Module 8.2 The Respiratory System PDF

MODULE 8.2: THE RESPIRATORY SYSTEM More than 80% of the O2 dissolved in the water is removed as water passes over the respiratory Gas Exchange: Uptake of O2 for cellular respiration surface. and disposal of CO2 to th...

MODULE 8.2: THE RESPIRATORY SYSTEM More than 80% of the O2 dissolved in the water is removed as water passes over the respiratory Gas Exchange: Uptake of O2 for cellular respiration surface. and disposal of CO2 to the environment. Partial Pressure: The pressure exerted by a particular Tracheal Systems in Insects gas in a mixture of gasses. It also applies to gasses dissolved in liquids such as water. It consists of a network of branching tubes throughout the body. Net Diffusion: Gasses undergo this process from a region of higher partial pressure to a region of The respiratory and circulatory systems are lower partial pressure. separate. Larger insects must ventilate their tracheal system to meet O2 demands. Respiratory Media: In a given volume, there is less O2 available in water than in air. Obtaining O2 from Lungs water requires greater efficiency than air breathing. It is the infolding of the body surface. The circulatory Respiratory Surfaces: Animals require large, moist (open or closed) transports gasses between the respiratory surfaces for exchange of gasses lungs and the rest of the body. between their cells and the respiratory medium, either air or water. The size and complexity of lungs correlate with an animal’s metabolic rate. Gas exchange across respiratory surfaces takes place by diffusion. Respiratory surfaces vary by MAMMALIAN RESPIRATORY SYSTEMS animal and can include the skin, gills, tracheae, A system of branching ducts conveys air to the and lungs. lungs. GILLS IN AQUATIC ANIMALS Nostrils: It is where inhaled air is filtered, warmed, It is the outfoldings of the body that create a large humidified, and sampled for odors. surface area for gas exchange. Pharynx: It directs air to the lungs and food to the Ventilation: It moves the respiratory medium over stomach. the respiratory surface. Aquatic animals move through water or move water over their gills for Larynx: Swallowing moves the larynx upward and ventilation. tips the epiglottis over the glottis in the pharynx (closed). Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs. Vocal Cords in Larynx: This is where exhaled air Fish Gills: It uses a countercurrent exchange system, passes over to create sounds. where blood flows in the opposite direction to water passing over the gills. Cilia & Mucus: These line the epithelium of the air ducts and move particles up to the pharynx. 28 Alveoli: Air sacs at the tips of bronchioles where gas Negative Pressure Breathing: Pulls air into the lungs. exchange takes place. Governed by the diaphragm, rib cage, and rib Oxygen diffuses through the moist film of the muscles. epithelium and into capillaries. Lung Volume: It increases as the rib muscles and Carbon dioxide diffuses from the capillaries across diaphragm contract. the epithelium and into the air space. Tidal Volume: The volume of air inhaled and Surfactants: Secretions that coat the surface of exhaled with each breath. the alveoli and prevent the alveoli from collapsing. Preterm babies lack surfactant. Vital Capacity: The maximum tidal volume. Residual Volume: Air that remains in the lungs Breathing: This is the process that ventilates the after exhalation. lungs. It is the alternation of inhalation and exhalation of air. Control of Breathing in Humans How an Amphibian Breathes It is usually regulated by involuntary mechanisms. An amphibian such as a frog ventilates its lungs by Medulla Oblongata of the Brain: It is where positive pressure breathing, which forces air down breathing control centers are found. It regulates the the trachea. rate and depth of breathing in response to pH changes in the cerebrospinal fluid. COORDINATION OF CIRCULATION AND GAS EXCHANGE Blood arriving in the lungs has a low partial pressure of O2 and a high partial pressure of CO2 relative to air in the alveoli. How a Bird Breathes In the alveoli, O2 diffuses into the blood and CO2 Birds have 8 or 9 air sacs. These function as bellows diffuses into the air. that keep air flowing through the lungs. In tissue capillaries, partial pressure gradients favor Air passes through the lungs in one direction only. diffusion of O2 into the interstitial fluids and CO2 into the blood. Passage of air through the entire system of lungs and air sacs requires two cycles of inhalation and RESPIRATORY PIGMENTS exhalation. These are proteins that transport oxygen, greatly increasing the amount of oxygen that blood can Parabronchi: Site of gas exchange. carry. Ventilation in birds is highly efficient. Hemocyanin: Arthropods and many molluscs have these with copper as the oxygen-binding How a Mammal Breathes component. 29  can store oxygen in their muscles in myoglobin Hemoglobin: Most vertebrates and some proteins. invertebrates use hemoglobin. In vertebrates, it is contained within erythrocytes and has iron as the Diving mammals also conserve oxygen by: oxygen binding component. Changing their buoyancy to glide passively Decreasing blood supply to muscles A single hemoglobin molecule can carry four Deriving ATP in muscles from fermentation molecules of O2, one molecule of each once oxygen is depleted. iron-containing heme group. The hemoglobin dissociation curve shows that a small change in the partial pressure of oxygen can result in a large change in delivery of O2. Hemoglobin plays a minor role in transport of CO2 and assists in buffering the blood. Carbon Dioxide Some of CO2 from respiring cells diffuses into the blood and is transported in blood plasma, bound to hemoglobin. The remainder diffuses into erythrocytes and reacts with water to form H2CO3, which dissociates into H+ and bicarbonate ions (HCO3-). In the lungs the relative partial pressures of CO2 favor the net diffusion of CO2 out of the blood. Respiratory Adaptation of Diving Mammals It allows them to perform extraordinary feats. (Ex: Weddell seals in Antarctica can remain underwater for 20 minutes to an hour) These animals have a high blood to body volume ratio. They stockpile O2 and deplete it slowly. They 30