Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Living World Fifth Edition George B. Johnson Jonathan B. Losos Chapter 29 Circulation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 29.1 Open and Closed Circulatory Systems • Among the unicellular protists, oxygen and nutrients are obtained directly by simple diffusion • Cnidarians and flatworms have cells that are directly exposed to either the external environment or to a body cavity that functions in digestion, the gastrovascular cavity 29.1 Open and Closed Circulatory Systems • Large animals have tissues that are several cell layers thick so that many cells are too far away for surface exchange instead, oxygen and nutrients are transported from the environment and digestive cavity to the body cells by an internal fluid within a circulatory system • there are two main types of circulatory systems – open circulatory system – closed circulatory system 29.1 Open and Closed Circulatory Systems • In open circulatory systems, there is no distinction between the circulating fluid (blood) and the extracellular fluid of the body tissues (interstitial fluid or lymph) this fluid is called hemolymph insects have a muscular tube that serves as a heart to pump the hemolymph through a network of open-ended channels 29.1 Open and Closed Circulatory Systems • In a closed circulatory system, the circulating fluid (blood) is always enclosed within blood vessels that transport blood away from and back to a heart annelids and all vertebrates have a closed circulatory system as blood plasma passes through capillaries, the pressure of the blood forces some fluid out of the capillary walls • this fluid is called interstitial fluid – some of it will return to the blood but some becomes lymph and travels through the lymph vessels Figure 29.1 Three types of circulatory systems found in the animal kingdom 29.1 Open and Closed Circulatory Systems • The functions of the circulatory system can be divided into three areas transportation • substances essential for cellular functions are transported by the circulatory system regulation • the cardiovascular system participates in heat exchange, such as by countercurrent heat exchange protection • The circulatory system protects again injury and foreign microbes or toxins introduced into the body Figure 29.2 Countercurrent heat exchange 29.2 Architecture of the Vertebrate Circulatory System • The vertebrate circulatory system (also known as the cardiovascular system) is made up of three elements heart—a muscular pump that pushes blood through the body blood vessels—a network of tubes through which the blood moves blood—fluid that circulates through the vessels 29.2 Architecture of the Vertebrate Circulatory System • Blood moves through the body in cycle, from the heart, through a system of vessels heart veins venules arteries arterioles capillaries 29.2 Architecture of the Vertebrate Circulatory System • Although each capillary is very narrow, there are so many of them that the capillaries have the greatest total crosssectional area of any other type of blood vessel capillary beds can be opened or closed based on the physiological needs of the tissues • precapillary sphincters can contract or relax and affect whether blood flows into a capillary bed for exchange of gases and metabolites Figure 29.3 The capillary network connects arteries with veins 29.2 Architecture of the Vertebrate Circulatory System • An artery is more than a simple pipe it needs to be able to expand with the pressure caused by contraction of the heart for this reason, the layers of the arterial wall are elastic • Arterioles differ from arteries in that they are smaller in diameter and respond to nervous and hormonal stimulation they can constrict and limit blood flow during periods of stress or low temperature Figure 29.4 (a) The structure of blood vessels 29.2 Architecture of the Vertebrate Circulatory System • Capillaries are where oxygen and food molecules are transferred from the blood to the body’s cells capillaries are narrow and have thin walls for exchange almost all cells of the vertebrate body are no more than 100 micrometers from a capillary the blood pressure is actually far lower in the capillaries than in the arteries Capillary Structure Figure 29.4 (b) The structure of blood vessels Figure 29.5 Red blood cells within a capillary 29.2 Architecture of the Vertebrate Circulatory System • Veins are vessels that return blood to the heart the walls of veins are thinner because the blood pressure is not great veins have unidirectional valves that prevent the flow of blood backwards Structure of Veins Figure 29.4 (c) The structure of blood vessels Figure 29.6 Veins and arteries Figure 29.7 Flow of blood through veins 29.3 The Lymphatic System: Recovering Lost Fluid • The cardiovascular system is very leaky from capillary exchange, the body loses about 4 liters of fluid each day to collect and recycle this fluid, the body uses a second circulatory system called the lymphatic system • the lymphatic system is also a network of vessels filled with a fluid called lymph • ultimately the lymph reenters the bloodstream into veins in the neck Figure 29.8 The human lymphatic system Figure 29.9 Lymphatic capillaries reclaim fluid from interstitial fluid 29.3 The Lymphatic System: Recovering Lost Fluid • The lymphatic system has three important functions it returns proteins to circulation • if this protein remains in the tissues, it would cause swelling or edema it transports fats absorbed from the intestine it aids in the body’s defense • swellings along lymph vessels called lymph nodes where lymph-borne bacteria and dead blood cells are destroyed 29.4 Blood • Blood plasma is a complex solution of water with three kind of substances dissolved in it metabolites and wastes • for example—glucose, vitamins, hormones, etc. salts and ions • the chief plasma ions are sodium, chloride, and bicarbonate proteins • proteins help keep water in the plasma – serum albumin functions in maintaining osmotic balance • other plasma proteins include antibodies, globulins, and fibrinogen – fibrinogen is required for blood clotting Figure 29.10 Threads of fibrin 29.4 Blood • Nearly half the volume of blood is occupied by cells the three principal cell types are • erythrocytes (red blood cells) – hematocrit is the fraction of the total volume of the blood that is occupied by red blood cells – in humans, the hematocrit is usually about 45% • leukocytes (white blood cells) • platelets 29.4 Blood • Erythrocytes resemble flat disks with a central depression on both sides almost the entire interior is packed with hemoglobin, which carries oxygen because these cells have no nucleus they are short-lived and must be replaced by new cells synthesized in the bone marrow 29.4 Blood • leukocytes contain no hemoglobin and are essentially colorless there are several different kinds, all of which help defend the body against invading microorganisms and other foreign substances • Platelets are cell fragments, pinched from large cells in the bone marrow, called megakaryocytes, that play a key role in clotting Figure 29.11 Types of blood cells 29.5 Fish Circulation • The evolution of gills by fishes required a more efficient pump, a true chamber-pump heart the fish heart is essentially a tube with fours chambers arrayed one after another • the first two chambers are collecting chambers while the second two chambers are pumping chambers • the chambers contract in a peristaltic sequence • the blood that is pumped to the body is fully oxygenated because it passes through the gills first Figure 29.12 The heart and circulation of a fish 29.6 Amphibian and Reptile Circulation • The advent of lungs involved a major change in the pattern of circulation after blood is pumped by the heart to the lungs, it does not go directly to the tissues of the body but instead returns to the heart • pulmonary circulation goes to and from the heart and lungs • systemic circulation goes to and from the heart and the rest of the body 29.6 Amphibian and Reptile Circulation • The amphibian heart has structural features to prevent the mixing of deoxygenated and oxygenated blood the atrium is divided by a septum that separates the blood coming from the body and from the lungs some species of amphibians have folds in the ventricle that direct the flow of blood from the atria the conus arteriosus is branched Figure 29.13 The amphibian heart and circulation in reptiles 29.6 Amphibian and Reptile Circulation • Amphibians in water supplement the oxygenation of their blood by obtaining additional oxygen by diffusion across their skin this is called cutaneous respiration • The reptilian heart is additionally specialized by having a partial septum in the ventricle 29.7 Mammalian and Bird Circulation • mammals, birds, and crocodiles have a four-chambered heart with two complete pumping circuits this increased efficiency of the double circulation in mammals and birds may have been important in the evolution of endothermy • more efficient circulation is necessary to support the high metabolic rate required Figure 29.14 (a) The heart and circulation of mammals and birds 29.7 Mammalian and Bird Circulation • The contraction of the heart consists of a carefully orchestrated series of muscle contractions first the atria contract, followed by the ventricles • The sinoatrial (SA) node in the wall of the right atrium is the site where each heartbeat originates it is the pacemaker of the heart and determines the rhythm of the heart’s beating 29.7 Mammalian and Bird Circulation • Contraction of the atria is initiated by the SA node • The wave of depolarization does not immediately spread to the ventricles because it must pass first through the atrioventricular (AV) node this delays the signal for about 0.1 sec until the atria have finished contracting 29.7 Mammalian and Bird Circulation • The ventricles finally contract after the signal passes from the AV node to an atrioventricular bundle called the bundle of His • The bundle branches and divides into fastconducting Purkinje fibers which initiate the almost simultaneous contraction of the right and left ventricles • The electrical activity of the heart can be measured by a recording called an electrocardiogram (ECG or EKG) Figure 29.15 How the mammalian heart contracts 29.7 Mammalian and Bird Circulation • The simplest way to monitor heartbeat is to listen using a stethoscope “lub” is sound made by the closing of the bicuspid and tricuspid valves at the start of ventricular contraction “dub” is the sound made by the closing of the pulmonary and aortic valves at the end of ventricular contraction • A heart murmur is heard due to turbulence created by the valves not closing fully 29.7 Mammalian and Bird Circulation • Another way to examine the events of the heartbeat is to monitor the blood pressure a device called a sphygmomanometer is used to measure the blood pressure in the brachial artery of the arm diastolic pressure is the low pressure when the atria are filling systolic pressure is the high pressure associated with the ventricles contracting Figure 29.16 Measuring blood pressure 29.8 Cardiovascular Diseases • Cardiovascular diseases are the leading cause of death in the US heart attacks result from an insufficient supply blood reaching one or more parts of the heart • angina pectoris, or chest pains, may signal that the blood supply to the heart is inadequate strokes are caused by an interference with the blood supply to the brain 29.8 Cardiovascular Diseases • Atherosclerosis is an accumulation within the arteries that cause a reduction in blood flow • Arteriosclerosis is a hardening of the arteries when calcium is deposited in arterial walls because they are not elastic, the heart has to work harder Figure 29.17 The path to a heart attack 29.8 Cardiovascular Diseases • There are many possible treatments for blocked coronary arteries non-invasive • drugs, such as enzymes, that breakdown clots or anticoagulants that prevent clots from forming • nitroglycerin to cause blood vessels to dilate invasive • angioplasty/stent • coronary bypass • heart transplant Inquiry & Analysis • All mammals have the same size hearts relative to their body size. Do their hearts beat at the same rate? • What general statement can be made regarding the effect of body size on heart rate in mammals? Graph of the Effect of Body Size on Heart Rate in Mammals