Biol. 12 THE RESPIRATORY SYSTEM KEY 1. 2. Label the diagram of the respiratory system with the following structures. Give the function and special structural characteristics of each part. a. Larynx : Found at the entrance of the trachea. Triangular section of cartilage, the front of which forms the Adam’s apple. Referred to as the voice box since the vibrations of the vocal cords, which are stretched across the top of the larynx, creates our “voice”. b. Pharynx: Chamber where air and food channels cross (common passage). Food is prevented from entering larynx by the epiglottis. c. Trachea: Wind pipe; surrounded by C-shaped cartilaginous rings to maintain opening of tube. Allows the passage of air to the bronchi. d. Bronchus: (bronchi pl.) 2 branches form from trachea that enter the right and left lung; continues the path for continuous column of air. e. Bronchioles: smaller branches off of the bronchus; walls become very thin with no cartilage. f. Alveoli: air pockets at the end of bronchioles are the exchange site for gases. g. Diaphragm: dome-shaped muscle that forms the floor of the thoracic cavity separating it from the abdominal cavity. Aids in breathing. h. Pleural membranes: inner membrane surrounds and is fused to the lungs. Outer membrane is fused to the rib cage and the diaphragm. Very little space between the two, which is filled with a film of fluid. Aids in breathing and reduces friction between lungs and thoracic wall. i. Lungs: Made up of millions of alveoli, the lungs are the respiratory surfaces where gases are exchanged. j. Thoracic Cavity: That part of the coelom that houses the lungs and heart. Divided from the abdominal cavity by the diaphragm. k. Ribs: Bones that surround lungs to give support and protection to them. They play a major role in breathing. List 4 ways alveoli structure lends itself to their particular function? The aveloli are microscopic sacs that are only 1 layer of squamous epithelial cells thick, surrounded by capillaries. This makes for very efficient gas exchange since the gasses must only diffuse through 2 layers of cells and there is a huge surface area. They also secrete surfactant, which allows the alveoli to refill with air once they collapse and helps keep the surfaces moist allowing diffusion to occur. 2 3. Where would you find cilia and mucus in the respiratory tract? What are each of their functions? Cilia are found in the nasal, trachea and bronchi passages. They keep debris out of the lungs. Mucus is important to moisten air before it reaches the lungs and to trap dirt, bacteria and other debris to protect the lungs. It can be found at all levels of the respiratory system. 4. Read carefully pg. 276-277 Explain what occurs during INSPIRATION and EXPIRATION to the rib cage, the diaphragm and the pressure in the lungs. (Diagram on pg. 276 will help). Use terms such as partial vacuum and negative pressure. Inspiration: The intercostal muscles of the rib cage contract causing the ribs to move up and out. The diaphragm also contracts, flattening out. Both these processes cause the thoracic cavity to expand. This will cause the lungs to expand as the plural membranes are pulled outward with the ribs, thus creating a negative pressure, i.e. one lower than atmospheric pressure within the lungs. Air will rush into this partial vacuum in order to balance the pressures. Expiration: The muscles of the ribs and diaphragm will relax (ribs move down and in, the diaphragm moves up), the lungs “rebound”, creating a rise in pressure, which will force the air out of the lungs. 5. Explain how the respiratory center of the medulla oblongata is involved in inspiration and expiration (identify the afferent nerve, nerve leading to the lung and efferent nerve). The medulla oblongata monitors and maintains regular breathing by sending nerve impulses along the phrenic nerve and the intercostal nerve (afferent nerves) at a rate of about 15 breaths per minute. These stimuli cause both the diaphragm and intercostal muscles to contract. As the lungs fill with air, the medulla stops sending impulses to the muscles of the thoracic cavity and expiration occurs as the muscles relax. The medulla can be inhibited when either the concentration of carbon dioxide falls or stretch receptors in the alveoli respond by sending an inhibitory impulse to the medulla along the vagus nerve (efferent nerve) causing the muscles to relax and expiration to occur. 6. What is the role CO2 and H+ ions play in breathing? Explain where their concentrations are detected (3 chemoreceptor sites in the body) and the effect rising concentrations have on breathing. It is the concentration of these 2 substances in the blood, not O2, that regulate breathing. They are detected by chemoreceptors in the medulla oblongata. There are also chemoreceptors that detect these substances (and O2 levels) within the carotid bodies on the carotid artery and within aortic bodies on the aorta. As the concentrations of CO2 and H+ rise in the blood (due to an increase in the metabolic rate of the cells) the medulla sends impulses to the intercostal muscles to increase the rate and depth of breathing, and so match breathing to heart rate and oxygen needs. 3 7. What is the role the pleural membranes play in breathing? Because the membranes are fused to the lungs and the surrounding tissues they maintain a closed system within the thoracic cavity. As the ribs move outward they pull both membranes and therefore the lungs with them. This increases the volume of the thoracic cavity creating a negative pressure within the lungs. Also, the fluid between the membranes has a pressure less than that of the atmosphere. This situation allows the lungs to expand with the ribs. If the membranes were pierced then air from the outside, with the greater pressure, would force the lungs to collapse. 8. Define the following: a. reduced hemoglobin hemoglobin that carries hydrogen = HHb. Helps as a buffer by picking up excess H+. b. carbominohemoglobin hemoglobin that carries carbon dioxide = CO2 . c. oxyhemoglobin hemoglobin that carries oxygen. d. bicarbonate ion main molecule for the transport of carbon dioxide in the blood. Forms from the dissociation of carbonic acid, a chemical created when water and carbon dioxide are joined. e. carbonic anhydrase an enzyme needed for the efficient union of water and carbon dioxide in the red blood cells. (also catalyzes the breakdown of that union) 9. Name and explain the four parts of respiration. Breathing = the taking of air into the lungs. External respiration = the exchange of gases between environment and blood of the lungs. Internal respiration = the exchange of gases between the blood and the cells of the body. Cellular respiration = the use of oxygen and glucose to generate energy for the formation of ATP. 10. Discuss the events of external respiration. Include two pertinent equations in your discussion. External Respiration: the exchange of gases between air and blood. The partial pressure of O2 is lower in the blood than the air, therefore O2 will diffuse into the blood, and since the opposite partial pressures exists for CO2, diffusion will occur out of the blood and into the alveoli. As CO2 leaves the blood additional CO2 comes out of solution from its major transferred state i.e. bicarbonate ion. It will combine with free H+ ions to form carbonic acid, which quickly decomposes (with the aid of carbonic anhydrase), into water and carbon dioxide. Losing H+ increases the pH, which makes the uptake of O2 more efficient (the cooler temperature of lung tissues also increases the uptake of oxygen). Here is the equation showing the loss of CO2 from the blood. 4 H+ + HCO3- H2CO3 H2O + CO2 The loss of CO2 from the blood drives this reaction continuously to the right. The hemoglobin that is freed when both CO2 and H are released from it, is immediately bonded to the O2 diffusing into the red blood cells. The equation showing this process is: Hb + O2 HbO2 11. What two equations pertain to the exchange of gases during internal respiration? During internal respiration the process is reversed due to changes in partial pressures of CO2 and O2. Of course conditions are also different at the tissues to encourage the loss of O2 from the blood to the tissues i.e. pH is lower and temperatures are warmer. From cells to blood: CO2 + H2O H2CO3 H+ + HCO3At the same time the cells will absorb O2. HbO2 Hb + O2 12. State 3 factors that influence hemoglobin’s O2 binding capacity and relate them to the environmental conditions in the lungs and tissues. Hemoglobin is bonded more easily with oxygen at lower temperatures, higher pH and higher partial pressure. Each of these conditions is more favorable at the lungs so oxygen is taken up by hemoglobin. The opposite conditions exist at the tissues so oxygen is released by hemoglobin. 1. 13. Why is it better to give a non-breathing person a mixture of oxygen and carbon dioxide rather than pure oxygen? You would not give a NONBREATHING person pure oxygen because you need CO2 to trigger the breathing center to send the nerve impulse to initiate breathing.