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2D2 Digestive systems, Respiratory systems (gas exchange), Blood/Osmolarity/Osmotic Balance, Urinary systems (removal of nitrogen wastes)

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Presentation on theme: "2D2 Digestive systems, Respiratory systems (gas exchange), Blood/Osmolarity/Osmotic Balance, Urinary systems (removal of nitrogen wastes)"— Presentation transcript:

1 2D2 Digestive systems, Respiratory systems (gas exchange), Blood/Osmolarity/Osmotic Balance, Urinary systems (removal of nitrogen wastes)

2 Types of Digestive Systems Heterotrophs are divided into three groups based on their food sources 1.Herbivores are animals that eat plants exclusively 2.Carnivores are animals that eat other animals 3.Omnivores are animals that eat both plants and other animals 2

3 Types of Digestive Systems Single-celled organisms and sponges digest their food intracellularly Other multicellular animals digest their food extracellularly – Within a digestive cavity Cnidarians and flatworms have a gastrovascular cavity – Only one opening, and no specialized regions 3

4 Types of Digestive Systems Specialization occurs when the digestive tract has a separate mouth and anus – Nematodes have the most primitive digestive tract Tubular gut lined by an epithelial membrane – More complex animals have a digestive tract specialized in different regions 4

5 Gas Exchange One of the major physiological challenges facing all multicellular animals is obtaining sufficient oxygen and disposing of excess carbon dioxide In vertebrates, the gases diffuse into the aqueous layer covering the epithelial cells that line the respiratory organs Diffusion is passive, driven only by the difference in O 2 and CO 2 concentrations on the two sides of the membranes and their relative solubilities in the plasma membrane 5

6 Gas Exchange Rate of diffusion between two regions is governed by Fick’s Law of Diffusion R = Rate of diffusion D = Diffusion constant A = Area over which diffusion takes place  p = Pressure difference between two sides d = Distance over which diffusion occurs 6 R = DA  p d

7 Gas Exchange Evolutionary changes have occurred to optimize the rate of diffusion R – Increase surface area A – Decrease distance d – Increase concentration difference  p 7

8 Gas Exchange Gases diffuse directly into unicellular organisms However, most multicellular animals require system adaptations to enhance gas exchange Amphibians respire across their skin Echinoderms have a poorly developed respiratory system. They use their tube feet to take in oxygen and pass out carbon dioxide Insects have an extensive tracheal system throughout their bodies. It is a complex network of tubes with openings called spiracles. Fish use gills Mammals have a large network of alveoli 8

9 Blood Type of connective tissue composed – Fluid matrix called plasma – Formed elements Functions of circulating blood 1.Transportation 2.Regulation 3.Protection 9

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11 Blood plasma 92% water Contains the following solutes – Nutrients, wastes, and hormones – Ions – Proteins Albumin, alpha (  ) and beta (  ) globulins Fibrinogen – If removed, plasma is called serum 11

12 Formed elements Red blood cells (erythrocytes) – About 5 million per microliter of blood – Hematocrit is the fraction of the total blood volume occupied by red blood cells – Mature mammalian erythrocytes lack nuclei – RBCs of vertebrates contain hemoglobin Pigment that binds and transports oxygen 12

13 Osmolarity and Osmotic Balance Water in a multicellular body distributed between – Intracellular compartment – Extracellular compartment Most vertebrates maintain homeostasis for – Total solute concentration of their extracellular fluids – Concentration of specific inorganic ions 13

14 Osmolarity and Osmotic Balance Important ions – Sodium (Na + ) is the major cation in extracellular fluids – Chloride (Cl – ) is the major anion – Divalent cations, calcium (Ca 2+ ) and magnesium (Mg 2 + ), the monovalent cation K +, as well as other ions, also have important functions and are maintained at constant levels 14

15 15 Animal body H 2 O (Sweat) CO 2 and H 2 O O2O2 Solutes and H 2 O CO 2 and H 2 O Food and H 2 O External environment Urine (excess H 2 O) Waste Extracellular compartment (including blood) O2O2 Intracellular compartment Intracellular compartment Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

16 Osmolarity and Osmotic Balance Osmotic pressure – Measure of a solution’s tendency to take in water by osmosis Osmolarity – Number of osmotically active moles of solute per liter of solution Tonicity – Measure of a solution’s ability to change the volume of a cell by osmosis – Solutions may be hypertonic, hypotonic, or isotonic 16

17 Osmolarity and Osmotic Balance Osmoconformers – Organisms that are in osmotic equilibrium with their environment Among the vertebrates, only the primitive hagfish are strict osmoconformers Sharks and relatives (cartilaginous fish) are also isotonic All other vertebrates are osmoregulators – Maintain a relatively constant blood osmolarity despite different concentrations in their environment 17

18 Osmolarity and Osmotic Balance Freshwater vertebrates – Hypertonic to their environment – Have adapted to prevent water from entering their bodies, and to actively transport ions back into their bodies Marine vertebrates – Hypotonic to their environment – Have adapted to retain water by drinking seawater and eliminating the excess ions through kidneys and gills 18

19 Osmolarity and Osmotic Balance Terrestrial vertebrates – Higher concentration of water than surrounding air – Tend to lose water by evaporation from skin and lungs – Urinary/osmoregulatory systems have evolved in these vertebrates that help them retain water 19

20 Osmoregulatory Organs In many animals, removal of water or salts is coupled with removal of metabolic wastes through the excretory system A variety of mechanisms have evolved to accomplish this – Single-celled protists and sponges use contractile vacuoles – Other multicellular animals have a system of excretory tubules to expel fluid and wastes 20

21 Osmoregulatory Organs Invertebrates – Flatworms Use protonephridia ( All except the simplest flatworms have nephridial tubules, called protonephridia, usually distributed throughout the body. Such structures consist of an external opening and a tubule that branches internally, terminating in a number of blind, bulb-shaped structures called flame bulbs, which bear tufts of cilia.) They probably function as excretory and osmoregulatory organs which branch into bulblike flame cells Open to the outside of the body, but not to the inside – Earthworms Use nephridia Open both to the inside and outside of the body 21

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24 Osmoregulatory Organs Insects – Use Malpighian tubules Extensions of the digestive tract – Waste molecules and K + are secreted into tubules by active transport – Create an osmotic gradient that draws water into the tubules by osmosis – Most of the water and K + is then reabsorbed into the open circulatory system through hindgut epithelium 24

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26 Osmoregulatory Organs Vertebrate kidneys – Create a tubular fluid by filtering the blood under pressure through the glomerulus – Filtrate contains many small molecules, in addition to water and waste products – Most of these molecules and water are reabsorbed into the blood Selective reabsorption provides great flexibility – Waste products are eliminated from the body in the form of urine 26

27 Evolution of the Vertebrate Kidney Made up of thousands of repeating units – nephrons Although the same basic design has been retained in all vertebrate kidneys, a few modifications have occurred All vertebrates can produce a urine that is isotonic or hypotonic to blood Only birds and mammals can make a hypertonic urine 27

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29 Evolution of the Vertebrate Kidney Kidneys are thought to have evolved among the freshwater teleosts, or bony fishes Body fluids are hypertonic with respect to surrounding water, causing two problems 1.Water enters body from environment Fishes do not drink water and excrete large amounts of dilute urine 2.Solutes tend to leave the body Reabsorb ions across nephrons Actively transport ions across gills into blood 29

30 Evolution of the Vertebrate Kidney In contrast, marine bony fishes have body fluids that are hypotonic to seawater Water tends to leave their bodies by osmosis across their gills Drink large amounts of seawater Eliminate ions through gill surfaces and urine Excrete urine isotonic to body fluids 30

31 31 Evolution of the Vertebrate Kidney

32 Cartilaginous fish, including sharks and rays, reabsorb urea from the nephron tubules Maintain a blood urea concentration that is 100 times higher than that of mammals Makes blood isotonic to surrounding sea These fishes do not need to drink seawater or remove large amounts of ions from their bodies 32

33 Evolution of the Vertebrate Kidney Amphibian kidney is identical to that of freshwater fish Kidneys of reptiles are very diverse – Marine reptiles drink seawater and excrete an isotonic urine Eliminate excess salt via salt glands – Terrestrial reptiles reabsorb much of the salt and water in their nephron tubules Don’t excrete urine, but empty it into cloaca 33

34 Evolution of the Vertebrate Kidney Mammals and birds are the only vertebrates that can produce urine that is hypertonic to body fluids Accomplished by the loop of Henle Birds have relatively few or no nephrons with long loops, and so cannot produce urine as concentrated as that of mammals Marine birds excrete excess salt from salt glands near the eyes 34

35 35 Evolution of the Vertebrate Kidney

36 Nitrogenous Wastes When amino acids and nucleic acids are catabolized, they produce nitrogenous wastes that must be eliminated from the body First step is deamination – Removal of the amino (―NH 2 ) group – Combined with H + to form ammonia (NH 3 ) in the liver Toxic to cells, and thus it is only safe in dilute concentrations 36

37 Nitrogenous Wastes Bony fishes and amphibian tadpoles eliminate most of the ammonia by diffusion via gills Elasmobranchs, adult amphibians, and mammals convert ammonia into urea, which is soluble in water Birds, reptiles, and insects convert ammonia into the water-insoluble uric acid – Costs most energy, but saves most water 37

38 Nitrogenous Wastes Mammals also produce uric acid, but from degradation of purines, not amino acids Most have an enzyme called uricase, which convert uric acid into a more soluble derivative called allantoin Humans lack this enzyme Excessive accumulation of uric acid in joints causes gout 38

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40 The Mammalian Kidney Each kidney receives blood from a renal artery Produces urine from this blood Urine drains from each kidney through a ureter into a urinary bladder Urine is passed out of the body through the urethra 40

41 The Mammalian Kidney Within the kidney, the mouth of the ureter flares open to form the renal pelvis Receives urine from the renal tissue Divided into an outer renal cortex and inner renal medulla 41

42 42 The Mammalian Kidney

43 The kidney has three basic functions – Filtration Fluid in the blood is filtered out of the glomerulus into the tubule system – Reabsorption Selective movement of solutes out of the filtrate back into the blood via peritubular capillaries – Secretion Movement of substances from the blood into the extracellular fluid, then into the filtrate in the tubular system 43

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45 The Mammalian Kidney Each kidney is made up of about 1 million functioning nephrons – Juxtamedullary nephrons have long loops that dip deeply into the medulla – Cortical nephrons have shorter loops Blood is carried by an afferent arteriole to the glomerulus Blood is filtered as it is forced through porous capillary walls 45

46 The Mammalian Kidney Blood components that are not filtered drain into an efferent arteriole, which empties into peritubular capillaries – Vasa recta in juxtamedullary nephrons Glomerular filtrate enters the first region of the nephron tubules – Bowman’s capsule Goes into the proximal convoluted tubule Then moves down the medulla and back up into cortex in the loop of Henle 46

47 The Mammalian Kidney After leaving the loop, the fluid is delivered to a distal convoluted tubule in the cortex Drains into a collecting duct Merges with other collecting ducts to empty its contents, now called urine, into the renal pelvis 47

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49 Reabsorption and Secretion Approximately 2000 L of blood passes through the kidneys each day 180 L of water leaves the blood and enters the glomerular filtrate Most of the water and dissolved solutes that enter the glomerular filtrate must be returned to the blood by reabsorption Water is reabsorbed by the proximal convoluted tubule, descending loop of Henle, and collecting duct 49

50 Reabsorption and Secretion Reabsorption of glucose and amino acids is driven by active transport and secondary active transport – Maximum rate of transport – Glucose remains in the urine of untreated diabetes mellitus patients Secretion of waste products involves transport across capillary membranes and kidney tubules into the filtrate – Penicillin must be administered several times a day 50

51 Excretion Major function of the kidney is elimination of a variety of potentially harmful substances that animals eat and drink In addition, urine contains nitrogenous wastes, and may contain excess K +, H +, and other ions that are removed from blood Kidneys are critically involved in maintaining acid–base balance of blood 51

52 Transport in the Nephron Proximal convoluted tubule – Reabsorbs virtually all nutrient molecules in the filtrate, and two-thirds of the NaCl and water – Because NaCl and water are removed from the filtrate in proportionate amounts, the filtrate that remains in the tubule is still isotonic to the blood plasma 52

53 Transport in the Nephron Loop of Henle – Creates a gradient of increasing osmolarity from the cortex to the medulla – Actively transports Na +, and Cl – follows from the ascending loop Creates an osmotic gradient – Allows reabsorption of water from descending loop and collecting duct – Two limbs of the loop form a countercurrent multiplier system Creates a hypertonic renal medulla 53

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55 Transport in the Nephron Distal convoluted tubule and collecting duct – Filtrate that enters is hypotonic – Hypertonic interstitial fluid of the renal medulla pulls water out of the collecting duct and into the surrounding blood vessels Permeability controlled by antidiuretic hormone (ADH) – Kidneys also regulate electrolyte balance in the blood by reabsorption and secretion K +, H +, and HCO 3 – 55

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57 Hormones Control Osmoregulation Kidneys maintain relatively constant levels of blood volume, pressure, and osmolarity Also regulate the plasma K + and Na + concentrations and blood pH within narrow limits These homeostatic functions of kidneys are coordinated primarily by hormones 57

58 Hormones Control Osmoregulation Antidiuretic hormone (ADH) – Produced by the hypothalamus and secreted by the posterior pituitary gland – Stimulated by an increase in the osmolarity of blood – Causes walls of distal tubule and collecting ducts to become more permeable to water Aquaporins – More ADH increases reabsorption of water Makes a more concentrated urine 58

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60 Hormones Control Osmoregulation Aldosterone – Secreted by the adrenal cortex – Stimulated by low levels of Na + in the blood – Causes distal convoluted tubule and collecting ducts to reabsorb Na + – Reabsorption of Cl – and water follows – Low levels of Na + in the blood are accompanied by a decrease in blood volume Renin-angiotensin-aldosterone system is activated 60

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62 Hormones Control Osmoregulation Atrial natriuretic hormone (ANH) – Opposes the action of aldosterone in promoting salt and water retention – Secreted by the right atrium of the heart in response to an increased blood volume – Promotes the excretion of salt and water in the urine and lowering blood volume 62

63 Formed elements White blood cells (leukocytes) – Less than 1% of blood cells – Larger than erythrocytes and have nuclei – Can migrate out of capillaries into tissue fluid – Types Granular leukocytes – Neutrophils, eosinophils, and basophils Agranular leukocytes – Monocytes and lymphocytes 63

64 Formed elements Platelets Cell fragments that pinch off from larger cells in the bone marrow Function in the formation of blood clots 64

65 Formed elements All develop from pluripotent stem cells Hematopoiesis is blood cell production Occurs in the bone marrow Produces 2 types of stem cells – Lymphoid stem cell  Lymphocytes – Myeloid stem cell  All other blood cells Erythropoietin stimulates the production of erythrocytes (erythropoiesis) 65

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67 Invertebrate Circulatory Systems Sponges, Cnidarians, and nematodes lack a separate circulatory system Sponges circulate water using many incurrent pores and one excurrent pore Hydra circulate water through a gastrovascular cavity (also for digestion) Nematodes are thin enough that the digestive tract can also be used as a circulatory system 67

68 Invertebrate Circulatory Systems Nature of the circulatory system in multicellular invertebrates is directly related to the size, complexity, and lifestyle of the organism No circulatory system – Sponges and most cnidarians utilize water from the environment as a circulatory fluid Gastrovascular cavity – Nematodes Use the fluids of the body cavity for circulation Small or long and thin 68

69 Invertebrate Circulatory Systems Larger animals require a separate circulatory system for nutrient and waste transport Open circulatory system – No distinction between circulating and extracellular fluid – Fluid called hemolymph Closed circulatory system – Distinct circulatory fluid enclosed in blood vessels and transported away from and back to the heart 69

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71 Vertebrate Circulatory Systems Fishes – Evolved a true chamber-pump heart – Four structures are arrayed one after the other to form two pumping chambers First chamber – sinus venosus and atrium Second chamber – ventricle and conus arteriosus – These contract in the order listed Blood is pumped through the gills, and then to the rest of the body 71

72 72 Vertebrate Circulatory Systems

73 Amphibians – Advent of lungs required a second pumping circuit, or double circulation – Pulmonary circulation moves blood between the heart and lungs – Systemic circulation moves blood between the heart and the rest of the body 73

74 Vertebrate Circulatory Systems Amphibian heart – 3-chambered heart 2 atria and 1 ventricle – Separation of the pulmonary and systemic circulations is incomplete – Amphibians living in water obtain additional oxygen by diffusion through their skin – Reptiles have a septum that partially subdivides the ventricle, thereby further reducing the mixing of blood in the heart 74

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76 Vertebrate Circulatory Systems Mammals, birds, and crocodilians – 4-chambered heart – 2 separate atria and 2 separate ventricles – Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs – Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps it to rest of the body 76

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78 78 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. LanceletsFishMammalsTurtlesAmphibiansCrocodilians Squamates Birds 4-chamber heart 4-chamber heart 3-chamber heart 2-chamber heart

79 The Cardiac Cycle Heart has two pairs of valves – Atrioventricular (AV) valves Maintain unidirectional blood flow between atria and ventricles Tricuspid valve = On the right Bicuspid, or mitral, valve = On the left – Semilunar valves Ensure one-way flow out of the ventricles to the arterial systems Pulmonary valve located at the exit of the right ventricle Aortic valve located at the exit of the left ventricle 79

80 The Cardiac Cycle Valves open and close as the heart goes through the cardiac cycle Ventricles relaxed and filling (diastole) Ventricles contracted and pumping (systole) “Lub-dub” sounds heard with stethoscope – Lub – AV valves closing – Dub – closing of semilunar valves 80

81 Right ventricle 1. The atria contract. Diastole “Lub”“Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. Time (seconds) 65 mL 130 mL 81 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

82 Right ventricle 1. The atria contract. Diastole “Lub”“Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 82 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

83 Right ventricle 1. The atria contract. Diastole “Lub” 1. “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 83 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

84 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 84 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

85 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 85 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

86 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 86 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

87 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle Time (seconds) 65 mL 130 mL 87 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

88 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle pressure in aorta Time (seconds) 65 mL 130 mL 88 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

89 Right ventricle 1. The atria contract. Diastole “Lub” “Dup” DiastoleSystole Pressure (mm Hg) Pulmonary valve Right atrium AV valves Left ventricle Left atrium Aortic valve 2. “Lub”: The ventricles contract, the atrioventricular (AV) valves close, and pressure in the ventricles builds up until the aortic and pulmonary valves open. 3. Blood is pumped out of ventricles and into the aorta and pulmonary artery. 5. The ventricles fill with blood. 4. “Dup”: The ventricles relax, the pressure in the ventricles falls at the end of systole, and since pressure is now greater in the aorta and pulmonary artery, the aortic and pulmonary valves slam shut. pressure in left ventricle pressure in aorta Time (seconds) 65 mL 130 mL volume in left ventricle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 89

90 The Cardiac Cycle Heart contains “self-excitable” autorhythmic fibers Most important is the sinoatrial (SA) node – Located in wall of right atrium – Acts as pacemaker – Autonomic nervous system can modulate rate 90

91 The Cardiac Cycle Each SA depolarization transmitted – To left atrium – To right atrium and atrioventricular (AV) node AV node is only pathway for conduction to ventricles – Spreads through atrioventricular bundle – Purkinje fibers – Directly stimulate the myocardial cells of both ventricles to contract 91

92 The Cardiac Cycle Electrical activity can be recorded on an electrocardiogram (ECG or EKG) – First peak (P) is produced by depolarization of atria (atrial systole) – Second, larger peak (QRS) is produced by ventricular depolarization (ventricular systole) – Last peak (T) is produced by repolarization of ventricles (ventricular diastole) 92

93 Seconds R T wave 1 sec +1 0 Purkinje fibers Left atrium Right atrium Purkinje fibers AV bundle SA node (pacemaker) AV node AV bundle Interventricular septum Left and right bundle branches 1. The impulse begins at the SA node and travels to the AV node. Internodal pathway AV 2. The impulse is delayed at the AV node. It then travels to the AV bundle. P wave Millivotts Q S Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 93

94 Seconds R T wave 1 sec +1 0 Purkinje fibers AV bundle Interventricular septum 3. From the AV bundle, the impulse travels down the interventricular septum. Left and right bundle branches 5. Finally reaching the Purkinje fibers, the impulse is distributed throughout the ventricles. 4. The impulse spreads to branches from the interventricular septum. P wave Millivotts 94 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Q S

95 The Cardiac Cycle Right and left pulmonary arteries deliver oxygen-depleted blood from the right ventricle to the right and left lungs Pulmonary veins return oxygenated blood from the lungs to the left atrium of the heart 95

96 The Cardiac Cycle Aorta and all its branches are systemic arteries, carrying oxygen-rich blood from the left ventricle to all parts of the body – Coronary arteries supply oxygenated blood to the heart muscle Blood from the body drains into the right atrium – Superior vena cava drains upper body – Inferior vena cava drains lower body 96

97 The Cardiac Cycle Arterial blood pressure can be measured with a sphygmomanometer Systolic pressure is the peak pressure at which ventricles are contracting Diastolic pressure is the minimum pressure between heartbeats at which the ventricles are relaxed Blood pressure is written as a ratio of systolic over diastolic pressure 97

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99 Characteristics of Blood Vessels Blood leaves heart through the arteries Arterioles are the finest, microscopic branches of the arterial tree Blood from arterioles enters capillaries Blood is collected into venules, which lead to larger vessels, veins Veins carry blood back to heart 99

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103 Gills Specialized extensions of tissue that project into water Increase surface area for diffusion External gills are not enclosed within body structures – Found in immature fish and amphibians – Two main disadvantages Must be constantly moved to ensure contact with oxygen- rich fresh water Are easily damaged 103

104 Gills Branchial chambers – Provide a means of pumping water past stationary gills – Internal mantle cavity of mollusks opens to the outside and contains the gills Draw water in and pass it over gills – In crustaceans, the branchial chamber lies between the bulk of the body and the hard exoskeleton of the animal Limb movements draw water over gills 104

105 Gills Gills of bony fishes are located between the oral (buccal or mouth) cavity and the opercular cavities These two sets of cavities function as pumps that alternately expand Move water into the mouth, through the gills, and out of the fish through the open operculum or gill cover 105

106 106 Gills

107 Some bony fish have immobile opercula – Swim constantly to force water over gills – Ram ventilation Most bony fish have flexible gill covers Remora switch between ram ventilation and pumping action 107

108 Gills 3–7 gill arches on each side of a fish’s head Each is composed of two rows of gill filaments Each gill filament consist of lamellae – Thin membranous plates that project into water flow – Water flows past lamellae in 1 direction only 108

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110 Gills Within each lamella, blood flows opposite to direction of water movement – Countercurrent flow – Maximizes oxygenation of blood – Increases  p Fish gills are the most efficient of all respiratory organs 110

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112 Gills Many amphibians use cutaneous respiration for gas exchange In terrestrial arthropods, the respiratory system consists of air ducts called trachea, which branch into very small tracheoles – Tracheoles are in direct contact with individual cells – Spiracles (openings in the exoskeleton) can be opened or closed by valves 112

113 Lungs Gills were replaced in terrestrial animals because – Air is less supportive than water – Water evaporates The lung minimizes evaporation by moving air through a branched tubular passage A two-way flow system – Except birds 113

114 Lungs Air exerts a pressure downward, due to gravity A pressure of 760 mm Hg is defined as one atmosphere (1.0 atm) of pressure Partial pressure is the pressure contributed by a gas to the total atmospheric pressure 114

115 Lungs Partial pressures are based on the % of the gas in dry air At sea level or 1.0 atm – P N 2 = 760 x 79.02% = mm Hg – P O 2 = 760 x 20.95% = mm Hg – P CO 2 = 760 x 0.03% = 0.2 mm Hg At 6000 m the atmospheric pressure is 380 mm Hg – P O 2 = 380 x 20.95% = 80 mm Hg 115

116 Lungs Lungs of amphibians are formed as saclike outpouchings of the gut Frogs have positive pressure breathing – Force air into their lungs by creating a positive pressure in the buccal cavity Reptiles have negative pressure breathing – Expand rib cages by muscular contractions, creating lower pressure inside the lungs 116

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118 Lungs Lungs of mammals are packed with millions of alveoli (sites of gas exchange) Inhaled air passes through the larynx, glottis, and trachea Bifurcates into the right and left bronchi, which enter each lung and further subdivide into bronchioles Alveoli are surrounded by an extensive capillary network 118

119 119 Lungs

120 Lungs of birds channel air through very tiny air vessels called parabronchi Unidirectional flow Achieved through the action of anterior and posterior sacs (unique to birds) When expanded during inhalation, they take in air When compressed during exhalation, they push air in and through lungs 120

121 Lungs Respiration in birds occurs in two cycles – Cycle 1 = Inhaled air is drawn from the trachea into posterior air sacs, and exhaled into the lungs – Cycle 2 = Air is drawn from the lungs into anterior air sacs, and exhaled through the trachea Blood flow runs 90 o to the air flow – Crosscurrent flow – Not as efficient as countercurrent flow 121

122 122 Lungs

123 Gas Exchange Gas exchange is driven by differences in partial pressures Blood returning from the systemic circulation, depleted in oxygen, has a partial oxygen pressure (P O 2 ) of about 40 mm Hg By contrast, the P O 2 in the alveoli is about 105 mm Hg The blood leaving the lungs, as a result of this gas exchange, normally contains a P O 2 of about 100 mm 123

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125 Lung Structure and Function Outside of each lung is covered by the visceral pleural membrane Inner wall of the thoracic cavity is lined by the parietal pleural membrane Space between the two membranes is called the pleural cavity – Normally very small and filled with fluid – Causes 2 membranes to adhere – Lungs move with thoracic cavity 125

126 Lung Structure and Function During inhalation, thoracic volume increases through contraction of two muscle sets – Contraction of the external intercostal muscles expands the rib cage – Contraction of the diaphragm expands the volume of thorax and lungs Produces negative pressure which draws air into the lungs 126

127 Lung Structure and Function Thorax and lungs have a degree of elasticity Expansion during inhalation puts these structures under elastic tension Tension is released by the relaxation of the external intercostal muscles and diaphragm This produces unforced exhalation, allowing thorax and lungs to recoil 127

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130 Lung Structure and Function Tidal volume – Volume of air moving in and out of lungs in a person at rest Vital capacity – Maximum amount of air that can be expired after a forceful inspiration Hypoventilation – Insufficient breathing – Blood has abnormally high P CO 2 Hyperventilation – Excessive breathing – Blood has abnormally low P CO 2 130

131 Lung Structure and Function Each breath is initiated by neurons in a respiratory control center in the medulla oblongata Stimulate external intercostal muscles and diaphragm to contract, causing inhalation When neurons stop producing impulses, respiratory muscles relax, and exhalation occurs Muscles of breathing usually controlled automatically – Can be voluntarily overridden – hold your breath 131

132 Lung Structure and Function Neurons are sensitive to blood P CO 2 changes A rise in P CO 2 causes increased production of carbonic acid (H 2 CO 3 ), lowering the blood pH Stimulates chemosensitive neurons in the aortic and carotid bodies Send impulses to respiratory control center to increase rate of breathing Brain also contains central chemoreceptors that are sensitive to changes in the pH of cerebrospinal fluid (CSF) 132

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134 Respiratory Diseases Chronic obstructive pulmonary disease (COPD) – Refers to any disorder that obstructs airflow on a long-term basis – Asthma Allergen triggers the release of histamine, causing intense constriction of the bronchi and sometimes suffocation 134

135 Respiratory Diseases Chronic obstructive pulmonary disease (COPD) (cont.) – Emphysema Alveolar walls break down and the lung exhibits larger but fewer alveoli Lungs become less elastic People with emphysema become exhausted because they expend three to four times the normal amount of energy just to breathe Eighty to 90% of emphysema deaths are caused by cigarette smoking 135

136 Respiratory Diseases Lung cancer accounts for more deaths than any other form of cancer Caused mainly by cigarette smoking Follows or accompanies COPD Lung cancer metastasizes (spreads) so rapidly that it has usually invaded other organs by the time it is diagnosed Chance of recovery from metastasized lung cancer is poor, with only 3% of patients surviving for 5 years after diagnosis 136

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138 138 Types of Digestive Systems

139 Ingested food may be stored or first subjected to physical fragmentation Chemical digestion occurs next – Hydrolysis reactions liberate the subunit molecules Products pass through gut’s epithelial lining into the blood (absorption) Wastes are excreted from the anus 139

140 Vertebrate Digestive Systems Consists of a tubular gastrointestinal tract and accessory organs Mouth and pharynx – entry Esophagus – delivers food to stomach Stomach – preliminary digestion Small intestine – digestion and absorption Large intestine – absorption of water and minerals Cloaca or rectum – expel waste 140

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142 Vertebrate Digestive Systems Accessory organs – Liver Produces bile – Gallbladder Stores and concentrates bile – Pancreas Produces pancreatic juice Digestive enzymes and bicarbonate buffer 142

143 Vertebrate Digestive Systems Gastrointestinal tract is layered – Mucosa – innermost Epithelium that lines the interior, or lumen, of the tract – Submucosa Connective tissue – Muscularis Circular and longitudinal smooth muscle layers – Serosa – outermost Epithelium covering external surface of tract 143

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145 Mouth and Teeth Many vertebrates have teeth used for chewing or mastication Birds – Lack teeth – Break up food in a two-chambered stomach – Gizzard – muscular chamber that uses ingested pebbles to pulverize food 145

146 Carnivores – pointed teeth that lack flat grinding surfaces Herbivores – large flat teeth suited for grinding cellulose cell walls of plant tissues Humans have carnivore-like teeth in the front and herbivore-like teeth in the back 146

147 Mouth and Teeth Inside the mouth, the tongue mixes food with saliva – Moistens and lubricates the food – Contains salivary amylase, which initiates the breakdown of starch – Salivation is controlled by the nervous system Tasting, smelling, and even thinking or talking about food stimulate increased salivation 147

148 Mouth and Teeth Swallowing – Starts as voluntary action Continued under involuntary control – When food is ready to be swallowed, the tongue moves it to the back of the mouth – Soft palate seals off nasal cavity – Elevation of the larynx (voice box) pushes the glottis against the epiglottis Keeps food out of respiratory tract 148

149 149 Mouth and Teeth


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