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lecture 4 - circulatory

lecture 4 - circulatory - Circulation and gas exchange...

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Circulation and gas exchange: Basic function - to provide the body with oxygen, nutrients, remove wastes and CO 2 . (lungs/gills generally don’t do much with nutrients and wastes, but, as usual, there are exceptions) Reason for having a circulatory system: all cells in the body need access to oxygen, etc. Methods of granting access to oxygen/nutrients [Fig., similar to 23.1, p. 468] : - open circulatory system - some blood vessels may be present, but no capillaries. In other words, heart beats, fluid moves into some large vessels, and from there into the body. All parts of the body are therefore “bathed” in this fluid [e.g., insects, many arthropods]. - closed circulatory system - blood is always confined to blood vessels. Small blood vessels are present throughout the tissues and thus insure that blood can get to all parts of the body [e.g., cephalopods, earthworms, vertebrates]. Vertebrate cardiovascular systems: - heart is composed of at least two parts: an atrium and a ventricle. But higher vertebrates may add to this (e.g., two atria). - atrium receives blood from the body, then moves blood to ventricle, ventricle pumps blood out of heart. - arteries -> arterioles -> capillaries (&capillary beds) -> venules -> veins (NOTE that this says nothing about what parts of the body the blood is going to, just the names of the blood vessels) The flow of blood in mammals [Fig. 23.2, p. 469] : - compared to other animals, all parts of the body get newly oxygenated blood under high pressure. Mammals: right ventricle -> lungs -> left atrium -> left ventricle -> body -> right atrium -> right ventricle.
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But we need special arrangements in a fetus: [Fig., not in book] : _____________________________________________ | | \/ | right ventricle -> dutus arteriosus -> BODY -> right <- /\ atrium | | | | ____| | | | | | ___________________________________| | | | | \/ | | left atrium -> left ventricle -> BODY -------- (note: the above “diagram” may not show up correctly using ASCII text (i.e., it might not look right on the web)) “body” is actually “body & placenta” * Note that blood going to the lungs is considered to be in the “pulmonary circuit”, whereas blood going to the body is in the “systemic circuit”. Human heart - details: [Figs. 23.3A and 23.3B, p. 470] . - go through overheads, mention all parts (mostly a review of the above). Cardiac cycle: basically, what happens from one heart contraction to the next. First a few terms: heart rate - # of times heart beats in one minute (pulse is always recorded as beats/ minute, though often is measured over 30 seconds or so - average is about 70). stroke volume - amount of blood pumped by left ventricle with one beat (average, about 75ml per beat). cardiac output - amount of blood pumped by left ventricle [Question - what about the right?] in one minute (cardiac output is about 5.25 L if heart rate is about 70.
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