Chapter%2022%20Respiratory - Surviving in Thin Air THE HIGH...

Info icon This preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 12
Image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 14
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Surviving in Thin Air THE HIGH MOUNTAINS of the Himalayas have claimed the lives of even the world’s top mountain climbers; the journey into thin air can weaken their muscles, cloud their minds, and sometimes fill their lungs with fluid. The air at the height of the world's high- est peak, 9,700mm Mount Everest, is so low in oxygen (02) that most people would pass out instantly if exposed to it. But if you were ever to make it to the top of Mount Everest, you might see birds flying by. Twice a year, flocks of geese migrate over the Himalayas, traveling between winter quarters in India and summer breeding grounds in Russia. These geese, along with other species of migratory birds, can travel easily at heights that would leave most people drowsy, lethargic, or dead. How do geese and ducks manage to fly at such heights? One factor is the efficiency of their lungs, which can draw far more oxygen from the air than our own lungs can. These birds also have blood containing hemoglobin With a very high It is the continuou , affinity for oxygen, picking it b- d 0 up in the lungs and carrying supply of axygen to it to tissues throughout the cells that makes the body. Their circulatory system difference between has large number of capillar- ies (tiny blood vessels} that and death in the thin carry oxygen-rich blood to of the Himalayas; their flight muscles, and the muscles themselves pack a protein that stores a ready supply 0f oxygen. All these adaptations allow the high-flying birds YOU see in these photos to travel even where the air is very thin. Humans can try to adapt to higher elevations, but success less certain. Most people function well only below 3,300 m and are helpless at higher elevations without an oxygen mask. The: are permanent villages at extremely high elevations in the Hi malayas and the Andes, but the people living there have adapt? in ways that allow them to function with relatively little oxygéfl including large lungs, a large heart, and blood that carries addi your blood to carry more oxygen. After long-term training, some Everest climbers have been able to sur- vive for a short time at the top of the world’s highest peak without oxygen masks. Runners and cyclists may also use this type of training, moving to high altitudes to gain stronger lungs and more oxygen-rich blood and then returning to sea level to blow past competitors who trained at lower elevations. Our study of cellular respiration in Chapter 6 showed why animals require oxygen. Without 02, the metabolic machinery that releases energy from food molecules shuts down. It is the continuous supply of O2 to body cells that makes the difference between life and death in the thin air of the Himalayas. The process of gas exchange, often called respiration, is the interchange of O2 and the waste product C02 be- tween an animal and its environment. In this chap- ter, we will explore the respiratory systems of animals. I I n ' high Himalayas. But many die doing such work, their bodies succumbing to altitude— related illnesses under the burdens of long travel and heavy loads. Altitude-caused disorders include everything from mild headaches, dizziness, and nausea to life-threatening fluid buildup in the lungs and swelling of the brain. Avoiding these disorders requires careful conditioning for high altitudes, and the higher one goes, the longer the adjustment takes. As you ' move from sea level up into the mountains, your body starts ad— justing immediately. Your heart pumps faster, and some blood ' vessels may increase in diameter if you stay in the mountains more than a few days. Within weeks, the rate and depth of your breathing increase to bring more air into your lungs. ‘ At the same 1time, your body m._ may develop more capillar— ‘r _ r ies, and your red blood ‘ _ cell count may go 7 up, allowing Gas exchange makes it possible for animals to put to work the food molecules the digestive system provides. Figure “22§1.ptesents an overview of the three phases of gas ex? change an animal with lungs. 0 Breathing is the first phase of the gas exchange process. When an animal breathes, a large, moist internal surface is exposed to air. 02 diffuses across the cells lining the lungs and into surround- ing blood vessels. At the same time, CO2 diffuses out of the blood and into the lungs. As the animal exhales, C02 is re- moved from the body. 9 A second phase of gas exchange is the transport of gases by the circulatory system. The 02 that has diffused into the blood attaches to hemoglobin in red blood cells and is carried from the lungs to the body’s tissues. C02 is also transported in blood from the tissues back to the lungs. -. 9 In the third phase of gas exchange, body cells take up 02 from the blood and release C02 to the blood. This 02 is required for cells to obtain energy from the food molecules the body has digested and absorbed. As we learned in Mod- ule 6.4, 02 functions in cellular respiration as the final elec- tron acceptor in the stepwise breakdown of fuel molecules. H20 and CO2 are waste products, and ATP is produced to power Cellular work. Thus, our cells require a continuous supply of 02 and must dispose of €02. Gas exchange involves the respiratory system and the circulatory system in servicing the cells of the body. Humans cannot survive for more than a “few minutes without 02.- Why? 'agp LIJ51U25JO aui pue sues My mouth“ 'dlv 51L]: aanpmd or E0 seignbai UOQBJldSBJ Jelnnaj 'uolpuru or, iapro u! div to ([ddns (pears e aJli'IbaJ snag a The part of an animal where gases are exchanged with the en- vironment is called the respiratory surface. (In this context, the word respiratory refers to the process of breathing, not to cellular respiration.) Respiratory surfaces are made up of liv— ing cells, whose plasma membranes must be wet to_ function properly. Thus, the respiratory surfaces of terrestrial as well as aquatic animals must be moist, and gases must be dissolved in water before they can diffuse across them. The surface area of the respiratory surface must be extensive enough to take up sufficient 02 for every cell in the body and to dispose of all waste COZ. Usually, a single layer of cells covers or lines the entire respiratory surface. Being thin and moist, the layer al- lows O2 to difiuse rapidly into the circulatory system or di— rectly into body tissues and allows CO2 to difiuse out. The four figures on the facing page illustrate, in simplified form, four types of respiratory organs, structures where gas 454 UNIT V Animals: Form and Function Overview: Gas exchange involves breathing, transport of gases, and exchange of gases with tissue cells l Animals exchange 02 and C02 across moist body surfaces Lung Circulatory system 9 Transport ofgases by the circulatory system Mitochondria 9 Exchange of gases with body cells Capillary Figure 22.1 The three phases of gas exchange exchange with the external environment occurs- In eaCh case, the circle represents a cross section of the animal’s body through the respiratory surface. The yellow areas repre- Sent the respiratOry surfaces; the green circles represent bodl’ surfaces with little or no role in respiration. The boxed eIl largements show a portion of the respiratory surface in the process of exchanging 02 and COZ. ' ' ' Some animals use their entire outer skin as a gas EX change organ. The earthworm in Figure 222A is an exam ple. Notice in the cross-sectional diagram that its -Wh01 body surface is yellow; there are no specialized gas exchafllir surfaces. Oxygen diffuses into a dense net of thin—iii'fillle capillaries lying just beneath the skin. Earthworms 311 other "skin-breathers” must live in damp places or in WaleI because their whole body surface has to stay moist. Animals that breathe only through their skin and lack specialized Ea. Cross section of respiratory surface (the skin covering the body) '— Capillaries Body surface Respiratory surface (gill) Capillary exchange organs are generally small, and many are long and thin or flattened. Small size or flatness provides a high ratio of respiratory Surface to body volume, allowing for sufficient ‘ gas exchange for the entire body. In most animals, the skin surface is not extensive enough i to exchange gases for the whole body. Consequently, certain ‘ parts of the body have become adapted as respiratory sur- faces. Gills have evolved in most aquatic animals. Lungs or an internal system of gas exchange tubes called tracheae have evolved in most terrestrial animals. Gills, lungs, and UaCheae all have extensive surfaces for gas exchange, as ; ShOWn in Figures 22.2B—22.2D. Gills are extensions, or outfoldings, of the body surface ' Specialized for gas exchange. Many marine worms have flap- l-lke gills that extend from each body segment. The gills of C1611113 and crayfish are clustered in one body location. A fish figure 22.2B).has a set of feather-like gills on each side of its head. As indicated in the enlargement, O2 djfiuses across the gill surfaces into capillaries, and CO2 diffuses in the op- Posite direction, out of the capillaries and into the external e11ViIOImlerrt. Since the respiratory surfaces of aquatic ani- mals extend into the surrounding water, keeping the surface IHoist is not a problem. In most terrestrial animals, the respiratory surfaces are f0ltfled into the body rather than projecting from it. The in- Body surface Respiratory surface (air tubes) (no capillaries) Figure 22.2C Tracheal system Figure 22.2D Lungs Body surface Respiratory surface (within lung) Capillary folded surfaces open to the air only through narrow tubes, an arrangement that helps retain the moisture that is essen— tial for the cells of the respiratory. surfaces to function. The tracheal system of insects is an extensive system of branching internal tubes (Figure 22.2C). As we will see in Module 2.2.4, the smallest branches exchange gases directly with body cells. Thus, gas exchange in insects requires no as- sistance from the circulatory system. Most terrestrial vertebrates have lungs (Figure 22.2D), which are internal sacs lined with moist epithelium. As the di- agram indicates, the inner surfaces of the lungs branch‘extene sively, forming a large respiratory surface. Gases are carried between the lungs and the body cells by the circulatory system. We examine gills, tracheae, and lungs more closely in the next Several modules. I ' What is the main difference between gills and lungs in terms of- their spatial relationship to the rest of an animal’s body? 'saaeiins KJOZLQJgClSBJ {mm 5325 leuJalul are sfiung asenuoo or 50932:“) suatuuorytua Buipunonns our oiug Kpoq eLn Luci; piemno spuarxa smfi i0 aoeyns {hounds-cu engsuaixe aqi . CHAPTER 22 Gas Exchange 455 Gills are adapted for gas exchange in aquatic environments Oceans, lakes, and other bodies of water contain 02 in the to any mechanism that increases the flow of the surroun - ' form of dissolved gas. The gills of fishes and many inverte— water or air over the respiratory surface (gills, tracheae' OI brate animals, including lobsters and clams, tap this source lungs). Increasing this flow ensures a fresh supply of 02 and: of Oz. The total surface area of the gills is often much greater the removal of C02. The blue arrows in the drawings repre ' than that of the rest of the body. - sent the one-way flow of water into the mouth, across th An advantage of exchanging gases in water is that there is gills, and out the side of the fish’s body. Swimming fish 33m no problem keeping the respiratory surface wet. On the ply open then mouths and let water flow past the gills, Fish I ‘ other—hand, the amount of available oxygen (dissolved 02) also pump water across the gills by the coordinated Openin ' in water is only about 3—5% of What it is in the air, and the and closing of the mouth and operculum, the stiff flap tha warmer and saliie‘r the water, the less dissolved 02 it holds. covers and protects the gills. Because water is dense and con Thus, gills—especially those of large, active animals in Warm rains so little oxygen, most fish must expend considerable oceans-must be very efficient to obtain enough oxygen energyinventilating their from water. _ The arrangement of capillaries in a fish gill greatly en_ The drawings in Figure 22.3 show the architecture of fish hances gas exchange. Blood flows in the direction Opposit'e gills, which are among the most efficient gas exchange or- to the movement of water past the gills. This makes it possi. gans in the aquatic world. There are four supporting gill ble to transfer oxygen to the blood by a very efficient process arches on each side of the body. Two rows of filaments called countercurrent exchange. Countercurrent exchange project from each gill arch. Each filament bears many plate- is the transfer of something from a fluid moving in one (ii- like structures called lamellae (singular, 1amella),rwhich are rection to another fluid moving in the opposite direction, the actual respiratory surfaces. A lamella is full of‘tiny capil- The name comes from the fact that the two fluids are mov- laries that are separated from the outside by only one or a ing counter to each other. Their opposite flow maintains a dif. few layers of cells. Capillaries are so narrow that red blood fusion gradient that enhances transfer of the substance. Let’s cells must pass through them in single file. As a result, every see how this principle works in a fish gill. ' red blood cell comes in close contact with oxygen dissolved In the circular enlargement on the right of Figure 22.3, in the surrounding water. notice that the direction of water flow over the surface of a What you can’t see in the drawings are the movements lamella (blue arrow) is opposite that of the blood flow that ventilate the gills, We use the term ventilation to refer the lamella (arrow turning from blue to red). The changingin Gill arch Oxygen-poor blood \ Direction of water 7 ' flow ' Oxygen-rich blood \ ‘ Gill arch % 02 in water flowing over lamellae LM 250x % 02 in blood flowing through capillaries in lamellae Gill filaments Countercurrent eXchange Figure 22.3 The structure of fish gills 4:56 UNIT V Animals: Form and Function tensities of these arrows and the numbers on them indicate the changing amount of Oz dissolved in each fluid: the darker the color, the more 02. Notice that as blood flows through a lamella and picks up more and more 02, the blood ‘ comes in contact with water that has even more 02 available because it is just beginning its passage over the gills. As a re- sult, a diffusion gradient is maintained that favors the trans- fer of 02 from the water to the blood along the entire length of the Capillary. r This countercurrent exchange mechanism is so efficient that fish gills can remove more than 80% of the oxygen dis- solved in the water flowing through them. The basic mecha— nism of countercurrent exchange is also important in temperature regulation, as you will see in Chapter 25. between the air and body cells There are two big advantages to exchanging gases by breath— ing air: Air contains a much higher concentration of Oz, and air is much lighter and easier to move than water. Thus, a terrestrial animal expends much less energy than an aquatic animal ventilating its respiratory surface. The main problem facing any aierreathing animal is the loss of water to the air by evaporation. With respiratory surfaces occurring as tiny tubes deep in the body of an insect, evaporation is reduced, and the respiratory system loses very little water. The trachea] system of insects is made up of air tubes that branch throughout the body (Figure 22.4.4). The largest Tracheae Opening for ait The tracheal system of an insect The tracheal/system of insects provides direct exchange Gills are unsuitable for'an animal living on land. An expan- sive surface of wet membrane extending out from the body and exposed to air would lose too much water to evaporation. Most terrestrial animals house their respiratory surfaces within the body, opening to the atmosphere through narrow tubes, as we see next. (This is a tough one!) What would be the maximum per- ' Centage of the water’s oxygen a gill could extract if its blood flowed in the same direction as the water instead of counter to it? poem 0:, REM mug. asngip lafiuol ou nine: 20 pure ’qioq u! paniossgp 20 lo iunome auras our SEM slain mun daais 5:31 pm! ssal awoaaq p]n0M quaipeifi uonenuaauoa aqi 'uonoaiip auras an), u! pamog (an; 52 poogq an; only JalEM our LU!)le pasngip 2(j w 134,05 I tubes, called tracheae, open to the outside and are reinforced by rings of chitin, as shown in the blowup on the bottom right of the figure. Enlarged portions of tracheae form air sacs near organs that require a large supply of 02. The micrograph in Figure 22.4A shows how these tubes branch repeatedly. The smallest branches, called tr‘acheoles, extend to nearly every cell in the insects body. The tiny tips of the tracheoles are closed and contain fluid (dark blue in the figure). Gas is exchanged with body cells by diffusion across the moist epithelium that lines these tips. Thus, the circulatory system of insects is not involved in transporting oxygen. For a small insect, diffusion through the tracheae brings in enough 02 and removes enough (302 to support cellular respiration. larger insects may ventilate their tracheal sys- tems with rhythmic body movements that compress and ex pand the air tubes like bellows. An inS‘ect in flight (Figure 22.413) has a very high metabolic rate and consumes 10 to 200 times more 02 than it does at rest. In many insects, al— ternating contraction and relaxation of the flight muscles rapidly pumps air through the tracheal system. in what basic way does the process of gas exchange in insects differ from that in both fish and humans? 'snaa Kpoq our mos; pue or sariin Buinodsuen u! pa/qmui iou 5; spam! lo ulaisA's Morelnzup eql a Figure 2.43 A grasshopper in flight 457' CHAPTER 22 Gas Exchange Reptiles (including birds), mammals, and most amphibians exchange gases in lungs. In contrast to the tracheae of in- sects, lungs are restricted to one location in the body. There- fore, the circulatory system must transport gases between the lungs and the rest of the body. Amphibians have small lungs (some salamanders lack lungs altogether) and rely heavily on the diffusion of gases across body surfaces. The skin of frogs, for example, Supple- ments gas exchange in the lungs. Most reptiles (including all birds) and mammals rely entirely on lungs for gas exchange. In general, the size and complexity of lungs are correlated with an animal's metabolic rate (and thus oxygen need). For example, the lungs of endotherms (birds and mammals) have a greater area of exchange surface than the lungs of sim- ilar-sized ectotherms (amphibians and nonbird reptiles). The total-respiratory surface of human lungs is about 100 m2, equal to the surface area of a racquetball court. Figure 22.5A shows the human respiratory system (along with the eSOphag-us and heart, for orientation). Our lungs are in the chest cavity, which is bounded at the bot- tom by a sheet of muscle called the diaphragm. Air passes to our lungs via a system of branching narrow tubes. Air usually enters our respiratory system through‘the nos— trils. It is filtered byhairs and warmed, humidified, and sam- pled for odors as it flows through a maze of spaces in the Pha rynx (Esophagus) Larynx Trachea Right lung Bronchus Bronchiole Diaphragm Figure 22.5A The human respiratory system 458 {MT V Animals: Form and Function Terrestrial vertebrates have lungs Nasal -r cavity left lung nasal cavity. We can also draw in air through the mouth, but ea: mouth breathing does not allow the air to be processed by} for the nasal cavity. From the nasal cavity or mouth, air passeg _ at to the pharynx, where the paths for air and food cross. A5 . th' we saw in Module 21.6, the air passage in the pharynx is ro‘ . {Tc open for breathing except when we swallow. _ From the pharynx, air is inhaled into the larynx...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern