Keywords • Fish gill – Filaments – Lamellae Circulation and gas exchange • Tracheal system – Tracheoles II (Chapter 42) • Gastrovascular cavity • Lung • Tidal ventilation • Ventilation in birds Examples of gills Examples of gills Rather than being a solid Fish Gill structure, the fish gill is finely subdivided to enhance gas exchange area 1 filaments lamellae Lamellae Countercurrent flow Are gills effective in increasing Countercurrent surface area? Surface area 1 kg 0.06 m 2 Lime jello cube 1 kg 1.16 m 2 • 20 fold increase due to gills 2 How do gill surface areas compare among different Tracheal systems in insects fishes? • Numbers correspond to arbitrary units per gram body weight Diffusion distance from Tracheoles supply tissues tracheole to mitochondria is short 3 Tracheal system grasshopper • Juvenile and adult “femur” • Adult femur volume is primarily tracheal system X-rays show that in beetles ranging over 1000X in size tracheal system Lungs increasingly takes up more leg space • Internal sacs • Unlike insect tracheal system lungs do not contact entire body • Circulatory system draws oxygen from lungs to tissues • Found in snails, a few fishes, spiders, vertebrates Structure of the mammalian lung http:// www.youtube.com/watch?v =vu_ONM3Bj9A 4 Tidal ventilation of mammalian lung • Negative pressure breathing Birds have a more Tidal ventilation “sophisticated” type of lung ventilation • Tidal volume - volume inhaled and • Birds have high metabolic rates exhaled (around 500 ml in humans) • Can be exposed to lower oxygen • Tidal volume is much less than total concentrations in high altitude flight volume of lungs (several liters in • Ventilation is not tidal humans) • Air flows through the lungs • Thus residual volume remains after exhaling • This is inefficient 5 The avian respiratory system 6 Animation of avian lung The control of breathing • http://www.youtube.com/watch?v=LbJU0o • Human brain monitors carbon dioxide level cOKdo (detected as a drop in blood pH) • Hyperventilation in divers • Diving mammals can tolerate high blood carbon dioxide Organismal respiration -- a simple view O2 O2 mitochondria O2 CO 2+H 2O CO 2 - H+ CO 2 HCO 3 + Adaptations for Diving : • Rapid breathing prior to dive -known as apneustic breathing • Lungs remove 90% of O 2 from air (as opposed to 20% for humans) • Elastic tissue in lungs helps them expand the lungs temporarily during apneustic breathing • Marine mammals have more blood than non -diving mammals for their size (means more hemoglobin to carry oxygen) • Muscles contain more myoglobin to hold oxygen in tissues • The heart rate slows dramatically during a dive – known as bradycardia • Blood flow is reduced to extremities and digestive system • Muscles employ anaerobic respiration as necessary (results in lactic acid build -up) • Marine mammals can tolerate more lactic acid than other mammals • Rib cage and lungs collapse during dive to force air into tissues and prevent decompression sickness 41 7.