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AP BIOLOGY ANIMAL FORM AND FUNCTION Respiratory System Gas Exchange Occurs Across Specialized Respiratory Surfaces Animal cells require O2 for aerobic respiration. If cells are not directly exposed to the outside environment, then some mechanism must provide gas exchange to internal cells—delivering O2 and removing waste CO2. Respiration vs. Cellular Respiration Respiration—the movement of gases into and out of the entire organism. It is also used to describe cellular respiration—the process of producing ATP within mitochondria Gas Exchange in Different Animals Direct with environment: some animals are small enough they can exchange gas directly with the environment. Many of these animals such as the Platyhelminthes (flatworms) have large surface areas—every cell is either exposed to the environment or close enough so that gases can diffuse directly in and out. Gills Gills are evaginated structures (outgrowths from the body) that have large surface areas over which gas exchange occurs. Inside the gills, a circulatory system removes the oxygen and delivers waste CO2. In some animals, such as Polychaete worms (Annelids), the gills are external and unprotected. In other animals such as fish, gills are internal and protected. In fish, water enters the mouth, passes over the gills, and exits through the gill cover (operculum). Countercurrent exchange between the opposing movements of water and blood maximizes diffusion of O2 in and CO2 out. Tracheae Insects have chitin-lined tubes, or tracheae, that permeate their bodies. Oxygen enters (and CO2 exits) the tracheae through openings called spiracles Diffusion occurs across moistened tracheal endings. Lungs Lungs are invaginated surfaces (cavities within the body of the animal). Special kinds of lungs, called book lungs occur in many spiders—they are stacks of flattened membranes enclosed in an internal chamber. Gas Exchange in Humans Many different organs are involved in human gas exchange: Nose Pharynx Larynx Trachea Bronchi, Bronchioles Alveolus Lungs Diaphragm Nose, Pharynx, Larynx Air enters the nose and passes through the nasal cavity, pharynx and larynx. Larynx—voice box that contains the vocal cords Pharynx—intersection where paths for food and air cross Nasal cavity—warms and cleans the air Trachea After passing through the larynx, air enters the trachea The trachea is a cartilage-lined tube. When the animal is swallowing, a special flap called the epiglottis covers the trachea, preventing the entrance of solid and liquid material. Bronchi, Bronchioles The trachea branches into two bronchi, which enter the lungs and then branch repeatedly, forming narrower tubes called bronchioles. Alveoli and Capillaries The bronchioles end in little air sacs called aleveoli. Each alveoli is densely covered with capillaries. The arteries are carrying deoxygenated blood from the heart. Alveolus Gas exchange occurs by diffusion across the moist, sac membranes of the alveoli. Oxygen diffuses into the moisture covering the membrane, through the alveolar wall, through the blood capillary wall, into the blood, and into red blood cells. CO2 diffuses in the opposite direction. http://highered.mcgrawhill.com/sites/0072495855/s tudent_view0/chapter25/ani mation__gas_exchange_durin g_respiration.html Bulk flow of O2 The circulatory system transports O2 throughout the body within red blood cells. Red blood cells contain hemoglobin, ironcontaining proteins to which O2 bonds. Oxygen diffuses out of red blood cells, across capillary walls, into interstitial fluids (the fluids surrounding the cells) and across cell membranes. Bulk flow of CO2 Most CO2 is transported as dissolved bicarbonate ions (HCO3-) in the plasma, the liquid portion of the blood. The formation of HCO3- occurs in the red blood cells, then it diffuses back into the plasma. Some CO2 does not become HCO3-, instead it mixes directly with the plasma or binds to amino groups of the hemoglobin in red blood cells. Mechanics of Respiration Air is moved into and out of lungs by changing their volume. The volume of the lungs is controlled by the contraction of the diaphragm (a thin muscle under the lungs) When the lung volume increases, the air pressure inside the lungs decreases and air rushes into the lungs. http://highered. mcgrawhill.com/sites/0 072507470/stu dent_view0/cha pter23/animatio n__alveolar_pr essure_change s_during_inspir ation_and_expi ration.html When the diaphragm and intercostal muscles relax, the volume of the lungs decreases, raising the pressure on the air, causing the air to rush out. Control of Respiration Chemo-receptors in the carotid arteries (arteries that supply blood to the brain) monitor the pH of the blood. When a body is active, CO2 production increases. When the CO2 that enters the plasma is converted to HCO3- and H+, the blood pH drops. In response, the chemo-receptors send nerve impulses to the diaphragm and respiratory rate is increased. This results in a faster turnover in gas exchange and blood pH returns to normal. Respiratory System Quiz http://www.rcs.rome.g a.us/hargett/anatomy /lungs/rspdia.htm Amazing facts about the respiratory system: http://warriors.warren .k12.il.us/dburke/ama zingfactsrespiratory.ht m
