Circulatory Systems (Ch. 42) Take a look at a skeleton and see how well a heart is protected open heart surgery takes breaking a body to get to the heart. Exchange of materials Animal cells exchange material across their cell membrane fuels for energy nutrients oxygen waste (urea, CO2) If you are a 1-cell organism thats easy!
diffusion If you are many-celled thats harder Overcoming limitations of diffusion Diffusion is not adequate for moving material across more than 1-cell barrier CO2 CO2 aa O2 CH aa NH3 CO2 CO2
CHO NH3 CHO CH O2 aa NH3 aa O2 aa CH NH3 CO2 NH3
CO2 NH3 CO2 CO2 NH3 O2 NH3 CO2 CO2 NH3 CHO CO2
aa In circulation What needs to be transported nutrients & fuels from digestive system respiratory gases O2 & CO2 from & to gas exchange systems intracellular waste waste products from cells: water, salts, nitrogenous wastes protective agents immune defenses regulatory molecules hormones Circulatory systems All animals have: circulatory fluid = blood
tubes = blood vessels muscular pump = heart open hemolymph closed blood Open circulatory system Taxonomy invertebrates insects, arthropods, mollusks Structure no separation between blood & interstitial fluid hemolymph
The fact that open and closed circulatory systems are each widespread among animals suggests that both offer advantages. For example, the lower hydrostatic pressures associated with open circulatory systems make them less costly than closed systems in terms of energy expenditure. Furthermore, because they lack an extensive system of blood vessels, open systems require less energy to build and maintain. And in some invertebrates, open circulatory systems serve a variety of other functions. For example, in molluscs and freshly molted aquatic arthropods, the open circulatory system functions as a hydrostatic skeleton in supporting the body. Closed circulatory system Taxonomy invertebrates earthworms, squid, octopuses vertebrates Structure blood confined to vessels & separate from
interstitial fluid 1 or more hearts large vessels to smaller vessels material diffuses between blood vessels & interstitial fluid closed system = higher pressures What advantages might be associated with closed circulatory systems? Closed systems, with their higher blood pressure, are more effective at transporting circulatory fluids to meet the high metabolic demands of the tissues and cells of larger and more active animals. For instance, among the molluscs, only the large and active squids and octopuses have closed circulatory systems. And although all arthropods have open circulatory systems, the larger crustaceans, such as the lobsters and crabs, have a more developed system of arteries and veins as well as an accessory pumping organ that helps maintain blood pressure. Closed circulatory
systems are most highly developed in the vertebrates. Vertebrate circulatory system Adaptations in closed system number of heart chambers differs 2 low pressure to body 3 4 low O2 to body high pressure
& high O2 to body Whats the adaptive value of a 4 chamber heart? 4 chamber heart is double pump = separates oxygen-rich & oxygen-poor blood; maintains high pressure Evolution of vertebrate circulatory system AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS Lung and skin capillaries Lung capillaries Lung capillaries FISHES
Gill capillaries Artery Pulmocutaneous circuit Gill circulation Heart: ventricle (V) A Atrium (A) Systemic circulation Vein Systemic capillaries A V
Left Right Systemic circuit Systemic capillaries Right systemic aorta Pulmonary circuit A Pulmonary circuit A Left
Systemic Birds AND aorta V V Right mammals! Left Wassssup?! Systemic capillaries A V Right A V Left Systemic circuit Systemic capillaries
Evolution of 4-chambered heart Selective forces increase body size protection from predation bigger body = bigger stomach endothermy can colonize more habitats flight decrease predation & increase hunting Effect of higher metabolic rate greater need for energy, fuels, O2, waste removal endothermic animals need 10x energy need to deliver 10x fuel & O2 to cells convergent evolution Vertebrate cardiovascular system Chambered heart atrium = receive blood
ventricle = pump blood out Blood vessels arteries = carry blood away from heart arterioles veins = return blood to heart venules capillaries = thin wall, exchange / diffusion capillary beds = networks of capillaries Arteries, veins, and capillaries are the three main kinds of blood vessels, which in the human body have a total length of about 100,000 km. Notice that arteries and veins are distinguished by the direction in which they carry blood, not by the characteristics of the blood they contain. All arteries carry blood from the heart toward capillaries, and veins return blood to the heart from capillaries. A significant exception is the hepatic portal vein that carries blood from capillary beds in the digestive system to capillary beds in the liver. Blood flowing from the liver passes into the hepatic vein, which conducts blood to the
heart. Blood vessels arteries veins artery venules arterioles arterioles capillaries venules veins Arteries: Built for high pressure pump Arteries thicker walls provide strength for high pressure
pumping of blood narrower diameter elasticity elastic recoil helps maintain blood pressure even when heart relaxes Veins: Built for low pressure flow Veins thinner-walled wider diameter Blood flows toward heart Open valve blood travels back to heart at low velocity & pressure lower pressure distant from heart blood must flow by skeletal muscle
contractions when we move Closed valve squeeze blood through veins valves in larger veins one-way valves allow blood to flow only toward heart Capillaries: Built for exchange Capillaries Precapillary sphincters Thoroughfare channel very thin walls lack 2 outer wall layers only endothelium enhances exchange across capillary Arteriole
(a) Sphincters relaxed Capillaries Venule diffusion exchange between blood & cells Arteriole Venule (b) Sphincters contracted (c) Capillaries and larger vessels (SEM) 20 m Controlling blood flow to tissues Blood flow in capillaries controlled by pre-capillary sphincters supply varies as blood is needed after a meal, blood supply to digestive tract increases during strenuous exercise, blood is diverted from digestive tract to
skeletal muscles capillaries in brain, heart, kidneys & liver usually filled to capacity Why? sphincters open sphincters closed Exchange across capillary walls Fluid & solutes flows out of capillaries to tissues due to blood pressure Lymphatic capillary bulk flow Interstitial fluid flows back into capillaries due to osmosis
plasma proteins osmotic pressure in capillary BP > OP BP < OP Interstitial fluid What about edema? Blood flow 85% fluid returns to capillaries Capillary Arteriole
15% fluid returns via lymph Venule About 85% of the fluid that leaves the blood at the arterial end of a capillary bed reenters from the interstitial fluid at the venous end, and the remaining 15% is eventually returned to the blood by the vessels of the lymphatic system. Systolic pressure Venae cavae Veins Venules Capillaries
Velocity (cm/sec) 5,000 4,000 3,000 2,000 1,000 0 Pressure (mm Hg) Area (cm2) The interrelationship of blood flow velocity, cross-sectional area of blood vessels, and blood pressure Lymphatic system Parallel circulatory system transports white blood cells defending against infection collects interstitial fluid & returns
to blood maintains volume & protein concentration of blood drains into circulatory system near junction of vena cava & right atrium Lymph system Production & transport of WBCs Traps foreign invaders lymph vessels (intertwined amongst blood vessels) lymph node Mammalian circulation systemic pulmonary
systemic What do blue vs. red areas represent? Mammalian heart to neck & head & arms Coronary arteries Coronary arteries bypass surgery Heart valves 4 valves in the heart flaps of connective tissue prevent backflow SL Atrioventricular (AV) valve between atrium & ventricle
keeps blood from flowing back into atria when ventricles contract lub Semilunar valves between ventricle & arteries prevent backflow from arteries into ventricles while they are relaxing dub AV AV The heart sounds heard with a stethoscope are caused by the closing of the valves. (Even without a stethoscope, you can hear these sounds by pressing your ear tightly against the chest of a frienda close friend.) The sound pattern is lubdup, lubdup, lubdup. The first heart sound (lub) is created by the recoil of blood against the closed AV valves. The second sound (dup) is the recoil of blood against the semilunar valves.
Lub-dub, lub-dub Heart sounds closing of valves Lub recoil of blood against closed AV valves Dub recoil of blood against semilunar valves SL AV AV Heart murmur defect in valves causes hissing sound when stream of blood squirts backward through valve Cardiac cycle 1 complete sequence of pumping heart contracts & pumps
heart relaxes & chambers fill contraction phase systole ventricles pumps blood out relaxation phase diastole atria refill with blood systolic ________ diastolic pump (peak pressure) _________________ fill (minimum pressure) 110 ____ The control of heart rhythm 1 Pacemaker generates
2 Signals are delayed wave of signals to contract. SA node (pacemaker) ECG 3 Signals pass to heart apex. at AV node. AV node 4 Signals spread throughout ventricles.
0.3 sec 0.4 sec AV valve open 1 Atrial and ventricular diastole AV valve closed 3 Ventricular systole; atrial diastole Measurement of blood pressure Pressure in cuff above120 Rubber cuff
inflated with air Artery 120 Pressure in cuff below 120 Blood pressure Reading: 120/170 Pressure in cuff below 70 120 70 Sounds audible in
stethoscope Artery closed High Blood Pressure (hypertension) if top number (systolic pumping) > 150 if bottom number (diastolic filling) > 90 Sounds stop The composition of mammalian blood Plasma 55% Constituent Major functions Water Solvent for carrying other substances
Icons (blood electrolytes Sodium Potassium Calcium Magnesium Chloride Bicarbonat e Plasma proteins Albumin Fibringen Osmotic balance pH buffering, and regulation of membrane permeability Cellular elements 45% Cell type Erythrocytes
(red blood cells) Separated blood elements Functions Number per L (mm3) of blood Leukocytes (white blood cells) 56 million Transport oxygen and help transport carbon dioxide 5,00010,000 Defense and immunity
Osmotic balance, pH buffering Clotting Immunoglobulins Defense (antibodies) Substances transported by blood Nutrients (such as glucose, fatty acids, vitamins) Waste products of metabolism Respiratory gases (O2 and CO2) Hormones Lymphocyte Basophil Eosinophil Neutrophil Platelets Monocyte 250,000
400,000 Blood clotting Differentiation of blood cells Pluripotent stem cells (in bone marrow) Lymphoid stem cells Myeloid stem cells Basophils B cells T cells Lymphocytes Eosinophils Neutrophils
Erythrocytes Platelets Monocytes Blood clotting 2 The platelets form a 1 The clotting process begins plug that provides emergency protection against blood loss. 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.
Collagen fibers Platelet releases chemicals that make nearby platelets sticky Platelet plug 3 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). Fibrin clot
Clotting factors from: Platelets Damaged cells Plasma (factors include calcium, vitamin K) Prothrombin Thrombin Fibrinogen Fibrin 5 m Red blood cell Atherosclerosis Connective tissue (a) Normal artery
Smooth muscle Endothelium 50 m Plaque (b) Partly clogged artery 250 m Coronary Embolism Cerebral Aneurysm Bloody well ask some questions, already! Make sure you can do the following: 1. Label all parts of the mammalian heart and diagram blood flow through it. 2. Explain the causes of circulatory system disruptions and how disruptions of the
circulatory system can lead to disruptions of homeostasis.
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