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1/05/12 Overview: Trading Places Circulatory System or Blood!! BIOL212 • Every organism must exchange materials with its environment • Exchanges ul?mately occur at the cellular level by crossing the plasma membrane • In unicellular organisms, these exchanges occur directly with the environment © 2011 Pearson Education, Inc. Figure 42.1 • For most cells making up mul?cellular organisms, direct exchange with the environment is not possible • Gills are an example of a specialized exchange system in animals – O2 diffuses from the water into blood vessels – CO2 diffuses from blood into the water • Internal transport and gas exchange are func?onally related in most animals © 2011 Pearson Education, Inc. Concept 42.1: Circulatory systems link exchange surfaces with cells throughout the body • Diffusion ?me is propor?onal to the square of the distance • Diffusion is only efficient over small distances • In small and/or thin animals, cells can exchange materials directly with the surrounding medium • In most animals, cells exchange materials with the environment via a fluid-‐filled circulatory system © 2011 Pearson Education, Inc. Gastrovascular Cavi?es • Some animals lack a circulatory system • Some cnidarians, such as jellies, have elaborate gastrovascular cavi?es • A gastrovascular cavity func?ons in both diges?on and distribu?on of substances throughout the body • The body wall that encloses the gastrovascular cavity is only two cells thick • Flatworms have a gastrovascular cavity and a large surface area to volume ra?o © 2011 Pearson Education, Inc. 1 1/05/12 Figure 42.2 Circular canal Figure 42.2a Circular canal Mouth Mouth Gastrovascular cavity Mouth Pharynx Radial canals 2 mm 5 cm (a) The moon jelly Aurelia, a cnidarian (b) The planarian Dugesia, a flatworm Radial canals 5 cm (a) The moon jelly Aurelia, a cnidarian Figure 42.2b Evolu?onary Varia?on in Circulatory Systems Gastrovascular cavity • A circulatory system minimizes the diffusion distance in animals with many cell layers Mouth Pharynx 2 mm (b) The planarian Dugesia, a flatworm © 2011 Pearson Education, Inc. General Proper+es of Circulatory Systems • A circulatory system has – A circulatory fluid – A set of interconnec?ng vessels – A muscular pump, the heart • The circulatory system connects the fluid that surrounds cells with the organs that exchange gases, absorb nutrients, and dispose of wastes • Circulatory systems can be open or closed, and vary in the number of circuits in the body © 2011 Pearson Education, Inc. Open and Closed Circulatory Systems • In insects, other arthropods, and most molluscs, blood bathes the organs directly in an open circulatory system • In an open circulatory system, there is no dis?nc?on between blood and inters??al fluid, and this general body fluid is called hemolymph © 2011 Pearson Education, Inc. 2 1/05/12 Figure 42.3 Figure 42.3a (a) An open circulatory system (a) An open circulatory system Heart (b) A closed circulatory system Heart Heart Interstitial fluid Hemolymph in sinuses surrounding organs Pores Hemolymph in sinuses surrounding organs Blood Small branch vessels in each organ Dorsal Auxiliary vessel hearts (main heart) Tubular heart Pores Ventral vessels Tubular heart Figure 42.3b (b) A closed circulatory system • In a closed circulatory system, blood is confined to vessels and is dis?nct from the inters??al fluid • Closed systems are more efficient at transpor?ng circulatory fluids to ?ssues and cells • Annelids, cephalopods, and vertebrates have closed circulatory systems Heart Interstitial fluid Blood Small branch vessels in each organ Dorsal Auxiliary vessel hearts (main heart) Ventral vessels © 2011 Pearson Education, Inc. Organiza?on of Vertebrate Circulatory Systems • Humans and other vertebrates have a closed circulatory system called the cardiovascular system • The three main types of blood vessels are arteries, veins, and capillaries • Blood flow is one way in these vessels © 2011 Pearson Education, Inc. • Arteries branch into arterioles and carry blood away from the heart to capillaries • Networks of capillaries called capillary beds are the sites of chemical exchange between the blood and inters??al fluid • Venules converge into veins and return blood from capillaries to the heart © 2011 Pearson Education, Inc. 3 1/05/12 Single Circula+on • Arteries and veins are dis?nguished by the direc?on of blood flow, not by O2 content • Vertebrate hearts contain two or more chambers • Blood enters through an atrium and is pumped out through a ventricle © 2011 Pearson Education, Inc. • Bony fishes, rays, and sharks have single circula?on with a two-‐chambered heart • In single circula7on, blood leaving the heart passes through two capillary beds before returning © 2011 Pearson Education, Inc. Figure 42.4 Figure 42.4a (a) Single circulation (a) Single circulation (b) Double circulation Pulmonary circuit Gill capillaries Gill capillaries Lung capillaries Artery Artery Heart: A Atrium (A) V Right Ventricle (V) Heart: A Atrium (A) V Left Ventricle (V) Vein Vein Systemic capillaries Body capillaries Body capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood Key Oxygen-rich blood Oxygen-poor blood Figure 42.4b (b) Double circulation Double Circula+on Pulmonary circuit Lung capillaries • Amphibian, rep?les, and mammals have double circula7on • Oxygen-‐poor and oxygen-‐rich blood are pumped separately from the right and le[ sides of the heart A V Right A V Left Systemic capillaries Key Systemic circuit Oxygen-rich blood Oxygen-poor blood © 2011 Pearson Education, Inc. 4 1/05/12 • In rep?les and mammals, oxygen-‐poor blood flows through the pulmonary circuit to pick up oxygen through the lungs • In amphibians, oxygen-‐poor blood flows through a pulmocutaneous circuit to pick up oxygen through the lungs and skin • Oxygen-‐rich blood delivers oxygen through the systemic circuit • Double circula?on maintains higher blood pressure in the organs than does single circula?on © 2011 Pearson Education, Inc. Adaptations of Double Circulatory Systems • Hearts vary in different vertebrate groups © 2011 Pearson Education, Inc. Figure 42.5a Amphibians Pulmocutaneous circuit Amphibians Lung and skin capillaries • Frogs and other amphibians have a three-‐chambered heart: two atria and one ventricle • The ventricle pumps blood into a forked artery that splits the ventricle s output into the pulmocutaneous circuit and the systemic circuit • When underwater, blood flow to the lungs is nearly shut off Atrium (A) Atrium (A) Right Left Ventricle (V) Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood © 2011 Pearson Education, Inc. Figure 42.5b Reptiles (Except Birds) Pulmonary circuit Reptiles (Except Birds) • Turtles, snakes, and lizards have a three-‐chambered heart: two atria and one ventricle • In alligators, caimans, and other crocodilians a septum divides the ventricle • Rep?les have double circula?on, with a pulmonary circuit (lungs) and a systemic circuit Lung capillaries Right systemic aorta Atrium (A) Ventricle (V) A Right V Left Left systemic aorta Incomplete septum Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood © 2011 Pearson Education, Inc. 5 1/05/12 Figure 42.5c Mammals and Birds Pulmonary circuit Mammals and Birds • Mammals and birds have a four-‐chambered heart with two atria and two ventricles • The le[ side of the heart pumps and receives only oxygen-‐rich blood, while the right side receives and pumps only oxygen-‐poor blood • Mammals and birds are endotherms and require more O2 than ectotherms Lung capillaries A Atrium (A) Ventricle (V) Right V Left Systemic capillaries Systemic circuit Key Oxygen-rich blood Oxygen-poor blood © 2011 Pearson Education, Inc. Figure 42.5 Amphibians Pulmocutaneous circuit Pulmonary circuit Lung and skin capillaries Atrium (A) Atrium (A) Right Pulmonary circuit Lung capillaries Lung capillaries Right systemic aorta A V Right Left Mammals and Birds Reptiles (Except Birds) A V Left • The mammalian cardiovascular system meets the body’s con?nuous demand for O2 Left systemic aorta Incomplete septum A V Right Concept 42.2: Coordinated cycles of heart contrac?on drive double circula?on in mammals A V Left Ventricle (V) Systemic capillaries Systemic capillaries Systemic capillaries Systemic circuit Systemic circuit Systemic circuit Key Oxygen-rich blood Oxygen-poor blood © 2011 Pearson Education, Inc. Mammalian Circula?on • Blood begins its flow with the right ventricle pumping blood to the lungs • In the lungs, the blood loads O2 and unloads CO2 • Oxygen-‐rich blood from the lungs enters the heart at the le[ atrium and is pumped through the aorta to the body ?ssues by the le[ ventricle • The aorta provides blood to the heart through the coronary arteries • Blood returns to the heart through the superior vena cava (blood from head, neck, and forelimbs) and inferior vena cava (blood from trunk and hind limbs) • The superior vena cava and inferior vena cava flow into the right atrium Anima?on: Path of Blood Flow in Mammals © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. 6 1/05/12 Figure 42.6 Superior vena cava Capillaries of head and forelimbs Pulmonary artery Pulmonary artery Capillaries of right lung Aorta Pulmonary vein Capillaries of left lung The Mammalian Heart: A Closer Look • A closer look at the mammalian heart provides a beder understanding of double circula?on Pulmonary vein Left atrium Right atrium Left ventricle Right ventricle Aorta Inferior vena cava Capillaries of abdominal organs and hind limbs © 2011 Pearson Education, Inc. Figure 42.7 Aorta Pulmonary artery Pulmonary artery Right atrium Left atrium Semilunar valve Semilunar valve Atrioventricular valve Atrioventricular valve Right ventricle Figure 42.8-1 Left ventricle • The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle • The contrac?on, or pumping, phase is called systole • The relaxa?on, or filling, phase is called diastole © 2011 Pearson Education, Inc. Figure 42.8-2 1 Atrial and ventricular diastole 2 Atrial systole and ventricular diastole 1 Atrial and ventricular diastole 0.1 sec 0.4 sec 0.4 sec 7 1/05/12 Figure 42.8-3 2 Atrial systole and ventricular diastole • The heart rate, also called the pulse, is the number of beats per minute • The stroke volume is the amount of blood pumped in a single contrac?on • The cardiac output is the volume of blood pumped into the systemic circula?on per minute and depends on both the heart rate and stroke volume 1 Atrial and ventricular diastole 0.1 sec 0.4 sec 0.3 sec 3 Ventricular systole and atrial diastole © 2011 Pearson Education, Inc. • Four valves prevent backflow of blood in the heart • The atrioventricular (AV) valves separate each atrium and ventricle • The semilunar valves control blood flow to the aorta and the pulmonary artery © 2011 Pearson Education, Inc. • The lub-‐dup sound of a heart beat is caused by the recoil of blood against the AV valves (lub) then against the semilunar (dup) valves • Backflow of blood through a defec?ve valve causes a heart murmur © 2011 Pearson Education, Inc. Figure 42.9-1 Maintaining the Heart s Rhythmic Beat • Some cardiac muscle cells are self-‐excitable, meaning they contract without any signal from the nervous system • The sinoatrial (SA) node, or pacemaker, sets the rate and ?ming at which cardiac muscle cells contract • Impulses that travel during the cardiac cycle can be recorded as an electrocardiogram (ECG or EKG) 1 SA node (pacemaker) ECG © 2011 Pearson Education, Inc. 8 1/05/12 Figure 42.9-2 1 Figure 42.9-3 2 SA node (pacemaker) 1 AV node 2 SA node (pacemaker) ECG AV node 3 Bundle branches Heart apex ECG Figure 42.9-4 1 2 SA node (pacemaker) AV node 3 Bundle branches 4 Heart apex • Impulses from the SA node travel to the atrioventricular (AV) node • At the AV node, the impulses are delayed and then travel to the Purkinje fibers that make the ventricles contract Purkinje fibers ECG © 2011 Pearson Education, Inc. • The pacemaker is regulated by two por?ons of the nervous system: the sympathe?c and parasympathe?c divisions • The sympathe?c division speeds up the pacemaker • The parasympathe?c division slows down the pacemaker • The pacemaker is also regulated by hormones and temperature © 2011 Pearson Education, Inc. Concept 42.3: Paderns of blood pressure and flow reflect the structure and arrangement of blood vessels • The physical principles that govern movement of water in plumbing systems also influence the func?oning of animal circulatory systems © 2011 Pearson Education, Inc. 9 1/05/12 Figure 42.10 Artery Vein LM Blood Vessel Structure and Func?on Red blood cells • A vessel s cavity is called the central lumen • The epithelial layer that lines blood vessels is called the endothelium • The endothelium is smooth and minimizes resistance 100 µm Valve Basal lamina Endothelium Endothelium Smooth muscle Connective tissue Smooth muscle Connective tissue Capillary Artery Vein Arteriole 15 µm Venule Red blood cell LM Capillary © 2011 Pearson Education, Inc. Figure 42.10a Figure 42.10b Valve Basal lamina Endothelium Smooth muscle Connective tissue Endothelium Capillary Smooth muscle Connective tissue Artery Artery Vein LM Vein Red blood cells Arteriole 100 µm Venule Capillary LM Red blood cell 15 µm Figure 42.10c • Capillaries have thin walls, the endothelium plus its basal lamina, to facilitate the exchange of materials • Arteries and veins have an endothelium, smooth muscle, and connec?ve ?ssue • Arteries have thicker walls than veins to accommodate the high pressure of blood pumped from the heart • In the thinner-‐walled veins, blood flows back to the heart mainly as a result of muscle ac?on © 2011 Pearson Education, Inc. 10 1/05/12 Figure 42.11 Systolic pressure V ca en va ae e A A A r C teri ap o ill les Ve arie nu s le s Ve in s a ie s Diastolic pressure or t 120 100 80 60 40 20 0 er 50 40 30 20 10 0 rt Velocity (cm/sec) 5,000 4,000 3,000 2,000 1,000 0 Pressure (mm Hg) • Physical laws governing movement of fluids through pipes affect blood flow and blood pressure • Velocity of blood flow is slowest in the capillary beds, as a result of the high resistance and large total cross-‐ sec?onal area • Blood flow in capillaries is necessarily slow for exchange of materials Area (cm2) Blood Flow Velocity © 2011 Pearson Education, Inc. Blood Pressure • Blood flows from areas of higher pressure to areas of lower pressure • Blood pressure is the pressure that blood exerts against the wall of a vessel • In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost © 2011 Pearson Education, Inc. Changes in Blood Pressure During the Cardiac Cycle • Systolic pressure is the pressure in the arteries during ventricular systole; it is the highest pressure in the arteries • Diastolic pressure is the pressure in the arteries during diastole; it is lower than systolic pressure • A pulse is the rhythmic bulging of artery walls with each heartbeat © 2011 Pearson Education, Inc. Regula+on of Blood Pressure • Blood pressure is determined by cardiac output and peripheral resistance due to constric?on of arterioles • Vasoconstric7on is the contrac?on of smooth muscle in arteriole walls; it increases blood pressure • Vasodila7on is the relaxa?on of smooth muscles in the arterioles; it causes blood pressure to fall © 2011 Pearson Education, Inc. • Vasoconstric?on and vasodila?on help maintain adequate blood flow as the body s demands change • Nitric oxide is a major inducer of vasodila?on • The pep?de endothelin is an important inducer of vasoconstric?on © 2011 Pearson Education, Inc. 11 1/05/12 Figure 42.12 Blood Pressure and Gravity • Blood pressure is generally measured for an artery in the arm at the same height as the heart • Blood pressure for a healthy 20 year old at rest is 120 mm Hg at systole and 70 mm Hg at diastole Blood pressure reading: 120/70 1 3 2 120 120 70 Artery closed Sounds audible in stethoscope Sounds stop © 2011 Pearson Education, Inc. Figure 42.13 • Fain?ng is caused by inadequate blood flow to the head Direction of blood flow in vein (toward heart) • Animals with longer necks require a higher systolic pressure to pump blood a greater distance against gravity Valve (open) Skeletal muscle • Blood is moved through veins by smooth muscle contrac?on, skeletal muscle contrac?on, and expansion of the vena cava with inhala?on Valve (closed) • One-‐way valves in veins prevent backflow of blood © 2011 Pearson Education, Inc. Capillary Func?on • Blood flows through only 5-‐10% of the body s capillaries at a ?me • Capillaries in major organs are usually filled to capacity • Blood supply varies in many other sites • Two mechanisms regulate distribu?on of blood in capillary beds – Contrac?on of the smooth muscle layer in the wall of an arteriole constricts the vessel – Precapillary sphincters control flow of blood between arterioles and venules • Blood flow is regulated by nerve impulses, hormones, and other chemicals © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. 12 1/05/12 Figure 42.14 Precapillary sphincters Thoroughfare channel Arteriole (a) Sphincters relaxed Arteriole • The exchange of substances between the blood and inters??al fluid takes place across the thin endothelial walls of the capillaries • The difference between blood pressure and osmo?c pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end • Most blood proteins and all blood cells are too large to pass through the endothelium Capillaries Venule Venule (b) Sphincters contracted © 2011 Pearson Education, Inc. Figure 42.15 Fluid Return by the Lympha?c System INTERSTITIAL FLUID Net fluid movement out Body cell Blood pressure Osmotic pressure Arterial end of capillary Direction of blood flow • The lympha7c system returns fluid that leaks out from the capillary beds • Fluid, called lymph, reenters the circula?on directly at the venous end of the capillary bed and indirectly through the lympha?c system • The lympha?c system drains into veins in the neck • Valves in lymph vessels prevent the backflow of fluid Venous end of capillary © 2011 Pearson Education, Inc. Figure 42.16 • Lymph nodes are organs that filter lymph and play an important role in the body s defense • Edema is swelling caused by disrup?ons in the flow of lymph © 2011 Pearson Education, Inc. 13 1/05/12 Concept 42.4: Blood components contribute to exchange, transport, and defense • With open circula?on, the fluid that is pumped comes into direct contact with all cells • The closed circulatory systems of vertebrates contain blood, a specialized connec?ve ?ssue © 2011 Pearson Education, Inc. Blood Composi?on and Func?on • Blood consists of several kinds of cells suspended in a liquid matrix called plasma • The cellular elements occupy about 45% of the volume of blood © 2011 Pearson Education, Inc. Figure 42.17 Figure 42.17a Plasma 55% Cellular elements 45% Plasma 55% Constituent Water Solvent for carrying other substances Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance, pH buffering, and regulation of membrane permeablity Plasma proteins Albumin Fibrinogen Cell type Major functions Number per µL (mm3) of blood Functions 5,000–10,000 Defense and immunity Leukocytes (white blood cells) Separated blood elements Constituent Lymphocytes Basophils Eosinophils Neutrophils Osmotic balance, pH buffering Monocytes Platelets 250,000–400,000 Clotting Immunoglobulins Defense (antibodies) Erythrocytes (red blood cells) 5–6 million Substances transported by blood Blood clotting Transport of O2 and some CO2 Nutrients Waste products Respiratory gases Hormones Major functions Water Solvent for carrying other substances Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance, pH buffering, and regulation of membrane permeablity Plasma proteins Albumin Fibrinogen Immunoglobulins (antibodies) Separated blood elements Osmotic balance, pH buffering Clotting Defense Substances transported by blood Nutrients Waste products Respiratory gases Hormones Figure 42.17b Cellular elements 45% Cell type Leukocytes (white blood cells) Separated blood elements Number per µL (mm3) of blood Functions 5,000–10,000 Defense and immunity Lymphocytes Basophils Eosinophils Neutrophils Monocytes Platelets Erythrocytes (red blood cells) 250,000–400,000 5–6 million Blood clotting Plasma • Blood plasma is about 90% water • Among its solutes are inorganic salts in the form of dissolved ions, some?mes called electrolytes • Another important class of solutes is the plasma proteins, which influence blood pH, osmo?c pressure, and viscosity • Various plasma proteins func?on in lipid transport, immunity, and blood clojng Transport of O2 and some CO2 © 2011 Pearson Education, Inc. 14 1/05/12 Cellular Elements • Suspended in blood plasma are two types of cells – Red blood cells (erythrocytes) transport oxygen O2 – White blood cells (leukocytes) func?on in defense • Platelets, a third cellular element, are fragments of cells that are involved in clojng © 2011 Pearson Education, Inc. Erythrocytes • Red blood cells, or erythrocytes, are by far the most numerous blood cells • They contain hemoglobin, the iron-‐containing protein that transports O2 • Each molecule of hemoglobin binds up to four molecules of O2 • In mammals, mature erythrocytes lack nuclei and mitochondria © 2011 Pearson Education, Inc. • Sickle-‐cell disease is caused by abnormal hemoglobin proteins that form aggregates • The aggregates can deform an erythrocyte into a sickle shape • Sickled cells can rupture, or block blood vessels © 2011 Pearson Education, Inc. Leukocytes • There are five major types of white blood cells, or leukocytes: monocytes, neutrophils, basophils, eosinophils, and lymphocytes • They func?on in defense by phagocy?zing bacteria and debris or by producing an?bodies • They are found both in and outside of the circulatory system © 2011 Pearson Education, Inc. Blood CloCng Platelets • Platelets are fragments of cells and func?on in blood clojng © 2011 Pearson Education, Inc. • Coagula?on is the forma?on of a solid clot from liquid blood • A cascade of complex reac?ons converts inac?ve fibrinogen to fibrin, forming a clot • A blood clot formed within a blood vessel is called a thrombus and can block blood flow © 2011 Pearson Education, Inc. 15 1/05/12 Figure 42.18 Figure 42.18a 2 1 3 2 1 3 Collagen fibers Collagen fibers Platelet plug Platelet Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Platelet plug Platelet Fibrin clot Red blood cell Fibrin clot formation Fibrin clot 5 µm Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Fibrin clot formation Enzymatic cascade Prothrombin + Thrombin Fibrinogen Enzymatic cascade Prothrombin Fibrin + Thrombin Fibrinogen Fibrin Figure 42.18b Stem Cells and the Replacement of Cellular Elements Fibrin clot Red blood cell 5 µm • The cellular elements of blood wear out and are being replaced constantly • Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones, especially ribs, vertebrae, sternum, and pelvis • The hormone erythropoie7n (EPO) s?mulates erythrocyte produc?on when O2 delivery is low © 2011 Pearson Education, Inc. Figure 42.19 Stem cells (in bone marrow) Myeloid stem cells Lymphoid stem cells B cells T cells Erythrocytes Lymphocytes Monocytes Neutrophils Platelets Cardiovascular Disease • Cardiovascular diseases are disorders of the heart and the blood vessels • Cardiovascular diseases account for more than half the deaths in the United States • Cholesterol, a steroid, helps maintain membrane fluidity Basophils Eosinophils © 2011 Pearson Education, Inc. 16 1/05/12 • Low-‐density lipoprotein (LDL) delivers cholesterol to cells for membrane produc?on • High-‐density lipoprotein (HDL) scavenges cholesterol for return to the liver • Risk for heart disease increases with a high LDL to HDL ra?o • Inflamma?on is also a factor in cardiovascular disease © 2011 Pearson Education, Inc. • One type of cardiovascular disease, atherosclerosis, is caused by the buildup of plaque deposits within arteries © 2011 Pearson Education, Inc. Figure 42.20 Lumen of artery Endothelium Smooth muscle 1 LDL Atherosclerosis, Heart AFacks, and Stroke Foam cell Macrophage Plaque rupture Plaque 2 Extracellular matrix • A heart aGack, or myocardial infarc?on, is the death of cardiac muscle ?ssue resul?ng from blockage of one or more coronary arteries • Coronary arteries supply oxygen-‐rich blood to the heart muscle • A stroke is the death of nervous ?ssue in the brain, usually resul?ng from rupture or blockage of arteries in the head • Angina pectoris is caused by par?al blockage of the coronary arteries and results in chest pains Smooth muscle cell T lymphocyte 4 3 Fibrous cap Cholesterol © 2011 Pearson Education, Inc. Figure 42.21 • The propor?on of LDL rela?ve to HDL can be decreased by exercise, not smoking, and avoiding foods with trans fats • Drugs called sta?ns reduce LDL levels and risk of heart adacks RESULTS Average = 105 mg/dL 30 20 10 0 0 50 100 150 200 250 300 Plasma LDL cholesterol (mg/dL) Individuals with two functional copies of PCSK9 gene (control group) Percent of individuals • A high LDL to HDL ra?o increases the risk of cardiovascular disease Percent of individuals Risk Factors and Treatment of Cardiovascular Disease Average = 63 mg/dL 30 20 10 0 0 50 100 150 200 250 300 Plasma LDL cholesterol (mg/dL) Individuals with an inactivating mutation in one copy of PCSK9 gene © 2011 Pearson Education, Inc. 17 1/05/12 • Inflamma?on plays a role in atherosclerosis and thrombus forma?on • Aspirin inhibits inflamma?on and reduces the risk of heart adacks and stroke • Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart adack and stroke • Hypertension can be reduced by dietary changes, exercise, and/or medica?on © 2011 Pearson Education, Inc. Par?al Pressure Gradients in Gas Exchange • A gas diffuses from a region of higher par?al pressure to a region of lower par?al pressure • Par7al pressure is the pressure exerted by a par?cular gas in a mixture of gases • Gases diffuse down pressure gradients in the lungs and other organs as a result of differences in par?al pressure © 2011 Pearson Education, Inc. Respiratory Surfaces • Animals require large, moist respiratory surfaces for exchange of gases between their cells and the respiratory medium, either air or water • Gas exchange across respiratory surfaces takes place by diffusion • Respiratory surfaces vary by animal and can include the outer surface, skin, gills, tracheae, and lungs © 2011 Pearson Education, Inc. Concept 42.5: Gas exchange occurs across specialized respiratory surfaces • Gas exchange supplies O2 for cellular respira?on and disposes of CO2 © 2011 Pearson Education, Inc. Respiratory Media • Animals can use air or water as a source of O2, or respiratory medium • In a given volume, there is less O2 available in water than in air • Obtaining O2 from water requires greater efficiency than air breathing © 2011 Pearson Education, Inc. Gills in Aqua?c Animals • Gills are ouloldings of the body that create a large surface area for gas exchange © 2011 Pearson Education, Inc. 18 1/05/12 Figure 42.22 Figure 42.22a Coelom Gills Parapodium (functions as gill) (a) Marine worm Gills Tube foot (b) Crayfish (c) Sea star Parapodium (functions as gill) (a) Marine worm Figure 42.22b Figure 42.22c Coelom Gills Gills Tube foot (c) Sea star (b) Crayfish Figure 42.23 O2-poor blood • Ven7la7on moves the respiratory medium over the respiratory surface • Aqua?c animals move through water or move water over their gills for ven?la?on • Fish gills use a countercurrent exchange system, where blood flows in the opposite direc?on to water passing over the gills; blood is always less saturated with O2 than the water it meets Gill arch O2-rich blood Lamella Blood vessels Gill arch Water flow Operculum Water flow Blood flow Countercurrent exchange PO2 (mm Hg) in water Gill filaments 150 120 90 60 30 Net diffusion of O2 140 110 80 50 20 PO 2 (mm Hg) in blood © 2011 Pearson Education, Inc. 19 1/05/12 Figure 42.23a Figure 42.23b Gill arch O2-poor blood O2-rich blood Lamella Blood vessels Gill arch Water flow Operculum Water flow Blood flow Countercurrent exchange PO2 (mm Hg) in water 150 120 90 60 30 Gill filaments Net diffusion of O2 Figure 42.24 140 110 80 50 20 PO2 (mm Hg) in blood Tracheoles Mitochondria Muscle fiber Tracheal Systems in Insects 2.5 µm • The tracheal system of insects consists of ?ny branching tubes that penetrate the body • The tracheal tubes supply O2 directly to body cells • The respiratory and circulatory systems are separate • Larger insects must ven?late their tracheal system to meet O2 demands Tracheae Body cell Air sac Air sacs Tracheole Trachea External opening Air © 2011 Pearson Education, Inc. Figure 42.24a Lungs Muscle fiber • Lungs are an infolding of the body surface • The circulatory system (open or closed) transports gases between the lungs and the rest of the body • The size and complexity of lungs correlate with an animal s metabolic rate 2.5 µm Tracheoles Mitochondria © 2011 Pearson Education, Inc. 20 1/05/12 Figure 42.25 Mammalian Respiratory Systems: A Closer Look • A system of branching ducts conveys air to the lungs • Air inhaled through the nostrils is warmed, humidified, and sampled for odors • The pharynx directs air to the lungs and food to the stomach • Swallowing ?ps the epiglojs over the glojs in the pharynx to prevent food from entering the trachea Branch of pulmonary vein (oxygen-rich blood) Terminal bronchiole Branch of pulmonary artery (oxygen-poor blood) Nasal cavity Pharynx Left lung Larynx (Esophagus) Alveoli 50 µm Trachea Right lung Capillaries Bronchus Bronchiole Diaphragm (Heart) Dense capillary bed enveloping alveoli (SEM) © 2011 Pearson Education, Inc. Figure 42.25a Figure 42.25b Branch of pulmonary vein (oxygen-rich blood) Nasal cavity Pharynx Terminal bronchiole Branch of pulmonary artery (oxygen-poor blood) Left lung Larynx (Esophagus) Trachea Right lung Bronchus Alveoli Bronchiole Diaphragm (Heart) Capillaries Figure 42.25c 50 µm Dense capillary bed enveloping alveoli (SEM) • Air passes through the pharynx, larynx, trachea, bronchi, and bronchioles to the alveoli, where gas exchange occurs • Exhaled air passes over the vocal cords in the larynx to create sounds • Cilia and mucus line the epithelium of the air ducts and move par?cles up to the pharynx • This mucus escalator cleans the respiratory system and allows par?cles to be swallowed into the esophagus © 2011 Pearson Education, Inc. 21 1/05/12 • Gas exchange takes place in alveoli, air sacs at the ?ps of bronchioles • Oxygen diffuses through the moist film of the epithelium and into capillaries • Carbon dioxide diffuses from the capillaries across the epithelium and into the air space © 2011 Pearson Education, Inc. © 2011 Pearson Education, Inc. Figure 42.26 RDS deaths RESULTS Surface tension (dynes/cm) • Alveoli lack cilia and are suscep?ble to contamina?on • Secre?ons called surfactants coat the surface of the alveoli • Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by ar?ficial surfactants Deaths from other causes 40 Concept 42.6: Breathing ven?lates the lungs • The process that ven?lates the lungs is breathing, the alternate inhala?on and exhala?on of air 30 20 10 0 0 800 1,600 2,400 3,200 4,000 Body mass of infant (g) © 2011 Pearson Education, Inc. How an Amphibian Breathes • An amphibian such as a frog ven?lates its lungs by posi7ve pressure breathing, which forces air down the trachea © 2011 Pearson Education, Inc. How a Bird Breathes • Birds have eight or nine air sacs that func?on as bellows that keep air flowing through the lungs • Air passes through the lungs in one direc?on only • Every exhala?on completely renews the air in the lungs © 2011 Pearson Education, Inc. 22 1/05/12 Figure 42.27 Figure 42.27a Anterior air sacs Posterior air sacs Lungs Airflow Air tubes (parabronchi) in lung Airflow 1 mm Posterior air sacs Lungs 3 Air tubes (parabronchi) in lung Anterior air sacs 2 1 mm 4 1 1 First inhalation 3 Second inhalation 2 First exhalation 4 Second exhalation Figure 42.28 How a Mammal Breathes • Mammals ven?late their lungs by nega7ve pressure breathing, which pulls air into the lungs • Lung volume increases as the rib muscles and diaphragm contract • The 7dal volume is the volume of air inhaled with each breath 1 2 Rib cage expands. Air inhaled. Rib cage gets smaller. Air exhaled. Lung Diaphragm © 2011 Pearson Education, Inc. Control of Breathing in Humans • The maximum ?dal volume is the vital capacity • A[er exhala?on, a residual volume of air remains in the lungs © 2011 Pearson Education, Inc. • In humans, the main breathing control centers are in two regions of the brain, the medulla oblongata and the pons • The medulla regulates the rate and depth of breathing in response to pH changes in the cerebrospinal fluid • The medulla adjusts breathing rate and depth to match metabolic demands • The pons regulates the tempo © 2011 Pearson Education, Inc. 23 1/05/12 Figure 42.29 Homeostasis: Blood pH of about 7.4 • Sensors in the aorta and caro?d arteries monitor O2 and CO2 concentra?ons in the blood • These sensors exert secondary control over breathing CO2 level decreases. Response: Rib muscles and diaphragm increase rate and depth of ventilation. Stimulus: Rising level of CO2 in tissues lowers blood pH. Carotid arteries Aorta Sensor/control center: Cerebrospinal fluid Medulla oblongata © 2011 Pearson Education, Inc. Concept 42.7: Adapta?ons for gas exchange include pigments that bind and transport gases • The metabolic demands of many organisms require that the blood transport large quan??es of O2 and CO2 © 2011 Pearson Education, Inc. Figure 42.30a 2 Alveolar spaces O2 Alveolar capillaries 7 Pulmonary arteries 3 Pulmonary veins 6 Systemic veins 4 Systemic arteries Heart CO2 O2 Systemic capillaries Partial pressure (mm Hg) 1 Inhaled air 8 Exhaled air CO2 • Blood arriving in the lungs has a low par?al pressure of O2 and a high par?al pressure of CO2 rela?ve to air in the alveoli • In the alveoli, O2 diffuses into the blood and CO2 diffuses into the air • In ?ssue capillaries, par?al pressure gradients favor diffusion of O2 into the inters??al fluids and CO2 into the blood © 2011 Pearson Education, Inc. Figure 42.30 Alveolar epithelial cells Coordina?on of Circula?on and Gas Exchange 160 PO2 PCO2 Inhaled air 1 Inhaled air 8 Exhaled air Alveolar epithelial cells 2 Alveolar spaces CO2 O2 Alveolar capillaries Exhaled air 120 7 Pulmonary arteries 80 3 Pulmonary veins 40 0 1 2 3 4 5 6 7 8 6 Systemic veins 4 Systemic arteries Heart (b) Partial pressure of O2 and CO2 at different points in the circulatory system numbered in (a) 5 Body tissue (a) The path of respiratory gases in the circulatory system CO2 O2 Systemic capillaries 5 Body tissue (a) The path of respiratory gases in the circulatory system 24 1/05/12 Partial pressure (mm Hg) Figure 42.30b PO2 PCO 2 Inhaled air 160 Exhaled air 120 80 40 0 1 2 3 4 5 6 7 8 Respiratory Pigments • Respiratory pigments, proteins that transport oxygen, greatly increase the amount of oxygen that blood can carry • Arthropods and many molluscs have hemocyanin with copper as the oxygen-‐binding component • Most vertebrates and some invertebrates use hemoglobin • In vertebrates, hemoglobin is contained within erythrocytes (b) Partial pressure of O2 and CO2 at different points in the circulatory system numbered in (a) © 2011 Pearson Education, Inc. Figure 42.UN01 Hemoglobin • A single hemoglobin molecule can carry four molecules of O2, one molecule for each iron containing heme group • The hemoglobin dissocia?on curve shows that a small change in the par?al pressure of oxygen can result in a large change in delivery of O2 • CO2 produced during cellular respira?on lowers blood pH and decreases the affinity of hemoglobin for O2; this is called the Bohr shiM Iron Heme Hemoglobin © 2011 Pearson Education, Inc. O2 unloaded to tissues at rest 80 O2 unloaded to tissues during exercise 60 40 20 0 0 20 40 60 Tissues during Tissues at rest exercise PO2 (mm Hg) 80 100 Lungs (a) PO2 and hemoglobin dissociation at pH 7.4 100 pH 7.4 80 pH 7.2 Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 40 20 0 0 20 40 60 80 PO2 (mm Hg) 100 O2 saturation of hemoglobin (%) 100 Figure 42.31a O2 saturation of hemoglobin (%) O2 saturation of hemoglobin (%) Figure 42.31 100 O2 unloaded to tissues at rest 80 O2 unloaded to tissues during exercise 60 40 20 0 0 20 40 60 80 100 (b) pH and hemoglobin dissociation Tissues during Tissues at rest exercise PO2 (mm Hg) Lungs (a) PO2 and hemoglobin dissociation at pH 7.4 25 1/05/12 O2 saturation of hemoglobin (%) Figure 42.31b 100 Carbon Dioxide Transport pH 7.4 80 pH 7.2 Hemoglobin retains less O2 at lower pH (higher CO2 concentration) 60 40 • Hemoglobin also helps transport CO2 and assists in buffering the blood • CO2 from respiring cells diffuses into the blood and is transported either in blood plasma, bound to hemoglobin, or as bicarbonate ions (HCO3–) 20 0 Anima?on: O2 from Blood to Tissues Anima?on: CO2 from Tissues to Blood 0 20 40 60 80 100 Anima?on: CO2 from Blood to Lungs PO2 (mm Hg) Anima?on: O2 from Lungs to Blood (b) pH and hemoglobin dissociation © 2011 Pearson Education, Inc. Figure 42.32 Figure 42.32a Body tissue Body tissue CO2 transport from tissues CO2 produced CO2 produced Interstitial CO2 fluid Plasma CO2 within capillary Capillary wall CO2 transport from tissues Interstitial CO2 fluid CO2 H 2O Red blood cell H2CO3 Hb Carbonic acid HCO3- + Bicarbonate HCO3- HCO3 H2CO3 Plasma CO2 within capillary Capillary wall CO2 To lungs H 2O CO2 transport to lungs - HCO3- + Hemoglobin (Hb) picks up CO2 and H+. H+ Red blood cell H+ Hb Hemoglobin releases CO2 and H+. H2CO3 Hb Carbonic acid HCO3- + Bicarbonate H 2O CO2 Hemoglobin (Hb) picks up CO2 and H+. H+ CO2 HCO3- CO2 To lungs CO2 Alveolar space in lung Figure 42.32b To lungs CO2 transport to lungs HCO3HCO3- + H2CO3 H+ Hb Hemoglobin releases CO2 and H+. H 2O CO2 CO2 Respiratory Adapta?ons of Diving Mammals • Diving mammals have evolu?onary adapta?ons that allow them to perform extraordinary feats – For example, Weddell seals in Antarc?ca can remain underwater for 20 minutes to an hour – For example, elephant seals can dive to 1,500 m and remain underwater for 2 hours • These animals have a high blood to body volume ra?o CO2 CO2 Alveolar space in lung © 2011 Pearson Education, Inc. 26 1/05/12 Figure 42.UN02 Inhaled air Exhaled air Alveolar epithelial cells • Deep-‐diving air breathers stockpile O2 and deplete it slowly • Diving mammals can store oxygen in their muscles in myoglobin proteins • Diving mammals also conserve oxygen by Alveolar spaces CO2 O2 Alveolar capillaries Pulmonary arteries Pulmonary veins Systemic veins – Changing their buoyancy to glide passively – Decreasing blood supply to muscles – Deriving ATP in muscles from fermenta?on once oxygen is depleted Systemic arteries Heart CO2 O2 Systemic capillaries Body tissue © 2011 Pearson Education, Inc. Figure 42.UN04 O2 saturation of hemoglobin (%) Figure 42.UN03 100 80 60 Fetus Mother 40 20 0 0 20 40 60 80 100 PO2 (mm Hg) 27