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Gas Exchange in animals Consider the following What is gas exchange? Why do animals need to exchange gases with the environment? By what process does gas enter a cell? But what process does gas leave a cell? Breathing Systems Diffusion: single celled organisms such as euglena or ameoba as well as more simple multicellular organisms such as jelly fish. But note; all organisms use diffusion in some form Lungs:mammals, birds, reptiles Gills: fish, Axolotl, lobster Tracheae: insects Amoeba Single celled organism Small: large surface area to volume ratio Gas exchange across the membrane of the cell directly into cell cytosol Axolotl Mexican walking fish External Gills An axolotl has three pairs of featherlike gills at the back of its head. As water passes across the gills, the axolotl takes in the oxygen from it and carbon dioxide passes into the water Gills of Fish Gills Thin surface thus short diffusion pathway Blood supply close by; other side of exchange surface Gill Filaments are separated from each other by the buoyancy of water they have a large surface area Gills of Fish Often counter current pathways exists to increase the rate of diffusion Tracheal system Insects Opening called spiracles lead to tubes called trachea Air is usually drawing into trachea, it passes down tracheal tubes and directly into tissues Characteristics common to Respiratory Surfaces The surface must be very thin The surface must be moist It must have a fresh/renewed source of oxygenit must be able to maintain a concentration gradient along which gases can diffuse Extensive: A large surface area over which gas exchange can occur. In large multicellular organisms such as humans: This surface must be in contact with a transport system Gas Exchange in Mammals Life’s so hard! Its breathe, breathe, breathe all the time! Inhaling and Exhaling INHALING EXHALING RIB CAGE INTERCOSTAL MUSCLEs DIAPHRAGM MUSCLE Ventilation of the LUNGS Inhalation/Inspiration Thoracic cavity is increased in volume due to: Exhalation/Expiration Thoracic cavity is decreased in volume due to: Rid cage rises Rid cage lowers Diaphragm flattens Diaphragm domes upwards Air pressure in the cavity falls Air pressure in the cavity rises air moves into lungs air moves out of lungs Nasal cavity pharynx epiglottis larynx Trachea Bronchiole Lung(right lobe) Right Bronchus Secondary Bronchi rib Pleura Intercostal muscle Diaphragm muscle Nose Filters air: Warms air: Coarse hairs Lots of surface capillaries carrying warm blood Moistens air: Goblet cells mucus: evaporation of water from mucus helps moisten air entering lungs Trachea Goblet cells mucus Mucus traps dust and bacteria Cilia beat rhythmically to move mucus (with trapped particles) upwards to pharynx Changing Structure of Lung plumbing Terminal Bronchioles Respiratory Bronchioles ALVEOLI Transport of gases in mammals Oxygen + Haemoglobin oxyhaemoglobin Oxyhaemoglobin Oxygen + Haemoglobin Transport of Oxygen ~ 98% of oxygen(MOST): binds with haemoglobin to form oxyhaemoglobin; transported via red blood cells ~2% of oxygen: dissolved as oxygen gas in plasma Transport of Carbon Dioxide ~70% of carbon dioxide(MOST): as Bicarbonate ions in the plasma ~23% of carbon dioxide: combined with haemoglobin to form carbohaemoglobin and carried on red blood cells. ~7% of carbon dioxide: transported in plasma as dissolved carbon dioxide gas You don’t need to know all of the chemistry on the picture slides following. This is for your interest. At lungs carbohemoglobin Carbonic acid Oxygen + Haemoglobin bicarbonate Oxyhaemoglobin At Tissues carbohemoglobin Carbonic acid bicarbonate Surfactant Phospholipid and protein Produced by alveolar cells Prevents collapsing of lung at end of expiration Assists with expansion of lungs