Pre-lab homework Lab 6: Respiration and Gas exchange

Transcription

1 Lab Section: Pre-lab homework Lab 6: Respiration and Gas exchange Name: 1. Name the organs used for gas exchange in each of the following organisms: Humans Fish Insects 2. What are three features common to most respiratory systems and why do they share these features? hint: you may need to review your text book discussion of gas exchange on p. 572 (Audesirk) or section 22.2 starting on page 425 (Cain) 3. Which lung volumes will you be able to measure in lab today? Print Lab 9 and bring it to class. We will start the plant hormone study this week!! 1

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3 Lab 6: Respiration and Gas exchange Lab section Name: Objectives: Upon completion of this activity, you should be able to: Identify the basic structures used for gas exchange in fish, insects, and mammals. Describe the adaptations that can increase rates of gas exchange. Explain how diffusion is related to gas exchange. Identify the structures used to exchange gasses in plants. Introduction: Plant and animal cells generate and consume gases that need to be transported to and from these cells. In very small organisms or organisms that have large surface area to volume ratios this transport can be accomplished by simple diffusion of gases but as organisms increase in size and complexity their need for specialized gas exchange organs increases. Exercise 1: Diffusion: To help understand the basic process of gas exchange we will perform a simple experiment with diffusion to help review the process. Setting it up: Take a piece of dialysis tubing tied at one end and add about 10ml of starch solution. Tie the bag and set it in a 400 ml beaker with approximately ml of water. Now add either 1 or 4 droppers full of iodine (your instructor will tell you which) and let the setup sit for about 20 minutes. Now draw a simplified sketch showing how the iodine and starch behaved in your bag. Questions: Do both molecules move freely? How do you know? Why do you think this is? Dialysis bag showing movement of starch and iodine Does the amount of iodine added have any effect on the dialysis? 3

4 Exercise 2: Respiration in Mammals: Examine the dried sheep lungs. These lungs show several of the structures very clearly and you should be able to see; the Trachea the tube leading into the lungs, the Bronchi the first branches off the trachea leading into the lobes of the lung, the open space where the heart was located, and the blood vessels flowing into and out of the lungs. Sheep lungs Now examine the sections of human lung at the side of the room. One section is from a person who had emphysema while the other is a healthy lung. Try to note any differences you can. Normal lung section Section of lung with emphysema Now examine a slide of normal lung tissue. Note the circular sacs (alveoli) the thick walled air tubes (bronchioli) and vessels (arterioles and venules). Draw a sketch then compare this to the slide of lung tissue with emphysema. Normal lung Lung with emphysema 4

5 Lung Volumes in Humans The chart below is called a spirogram. It is a graph of lung volumes and capacities. First study the chart and the definition of terms. from: Tidal Volume (TV) quiet relaxed inhalation and exhalation (normal breathing) Inspiratory Reserve Volume (IRV) the additional amount of air you can inhale after a normal inhalation Expiratory Reserve Volume (ERV) the additional amount of air you can exhale after a normal exhalation Vital Capacity (VC) the total amount of air that can be inhaled and exhaled Residual Volume (RV) the amount of air that remains in the lungs after a forced exhalation 5

6 Now that you are familiar with a spirogram you will be able to measure your own lung volumes using a spirometer. Here are a few general instructions for using a spirometer: When using a spirometer each student must use their own disposable mouthpiece. These spirometers are designed for exhalation only! Do not inhale through the spirometer. It is important that before you start and after every reading you reset the dial to zero. It is important that you pinch your nose closed when exhaling into the spirometer as you want all of the air leaving your lungs to go through the machine. Practice exhaling into the spirometer several times before actually taking measurements. It will feel weird to you at first and by practicing you will be able to take more accurate measurements. When measuring your lung volumes you will want to take at least 3 measurements and average your results. Why do you think this is important? Once you are ready here is how you will calculate your lung volumes: Tidal Volume (TV) Inhale a normal breath of room air, pinch your nose closed and exhale a normal breath into the spirometer. The number you record is your TV. Expiratory Reserve Volume (ERV) Inhale a normal breath of room air, pinch your nose closed and exhale all the air you can! No slacking!! Bend over to allow your abdominal muscles to help you out!!! Use this formula to calculate your answer: ERV = Your recorded number TV Why do we have to subtract TV to get the correct value?? 6

7 Vital Capacity (VC) Inhale the biggest breath you can, pinch your nose closed and exhale all the air you can. Again no slacking!!! The number you record is your VC. Inspiratory Reserve Volume (IRV) Because you cannot inhale through the spirometer you cannot directly measure this volume. But, by using a little math you can still calculate this number. Here is the formula you will use to calculate IRV: IRV = VC (TV + ERV) Using the spirometer measure and record your lung volumes in the chart below. In addition to your lung volumes also record the lung volumes of 3 classmates. Name Tidal Volume Inspiratory Reserve Expiratory Reserve Vital Capacity What differences did you see between your lung volumes and those of your classmates? List as many factors as you can think of that may account for the differences you see. Spirometry similar to this is used to assess several different diseases including emphysema. Think about the lung section and lung slide you saw of an emphysemic lung. How do you think this would change the values you saw for Vital Capacity? Why? 7

8 Gas Exchange and surface area: Transfer of gases across the cells of a gas exchange organ occurs through diffusion. One crucial aspect that can increase gas exchange is the area of the exchange surface. In the lungs of mammals surface area is increased by having huge numbers of small sacs as the sites of exchange. In other organisms different tricks are used. 1. Leaf Cross section: in the space to the right sketch a cross section of a plant leaf. Notice the large open air spaces throughout the leaf and the small spaces (stomata) in the upper and lower epidermis. The spaces allow a large amount of surface area to contact the air that passes into and out of the stomata. Cross section of a plant leaf 2. Trachea in insects: Insects gas exchange organ is actually a large number of small highly branched tubes that are located throughout the body of the insect. How are plant leaf interiors similar to insect trachea? Why do you think they have these similarities? 8