Lecture 2-3 Chapter 42 Circulation and Gas Exchange

Transcription

1 General Biology II Lecture 2-3 Chapter 42 Circulation and Gas Exchange Before the class What is needed for trading with the environment? What is circulation system? How many types? What is the structure of our heart? How it works? What is the structure of blood vessels? What is the relationship between blood pressure and health? What is the components of blood? How oxygen is carried by blood? General Biology lectured by Han-Jia Lin 2 The feathery gills projecting from a salmon An example e of a specialized ed exchange system found in animals Outlines Part I Circulatory systems reflect phylogeny Double circulation in mammals Part 2 Physical principles govern blood circulation Blood is a connective tissue Part 3 Gas exchange Breathing ventilates the lungs Respiration ato pg pigments General Biology lectured by Han-Jia Lin 3 General Biology lectured by Han-Jia Lin 4

2 Concept 42.1 Circulatory systems link exchange surfaces with cells throughout the body Diffusion Time of diffusion is proportional to the square of the distance Most complex animals have internal transport systems circulate fluid, providing a lifeline between the aqueous environment of living cells and the exchange organs, such as lungs. General Biology lectured by Han-Jia Lin 5 Invertebrate Circulation The wide range of invertebrate body size and form Is paralleled by a great diversity in circulatory systems Simple animals, such as cnidarians ( ) Have a body wall only two cells thick that encloses a gastrovascular cavity The gastrovascular cavity Functions in both digestion and distribution of substances throughout the body General Biology lectured by Han-Jia Lin 6 Gastrovascular Cavities Open and Closed Circulatory Systems Circular canal Mouth Radial canals 5 cm (a) The moon jelly Aurelia, a cnidarian Gastrovascular cavity Mouth Pharynx 2mm (b) The planarian Dugesia, a flatworm More complex animals a Have one of two types of circulatory systems: open or closed Both of these types of systems have three basic components A circulatory fluid (blood) A set of tubes (blood vessels) A muscular pump (the heart) General Biology lectured by Han-Jia Lin 7 General Biology lectured by Han-Jia Lin 8

3 Open circulatory system In insects, other arthropods, and most molluscs Blood bathes the organs directly in an open circulatory system 3 components: Hemolymph, vessel, heart Body movements that squeeze the sinuses Help circulate the hemolymph Anterior vessel Lateral vessels Heart Hemolymph in sinuses surrounding ograns Ostia Closed circulatory system Blood is confined to vessels and is distinct from the interstitial fluid ( ) Are more efficient at transporting circulatory fluids to tissues and cells Heart Interstitial fluid Dorsal vessel (main heart) Small branch vessels in each organ Figure 42.3a Tubular heart (a) An open circulatory system General Biology lectured by Han-Jia Lin 9 Auxiliary hearts Ventral vessels General Biology lectured by Han-Jia Lin Figure 42.3b (b) A closed circulatory system 10 Survey of Vertebrate Circulation Humans and other vertebrates have a closed circulatory system Often called the cardiovascular system ( ) Blood flows in a closed cardiovascular system Consisting of blood vessels and a two- to fourchambered heart Heart and vessels Heart divides into Atria (atrium) and ventricle(s) Blood returning to the atria and pumping out from ventricles Arteries carry blood to capillaries The sites of chemical exchange between the blood and interstitial fluid Veins Return blood from capillaries to the heart Atria ventricle arteries capillaries veins General Biology lectured by Han-Jia Lin 11 General Biology lectured by Han-Jia Lin 12

4 More about blood vessels Arteries: Aorta, arterioles Capillary beds Vein: Vena cava, venules Arteries and veins are distinguished by the direction, not by the characteristics of the blood they contain. Exception: hepatic vein Fishes A fish heart has two main chambers One ventricle and one atrium Blood pumped from the ventricle Travels to the gills, where it picks up O 2 and disposes of CO 2 Blood must pass through two capillary bed during each circuit, that make the blood flows very slow in systemic circulation. General Biology lectured by Han-Jia Lin 13 General Biology lectured by Han-Jia Lin 14 Figure 42.4a (a) Single circulation Amphibians Artery Heart: Atrium (A) Ventricle (V) Vein Key Oxygen-rich blood Oxygen-poor blood Gill capillaries Body capillaries General Biology lectured by Han-Jia Lin 15 Frogs and other amphibians Have a three-chambered heart, with two atria and one ventricle Double circulation (pulmocutaneous and systemicstemic circuit) it) The blood is pumped p a second time! The ventricle pumps blood into a forked artery That splits the ventricle s output into the pulmocutaneous circuit and the systemic circuit General Biology lectured by Han-Jia Lin 16

5 Figure 42.5a Amphibians Reptiles (Except Birds) Pulmocutaneous circuit Lung and skin capillaries Atrium Atrium (A) (A) Right Left Ventricle (V) Systemic circuit Systemic capillaries Key Oxygen-rich blood Oxygen-poor blood Reptiles have double circulation With a pulmonary circuit (lungs) and a systemic circuit Turtles, snakes, and lizards Have a three-chambered heart Partially closed septum More efficient! General Biology lectured by Han-Jia Lin 17 General Biology lectured by Han-Jia Lin 18 Figure 42.5b Reptiles (Except Birds) Right systemic aorta Atrium (A) Ventricle Right (V) Pulmonary circuit A V Left Systemic circuit Lung capillaries Left systemic aorta Incomplete septum Systemic capillaries Key Oxygen-rich blood Oxygen-poor blood Mammals and Birds In all mammals and birds The ventricle is completely divided into separate right and left chambers The left side of the heart pumps and receives only oxygen-rich blood While the right side receives and pumps only oxygen-poor blood Endothermic animal (10X more energy consumption, 10X more efficient in transport system) General Biology lectured by Han-Jia Lin 19 General Biology lectured by Han-Jia Lin 20

6 Figure 42.5c Mammals and Birds Concept 42.2 Pulmonary circuit Lung capillaries Coordinated d cycles of heart contraction ti drive double circulation in mammals Atrium (A) Ventricle (V) A V Right Left Systemic circuit Systemic capillaries Key Oxygen-rich blood Oxygen-poor blood The structure and function of the human circulatory system can serve as a model Heart valves Dictate a one-way flow of blood through the heart General Biology lectured by Han-Jia Lin 21 General Biology lectured by Han-Jia Lin 22 Blood flow 1. Blood begins its flow With the right ventricle pumping blood to the lungs 2. In the lungs The blood loads O 2 and unloads CO 2 3. Oxygen-rich blood from the lungs Enters the heart at the left atrium and is pumped to the body tissues by the left ventricle Blood returns to the heart throughh the right atrium General Biology lectured by Han-Jia Lin 23 The mammalian cardiovascular system Anterior vena cava Capillaries of right lung Pulmonary vein Pulmonary artery 3 Right atrium Right ventricle Posterior vena cava Aorta Capillaries of head and forelimbs Left atrium Left ventricle Aorta Pulmonary artery 3 Capillaries of abdominal organs and hind limbs Capillaries of left lung Pulmonary vein Figure 42.6 General Biology lectured by Han-Jia Lin 24

7 The Mammalian Heart: A Closer Look Atria: thin walls, collection chamber Ventricles: thick walls (especially left ventricle), pump p out blood Figure 42.6 Pulmonary artery Anterior vena cava Right atrium Pulmonary veins Semilunar valve Atrioventricular valve Posterior vena cava Right ventricle Left ventricle Aorta Pulmonary artery Left atrium Semilunar valve Pulmonary veins Atrioventricular valve General Biology lectured by Han-Jia Lin 25 Cardiac cycle The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle Systole: The contraction, or pumping, phase of the cycle Diastole: The relaxation, or filling, phase of the cycle Heart rate, also called the pulse, is the number of beats per minute. The cardiac output is the volume of blood pumped into the systemic circulation per minute Cardiac output (~5.25 L) = heart rate (~70) x stroke volume (~75 ml) General Biology lectured by Han-Jia Lin 26 The cardiac valves 4 Valves, made of connective tissue Prevent backflow Keep blood moving 1 Atrial and ventricular diastole Atrioventricle valve (AV) Semilunar valve (SV) 0.1 sec Heart sounds are caused by the closing 0.4 sec of the valves. lub-dup sound and heart murmur 2 Atrial systole and ventricular diastole 0.3 sec 3 Ventricular systole and atrial diastole General Biology lectured by Han-Jia Lin 27 Maintaining the Heart s Rhythmic Beat Some cardiac muscle cells are self-excitable Meaning they contract without any signal from the nervous system A region of the heart called the sinoatrial (SA) node, or pacemaker Sets the rate and timing at which all cardiac muscle cells contract 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 General Biology lectured by Han-Jia Lin 28

8 Electrocardiogram The impulses are conducted through body fluids to the skin and can be recorded as an electrocardiogram (ECG or EKG) 1 Pacemaker generates 2 Signals are delayed d 3 Signals pass 4 Signals spread wave of signals at AV node. to heart apex. Throughout to contract. ventricles. SA node (pacemaker) ECG AV node Bundle branches Heart apex Purkinje fibers Figure 42.9 General Biology lectured by Han-Jia Lin 29 Pacemaker is influenced by. The pacemaker is regulated by two portions of the nervous system: the sympathetic ( ) and parasympathetic divisions The sympathetic division speeds up the pacemaker The parasympathetic ( ) division slows down the pacemaker The pacemaker is also regulated by hormones (epinephrine) and temperature (1 o C increased, 10 more beats) Exercise General Biology lectured by Han-Jia Lin 30 2 adrenoreceptor ( ) Beta-adrenergic blocking agents ( ) Beta-adrenergic agonist ( ) ( ) ( ) End of Part 1 Gastrovascular Cavities Open circulation system Closed circulation system What are the three component in circulation system? Single circulation vs double circulation! Blood flow in human! Structure of human heart! How human heart beats! General Biology lectured by Han-Jia Lin 31 General Biology lectured by Han-Jia Lin 32

9 Concept 42.3 Blood Vessel Structure and Function Patterns of blood pressure e and flow reflect ec the structure and arrangement of blood vessels The same physical principles i that t govern the movement of water in plumbing systems Also influence the functioning of animal circulatory systems The infrastructure of the circulatory system Is its network of blood vessels All blood vessels Are built of similar tissues Have three similar layers Outside: connective tissue and elastic fibers Middle layer: smooth muscle and elastic fibers Lining: endothelium Figure Artery Endothelium Artery Endothelium Vein 100 µm Endothelium Smooth muscle Capillary Smooth muscle Connective Connective tissue tissue Arteriole Venule Basement membrane Vein Valve General Biology lectured by Han-Jia Lin 33 General Biology lectured by Han-Jia Lin 34 Structural differences in blood vessels Correlate e with their different e functions Arteries have thicker walls To accommodate the high pressure of blood pumped p from the heart Capillaries Very thin walls (endothelium and basement membrane) Facilitates the exchange of substrates Veins In the thinner-walled veins Blood flows back to the heart mainly as a result of muscle action Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) General Biology lectured by Han-Jia Lin 35 General Biology lectured by Han-Jia Lin 36

10 Blood Flow Velocity Law of continuity Physical laws governing the movement of fluids through pipes influence blood flow and blood pressure The velocity of blood flow varies in the circulatory system Blood flow in capillaries is necessarily slow for exchange of materials Velocity (cm/s sec) Area (cm 2 ) 5,000 4,000 3,000 2,000 1, And is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area Press sure (mm Hg) Diastolic pressure Systolic pressur e Aorta Arteries Arterioles Capillaries Venules Veins Ven nae cavae General Biology lectured by Han-Jia Lin 37 General Biology lectured by Han-Jia Lin 38 Blood Pressure Blood flows from areas of higher pressure to areas of lower pressure Blood pressure is the pressure thatt blood exerts against the wall of a vessel In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost 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 General Biology lectured by Han-Jia Lin 39 General Biology lectured by Han-Jia Lin 40

11 Regulation of Blood Pressure Blood pressure is determined by cardiac output and peripheral resistance due to constriction of arterioles Maintain adequate blood flow as the body s demands change Vasoconstriction is the contraction of smooth muscle in arteriole walls (increases blood pressure) Vasodilation is the relaxation of smooth muscles in the arterioles (blood pressure fall) Nitric i oxide is a major inducer of vasodilation The peptide endothelin is an important inducer of vasoconstriction ti ti General Biology lectured by Han-Jia Lin 41 Measurement of blood pressure Blood pressure reading: 120/ Artery closed 120 Sounds audible in stethoscope th 120 Sounds stop General Biology lectured by Han-Jia Lin Factors affect blood pressure Blood pressure is determined by cardiac output peripheral resistance due to variable constriction of the arterioles Arteriole wall muscles control the blood flow rate and pressure by the action of Nerve impulses Hormones Stress (physical or emotional) General Biology lectured by Han-Jia Lin 43 Gravity and blood pressure 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 Fainting is caused by inadequate blood flow to the head Push blood above the level l of heart Human: 0.35 m, extra 27 mm Hg of pressure Giraffe: 2.5 m, extra 190 mm Hg of pressure General Biology lectured by Han-Jia Lin 44

12 Would a giraffe has a stroke lowering its head? Giraffe has a normal systolic pressure over 250 mm Hg Long neck dinosaurs:10-meter neck, 760 mm Hg systolic pressure? When it lowering its head Cause blood to flow downhill 2 meters from the heart Adding an extra 150 mm Hg of blood pressure to the brain Check valves, sinuses and feedback mechanism reduce cardiac output! General Biology lectured by Han-Jia Lin 45 Capillary Function Capillaries in major organs are usually filled to capacity But in many other sites, the blood supply varies (5-10% whole body) Blood flow is regulated by Arteriole nerve impulses, hormones, and other chemicals Precapillary sphincters Thoroughfare channel Capillaries Arteriole Venule (a) Sphincters relaxed Contraction of the smooth muscle layer in the wall of an arteriole Precapillary sphincters control the flow of blood between arterioles and venules Arteriole Venule (b) Sphincters contracted General Biology lectured by Han-Jia Lin 46 Fluid exchange across endothelial wall The difference between blood pressure and osmotic pressure drives fluids out of capillaries at the arteriole end and into capillaries at the venule end INTERSTITIAL Net fluid movement out Body cell Most blood FLUID proteins and Blood 80% water pressure recovery all blood cells Osmotic are too large pressure to pass through h the endothelium Arterial end Di ti f bl d fl Venous end of capillary Direction of blood flow of capillary General Biology lectured by Han-Jia Lin 47 Fluid Return by the Lymphatic System The lymphatic system Returns fluid (~4 liter/day) to the body from the capillary beds Lymph, the fluid insideid lymphatic system Lymph nodes Filtering the lymph Attacking viruses and bacteria by WBC Fluid reenters the circulation Directly at the venous end of the capillary bed and indirectly through the lymphatic system Edema is swelling caused by disruptions in the flow of lymph General Biology lectured by Han-Jia Lin 48

13 Concept 42.4 Blood components function in exchange, transport and defense Blood in the circulatory systems of vertebrates t Is a specialized connective tissue 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 General Biology lectured by Han-Jia Lin 49 Plasma Blood plasma is about 90% water Among its many solutes are Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes plasma proteins Albumin, which influence blood ph, osmotic pressure, and viscosity, lipid transport Various types of plasma proteins: function in immunity (immunoglobulin), and blood clotting (fibrinogen) Substances to transport: nutrients, wastes, gas, hormone General Biology lectured by Han-Jia Lin 50 Figure 42.17a Water Ions (blood electrolytes) Sodium Potassium Calcium Magnesium Chloride Bicarbonate Constituent Plasma proteins Albumin Fibrinogen Immunoglobulins (antibodies) Plasma 55% Solvent for carrying other substances Major functions Osmotic balance, ph buffering, and regulation of membrane permeablity Osmotic balance, ph buffering Clotting Defense Separated blood elements Cellular Elements Suspended in blood plasma are two classes of cells Red blood cells, which transport oxygen White blood cells, which function in defense A third cellular element, platelets Are fragments of cells that are involved in clotting Substances transported by blood Nutrients Respiratory gases Waste products Hormones General Biology lectured by Han-Jia Lin 51 General Biology lectured by Han-Jia Lin 52

14 Figure 42.17b Separated blood elements Cell type Cellular elements 45% Number per L (mm 3 ) of blood Leukocytes (white blood cells) 5,000 10,000 Basophils Neutrophils Eosinophils Lymphocytes Monocytes Functions Defense and immunity Platelets 250, ,000 Blood clotting Erythrocytes (red blood cells) 5 6 million Transport of O 2 and some CO 2 Erythrocytes Red blood cells, or erythrocytes Are by far the most numerous blood cells Transport oxygen throughout the body Lack nucleus and mitochondria Generate ATP exclusively by anaerobic metabolism An erythrocyte y contains about 250 million hemoglobulin, is capable of transporting a billion oxygen molecules. General Biology lectured by Han-Jia Lin 53 General Biology lectured by Han-Jia Lin 54 Leukocytes The blood contains five major types of white blood cells, or leukocytes Monocytes, neutrophils, basophils, eosinophils, and lymphocytes Phagocytizing bacteria and debris: monocytes, neutrophils Producing antibodies: B lymphocytes WBC spend most of their time outside the circulatory system Interstitial fluid, lymphatic system General Biology lectured by Han-Jia Lin 55 Platelets and blood clotting Platelets function in blood clotting When the endothelium of a blood vessel is damaged The clotting mechanism begins (clotting factor released from platelets) l t Fibrinogen becomes active form (fibrin) Clotting problems Hemophilia Thrombus General Biology lectured by Han-Jia Lin 56

15 Converts fibrinogen to fibrin, forming a clot A cascade of complex reactions Collagen fibers Platelet Platelet plug Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Prothrombin Enzymatic cascade Fibrinogen Thrombin Fibrin Fibrin clot Red blood cell Fibrin i clot formation General Biology lectured by Han-Jia Lin 57 5 m Stem Cells and the Replacement of Cellular Elements The cellular elements of blood wear out And are replaced constantly throughout a person s life Erythrocytes, leukocytes, and platelets all develop from a common source A single population p of cells called pluripotent p stem cells in the red marrow of bones Hormone controls the stem cell differentiation (Erythropoietin, EPO, from kidney, stimulates production of RBC) General Biology lectured by Han-Jia Lin 58 Pluripotent stem cells B cells T cells Lymphocytes Lymphoid stem cells Stem cells (in bone marrow) Myeloid stem cells Erythrocytes Neutrophils Basophils Cardiovascular Disease Cardiovascular diseases Are disorders of the heart and the blood vessels Account for more than half the deaths in the United States Nongenetic factors: smoking, lack of exercise, rich cholesterol blood. Monocytes Platelets Eosinophils General Biology lectured by Han-Jia Lin 59 General Biology lectured by Han-Jia Lin 60

16 Risk Factors and Treatment of Cardiovascular Disease Low-density lipoprotein (LDL) delivers cholesterol to cells for membrane production High-density lipoprotein (HDL) scavenges cholesterol for return to the liver Risk for heart disease increases with a high LDL to HDL ratio The proportion of LDL relative to HDL can be decreased by exercise, not smoking, and avoiding foods with trans fats Drugs called statins reduce LDL levels and risk of heart attacks Figure RESULTS iduals nt of indiv Perce Average 105 mg/dl iduals nt of indiv Perce Plasma LDL cholesterol (mg/dl) Individuals with two functional copies of PCSK9 gene (control group) 20 Average 63 mg/dl Plasma LDL cholesterol (mg/dl) Individuals with an inactivating mutation in one copy of PCSK9 gene General Biology lectured by Han-Jia Lin 61 General Biology lectured by Han-Jia Lin 62 Inflammation is also a factor in cardiovascular disease Inflammation plays a role in atherosclerosis and thrombus formation Aspirin i inhibits inflammation and reduces the risk of heart attacks and stroke Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke Hypertension can be reduced by dietary changes, exercise, and/or medication General Biology lectured by Han-Jia Lin 63 Atherosclerosis ( ) One type of cardiovascular disease caused by the buildup of cholesterol within arteries Encourage the adhesion of platelets, triggering the clotting process Connective tissue Smooth muscle Endothelium Plaque (a) Normal artery 50 µm (b) Partly clogged artery 250 µm General Biology lectured by Han-Jia Lin 64

17 Figure Lumen of artery Endothelium 1 Smooth muscle 2 Plaque Hypertension, or high blood pressure LDL 3 Foam cell Macrophage Plaque rupture Extracellular matrix 4 T lymphocyte Smooth muscle cell Fibrous cap Cholesterol General Biology lectured by Han-Jia Lin 65 Promotes atherosclerosis and increases the risk of heart attack and stroke A heart attack Is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries Coronary arteries supply oxygen-rich blood to the heart muscle Angina pectoris is caused by partial blockage of the coronary arteries and results in chest pains Astroke Is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head General Biology lectured by Han-Jia Lin 66 End of Part 2 Structures of vessels! Blood pressure! Components of blood! Cardiovascular disease General Biology lectured by Han-Jia Lin 67 Concept 42.5 Gas exchange occurs across specialized respiratory surfaces Occurs across specialized respiratory surfaces Supplies oxygen for cellular respiration and disposes of carbon dioxide Respiratory medium (air of water) Organismal level Cellular level Energy-rich molecules from food O 2 CO 2 Respiratory Animals require large, surface moist respiratory surfaces for the adequate diffusion of respiratory gases betweeneen their cells and the ATP respiratory medium, either air or water Circulatory system Cellular respiration General Biology lectured by Han-Jia Lin 68

18 Gills in Aquatic Animals Gills are outfoldings ofthe body surface Specialized for gas exchange In some invertebrates (a) Sea star. The gills of a sea star are simple tubular projections of the skin. The hollow core of each gill is an extension of the coelom (body cavity). Gas exchange occurs by diffusion across the gill surfaces, and fluid in the coelom circulates in and out of the gills, aiding gas transport. The surfaces of a sea star s tube feet also function in gas exchange. The gills have a simple shape and Figure are distributed over much of the body Coelom Tube foot Gills Gills are restricted to a local body region Gills Gills Parapodium Tube foot (functions as gill) (a) Marine worm (b) Crayfish (c) Sea star Coelom General Biology lectured by Han-Jia Lin 69 General Biology lectured by Han-Jia Lin 70 Gills of fish, effective gas exchanger The effectiveness of gas exchange in some gills, including those of fishes Is increased by ventilation and countercurrent flow of blood and water Gill arch Water flow Operculum Gill arch Gill filaments Blood vessel Oxygen-rich blood Oxygen-poor blood Lamella O Blood flow 2 Water flow through capillaries over lamellae in lamellae showing % O 2 showing % O 2 Countercurrent exchange General Biology lectured by Han-Jia Lin 71 Tracheal Systems in Insects The tracheal system of insects Consists of tiny branching tubes (tracheae) that penetrate the body Air sacs Tracheae Spiracle Body cell Tracheole Tracheoles (a) The respiratory system of an insect consists of branched internal tubes that deliver air directly to body cells. Rings of chitin reinforce (b) This micrograph shows cross the largest tubes, called tracheae, keeping them from collapsing. sections of tracheoles in a tiny Enlarged portions of tracheae form air sacs near organs that require piece of insect flight muscle (TEM). a large supply of oxygen. Air enters the tracheae through openings Each of the numerous mitochondria called spiracles on the insect s body surface and passes into smaller in the muscle cells lies within about tubes called tracheoles. The tracheoles are closed and contain fluid 5 µm of a tracheole. (blue-gray). When the animal is active and is using more O 2, most of the fluid is withdrawn into the body. This increases the surface area of air in contact with cells. Air sac Trachea Air Body wall Myofibrils Mitochondria 2.5 µm General Biology lectured by Han-Jia Lin 72

19 Lungs Lung, Tracheal versus Gill Air is lighter and diffuse faster than water Respiratory surface must keep moist (problem of losing water) Lung versus Tracheal Lung are restricted to one location Spiders, land snails, and most terrestrial vertebrates Have internal lungs Amphibian have relatively small lung General Biology lectured by Han-Jia Lin 73 Mammalian Respiratory Systems: A Closer Look A system of branching ducts Conveys air to the lungs Pharynx Larynx Esophagus Trachea Right lung Bronchus Bronchiole Diaphragm Heart Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Left lung 50 µm SEM µm 50 Branch from the pulmonary artery (oxygen-poor blood) Colorized SEM Alveoli Figure General Biology lectured by Han-Jia Lin 74 Figure Alveoli lack cilia and are susceptible to contamination Secretions called surfactants coat the surface of the alveoli Preterm babies lack surfactant and are vulnerable to respiratory distress syndrome; treatment is provided by artificial surfactants RESULTS Surf face tens sion (dy nes/cm) RDS deaths Deaths from other causes ,600 2,400 3,200 4,000 Body mass of infant (g) General Biology lectured by Han-Jia Lin 75 General Biology lectured by Han-Jia Lin 76

20 Concept 42.6 Breathing ventilates the lungs The process that ventilates the lungs is breathing The alternate inhalation and exhalation of air An amphibian such as a frog Ventilates its lungs by positive pressure breathing, which forces air down the trachea How a Mammal Breathes Mammals ventilate their lungs By negative pressure breathing, which pulls air into the lungs Rib cage expands as rib muscles contract Air inhaled Lung Diaphragm Rib cage gets smaller as rib muscles relax Air exhaled INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) General Biology lectured by Han-Jia Lin 77 General Biology lectured by Han-Jia Lin 78 Lung volume Tidal volume: the volume of air in each breath (inhales and exhales) 500 ml in resting human Tideal volume increases as the rib muscles and diaphragm contract Vital capacity: the maximum tidal volume during forced breathing 20-year-old female ~3.4 L; male ~4.8 L Muscles of the neck, back, and chest further raising the rib cage even more General Biology lectured by Han-Jia Lin 79 Residual volume of lung The remaining air in the lung even you forcefully exhale Residual volume increase Reasons: age, disease (emphysema). Cost: vital capacity Gas is not completely l exchanged in lung Residual CO 2 is critical for regulating the breathing rate General Biology lectured by Han-Jia Lin 80

21 How a Bird Breathes Birds have eight or nine air sacs that function as bellows that keep air flowing through the lungs Air passes through h the lungs in one direction only Every exhalation completely renews the air in the lungs Adapt high altitude Anterior air sacs Posterior air sacs Lungs 1 mm Airflow Posterior Lungs Anterior air sacs 3 air sacs Air tubes (parabronchi) in lung 2 4 General Biology lectured by Han-Jia Lin First inhalation 3 Second inhalation 2 First exhalation 4 Second exhalation General Biology lectured by Han-Jia Lin 82 Control of Breathing in Humans The main breathing control centers Are located in two regions of the brain, the medulla oblongata and the pons ( ) The medulla adjusts breathing rate and depth to match metabolic demands The pons regulates the tempo The sensors Medulla regulate the rate and depth of breathing in response to ph changes in the cerebrospinal fluid ( ) O 2 sensors in the aorta and carotid arteries. These sensors exert secondary control over breathing General Biology lectured by Han-Jia Lin 83 Automatic control of breathing Breathing control is coordinated with control of the cardiovascular system Homeostasis: Blood ph of about 7.4 CO 2 level decreases. Stimulus: Rising level of Response: CO 2 in tissues Rib muscles lowers blood ph. and diaphragm increase rate and depth of ventilation. Sensor/control center: Cerebrospinal fluid Carotid arteries Aorta Medulla oblongata General Biology lectured by Han-Jia Lin 84

22 Concept 42.7 Adaptations for gas exchange include pigments that bind and transport gases The metabolic demands of many organisms Require that the blood transport large titi f O dco quantities of O 2 and CO 2 A gas dissolves in the water is proportional o to.. Partial pressure in the air Solubility in water The Role of Partial Pressure Gradients Gases diffuse down pressure gradients Diffusion of a gas Depends on differences in a quantity called partial pressure A gas always diffuses from a region of higher partial pressure To a region of lower partial pressure In the lungs and in the tissues O 2 and CO 2 diffuse from where their partial pressures are higher to where they are lower General Biology lectured by Han-Jia Lin 85 General Biology lectured by Han-Jia Lin 86 Loading and unloading of respiratory gases 8 Exhaled air 1 Inhaled air 7 6 Alveolar epithelial cells Pulmonary arteries Systemic veins Inhaled air P O2 P CO2 2 Alveolar 160 spaces Exhaled CO 2 O 2 Heart Alveolar capillaries 3 4 Pulmonary veins Systemic arteries Systemic CO 2 O 2 capillaries 5 Body tissue (a) The path of respiratory gases in the circulatory system (mm Hg) al pressure ( Partia (b) Partial pressure of O 2 and CO 2 at different points in the circulatory system numbered in (a) air General Biology lectured by Han-Jia Lin 87 Respiratory Pigments Arthropods and many molluscs have hemocyanin with copper as the oxygenbinding component Most vertebrates and some invertebrates use hemoglobin Greatly increase the amount of oxygen that blood can carry 4.5 ml O 2 dissolved in 1 L blood without respiratory pigment 200 ml O 2 carried in 1L blood in mammalian blood General Biology lectured by Han-Jia Lin 88

23 Oxygen Transport The respiratory pigment of almost all vertebrates Is the protein hemoglobin, contained in the erythrocytes Hemoglobin must reversibly bind O 2 2, loading O 2 in the lungs and unloading it in other parts of the body Heme group Iron atom O 2 loaded in lungs O 2 O 2 unloaded In tissues O 2 Loading and unloading of O 2 Depend on cooperation between the subunits of the hemoglobin molecule The binding of O 2 to one subunit induces the other subunits to bind O 2 with more affinity Cooperative O 2 binding and release Is evident in the dissociation curve for hemoglobin AdropinpH(Bohr ph shift) Lowers the affinity of hemoglobin for O 2 Polypeptide chain General Biology lectured by Han-Jia Lin 89 General Biology lectured by Han-Jia Lin 90 Dissociation curves for hemoglobin Carbon Dioxide Transport (%) tion of hem moglobin O 2 saturat O 2 unloaded to tissues 80 at rest O 2 unloaded to tissues during exercise (%) tion of hem moglobin O 2 saturat Tissues during Tissues exercise at rest P O (mm Hg) 2 Lungs ph 7.4 ph 7.2 Hemoglobin retains less O 2 at lower ph (higher CO 2 concentration) ti P O (mm Hg) 2 (b) ph and hemoglobin dissociation Hemoglobin also helps transportt CO 2 And assists in buffering Carbon from respiring cells Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs (a) P O and hemoglobin dissociation at ph General Biology lectured by Han-Jia Lin 91 General Biology lectured by Han-Jia Lin 92

24 Carbon dioxide transport in the blood Body tissue CO 2 produced Interstitial CO fluid 2 CO 2 transport from tissues HCO 3 HCO 3 To lungs H + CO 2 transport to lungs Elite Animal Athletes Migratory and diving mammals Have evolutionary adaptations that allow them to perform extraordinary feats Plasma within capillary CO 2 H 2 O Red blood cell CO 2 Capillary wall Hemoglobin (Hb) H 2 CO 3 Hb picks up Carbonic CO 2 and H +. acid H 2 CO 3 H2 O CO 2 CO 2 Hb Hemoglobin releases CO 2 and H +. HCO 3 Bicarbonate H + CO 2 HCO 3 CO To lungs 2 Alveolar space in lung General Biology lectured by Han-Jia Lin 93 Pronghorn ( ) General Biology lectured by Han-Jia Lin 94 The Ultimate Endurance Runner Diving Mammals Pronghorn sprint 11 km in 10 mins. The extreme O 2 consumption of the pronghorn 5 times to goat Larger surface area in the lungs, more cardiac output, higher muscle mass, higher density of mitochondria, higher body temperature Deep-diving i air breathers Stockpile O 2 and deplete it slowly Less O 2 in lung, most in blood More blood volume Huge spleen High concentrate of myoglobin in muscles General Biology lectured by Han-Jia Lin 95 General Biology lectured by Han-Jia Lin 96

25 End of Part 3 Gas exchangers: gill, trachea and lung How reptiles, birds and mammals breath? How to control breathing? What are respiratory pigments, how they work? How animal athletes improve their abilities in sports? End of the class The key concepts which you have learned in Part 1 Part 2 Part 3 General Biology lectured by Han-Jia Lin 97 General Biology lectured by Han-Jia Lin 98