Gases
In a high-altitude environment like Mount Everest, the relative proportions of nitrogen, oxygen, and the other gases do not differ from their proportions at sea level. Oxygen represents almost 21% of the atmospheric gas molecules on the top of Mount Everest, just as it does at sea level. Nevertheless, it is more difficult to breathe on top of Mount Everest than at sea level. Most people need oxygen tanks to complete their climb. Clearly, the percentage of a gas in the atmosphere is not a useful measure of the actual amount of gas available for respiration. What is?

Nitrogen is the most abundant gas in the atmosphere while oxygen, which is necessary for life, is the second most prevalent.
Source: Infobase Learning.
Molecules of gas, such as oxygen (O 2 ) and nitrogen (N 2 ), are in continuous random motion and, as a result, they exert a pressure. The pressure of a gas depends on two primary factors: temperature and the concentration of the gas (or the number of gas molecules per unit volume). Dalton's Law states that in a mixture of gases, the pressure exerted by each gas in the mixture is independent of the pressure exerted by the other gases. For this reason, the total pressure of a mixture of gases is equal to the sum of all the individual pressures. These individual pressures are also known as the partial pressures.
The partial pressure of a gas is directly proportional to the concentration of the gas. The symbol for partial pressure is a "P" in front of the structural formula for the gas. For example, P N 2 is a symbol for the partial pressure of nitrogen (N 2 ), and P O 2 represents the partial pressure of oxygen (O 2 ). The units for pressure typically used by physiologists are "mm Hg," or millimeters of mercury. This unit of measure refers to the use of mercury-containing manometers to measure pressure.
Atmospheric gas is a mixture of individual gases such as oxygen and nitrogen. The sum of all the partial pressures of the individual gases in the atmosphere is called the total atmospheric pressure, or the barometric pressure. The total atmospheric pressure varies in different regions of the world as a result of differences in altitude and local weather conditions.
At sea level, the total atmospheric pressure is 760 mm Hg. Because 21% of the gas molecules in a given volume of air at