BIOL 204 Lecture 34-Circulation & Gas Exchange PDF

 Learning Objectives What is the function of a circulatory system? Distinguish between open and closed circulatory systems; single and double circulation (what is the benefit of double circulation?); arteries, veins, and capillaries Describe the course of blood through the bo...

 Learning Objectives What is the function of a circulatory system? Distinguish between open and closed circulatory systems; single and double circulation (what is the benefit of double circulation?); arteries, veins, and capillaries Describe the course of blood through the body of mammals Describe the steps of the cardiac cycle (what are diastole and systole?) Discuss different respiratory media Describe countercurrent gas exchange during ventilation in fish Describe ventilation in mammals, and birds  Exchange with Environment Nutrients, gases, and wastes must pass through cell membranes through diffusion Molecules  Exchange with Environment Nutrients, gases, and wastes must pass through cell membranes through diffusion Food CO2 Mouth O2 Animal body Exchange Respiratory system Interstitial Heart fluid Nutrients Cells Circulatory system Digestive Excretory system system 0.1 mm Anus Unabsorbed Metabolic waste matter (feces) products (nitrogenous waste)  Exchange with Environment Multicellular, simple body plans: gastrovascular cavity participates in both digestion and material exchange in many animals Mouth Gastrovascular Radial canals cavity Mouth 1 mm Circular canal 2.5 cm Pharynx (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm  Exchange with Environment Complex animals have a respiratory and circulatory system to aid in diffusion to cells  Circulatory Systems A circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes Composed of: Set of interconnecting vessels Muscular pump, the heart (moves fluid, increases pressure) Circulatory fluid (e.g., hemolymph, blood)  Circulatory Systems Open circulatory system – circulatory fluid called hemolymph bathes the organs directly Closed circulatory system – circulatory fluid called blood is confined to vessels apart from interstitial fluid (a) An open circulatory system (b) A closed circulatory system Heart Heart Interstitial fluid Hemolymph in sinuses Blood Small branch vessels in each organ Pores Dorsal Auxiliary vessel hearts (main heart) Tubular heart Ventral vessels  Circulatory Systems Pros of open circulatory system: – Lower hydrostatic pressures allow them to use less energy than closed system Pros of closed circulatory system: – High blood pressure enables effective (specific) delivery of oxygen and nutrients in larger and more active animals  Circulatory Systems Vertebrates have a closed circulatory system called the cardiovascular system – blood travels through one-way vessels – Arteries carry blood away from the heart – Veins carry blood to the heart – Capillaries connect arteries to veins Heart artery capillary vein (a) Single circulation: fish Gill capillaries Non-tetrapod vertebrates (i.e., “fishes”) have a two- chambered heart with Artery single circulation Heart: Atrium (A) Blood leaves heart and Ventricle (V) passes through two Vein capillary beds before returning to heart Body capillaries Key Oxygen-rich blood Oxygen-poor blood Figure 42.4a  Single circulation heart Cons: Lower blood pressure. Slow, inefficient (b) Double circulation: amphibian Tetrapods have a three or four- chambered heart with double Pulmocutaneous circuit circulation Lung Blood only goes through one and skin capillaries capillary bed before returning to heart Atrium Atrium (A) (A) – Pulmonary/pulmocutaenous circuit picks up O2 from heart/skin Right Left – low blood pressure Ventricle (V) Systemic – Systemic circuit delivers O2 to capillaries body cells – high blood pressure Systemic circuit Key Oxygen-rich blood Oxygen-poor blood Figure 42.4b ‘pulmo’ = lung ‘cutaneous’ = skin (b) Double circulation: amphibian Tetrapods have double Pulmocutaneous circuit circulation Lung and skin Amphibians, reptiles have 3- capillaries chambered hearts A A Two atria, and one ventricle with a ridge or partial septum to regulate direction of blood Right Left (inefficient re-oxygenation, V but energy efficient) Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood Figure 42.4b (c) Double circulation: mammal Tetrapods have double circulation Pulmonary circuit Lung In birds and mammals, 4 capillaries chambered hearts with completely divided ventricles (example of convergent A A V evolution) V Right Left Endothermic! Requires more energy, need more oxygen. Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood Figure 42.4c  Thin walled atria (sing. atrium) receive incoming blood Ventricles send blood back out (thick walls, contract forcefully)  Double circulation heart Pros: higher blood pressure. Efficient, fast  Mammalian Circulation The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle The contraction, or pumping, phase is called systole (blood is sent from heart during systole) The relaxation, or filling, phase is called diastole (blood is dumped into chambers during diastole)  Double circulation heart Pros: higher blood pressure. Efficient, fast  Mammalian Circulation Blood pressure is the strain on the walls of arteries – measured as systolic/diastolic blood pressure Systolic pressure is the pressure in the arteries during ventricular systole (sent) Diastolic pressure is the pressure in the arteries during diastole (dump) A pulse is the rhythmic bulging of artery walls with each heartbeat  Exchange with Environment Circulatory and respiratory systems work together to transport oxygen and carbon dioxide  Exchange with Environment Circulatory and respiratory systems work together to transport oxygen and carbon dioxide  Gas Exchange Gas exchange supplies O2 for cellular respiration and disposes of CO2 waste Animals can use air or water as the O2 source (respiratory medium) Ventilation moves the respiratory medium over the respiratory surface In a given volume, there is less O2 available in water than in air  Gas Exchange Gas exchange supplies O2 for cellular respiration and disposes of CO2 waste Animals can use air or water as the O2 source In a given volume, there is less O2 available in water than in air Obtaining O2 from water requires greater efficiency than air breathing  Gas Exchange Animals require large, moist respiratory surfaces for exchange of gases E.g., Gills are a specialized gas exchange system O2 diffuses from the water into blood vessels CO2 diffuses from blood into the water Coelom Gills Parapodium Gills (functions as gill) Tube foot (a) Marine worm (b) Crayfish (c) Sea star  Gas Exchange Fish gills use a countercurrent exchange system, where blood flows in the opposite direction to water passing over the gills; blood is always less saturated with O2 than the water it meets In fish gills, more than 80% of the O2 dissolved in the water is removed as water passes over the respiratory surface Figure 42.22 O2-poor blood Gill Water flow arch O2-rich blood Blood vessels Water Operculum flow Blood flow Countercurrent exchange PO in water 2 Gill filaments 150 120 90 60 30 140 110 80 50 20 PO in blood 2 Rate of diffusion depends on the gradient between the partial pressure of gases  Gas Exchange The tracheal system of insects consists of a network of branching tubes throughout the body The tracheal tubes supply O2 directly to body cells, separate from circulatory system  Gas Exchange Lungs are an infolding of the body surface The circulatory system (open or closed) transports gases from the lungs to the rest of the body Gas exchange takes place in specialized air sacs called alveoli Figure 42.24 Gas Exchange Branch of Branch of pulmonary vein pulmonary artery (oxygen-rich (oxygen-poor blood) blood) Terminal bronchiole Nasal Pharynx/throat cavity Larynx Alveoli Trachea Right lung Bronchus Capillaries Bronchiole Diaphragm Left lung (Heart) Dense capillary bed enveloping alveoli (SEM) Amphibian Ventilation Amphibians ventilate lungs through positive pressure breathing using a buccal pump  Bird Ventilation Airflow is unidirectional through lungs in birds (increases efficiency) Multiple sacs keep air flowing through the lungs – requires two cycles of inhalation and exhalation Figure 42.26 Anterior air sacs Posterior air sacs Lungs Airflow Air tubes (parabronchi) in lung 1 mm Posterior Lungs Anterior air sacs 3 air sacs 2 4 1 1 First inhalation 3 Second inhalation 2 First exhalation 4 Second exhalation  Mammal Ventilation Mammals ventilate their lungs by negative pressure breathing, air pulled into lungs Lung volume increases as the rib muscles and diaphragm contract Rib cage Rib cage expands as gets smaller rib muscles as rib muscles contract. relax. Lung Diaphragm 1 INHALATION: Diaphragm 2 EXHALATION: Diaphragm contracts (moves down). relaxes (moves up). Figure 42.5 Superior 7 Capillaries of vena cava head and forelimbs Pulmonary Pulmonary artery artery Capillaries 9 Aorta Capillaries of right lung of left lung 6 2 3 3 4 11 Pulmonary Pulmonary 5 vein 1 vein Right atrium 10 Left atrium Right ventricle Left ventricle Inferior Aorta vena cava Capillaries of 8 abdominal organs and hind limbs  Respiratory Adaptations of Diving Mammals E.g., Cuvier’s beaked whale dive ~ 2 miles deep & > 2 hours How? – Store a lot of Oxygen: high blood volume, high myoglobin – Conserve Oxygen: Dive passively, lower metabolic needs, decrease heart rate, blood shunted to vital areas (brain) – Exhale before diving, lungs can collapse (high pressure!)  Respiratory Adaptations of Diving Birds E.g., Emperor penguin (~ 1,500 feet)  Summary The circulatory system transports nutrients and oxygen throughout the body and removes waste and carbon dioxide Air has higher oxygen concentration and is a more efficient respiratory medium In all animals, gases and nutrients eventually diffuse across cell membranes (high concentration to low)