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10 31 07 - Cardiovascular System I

10 31 07 - Cardiovascular System I - *Chapter 14...

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*Chapter 14– Circulatory System* The functions of the circulatory system are to transport white and red blood cells, carry and deliver dissolved gasses, distribute nutrients, absorb metabolic wastes, distribute heat. Many invertebrates have an open circulatory system, with no directionality to the flow of “blood.” Vertebrates have a closed system, where blood is contained in a circuit of vessels. Arteries – carry blood away from heart, to capillaries Veins – carry blood to heart, from capillaries Blood vessels have 3 layers: - Tunica interna – endothelium - Tunica externa – fibrous outer coat of collagen - Tunica media – contains smooth muscle Capillaries have very thin walls (endothelium only) are the site of exchange between the blood and body cells The heart is a pump that pressurizes blood and forces it into an artery – the aorta - lined by endothelium (the endocardium ) - surrounded by pericardium - musclular region in the middle = myocardium Cardiac muscle is stimulated to contract my a network of modified muscle cells directed by a pacemaker, the sinoatrial node , and only modified by nerves.
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