1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 42 Circulation and Gas Exchange

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Mammalian Heart: A Closer Look A closer look at the mammalian heart provides a better understanding of how double circulation works Figure 42.6 Aorta Pulmonary veins Semilunar valve Atrioventricular valve Left ventricle Right ventricle Anterior vena cava Pulmonary artery Semilunar valve Atrioventricular valve Posterior vena cava Pulmonary veins Right atrium Pulmonary artery Left atrium

3. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The human heart Cone shaped organ located beneath the sternum and has a size of a clinched fist (a hand that is tightly closed). Surrounded by a sac with a two-layered wall. Comprised mostly of cardiac muscle tissue. The two atria have thin walls and function as collection chambers for blood returning to the heart, and pumping only the short distances to the ventricles The two ventricles have thick, powerful walls that pump blood to the organs. The left ventricle pumps blood to all the body organs. The heart chambers alternately; contract → pump blood or relax → fill with blood.

4. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The heart contracts and relaxes – In a rhythmic cycle called the cardiac cycle The contraction, or pumping, phase of the cycle – Is called systole The relaxation, or filling, phase of the cycle – Is called diastole The heart rate, also called the pulse – Is the number of beats per minute

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The cardiac cycle Figure 42.7 Semilunar valves closed AV valves open AV valves closed Semilunar valves open Atrial and ventricular diastole 1 Atrial systole; ventricular diastole 2 Ventricular systole; atrial diastole 3 0.1 sec 0.3 sec 0.4 sec

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The volume of blood per minute that the left ventricle pumps into the systemic circuit is called the cardiac output (5.25 liter per minute= the whole blood volume). The volume of pumped blood depends on; – Heart rate: The number of heart beats per minute. It is 60 beats in humans but also depends on the individual’s activity. Elephants hearts beat 25 per minute while shrew ( one type of mice) beats 600 per minute. – Stroke volume: The amount of blood pumped by the left ventricle each time it contracts (75 ml per beat).

7. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cardiac output can increase up to five fold during heavy exercise, this is equivalent to pumping amount of blood equal to 2-3 body weight in 2-3 minutes. There are four valves (flap of connective tissue) in the heart to prevent back flow of blood during systole (dictate a one way flow through the heart): Atrioventicular valves: found between each atrium and ventricle and keep blood from flowing back to the atria during ventricle contraction.

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Semilunar valves: located where the aorta leaves the left ventricle and where the pulmonary artery leaves the right ventricle. They prevent flow of blood back into ventricles when they relax (diastole) A heart murmur is a defect in ore or more valves that allows back flow of blood. In serious cases, a surgery involves replacing the valves is a must.

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Maintaining the Heart’s Rhythmic Beat Some cardiac muscle cells are self-excitable – Meaning they contract without any signal from the nervous system

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 (0.1 sec). – And then travel to the Purkinje fibers that make the ventricles contract

11. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The impulses that travel during the cardiac cycle produce electrical currents as they pass through cardiac muscle. Can be recorded as an electrocardiogram (ECG or EKG). Because the SA node of the human heart is made up of specialized cells and located within the heart itself, it is called myogenic heart. In contrast, pacemaker of most arthropod hearts originated in motor nerves arising from the outside, it is referred to as a neurogenic heart.

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The control of heart rhythm Figure 42.8 SA node (pacemaker) AV node Bundle branches Heart apex Purkinje fibers 2 Signals are delayed at AV node. 1 Pacemaker generates wave of signals to contract. 3 Signals pass to heart apex. 4 Signals spread Throughout ventricles. ECG

13. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings SA node is influenced by variety of physiological cues; two sets of nerves affect the heart rate; – one set speeds up the pacemaker – the other set slows it down SA is also affected by some hormones such as epinephrine (fight–or-flight hormone) which increases the heart rate body temperature is another factor that affect the pacemaker as an increase of 1C in the body temperature increases the heart rate of 10 beats/min.

14. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.3: Physical principles govern blood circulation The same physical principles that govern the movement of water in plumbing systems – Also influence the functioning of animal circulatory systems

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Vessel Structure and Function The “infrastructure” of the circulatory system – Is its network of blood vessels The walls of arteries and veins have three similar layers: – An outer layer of connective tissue with elastic fibers that permits stretching and recoil of the vessel. – A middle layer of smooth muscles and elastic fibers. – An inner endothelium of simple squamous epithelium i.e the lining of the vessels. – The middle and outer walls of arteries are thicker than that of veins.

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings All blood vessels Are built of similar tissues – Have three similar layers Figure 42.9 Artery Vein 100 µm Artery Vein Arteriole Venule Connective tissue Smooth muscle Endothelium Connective tissue Smooth muscle Endothelium Valve Endothelium Basement membrane Capillary

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Structural differences in arteries, veins, and capillaries – Correlate with their different functions Arteries have thicker walls – To accommodate the high pressure of blood pumped from the heart

18. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In the thinner-walled veins – Blood flows back to the heart mainly as a result of muscle action Figure 42.10 Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed)

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Flow Velocity Physical laws governing the movement of fluids through pipes influence blood flow and blood pressure – Blood flows about 30 cm/second in the aorta and about 0.026 cm/second in the capillaries. i.e approximately 1000 time faster. – The velocity decreases in accordance with the Law of Continuity: Fluid will flow faster through narrow portions of a pipe than wider portions if the volume of flow remains constant. – An artery give rise to so many arterioles and then capillaries that the total diameter of vessels is much greater in capillary beds than in the artery, thus blood flow slower.

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The velocity of blood flow varies in the circulatory system Figure 42.11 5,000 4,000 3,000 2,000 1,000 0 Aorta Arteries Arterioles Capillaries Venules Veins Venae cavae Pressure (mm Hg) Velocity (cm/sec) Area (cm 2 ) Systolic pressure Diastolic pressure 50 40 30 20 10 0 120 100 80 60 40 20 0

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Pressure Is the hydrostatic pressure that blood exerts against the wall of a vessel Pressure is greater in arteries than in veins and is greater during systole. Peripheral resistance: results from impedance by arterioles; blood enters arteries faster than it can leave. As a consequence of the elasticity of the arteries working against peripheral resistance there is a substantial blood pressure even at diastole. In veins, pressure is nearly zero. Blood return to the heart by the action of skeletal muscles around the veins. Veins have valves that allow blood to flow only towards the heart. The blood pressure of a healthy resting human oscillates between 120 Hg at systole and 70 mm Hg at diastole.

22. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Systolic pressure – Is the pressure in the arteries during ventricular systole – Is the highest pressure in the arteries Diastolic pressure – Is the pressure in the arteries during diastole – Is lower than systolic pressure

23. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood pressure Can be easily measured in humans Figure 42.12 Artery Rubber cuff inflated with air Artery closed 120 Pressure in cuff above 120 Pressure in cuff below 120 Pressure in cuff below 70 Sounds audible in stethoscope Sounds stop Blood pressure reading: 120/70 A typical blood pressure reading for a 20-year-old is 120/70. The units for these numbers are mm of mercury (Hg); a blood pressure of 120 is a force that can support a column of mercury 120 mm high. 1 A sphygmomanometer, an inflatable cuff attached to a pressure gauge, measures blood pressure in an artery. The cuff is wrapped around the upper arm and inflated until the pressure closes the artery, so that no blood flows past the cuff. When this occurs, the pressure exerted by the cuff exceeds the pressure in the artery. 2 A stethoscope is used to listen for sounds of blood flow below the cuff. If the artery is closed, there is no pulse below the cuff. The cuff is gradually deflated until blood begins to flow into the forearm, and sounds from blood pulsing into the artery below the cuff can be heard with the stethoscope. This occurs when the blood pressure is greater than the pressure exerted by the cuff. The pressure at this point is the systolic pressure. 3 The cuff is loosened further until the blood flows freely through the artery and the sounds below the cuff disappear. The pressure at this point is the diastolic pressure remaining in the artery when the heart is relaxed. 4 70

24. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood pressure is determined partly by cardiac output – And partly by peripheral resistance due to variable constriction of the arterioles – Nerve impulses, hormones and other signals (stress) can raise the blood pressure by constricting blood vessels – Cardiac output is adjusted in coordination with changes in peripheral resistance

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Capillary Function All tissues and organs receive a sufficient supply of blood even though only 5-10% of the capillaries are carrying blood at any given time. Capillaries in the brain, heart, kidneys and liver usually carry a full load of blood. During exercise blood is drew from the digestive tract to the skeletal muscles and skin that is why indigestion might occur if some one had a big meal and went directly to play or swim

26. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanism of blood distribution in capillaries In one mechanism – involves the contraction and relaxation of the smooth muscle layer of the arterioles.

27. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a second mechanism – Precapillary sphincters control the flow of blood between arterioles and venules Figure 42.13 a–c Precapillary sphincters Thoroughfare channel Arteriole Capillaries Venule (a)Sphincters relaxed increase blood flow (b) Sphincters contracted Reduce blood flow Venule Arteriole (c) Capillaries and larger vessels (SEM) 20  m

28. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The critical exchange of substances between the blood and interstitial fluid – Takes place across the thin endothelial walls of the capillaries – About 85% of fluid that leaves the blood at the arterial end of the capillary returns from the interstitial fluid at the venous end while the other 15% returned to the blood through the lymphatic system. – Fluid reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system –

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The difference between blood pressure and osmotic pressure – Drives fluids out of capillaries at the arteriole end and into capillaries at the venule end At the arterial end of a capillary, blood pressure is greater than osmotic pressure, and fluid flows out of the capillary into the interstitial fluid. Capillary Red blood cell 15  m Tissue cell INTERSTITIAL FLUID Capillary Net fluid movement out Net fluid movement in Direction of blood flow Blood pressure Osmotic pressure Inward flow Outward flow Pressure Arterial end of capillary Venule end At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary. Figure 42.14

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Fluid Return by the Lymphatic System capillary walls leak fluid about 4 L/day and some blood proteins which return to the blood via the Lymphatic System. Once inside the lymphatic system this fluid (blood and proteins) is called lymph The lymphatic system returns fluid to the body from the capillary beds Lymph is a fluid similar in composition to interstitial fluid. The lymphatic system drains into the circulatory system at two locations near the shoulders.

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lymph nodes are specialized swellings along the system that filter the lymph and attack viruses and bacteria thus participate in the defense system. Lymph capillaries penetrate small intestine villi and absorb fats, thus transporting it from the digestive system to the circulatory system. Inside the lymph nodes there is connective tissue filled with white blood cells specialized for defense.

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.4: Blood is a connective tissue with cells suspended in plasma Blood has a pH of 7.4 Humans have 4-6 liters of whole blood (plasma+ cellular elements). Cellular elements represent about 45% of the blood. Cellular elements can be separated form plasma by centrifugation

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Composition and Function 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

34. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

35. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The composition of mammalian plasma Plasma 55% Constituent Major functions Water Solvent for carrying other substances Sodium Potassium Calcium Magnesium Chloride Bicarbonate Osmotic balance pH buffering, and regulation of membrane permeability Albumin Fibringen Immunoglobulins (antibodies) Plasma proteins Ions (blood electrolytes) Osmotic balance, pH buffering Substances transported by blood Nutrients (such as glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O 2 and CO 2 ) Hormones Defense Figure 42.15 Separated blood elements Clotting

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Another important class of solutes is the plasma proteins – Which influence; blood pH, osmotic pressure, and viscosity Various types of plasma proteins – Function in lipid transport, immunity, and blood clotting Serum: is the blood plasma that has the clotting factors removed and normally contain the antibodies

37. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 42.15 Cellular elements 45% Cell type Number per  L (mm 3 ) of blood Functions Erythrocytes (red blood cells) 5–6 million Transport oxygen and help transport carbon dioxide Leukocytes (white blood cells) 5,000–10,000 Defense and immunity Eosinophil Basophil Platelets Neutrophil Monocyte Lymphocyte 250,000  400,000 Blood clotting The cellular elements of mammalian blood Separated blood elements

39. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Erythrocytes Each ml of human blood contains 5-6 million RBC and there are about trillion of these cells in the body’s 5 L of blood. Their main function is the transport of O 2 which depends on rapid diffusion of O 2 through plasma membrane Lack nuclei and mitochondria thus keeps all the space for larger amount of the hemoglobin generates ATP by anaerobic respiration therefore, they do not consume any of the oxygen they carry Contain hemoglobin, iron-containing trans protein. There are 250 million molecules of hemoglobin in each RBC, thus an RBC can carry about a billion oxygen molecules. Erythropoietin is a protein produced in kidneys in response to shortage of O 2 in tissues. This protein stimulates the production of RBC.

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Leukocytes; Blood contains five types of WBC function in defense and immunity. There are 5 types of leukocytes: basophils, eosinophils, neutrophils, lymphocytes and monocytes. Monocytes and neutrophils are phagocytes There are usually 5000-10000 WBC in each ml of blood but this number increase temporarily during infection. Spend most of their time outside the circulatory system in the interstitial fluid and lymphatic system. Lymphocytes become specialized during an infection and produce the body’s immune response.

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Platelets Fragments of cells, 2-3 um in diameter. Lack nuclei Inters blood and function in blood clotting.

42. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 circulate the blood for 3-4 months before being destroyed by phagocytic cells. The Pluripotent Stem Cells give rise to all three types of cellular elements. These cells are self renewable,found in the red bone marrow and arise in the early embryonic stage. They produce a number of new blood cells equivalent to the number of dying cells.

43. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Differentiation of blood cells from pluripotent stem cells B cells T cells Lymphoid stem cells Pluripotent stem cells (in bone marrow) Myeloid stem cells Erythrocytes Platelets Monocytes Neutrophils Eosinophils Basophils Lymphocytes Figure 42.16

44. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stem cells and replacement of cellular elements Erythrocyte production is controlled by a negative feed back mechanism. If tissue do not receive enough O 2, the kidneys synthesis and secrete a hormone called erythropoietin (EPO) that stimulates production of RBC. The reveres happens if tissues receive more O 2 than what they are suppose to have. EPO is used to treat anemia however, some athletes injects themselves with EPO to increase their RBC levels This practice is called blood doping and is banned by Olympic committee Pluripotent cells are used for regenerating the bone marrow after destroying it as a cancer treatment.

45. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood Clotting Blood clotting happened after an injury happens to the endothelium of vessels After the injury the connective tissue become exposed and the platelets adheres to the fibers A substance that makes nearby platelets sticky is released Platelets clump together to for a temporary plug and release clotting factors (12 clotting factors are known). Clotting factors result in conversion of inactive fibrinogen to active fibrin by the help of thrombin. Fibrin aggregates into threads that form the clot.

46. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A cascade of complex reactions Converts fibrinogen to fibrin, forming a clot Platelet plug Collagen fibers Platelet releases chemicals that make nearby platelets sticky Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Prothrombin Thrombin Fibrinogen Fibrin 5 µm Fibrin clot Red blood cell The clotting process begins when the endothelium of a vessel is damaged, exposing connective tissue in the vessel wall to blood. Platelets adhere to collagen fibers in the connective tissue and release a substance that makes nearby platelets sticky. 1 The platelets form a plug that provides emergency protection against blood loss. 2 This seal is reinforced by a clot of fibrin when vessel damage is severe. Fibrin is formed via a multistep process: Clotting factors released from the clumped platelets or damaged cells mix with clotting factors in the plasma, forming an activation cascade that converts a plasma protein called prothrombin to its active form, thrombin. Thrombin itself is an enzyme that catalyzes the final step of the clotting process, the conversion of fibrinogen to fibrin. The threads of fibrin become interwoven into a patch (see colorized SEM). 3 Figure 42.17

47. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hemophilia is a genetic disorder caused by mutations that affect blood clotting and is characterized by excessive bleeding from even minor cuts. Spontaneous clotting in the body without injury is inhibited by anti-clotting factors in blood. Some times platelets clump and fibrin coagulates within blood vessel making what is known as thrombus. These potentially dangerous clots are likely to form in individuals with cardiovascular diseases.

48. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cardiovascular Disease – Are disorders of the heart and the blood vessels – Account for more than half the deaths in the United States – Tendency to have cardiovascular disease might be inherited however, life style plays a major role, such as smoking, eating habits, lack of exercise, high concentration of cholesterol in the blood.

49. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cholesterol Normally high concentration of LDLs (low density lipoproteins, bad cholesterol) in the blood correlate with atherosclerosis. HDLs (high density lipoproteins, good cholesterol) reduce deposition of cholesterol in arterial plaques. Ratio of LDLs to HDLs is more reliable than total plasma cholesterol as indicator of impending cardiovascular disease Exercise increase HDLs. Diet also increases HDL example of such diet is the consumption of olive oil which is rich of monounsaturated fatty acids that was found to decrease LDL and increase HDL. Smoking increase LDL; HDL ratio therefore, increases the risk of cardiovascular disease.

50. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings One type of cardiovascular disease, atherosclerosis – Is caused by the buildup of cholesterol within arteries Figure 42.18a, b (a) Normal artery (b) Partly clogged artery 50 µm250 µm Smooth muscle Connective tissue Endothelium Plaque

51. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Atherosclerosis commonly known as hardening of arteries. Figure 4.18 Chronic cardiovascular disease characterized by plaques that develop in the inner walls of arteries and narrow the bore of the vessel Form at sites where smooth muscle layer of artery thickens abnormally and inner walls become rough Site become infiltrated with fibrus connective tissue and lipids such as cholesterol thus encouges thrombus formation. embolus more likely trapped in narrow vessels. Sings of Atherosclerosis; Angina pectoris: chest pain that occur when heart receives insufficient oxygen due to plaques in the arteries. Hypertension: High blood pressure, increase the risk of atheroseclerosis, heart attack and stroke.

52. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hypertension Promotes atherosclerosis by damaging endothelium layer of the blood vessels Increase risk of heart attack and stroke Atherosclerosis increase blood pressure by narrowing and reducing their elasticity. High blood pressure can be controlled by medication, diet, exercise or combination A diastolic pressure above 90 is a cause for concern

53. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A heart attack Is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries thus decreasing O2 supply to the cardiac muscle. A thrombus that causes heart attack/stroke may form; – In a coronary artery – Artery in the brain – Elsewhere in the circulatory system and reaches the heart. The thrombus occurs due to the accumulation of LDL in arteries triggering an inflammatory reaction similar to that caused by bacterial infection.

54. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Embolus is a moving clot from one place to another. – Cardiac or brain tissue downstream from obstruction may die – If damage in the heart interrupts conduction of electrical impulses through cardiac muscle, heart rate may change dramatically or the heart may stop beating – If cardiopulmonary resuscitation (CPR) within few minutes, person may survive. A stroke – Is the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head. Once happened survival depends on damage extent.

55. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammalian Respiratory Systems: A Closer Look A system of branching ducts – Conveys air to the lungs Branch from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Branch from the pulmonary artery (oxygen-poor blood) Alveoli Colorized SEM SEM 50 µm Heart Left lung Nasal cavity Pharynx Larynx Diaphragm Bronchiole Bronchus Right lung Trachea Esophagus Figure 42.23

56. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The lungs of mammals have a spongy texture and are honeycombed with a moist epithelium that functions as the respiratory surface Air inters through the nostrils and get filtered by hair, warmed, humidified and sampled for odor then flow through to pharynx then to larynx which works as a voice box that contains the vocal cords which produces the sound by vibrating. From the larynx air pass through the trachea (windpipe) which branches in two bronchi one leading to each lung. Each bronchus branches into finer tubes called bronchioles. At the air tips the bronchioles dead ends are called alveoli (singular alveolus)

57. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.6: Breathing ventilates the lungs The process that ventilates the lugs is called breathing, a frog ventilates its lungs by positive pressure while mammals ventilate their lungs by negative pressure (which forces air down the trachea). Negative pressure works like a suction pump pulling air instead of pushing it into the lungs in a process called inhalation. The alternate inhalation and exhalation of air ventilates the lungs.

58. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How a Mammal Breathes Mammals ventilate their lungs – By negative pressure breathing, which pulls air into the lungs Air inhaledAir exhaled INHALATION Diaphragm contracts (moves down) EXHALATION Diaphragm relaxes (moves up) Diaphragm Lung Rib cage expands as rib muscles contract Rib cage gets smaller as rib muscles relax Figure 42.24

59. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lung volume Vertebrates ventilate their lungs by Breathing Maintain a maximumO2 concentration and minimum CO2 concentration in the alveoli. When a mammal is at rest, most of the shallow inhalation results from contraction of the diaphragm. When the diaphragm contracts, it pushes down towards the abdomen, enlarging the thoracic cavity. Contraction of the rib muscles expands the rib cage by pulling the ribs upward and the breastbone upward. This change increase the lung volume and as a result the air pressure in the alveoli become lower than the atmospheric pressure.

60. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Because gas flow from region of higher pressure to the region of lower pressure, air pushes through and inhalation occurs. During exhalation, the rib muscles and diaphragm relax, lung volume is reduced and the air pressure is increased in the alveoli forcing air up to breathing tubes and out of the trachea to nostrils producing the exhalation. During exercise, contraction of the rib muscles increases lung volume

61. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Tidal Volume: the amount of air an animal inhales and exhales with each breath during normal breathing. (500 ml in humans). Vital Capacity: the maximum air volume that can be inhaled and exhaled during forced breathing. (4800 ml in young males, 3400 ml in females.) Residual Volume: is the amount of air that remains in the lungs even after forced breathing after exhalation. As lungs lose their resilience (strength) as a result of aging or disease the residual volume increases on the expense of the vital capacity which limits the effectiveness of gas exchange.

62. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control of Breathing in Humans The main breathing control centers – Are located in two regions of the brain, the medulla oblongata and the pons. Figure 42.26.

63. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Control of Breathing in Humans Figure 42.26 Pons Breathing control centers Medulla oblongata Diaphragm Carotid arteries Aorta Cerebrospinal fluid Rib muscles In a person at rest, these nerve impulses result in about 10 to 14 inhalations per minute. Between inhalations, the muscles relax and the person exhales. The medulla’s control center also helps regulate blood CO 2 level. Sensors in the medulla detect changes in the pH (reflecting CO 2 concentration) of the blood and cerebrospinal fluid bathing the surface of the brain. Nerve impulses relay changes in CO 2 and O 2 concentrations. Other sensors in the walls of the aorta and carotid arteries in the neck detect changes in blood pH and send nerve impulses to the medulla. In response, the medulla’s breathing control center alters the rate and depth of breathing, increasing both to dispose of excess CO 2 or decreasing both if CO 2 levels are depressed. The control center in the medulla sets the basic rhythm, and a control center in the pons moderates it, smoothing out the transitions between inhalations and exhalations. 1 Nerve impulses trigger muscle contraction. Nerves from a breathing control center in the medulla oblongata of the brain send impulses to the diaphragm and rib muscles, stimulating them to contract and causing inhalation. 2 The sensors in the aorta and carotid arteries also detect changes in O 2 levels in the blood and signal the medulla to increase the breathing rate when levels become very low. 6 5 3 4

64. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Control of Breathing Breathing is an automatic action. We inhale when nerves in the breathing control centers of the medulla oblonga and pons send impulses to the rib muscles or diaphragm, stimulating the muscles to contract. This occurs every 10-14 time per minute. The medulla’s control center also monitors blood and cerebrospinal fluid pH, which drops as blood CO 2 concentration increase.

65. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Control of Breathing … cont. When pH is dropped (increase of CO 2 ), the tempo and depth of breathing are increased and the excess CO 2 is removed in exhaled air. O 2 concentration in the blood only effects the breathing control centers when it becomes extremely low.

66. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sensors in the aorta and carotid arteries – Monitor O 2 and CO 2 concentrations in the blood – Exert secondary control over breathing by signaling the medulla to increase breathing rate.

67. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.7: Respiratory pigments bind and transport gases The metabolic demands of many organisms – Require that the blood transport large quantities of O 2 and CO 2

68. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Role of Partial Pressure Gradients The diffusion of gases, whether in air or water depends on partial pressure. The partial pressure of gas is the proportion of the total atmospheric pressure (760 mm Hg) contributed by the gas. Oxygen comprises 21% of the atmosphere: its partial pressure (PO 2 )= 160 mm, (0.21 x 760). CO 2 comprises about 0.03% of the atmosphere, (PCO 2 = 0.23 mm Hg). Gases diffuse always from areas of high partial pressure to those of low partial pressures. Blood arriving at the lungs from systemic circulation has a lower PO 2 and a higher PCO 2 than air in the alveoli.

69. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Thus the blood exchange gases with air in the alveoli and the PO 2 of the blood increases while the PCO 2 decreases. In systemic capillaries gradients of partial pressure favor diffusion of O 2 out of the blood and diffusion of CO 2 into it, since cellular respiration rapidly depletes interstitial fluid of O 2 and adds CO 2.

70. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

71. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Inhaled airExhaled air 160 0.2 O2O2 CO 2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 O2O2 40 45 100 40 104 40 120 27 CO 2 O2O2 Alveolar epithelial cells Pulmonary arteries Blood entering alveolar capillaries Blood leaving tissue capillaries Blood entering tissue capillaries Blood leaving alveolar capillaries CO 2 O2O2 Tissue capillaries Heart Alveolar capillaries of lung 45 Tissue cells Pulmonary veins Systemic arteries Systemic veins O2O2 CO 2 O2O2 Alveolar spaces 1 2 4 3 Figure 42.27

72. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Like all respiratory pigments – Hemoglobin must reversibly bind O 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 unloaded In tissues Polypeptide chain O2O2 O2O2 Figure 42.28

73. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxygen Transport oxygen is carried by respiratory pigments in the blood of most animals since oxygen is not very soluble in water. Hemoglobin is the oxygen transporting pigment in almost all vertebrates. Binding of oxygen to hemoglobin is reversible: binding occur in the lungs, release occurs in the tissues. Binding and release of oxygen depends on cooperation between subunits of hemoglobin in which the binding of O 2 to one subunit induces the other subunits to bind O 2 with more affinity..

74. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cooperative O 2 binding and release – Is evident in the dissociation curve for hemoglobin A drop in pH – Lowers the affinity of hemoglobin for O 2 thus releases O 2 to the tissues

75. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bohr’s shift is the lowering of hemoglobin’s affinity for oxygen upon a drop in pH. This occur in active tissues due to the entrance of CO 2 into the blood

76. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings O 2 unloaded from hemoglobin during normal metabolism O 2 reserve that can be unloaded from hemoglobin to tissues with high metabolism Tissues during exercise Tissues at rest 100 80 60 40 20 0 100 80 60 40 20 0 100 80 60 40 200 100 80 60 40 200 Lungs P O 2 (mm Hg) O 2 saturation of hemoglobin (%) Bohr shift: Additional O 2 released from hemoglobin at lower pH (higher CO 2 concentration) pH 7.4 pH 7.2 (a) P O 2 and Hemoglobin Dissociation at 37°C and pH 7.4 (b) pH and Hemoglobin Dissociation Figure 42.29a, b

77. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carbon Dioxide Transport Carbon dioxide is transported by the blood in three forms: – dissolved CO 2 in the plasma (7%). – Bound to the amino groups of hemoglobin (23%). – As biocarbonate ions in the plasma (70%). CO 2 from cells diffuses into the blood plasma and then into RBC. In the RBCs, CO 2 is converted into bicarbonate. The CO 2 reacts with water to form carbonic acid. Carbonic acid quickly disassociate to bicarbonate and hydrogen ions Bicarbonate then diffuse out of RBCs to the blood plasma. The hydrogen ions attach to the hemoglobin and other proteins. This process is reversed in the lungs.

78. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Carbon dioxide from respiring cells – Diffuses into the blood plasma and then into erythrocytes and is ultimately released in the lungs

79. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 42.30 Tissue cell CO 2 Interstitial fluid CO 2 produced CO 2 transport from tissues CO 2 Blood plasma within capillary Capillary wall H2OH2O Red blood cell Hb Carbonic acid H 2 CO 3 HCO 3 – H+H+ + Bicarbonate HCO 3 – Hemoglobin picks up CO 2 and H + HCO 3 – H+H+ + H 2 CO 3 Hb Hemoglobin releases CO 2 and H + CO 2 transport to lungs H2OH2O CO 2 Alveolar space in lung 2 1 3 4 5 6 7 8 9 10 11 To lungs Carbon dioxide produced by body tissues diffuses into the interstitial fluid and the plasma. Over 90% of the CO 2 diffuses into red blood cells, leaving only 7% in the plasma as dissolved CO 2. Some CO 2 is picked up and transported by hemoglobin. However, most CO 2 reacts with water in red blood cells, forming carbonic acid (H 2 CO 3 ), a reaction catalyzed by carbonic anhydrase contained. Within red blood cells. Carbonic acid dissociates into a biocarbonate ion (HCO 3 – ) and a hydrogen ion (H + ). Hemoglobin binds most of the H + from H 2 CO 3 preventing the H + from acidifying the blood and thus preventing the Bohr shift. CO 2 diffuses into the alveolar space, from which it is expelled during exhalation. The reduction of CO 2 concentration in the plasma drives the breakdown of H 2 CO 3 Into CO 2 and water in the red blood cells (see step 9), a reversal of the reaction that occurs in the tissues (see step 4). Most of the HCO 3 – diffuse into the plasma where it is carried in the bloodstream to the lungs. In the HCO 3 – diffuse from the plasma red blood cells, combining with H + released from hemoglobin and forming H 2 CO 3. Carbonic acid is converted back into CO 2 and water. CO 2 formed from H 2 CO 3 is unloaded from hemoglobin and diffuses into the interstitial fluid. 1 2 3 4 5 6 7 8 9 10 11

80. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings End of material requested from this chapter

81. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

82. Overview: Trading with the Environment Every organism must exchange materials with its environment – And this exchange ultimately occurs at the cellular level

83. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In unicellular organisms – These exchanges occur directly with the environment For most of the cells making up multicellular organisms – Direct exchange with the environment is not possible

84. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The feathery gills projecting from a salmon – Are an example of a specialized exchange system found in animals Figure 42.1

85. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.1: Circulatory systems reflect phylogeny Transport systems – Functionally connect the organs of exchange with the body cells

86. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Most complex animals have internal transport systems – That circulate fluid, providing a lifeline between the aqueous environment of living cells and the exchange organs, such as lungs, that exchange chemicals with the outside environment

87. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Invertebrate Circulation The wide range of invertebrate body size and form – Is paralleled by a great diversity in circulatory systems

88. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gastrovascular Cavities 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

89. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some cnidarians, such as jellies – Have elaborate gastrovascular cavities Figure 42.2 Circular canal Radial canal 5 cm Mouth

90. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Open and Closed Circulatory Systems More complex animals – 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)

91. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In insects, other arthropods, and most molluscs – Blood bathes the organs directly in an open circulatory system Heart Hemolymph in sinuses surrounding ograns Anterior vessel Tubular heart Lateral vessels Ostia (a) An open circulatory system Figure 42.3a

92. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a closed circulatory system – Blood is confined to vessels and is distinct from the interstitial fluid Figure 42.3b Interstitial fluid Heart Small branch vessels in each organ Dorsal vessel (main heart) Ventral vessels Auxiliary hearts (b) A closed circulatory system

93. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Closed systems – Are more efficient at transporting circulatory fluids to tissues and cells

94. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 four- chambered heart

95. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Arteries carry blood to capillaries – The sites of chemical exchange between the blood and interstitial fluid Veins – Return blood from capillaries to the heart

96. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

97. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Amphibians Frogs and other amphibians – Have a three-chambered heart, with 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

98. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reptiles (Except Birds) Reptiles have double circulation – With a pulmonary circuit (lungs) and a systemic circuit Turtles, snakes, and lizards – Have a three-chambered heart

99. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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

100. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A powerful four-chambered heart – Was an essential adaptation of the endothermic way of life characteristic of mammals and birds

101. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings FISHES AMPHIBIANSREPTILES (EXCEPT BIRDS)MAMMALS AND BIRDS Systemic capillaries Lung capillaries Lung and skin capillariesGill capillaries Right Left RightLeft Right Left Systemic circuit Pulmocutaneous circuit Pulmonary circuit Systemic circulation Vein Atrium (A) Heart: ventricle (V) Artery Gill circulation A V V VVV A A A AA Left Systemic aorta Right systemic aorta Figure 42.4 Vertebrate circulatory systems

102. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.2: Double circulation in mammals depends on the anatomy and pumping cycle of the heart The structure and function of the human circulatory system – Can serve as a model for exploring mammalian circulation in general

103. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mammalian Circulation: The Pathway Heart valves – Dictate a one-way flow of blood through the heart

104. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Blood begins its flow – With the right ventricle pumping blood to the lungs In the lungs – The blood loads O 2 and unloads CO 2

105. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 – Through the right atrium

106. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The mammalian cardiovascular system Pulmonary vein Right atrium Right ventricle Posterior vena cava Capillaries of abdominal organs and hind limbs Aorta Left ventricle Left atrium Pulmonary vein Pulmonary artery Capillaries of left lung Capillaries of head and forelimbs Anterior vena cava Pulmonary artery Capillaries of right lung Aorta Figure 42.5 1 10 11 5 4 6 2 9 3 3 7 8

107. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

108. How a Bird Breathes Besides lungs, bird have eight or nine air sacs – That function as bellows that keep air flowing through the lungs INHALATION Air sacs fill EXHALATION Air sacs empty; lungs fill Anterior air sacs Trachea Lungs Posterior air sacs Air 1 mm Air tubes (parabronchi) in lung Figure 42.25

109. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elite Animal Athletes Migratory and diving mammals – Have evolutionary adaptations that allow them to perform extraordinary feats

110. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Ultimate Endurance Runner The extreme O 2 consumption of the antelope- like pronghorn – Underlies its ability to run at high speed over long distances Figure 42.31

111. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Diving Mammals Deep-diving air breathers – Stockpile O 2 and deplete it slowly

112. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 42.5: Gas exchange occurs across specialized respiratory surfaces Gas exchange – Supplies oxygen for cellular respiration and disposes of carbon dioxide Figure 42.19 Organismal level Cellular level Circulatory system Cellular respiration ATP Energy-rich molecules from food Respiratory surface Respiratory medium (air of water) O2O2 CO 2

113. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animals require large, moist respiratory surfaces for the adequate diffusion of respiratory gases – Between their cells and the respiratory medium, either air or water

114. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gills in Aquatic Animals Gills are outfoldings of the body surface – Specialized for gas exchange

115. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In some invertebrates – The gills have a simple shape and are distributed over much of the body (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. Gills Tube foot Coelom Figure 42.20a

116. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many segmented worms have flaplike gills – That extend from each segment of their body Figure 42.20b (b) Marine worm. Many polychaetes (marine worms of the phylum Annelida) have a pair of flattened appendages called parapodia on each body segment. The parapodia serve as gills and also function in crawling and swimming. Gill Parapodia

117. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The gills of clams, crayfish, and many other animals – Are restricted to a local body region Figure 42.20c, d (d) Crayfish. Crayfish and other crustaceans have long, feathery gills covered by the exoskeleton. Specialized body appendages drive water over the gill surfaces. (c) Scallop. The gills of a scallop are long, flattened plates that project from the main body mass inside the hard shell. Cilia on the gills circulate water around the gill surfaces. Gills

118. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The effectiveness of gas exchange in some gills, including those of fishes – Is increased by ventilation and countercurrent flow of blood and water Countercurrent exchange Figure 42.21 Gill arch Water flow Operculum Gill arch Blood vessel Gill filaments Oxygen-poor blood Oxygen-rich blood Water flow over lamellae showing % O 2 Blood flow through capillaries in lamellae showing % O 2 Lamella 100% 40% 70% 15% 90% 60% 30% 5% O2O2

119. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure 42.22a Tracheae Air sacs Spiracle (a) The respiratory system of an insect consists of branched internal tubes that deliver air directly to body cells. Rings of chitin reinforce the largest tubes, called tracheae, keeping them from collapsing. Enlarged portions of tracheae form air sacs near organs that require a large supply of oxygen. Air enters the tracheae through openings called spiracles on the insect’s body surface and passes into smaller tubes called tracheoles. The tracheoles are closed and contain fluid (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. Tracheal Systems in Insects The tracheal system of insects – Consists of tiny branching tubes that penetrate the body

120. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The tracheal tubes – Supply O 2 directly to body cells Air sac Body cell Trachea Tracheole Tracheoles Mitochondria Myofibrils Body wall (b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole. Figure 42.22b 2.5 µm Air

121. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lungs Spiders, land snails, and most terrestrial vertebrates – Have internal lungs