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Circulation and Gas Exchange The Respiratory System What is its function? Why is it necessary? GETS oxygen for the body Needed for cellular respiration GETS RID of carbon dioxide Produced during cellular respiration Characteristics/Requirements of ALL Gas Exchange Mechanisms: MOIST membranes High surface area-to-volume ratio An animal’s respiratory surfaces must be large enough to provide oxygen and expel carbon dioxide for the entire body Respiration in Non-Mammals Small animals (earthworms, etc.) exchange gases by diffusion across its general body surface Gills are outfoldings of the body surface specialized for gas exchange for aquatic organisms Blood flowing through the capillaries picks up oxygen from the water Countercurrent Exchange- blood & water flow in opposite directions Countercurrent Exchange (Aquatic Animals) Countercurrent exchange allows for the efficient transfer of oxygen to the blood As blood flows through the capillary, it becomes more and more loaded with oxygen Steep concentration gradient allows for efficient uptake of oxygen Tracheae The respiratory system used by insects Tracheae are air tubes that branch throughout the insect body The finest branches of the tracheae extend to the surface of nearly every cell, where gas is exchanged by diffusion Lungs Lungs are found in terrestrial vertebrates Reptiles, birds, mammals, amphibians Lungs of mammals have a large enough surface area to carry out gas exchange for the entire body How do the gases get from the lungs throughout the rest of the body, though?? The circulatory system transports the gases throughout the body after they’re exchanged in the lungs Human Respiratory System Human Respiratory System Air enters the lungs by a system of branching ducts Nostrils Pharynx Larynx Trachea (w/ cilia) 2 bronchi Bronchioles Alveoli Alveoli Alveoli are clusters of air sacs at the end of bronchioles Alveoli have thin epithelium, which serve as the respiratory surface Oxygen diffuses from the alveoli into the web of capillaries around each alveolus The capillaries then transfer the oxygen throughout the body, via the circulatory system Why is the circulatory system necessary? TRANSPORTATION! Diffusion is not fast enough to transport chemicals throughout an animal’s body The circulatory system transports fluid throughout the body This solves the problem of diffusion by ensuring that no substance had to diffuse far to enter or leave a cell Open vs. Closed Circulatory Systems In open circulatory systems, hemolymph bathes the internal organs directly Insects, arthropods, mollusks In closed circulatory systems, blood is confined to vessels Blood exchanges materials with the ISF bathing the cells Earthworms, squids, octopuses, vertebrates Open vs. Closed Circulatory Systems Adaptations of the Vertebrate Circulatory System Fish - Heart with 2 chambers (one atrium, one ventricle) Amphibians (frogs)- 3-chambered heart (two atria, one ventricle) Reptiles – (3-chambered with partial septum) Birds/Mammals-4-chambered heart (two atria, two ventricles) Vertebrate circulatory systems AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS Lung and skin capillaries Lung capillaries Lung capillaries FISHES Gill capillaries Artery Pulmocutaneous circuit Gill circulation Right systemic aorta Pulmonary circuit Heart: ventricle (V) A A Atrium (A) V V Right Vein Systemic circulation Systemic capillaries A Left Right A Left Systemic V aorta Left A V Right A V Left Systemic circuit Systemic circuit Systemic capillaries Pulmonary circuit Systemic capillaries Systemic capillaries Double Pump Right side pumps to the lungs and back to left atrium (PULMONARY CIRCUIT) Left side pumps to the entire body and returns blood to right atrium (SYSTEMIC CIRCUIT) Oxygenated & deoxygenated blood never mix! The mammalian cardiovascular system 7 Capillaries of head and forelimbs Anterior vena cava Pulmonary artery Aorta Pulmonary artery 9 6 Capillaries of right lung Capillaries of left lung 2 4 3 Pulmonary vein 5 1 Right atrium 3 11 Left atrium Pulmonary vein 10 Left ventricle Right ventricle Aorta Posterior vena cava 8 Figure 42.5 Capillaries of abdominal organs and hind limbs The Heart About the size of a clenched fist Made up of mostly cardiac muscle tissue: striated with branches; involuntary Atria have thin walls, ventricles have thicker walls Why?? Ventricles must pump blood through the pulmonary & systemic circuits. (LONG DISTANCE) The Heart: Structure and Function AV Valves: Located between each atrium and ventricle Keep blood from flowing back into the atria Semilunar Valves: Located at the exits of the heart (at the bottom of each ventricle) Prevent blood from flowing back into the ventricles The Human Heart Blood Vessels Arteries carry blood away from the heart to organs throughout the body Arteries are thicker than veins…why?? Thick layer of smooth muscle (nonstriated; involuntary)+ elastic tissue Veins return blood to the heart Categorized by direction of flow, NOT whether or not they contain oxygen Thinner layer of smooth muscle; VALVES to prevent back flow of blood; not very elastic Capillaries are microscopic vessels with very thin, porous walls .9 Vein Artery Basement membrane Endothelium 100 µm Valve Endothelium Endothelium Smooth muscle Smooth muscle Capillary Connective tissue Connective tissue Artery Vein Venule Arteriole Venous Transport In the thinner-walled veins Blood flows back to the heart mainly as a result of muscle action Direction of blood flow in vein (toward heart) Valve (open) Skeletal muscle Valve (closed) Capillary Exchange The capillary wall is a single layer of flattened cells The transfer of substances occurs between the capillaries and the interstitial fluid (which bathes the cells) This occurs by bulk flow, the movement of fluid due to pressure Water, sugars, salts, oxygen, and urea pass through the capillary walls Capillary Exchange Area (cm2) 5,000 4,000 3,000 2,000 1,000 0 Velocity (cm/sec) 50 40 30 20 10 0 The velocity of blood flow varies in the circulatory system Systolic pressure Veins Venules Capillaries Arterioles Diastolic pressure Arteries 120 100 80 60 40 20 0 Aorta Pressure (mm Hg) Venae cavae e 42.11 Velocity, B. Pressure, & Area And is slowest in the capillary beds as a result of the high resistance and large total cross-sectional area Blood Pressure 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 Measured with sphygmomanometer Normal pressure = 120/80 mm Hg Control of the Heart Cardiac muscles contract (systole) and relax (diastole) in a rhythmic cycle The sinoatrial node (SA node), also known as the pacemaker, maintains the heart’s pumping rhythm by setting the rate at which all cardiac muscles contract Control of the Heart Cardiac Cycle Atria Systole Diastole Diastole Ventricles EKG Diastole P wave Systole QRSwave Diastole T wave 2.7 The cardiac cycle 2 Atrial systole; ventricular diastole Semilunar valves closed 0.1 sec Semilunar valves open 0.3 sec 0.4 sec AV valves open 1 Atrial and ventricular diastole AV valves closed 3 Ventricular systole; atrial diastole The Structure of Blood Blood is made up of plasma, red blood cells, white blood cells, and platelets Plasma, which makes up about 55% of blood volume, is mostly water Plasma also contains antibodies Plasma also contains fibrinogens, proteins that act as clotting factors Fibrinogen (inactive) is a protein in blood that is converted into fibrin (active), when needed Thrombin is the enzyme that activates the fibrinogen. K & Ca are important minerals for clotting reaction to occur. Hemophilia is an inherited disorder, characterized by excessive bleeding from minor cuts and bruises People with hemophilia can die from minor cuts The Structure of Blood Red Blood Cells (Erythrocytes) The human body contains 25 trillion red blood cells Major function is to transport oxygen Contains hemoglobin, an ironcontaining protein that carries oxygen Red blood cells are produced in the bone marrow Hemoglobin Carries Oxygen Like all respiratory pigments Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body Heme group Iron atom O2 loaded in lungs O2 unloaded In tissues Figure 42.28 Polypeptide chain O2 O2 Carbon Dioxide Transport Small amount binds to hemoglobin to form carboxyhemoglobin. MOST is transported as bicarbonate ion: CO2 + H2O H2CO3H+ + HCO3Serves as a buffer to control pH of blood. pH = 7.4 The Structure of Blood White blood cells (leukocytes) Major function is to fight infection 5 major types Monocytes, neutrophils, basophils, eosinophils, lymphocytes White blood cells spend most of their time patrolling through the ISF and the lymphatic system, where most of the battles against pathogens are waged The Structure of Blood Platelets (Thrombocytes) Platelets are fragments of cells Platelets enter the blood and function in the process of blood clotting Blood: An Overview Cardiovascular Disease Cardiovascular disease (diseases of the heart and blood vessels) cause more than half of all deaths in the US Heart attack: Death of cardiac muscle tissue as a result of blockage of a coronary artery Stroke: Death of nervous tissue in the brain, resulting from blockage of arteries in the head Artherosclerosis Plaque (cholesterol and triglycerides/fats) deposit in blood vessels Can lead to stroke or heart attack.
