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Gaseous exchange [all]



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  • 2. SYLLABUS REQUIREMENTS 4.6.1 Gaseous exchange in plants, insects, bony fish and mammals. Fick’s Law as applied to respiratory surfaces in order to maximise rate of diffusion (only a qualitative approach is required). Respiratory surface of plants to include mesophyll layer and root epidermal cells. Tracheal system of insects. Structure of the gills of bony fish; ventilation; countercurrent exchange to maximise diffusion. The structure and function of mammalian lungs; ventilation; control of rate and depth of breathing. When studying these respiratory organs emphasis must be given to how Fick’s Law is being reflected. Practical work may include use of simple respirometers and spirometer.
  • 3. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 4. The respiratory gases are: cells need to: obtain O2 WHY? eliminate CO2 WHY?
  • 5. The respiratory gases are: cells need to: obtain O2 to produce ATP eliminate CO2 to prevent toxic effects
  • 6. Gaseous exchange: is the exchange of oxygen and carbon dioxide between the environment and the organism takes place in all organisms by diffusion
  • 7. A ‘respiratory surface’ is the: area where gaseous exchange actually takes place
  • 8. Gas exchange occurs across : a specialised respiratory surface Organismal level Cellular level Circulatory system Cellular respiration ATP Energy-rich molecules from food Respiratory surface Respiratory medium (air of water) O2 CO2 Gas exchange:  supplies oxygen for cellular respiration  disposes of carbon dioxide
  • 9. Fick’s law of Diffusion  provides a way of considering how the maximum rate of diffusion of respiratory gases is achieved 1829 - 1901
  • 10. Fick’s law of Diffusion  diffusion rate (Q) of a respiratory gas through a respiratory surface is proportional to: difference in concentration of the gas on either side of the membrane (P1 – P2) surface area of the respiratory surface (A) thickness of the respiratory surface (D) X D P1 P2 A Q A (P1 – P2) D
  • 11. Fick’s law of Diffusion tells us: D P1 P2 A  Increased surface area for gas exchange (Q is directly proportional to A)  Decreased respiratory membrane thickness (Q is inversely proportional to D)  Maintain concentration differences (Q is directly proportional to P1 - P2) what is needed to maximise the rate of diffusion Q  A (P1 – P2) D
  • 12. Main properties of a respiratory surface Property Function Large surface area Facilitates high rate of exchange Moist Oxygen must dissolve before entering blood Thin Short diffusion path (diffusion is relatively slow) Permeable Respiratory gases must pass through it Well ventilated Efficient delivery of oxygen to (and carbon dioxide from) the surface Good blood supply Facilitates oxygen delivery to (and carbon dioxide from) the tissues
  • 13. Organisms acquire their oxygen: direct from the atmosphere dissolved in water 1 2
  • 14. Oxygen can be obtained more easily from air than from water: 1. The oxygen content of air is much higher than that of an equal volume of water. 2. Oxygen diffuses 8,000 times more rapidly in air than in water. 3. When an animal breathes, it does work to move water or air over its specialised respiratory surfaces. More energy is required to move water than to move air.
  • 15. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 16. As animals increase in size: What happens to their surface area to volume ratio? Surface area (cm): Volume (cm3): Surface area/volume:
  • 17. As animals increase in size: What happens to the rate of oxygen consumption? INCREASES What must happen to meet the increased demand? Specialised respiratory surfaces must develop
  • 18. Fig. 1 Types of respiratory surface Aquatic environment cell membrane gills (outgrowths of the body surface) Tadpole Axolotl Axolotl: an amphibian: adult has gills
  • 19. Fig. 1 Types of respiratory surface Semi-aquatic environment epidermis [Lungs of frogs are inefficient.]
  • 20. Fig. 1 Types of respiratory surface Terrestrial environment Tracheae (body surface turned inwards) Lungs (body surface turned inwards)
  • 21. Respiratory pigments are coloured molecules which act as O2 carriers by binding reversibly to O2 contain: a coloured non-protein portion e.g. haem linked to a protein Haem A protein molecule
  • 22. Blood that contains a respiratory pigment is efficient than one without. WHY? The respiratory pigments have a high affinity for oxygen. Dissolved O2 O2 combined to pigment taken up and transported
  • 23. Where is the respiratory pigment located? In vertebrates enclosed in red blood cells In other animals e.g. crustaceans, the pigment is in the haemolymph Heart Haemolymph in sinuses around organs
  • 24. Explain why having pigments "packaged" in cells is better than being in solution. The affinity of the respiratory pigment for O2 is dependent upon e.g.:  pH,  temperature  concentration of the gases. Conditions are more constant within cells.
  • 25. 1. the size & shape of the body  body is extremely small & elongated, as in microscopic nematode worms: short diffusion pathway  the body may be thin & flattened, producing a large surface area for diffusion (as in flatworms) Give TWO reasons for this statement: Some types of animals exchange gases without specialised respiratory structures. Nematode worm Flatworm
  • 26. 2. if energy demands are low:  the relatively slow rate of gas exchange by diffusion may suffice even for a larger, thicker body e.g. a jellyfish
  • 27. Animals without specialised respiratory structures live in moist habitats Sponges: beating flagella maintain a flow of water through the body cavity. Flatworms: increase their SA:Vol ratio by being flattened. Earthworm: has a rudimentary circulatory system to carry gases between the body surface and the underlying tissues.
  • 28. In the earthworm:  gases diffuse through the moist epidermis &  are distributed throughout the body by an efficient circulatory system Blood supply to the body wall of Lumbricus
  • 29. To maintain a concentration gradient that favours the diffusion inward, of more oxygen. Blood in skin capillaries rapidly carry off oxygen that has diffused through the skin. Why is this important?
  • 30. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 31. Flowering plants exchange gases by diffusion through:  Stomata – in leaves and green stems
  • 32. Flowering plants exchange gases by diffusion through:  Lenticels – in the cork of older stems
  • 33. Flowering plants exchange gases by diffusion through:  Root hairs – oxygen enters in solution in soil water
  • 34. Leaves are the main sites of gaseous exchange as they are: thin have a large surface area
  • 35. Plants rely on diffusion through spaces between the cells: no special ventilation mechanisms exist
  • 36. Spongy mesophyll shows each leaf cell is very close to air
  • 37. Explain how oxygen from the air reaches a palisade cell at night. 1. Diffusion through open stoma & into intercellular air space 2. Dissolves in moisture in cell wall 3. Diffusion into palisade cell
  • 38. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 39. The tracheal system of insects consists of tiny branching tubes that penetrate the body
  • 40. Air sacs Spiracle Tracheae  are pairs of holes found on the:  2nd & 3rd thoracic segments  first 8 abdominal segments  lead into air-filled sacs Spiracles: Air sacs: in some larger insects help to move air through the larger tracheae
  • 41. Body cell Tracheole Air sac Trachea Air Body wall The tracheal system of insects provides direct exchange between the air and body cells
  • 42.  branched tubes that lead from spiracles  each trachea secretes a thin layer of strong, supporting chitinous material around its outer surface Why is it important to support the tracheae? What are ‘tracheae’? If trachea collapses, surface area is greatly reduced
  • 43. Tracheoles:  spread among the insect tissues  end within cells in the more active tissues e.g. flight muscle So that the respiratory surface is very thin making the diffusion of oxygen into the cells easy Why do tracheoles lack a chitinous lining?
  • 44. Air enters the spiracle then flows into the: Tracheae Tracheoles Cells
  • 45. A closer look at a spiracle of a pupa
  • 46. Valves & hairs at a spiracle: reduce water loss Valve closedValve open
  • 47. The functioning of tracheoles Hypotonic fluids surround the tracheole. Fluids diffuse into the tracheole. Increased lactic acid makes the surrounding fluid hypertonic. Fluid is withdrawn from tracheoles. Air moves to replace it.
  • 48. Ventilation (Breathing) movements  ventilation is the active movement of air or water over an animal's respiratory surface  one-way flow of air through the animal occurs Air enters in: through the thorax Air emerges from the abdomen
  • 49. Ventilation (Breathing) movements Expiration:  muscles contract & flatten the body  volume of the tracheal system decreases  air is forced out Inspiration:  is achieved passively when the elastic nature of the body segments returns them to their original shape
  • 50. Compare Ventilation in mammals: Expiration:  muscles contract Inspiration:  is achieved passively Expiration:  muscles relax  is achieved passively Inspiration:  muscles contract
  • 51. In insects: the circulatory system is not involved in respiration blood is colourless (no respiratory pigment)
  • 52. The tracheal system imposes a limitation on the size of insects. WHY?  Although the tracheal system is a highly effective means of gaseous exchange, in most insects it relies on diffusion of O2 through the body  Diffusion can occur efficiently across small distances  Diffusion is only effective up to 1cm
  • 53. Largest insect [55.6cm long] Even though some stick insects may be up to 30 cm in length, no insect can be more than 2cm broad Phobaeticus chani
  • 54. Question: [Pg. 139] 1) Insects use a tracheal system for gas exchange, as shown below. a) On the diagram use a line labelled R to show the respiratory surface. (1) R
  • 55. b) State two advantages of using a tracheal system for gas exchange. (2) 1. Oxygen is transported directly to cells 2. Provides a large surface area for gaseous exchange
  • 56. Question: [pg. 140] 3) Gas exchange in insects involves pores in the cuticle which open into a network of tubes. These tubes have fine branches extending into all the tissues of the body. a) Name the following: The pores in the cuticle. (1) Spiracles The network of tubes. (1) Tracheal system
  • 57. b) In larger insects, such as locusts, the passage of air through the tubes is helped by pumping movements of the abdomen. A student carried out an experiment to investigate the effect of carbon dioxide on the rate of these pumping movements. She set up the apparatus as shown in the diagram below:
  • 58. The locust was left in the boiling tube for five minutes. The number of abdominal pumping movements during one minute was counted. The student then breathed out once through the straw into the boiling tube and immediately counted the number of abdominal movements during one minute. She repeated this procedure varying the number of times she breathed out into the boiling tube. The results are shown in the table below.
  • 59. i) State why the student left the locust in the boiling tube for five minutes before she began the first count. (1) For insect to acclimatise & reach a steady rate of breathing. Number of times student breathed into boiling tube Number of abdominal pumping movements in one minute 0 16 1 59 2 61 3 58 4 60
  • 60. ii) Describe and comment on the effect of breathing out into the boiling tube on the rate of abdominal pumping in the locust. (4) A slight increase in CO2 conc. Resulted in a high rise in breathing rate. Addition of more CO2 did not result in a further increase. Brain is sensitive to slight rise in CO2 . Number of times student breathed into boiling tube Number of abdominal pumping movements in one minute 0 16 1 59 2 61 3 58 4 60
  • 61. c) (i) During this experiment, the humidity of the air in the boiling tube may vary. Suggest how this experiment could be modified to control the humidity. (2) Adding silica gel. + water = pink
  • 62. (ii) Suggest two factors, other than a change in carbon dioxide concentration and humidity, which may have affected the rate of abdominal pumping. (2) An increase in temperature. Animal becomes stressed.
  • 63. Mosquito larva breathing tube.
  • 64. Mosquito larvae & pupa breathing tubes.
  • 65. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 66. Gill Structure
  • 67. Operculum is a:  movable gill cover that encloses and protects the gills
  • 68. Operculum
  • 69. Operculum controls:  movement of water in and out of the opercular cavity like a valve
  • 70. Usually 4 gill arches on either side of the fish:  support the gills  lie between the mouth cavity and the opercular flaps
  • 71. Gill: gill arch + gill filaments Gill arch Gill filaments
  • 72. Gill filaments are thin Gill filament Gill raker [for filter feeding] Upper limb Lower limb
  • 73. Each gill is made up of 2 rows of: gill filaments (primary lamellae) arranged in the shape of a V About 70 pairs of gill filaments
  • 74. The upper & lower flat surfaces of each gill filament has rows of: evenly spaced folds or gill plates (secondary lamellae)
  • 75. The gill plates (secondary lamellae): increase the surface area of the respiratory surface have a rich supply of blood capillaries
  • 76. What makes fish gills look red? A rich blood supply.
  • 77. The gill plates (secondary lamellae): are the exchange surfaces Plate-like secondary lamellae Primary lamellae or filaments
  • 78. The gill plates (secondary lamellae): are two-cell thick Longitudinal section of secondary lamella Water flowBlood flow Primary lamellae or filaments Plate-like secondary lamellae
  • 79. Gills are useless out of the water. WHY? Gill filaments stick together and surface area is reduced
  • 80. Countercurrent flow:  blood in the gill plates flows in the opposite direction to the water (in bony fish) Two types of flow: Parallel flow [concurrent]:  when the two fluids travel in the same direction (in cartilaginous fish)
  • 81. Countercurrent Mechanism
  • 82. Explain how a countercurrent flow increases the efficiency of gaseous exchange.
  • 83. Countercurrent Flow is more efficient: equlibrium is reached blood always comes in contact with water having a high O2 concentration
  • 84. Countercurrent Flow is more efficient
  • 85. Fish Gill Structure and Function •Gill lamellae provide large surface area (increase A) and are very thin (minimize D) •Counter current exchange maintains concentration gradient Q A (P1 – P2) D
  • 86. EXPIRATION Two pumps act in ventilation Suction pump phase INSPIRATION Pressure pump phase
  • 87. Inspiration Expiration
  • 88. Flow of water over gills
  • 89. Neighbouring gill filaments overlap at their tips, providing resistance to water flow. What is the importance of this? Passage of water over the gill lamellae is slowed down. More time is available for gaseous exchange. Water flow
  • 90. Compare the directional flow of gases in: Unidirectional flow Bidirectional flow
  • 91. Essay Titles 1. Compare and contrast the processes of gaseous exchange in insects, bony fish and mammals. [MAY, 2008] 2. Compare and contrast the gaseous exchange mechanisms in fish and mammals. [MAY, 2012]
  • 92. Question: [Pg. 139] 2) In the exchange of oxygen across the surface of a gill of an aquatic animal it is possible to have either of the following arrangements. a) (i) Which of the two systems is more efficient in gaseous exchange? Countercurrent
  • 93. (ii) State one reason for your answer. More oxygen can be extracted from the water when compared to parallel flow. b) Which system occurs in the majority of species of fish? Countercurrent
  • 94. c) The diagram below shows part of a single filament of a fish gill. The blood flow through the capillaries in each lamella is indicated by double-headed arrows. i) What is the name given to this flow arrangement? Countercurrent
  • 95. ii) Describe TWO ways, other than the flow arrangement, in which the gill filament is adapted as a respiratory surface.  Thin epithelium: narrow diffusion pathway  Dense capillary network: to carry O2 away  Gill lamellae: large surface area
  • 96. Question: [Pg. 142] 4) Fig. 1 shows the position and structure of the gills of a bony fish. a) Name the structures labelled A and B. (2) Operculum Gill arch
  • 97. 5) A number of factors influence the rate of diffusion. In the table below circle the letter which shows the combination of factors which give the most rapid rate of diffusion. (1)
  • 98. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 99. Key steps in getting oxygen to tissues
  • 100. Sequence air passes into human lungs: 2. Pharynx [throat] 1. nasal passages 3. larynx4. trachea 5. bronchi 6. bronchioles 7. alveoli lung
  • 101. Human Respiratory System
  • 102. What happens as air passes through the nasal passages? Cilia Cell membrane Mucus
  • 103. Give TWO functions of mucus in the respiratory system.
  • 104. Components of the Respiratory System The Respiratory Epithelium of the Nasal Cavity and Conducting System. Goblet cell Goblet cell
  • 105. Components of the lower respiratory tract
  • 106. The wall of the trachea is:  held open by horizontally C-shaped bands of cartilage  strengthened
  • 107. (a) Anterior view (a) Posterior view (a) Side view Tracheal cartilage C-shaped bands of cartilage
  • 108. trachea oesophagus
  • 109. Fig. 9 Human trachea and lungs.
  • 110. Each lung is surrounded by a pleural cavity Pleural cavity: contains pleural fluid is air-tight Pleural fluid: lubricates space between two layers
  • 111. Drainage from pleural cavity
  • 112. Pleural membranes line the pleural cavity Parietal pleura Parietal pleura Visceral pleura Visceral pleura Pleural cavity Pleural cavity Diaphragm
  • 113. The Pleura 1. protect the lungs 2. stop them leaking air into the thoracic cavity 3. reduce friction between the lungs and the wall of the thorax
  • 114. Alveoli are richly supplied by blood
  • 115. Alveoli form the gas exchange surface
  • 116. Moist squamous epithelium lines each alveolus Simple Columnar Squamous epithelium Cells produces surfactant
  • 117. How is squamous epithelium adapted for diffusion? consists of very thin, flattened cells: reducing the distance over which diffusion must occur Basement membrane Simple Squamous Simple Cuboidal Simple Columnar
  • 118. Diameter of capillary is smaller than that of a RBC and so: RBC move relatively slowly  more time for gaseous exchange RBC are squeezed  bend into an umbrella shape – expose more of their SA to the alveolus:  more uptake of O2
  • 119. Alveoli contain collagen & elastic fibres  elastic fibres allow alveoli to expand and recoil easily during breathing elastic fibres & collagen Surfactant-secreting cell What is ‘surfactant’?
  • 120. A detergent-like chemical secreted by special cells in the alveolus wall on the inside lining of the alveolus Surfactant-secreting cell Squamous epithelium
  • 121. Three functions of the surfactant: 1.lowers the surface tension of the fluid layer lining the alveolus: prevents fluid from beading up on alveolar surface prevents collapse of alveoli due to concentrated fluid weight High surface tension Low surface tension Low collapsing pressure. A small alveolus with surfactant
  • 122. The surfactant reduces the amount of effort needed to breathe in and inflate the lungs
  • 123. Functions of the surfactant: 2. A thinner layer of fluid makes gas diffusion easier 3. Helps to kill any bacteria that reach the alveoli
  • 124. Premature delivery before 28 weeks results in mechanical ventilation requirements. WHY?
  • 125. No surfactant in Premature babies  surfactant is first made in the lungs of a foetus when about 23 weeks old  baby has great difficulty breathing & may die Placenta
  • 126. Fig. 11 Gaseous exchange inside an alveolus.
  • 127. The mechanism of ventilation (breathing)
  • 128. A Respiratory Cycle  Consists of •An inspiration (inhalation) •An expiration (exhalation)
  • 129. Gas Pressure and Volume Relationships
  • 130. A change in volume causes pressure to change
  • 131. The volume of the thoracic cavity changes by:  movements of the: TWO types of intercostal muscles between each rib  diaphragm  intercostal muscles
  • 132.  slant forwards & downwards  contract during inspiration  slant backwards & downwards  contract during expiration
  • 133. Fig. 12 Position of intercostal muscles. The external intercostal muscles contract to pull the ribcage up and out The internal intercostal muscles contract for the ribcage to return back
  • 134. Ribs move like bucket handles Vertebra Sternum SternumLateral increase in volume Anterior increase in volume (a) (b)
  • 135. When ribs/bucket handles move up and out: VOLUME OF THORACIC CAVITY INCREASES. So what happens when volume increases? PRESSURE DECREASES...
  • 136. When PRESSURE DECREASES… Air gets PULLED IN.
  • 137. Diaphragm is “dome-shaped.” When it contracts, the dome flattens out. This INCREASES THORACIC VOLUME.
  • 138. Mammals ventilate their lungs by:  negative pressure breathing, which pulls air into the lungs Air inhaled Air exhaled INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Diaphragm Lung Rib cage expands as external intercostal muscles contract Rib cage gets smaller as external intercostal muscles relax
  • 139. Inspiration: an active process
  • 140. Expiration: is largely a passive process
  • 141. Control of breathing
  • 142. Breathing is an involuntary function of the CNS a respiratory / breathing center in the medulla oblongata [part of brain stem] :  establishes basic breathing pattern Brain stem Spinal cord
  • 143. Within limits the:  rate and  depth of breathing are also under voluntary control e.g. holding the breath
  • 144. During voluntary control: impulses originating in the cerebral hemispheres breathing centre: carries out the appropriate action
  • 145. Basic breathing rhythm is generated in the medulla & is modified by neurones in or above the pons If the brainstem is cut below the pons, but above the medulla, breathing continues but is irregular. If the spinal cord in the neck is severed, breathing ceases.
  • 146. Two centres: 1. inspiratory centre  increases the rate and depth of inspiration 2. expiratory centre  inhibits inspiration and stimulate expiration The breathing centres intercostal muscles by way of the intercostal nerves diaphragm by the phrenic nerves communicate with the:
  • 147. The bronchi and bronchioles (bronchial tree) are connected to the brain by the: Vagus nerve Constricts bronchi
  • 148. Rhythm of breathing  INSPIRATION inflates the lungs  stretch receptors in the bronchial tree are stimulated to send more and more nerve impulses via the vagus nerve to the expiratory centre
  • 149. Rhythm of breathing  this temporarily inhibits the inspiratory centre and inspiration  the external intercostal muscles relax, elastic recoil of the lung tissues occurs: EXPIRATION takes place Intercostal nerve to internal intercostal muscle to stimulate expiration
  • 150. Rhythm of breathing  the bronchial tree is no longer stretched and the stretch receptors no longer stimulated  thus the expiratory centre becomes inactive  INSPIRATION can begin again Phrenic nerve to diaphragm to stimulate inspiration Intercostal nerve to external intercostal muscle to stimulate inspiration
  • 151. Rhythm of breathing Inspiratory centre active Inspiratory centre inhibited
  • 152. A rise in CO2 = low pH: detected by chemoreceptors in: Medulla oblongata Carotid body Aortic body
  • 153. Central chemoreceptors in medulla:  are sensitive to H+ in cerebrospinal fluid resulting from CO2 in blood
  • 154. Peripheral chemoreceptors in carotid & aortic bodies are:  sensitive to:  carbon dioxide  pH  oxygen levels
  • 155. During exercise, the CO2 level in the blood rises, lowering the blood pH – This triggers a cascade of events Brain Cerebrospinal fluid BREATHING CONTROL CENTERS—stimulated by: CO2 increase / pH decrease in blood Nerve signal indicating low O2 level O2 sensor in artery Pons Medulla Nerve signals trigger contraction of muscles Diaphragm Rib muscles
  • 156. CO2 affects breathing rate A large drop in arterial O2 has little effect on breathing rates. A small amount of CO2 in the blood stimulates a large increase in breathing rate.
  • 157. Hypoventilation: Insufficient breathing -Blood has abnormally high PCO2 Hyperventilation: Excessive breathing -Blood has abnormally low PCO2
  • 158. Lung volumes & capacities
  • 159. Fig. 15 Lung volumes and capacities Volumes are measured. Capacities are the summation of volumes .
  • 160. Tidal volume  the volume of gas exchanged during one breath in and out
  • 161. Inspiratory reserve volume is the volume of gas inhaled after normal tidal inspiration
  • 162. Expiratory reserve volume is the volume of gas exhaled after normal tidal expiration
  • 163. Residual volume  is the volume of air remaining in the lungs after a forced expiration
  • 164.  enters alveoli  occupies dead space mainly in bronchi & bronchioles Air in lungs:
  • 165. Inspiratory capacity is the sum of the inspiratory reserve volume and tidal volume
  • 166. Functional residual capacity the volume of air remaining in the lungs after a normal exhalation
  • 167. Vital capacity  is the maximum volume of air that can be exchanged during one breath in and out (forced inspiration and expiration)
  • 168.  An average human breathing rate:  12-20 times per minute  Newborns:  30-40 breaths per minute Why does the breathing rate increase during exercise?
  • 169. Volume Value (litres) In men In women Inspiratory reserve volume 3.3 1.9 Tidal volume 0.5 0.5 Expiratory reserve volume 1.0 0.7 Residual volume 1.2 1.1 Total lung capacity 6.0 4.2 Total Lung capacity depends upon many factors such as: weight sex age activity
  • 170. Explain this statement: Persons who are born and live at sea level will have a smaller lung capacity than those who spend their life at a high altitude.
  • 171. Answer: This is because there is less oxygen in the air at high altitude, so the lungs gradually expand to process more air.
  • 172. The percentage composition by volume of gases in inspired, alveolar and expired air. Gas Inspired air Alveolar air Expired air Oxygen 20.95 13.8 16.4 Carbon dioxide 0.04 5.5 4.0 Nitrogen 79.01 80.7 79.6
  • 173. Topic Outline A) Respiratory gas exchange B) The need for special respiratory structures and pigments C) Gaseous exchange in flowering plants D) Gaseous exchange in insects E) Gaseous exchange in bony fish F) Gaseous exchange in a mammal G) The spirometer
  • 174. The Spirometer is:  an instrument which measures the volume of air which enters and leaves the lungs Capacity: 6 or more litres Rotating drum / Kymograph Tracer / Pen Tube Air chamberNose clip Soda limeCounterweight
  • 175. What are the functions of: counterweight: makes the chamber rise or fall as gas is passed in or drawn out soda lime absorbs the exhaled CO2 Mouthpiece Water level Kymograph Spirometer chamber
  • 176. A spirometer can measure the: tidal volume inspiratory reserve volume expiratory reserve volume What about residual volume?
  • 177. Expiratory reserve volume x 6 Residual volume = total lung capacity – vital capacity Total lung capacity is estimated:
  • 178. At rest After exercise One division represents 400 cm3 1 2 3 4 5 6 7 8 109 11 Surface speed of drum is one division in 10 seconds
  • 179. Spirometer Trace
  • 180. What can be measured from the spirometer readings? metabolic rate tidal volume rate of breathing consumption of oxygen
  • 181. The breathing rate is calculated as : the number of breaths taken per minute Surface speed of drum is one division in 10 seconds 1 division = 10 seconds 11 divisions = 110 seconds 1 2 3 4 5 6 7 8 109 11 22 breaths in 110 seconds in 60 seconds 60 x 22 = 12 110 12 breaths per minute One breath
  • 182. Pulmonary ventilation (PV) : is the volume of air exchanged between the subject and outside environment each minute e.g. breathing rate = 15 breaths per minute tidal volume = 400 cm3 PV = 15 x 400 = 600 cm3 per minute PV = the breathing rate x tidal volume
  • 183. How to measure the rate of O2 consumption  as the oxygen in the spirometer is used, the box gradually gets lower [assuming that CO2 is absorbed]  the rate of O2 consumption is measured as the overall drop in the box over a given time period
  • 184. How to measure the rate of O2 consumption 800 cm3 consumed in 100s 1 division = 400 cm3 2 divisions = 800 cm3 Surface speed of drum is one division in 10 seconds 10 x 10 = 100 sec consumed in 60 s 60 x 800 = 480 100 480 cm3 of O2 per minute 2 divisions
  • 185. Comment on trace obtained from a person with emphysema
  • 186. Proboscis as snorkel.