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Structure, Function, Homeostasis Circulation and Gas Exchange Invertebrate Circulation Membranes o Lower animals (sponges) o Exchange with environment achieved by water flowing across body membranes o Passive transport (osmosis) of water o Membrane 1 cell thick Gastrovascular cavities o Cnidarians (jellyfish, hydra), planarians, flatworms o One opening o Organism is 2 cells thick o Separates internal environment from external environment o Keeps all cells bathed in an aqueous solution o Only inner cells are able to exchange nutrients/wastes Open/closed circulatory systems o Basic components of circulatory system Circulatory fluid Interconnecting vessels Muscular pump (heart) o Open Arthropods (insects, spiders, crustaceans), mollusks (snails, clams) No distinction between blood and interstitial fluid (hemolymph) Heart Contracts – pushes blood out o Heart pumps hemolymph to interconnected sinuses that bathe tissues o Blood bathes organs directly Relaxes – draw blood in o Muscles in body contract to help push blood back into heart Advantages Lower blood pressure = lower energy expenditure No blood vessels = less energy to maintain Open circulatory system can serve other functions (mollusks = hydrostatic skeleton) Disadvantages Lower blood pressure Inability to control blood distribution/velocity Low metabolic rate (as a result of previous point) o Closed Vertebrates, some mollusks (squid, octopuses), earthworms Blood is confined to vessels and is distinct from interstitial fluid Advantages Every cell of the body is within one to three cells distance from a capillary o If more, it would take too long for blood to transport through all cells Greater control of oxygen delivery to tissues Allows for greater metabolic rate/activity Animals with high metabolic rates have more complex circulatory systems Structure, Function, Homeostasis Circulation and Gas Exchange Vertebrate Circulation Heart o Atrium (one) or atria (two) (different forms of the same word) Chamber that receives blood returning to the heart o Ventricles Chamber that pumps blood out of the heart Right Goes to lungs Smaller because short distance to lungs Left Goes to brain and extremities Larger because large distance to extremities Contract with greater force in order to reach extremities o Circulation Pulmonary Carries depleted blood to the lungs Returns oxygen-rich blood to the heart Lungs, gills Systemic Distributes oxygenated blood to the tissues of the body Body tissues Blood Vessel Arteries Structure Thick middle and outer layers Elastic (recoil) Arterioles Smaller diameter Capillaries Venules Veins Only an inner layer a few cells thick Large diameter Not as thick as arteries One-way valves Function Accommodates high blood pressure Maintains blood pressure even when heart relaxes Maintains pressure as blood goes to capillaries Gas exchange Connect capillaries to veins Blood pressure lower here Prevents backflow Structure, Function, Homeostasis Fish Two-chambered heart Single circuit of blood flow Amphibians Three-chambered heart Two circuits of blood flow o Pulmocutaneous o Systemic Some mixing of oxygen-rich and oxygen-poor blood Circulation and Gas Exchange Reptiles Three-chambered heart Two circuits of blood flow Septum partially divides the single ventricle o Reduces mixing of blood Cardiac Cycle One complete sequence of pumping o Systole (contraction phase) o Diastole (relaxation phase) Cardiac output depends on heart rate (number of beats per minute) and stroke volume o Average resting cardiac output: 5.25 L/min o Number goes up during exercise Regulated by electrical impulses that radiate throughout heart o Pacemaker Sets the rate and timing at which all cardiac muscle cells contract Located in the wall of the right atrium Myogenic heart Pacemaker located in the heart Pacemaker made up of specialized muscle tissues Neurogenic heart Pacemakers originate in motor nerves outside the heart Mammals and birds Four-chambered heart Completely separates oxygenrich and oxygenpoor blood Structure, Function, Homeostasis Circulation and Gas Exchange Blood Blood Types Blood Type A B AB O Antigens (Proteins) on Blood Cells A B A and B Neither A nor B Blood Type A B AB O Rh+ Rh- Antibodies in Plasma Anti-B Anti-A Neither anti Both anti Possible Alleles AA or AO BB or BO AB OO Rh+Rh+ or Rh+RhRh-Rh- Can Give Blood To A, AB B, AB AB O, A, B, AB Can Receive Blood From O, A O, B O, A, B, AB O Dominant/Recessive A dominant over O B dominant over O A and B are co-dominant O is recessive Rh+ is dominant Rh- is recessive Structure, Function, Homeostasis Cardiovascular disease Thrombus (non injury-induced clot) o Clogs coronary artery or artery to the brain o Heart attack Death of cardiac muscle tissue Due to prolonged blockages of coronary arteries o Stroke Death of nervous tissue in the brain Atherosclerosis o Growths (plaques) develop in the inner walls of the arteries Narrow vessels are more likely to tram an embolus and are common sites for thrombus formation o Risk factors Hypertension promotes atherosclerosis Can be controlled by lifestyle and diet Genetics Smoking, lack of exercise, high cholesterol LDL/HDL in blood Circulation and Gas Exchange