ANP 1105 Lecture : Chapter 19 blood vessels.doc

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Chapter 19: blood vessels blood vessels- form a closed delivery system that begins and ends at the heart. Walls of all blood vessels (except the smallest) have 3 distinct layers or tunics (coverings) that surround a central blood-containing space (the vessel lumen: tunica intima. This tunic has intimate contact with the blood in the lumen. Contains endothelium; simple squamous epithelium that lines the lumen of all vessels. The endothelium is continuous with the endocardial lining of the heart and its flat cells fit closely together to form a slick surface that minimizes friction as blood moves through the lumen. For blood vessels larger than 1mm in diameter, a subendothelial layer that consists of a basement membrane and loose connective tissue supports the endothelium: tunica media. Circularly arranged smooth muscle cells and sheets of elastin. Activity of smooth muscle is regulated by sympathetic vasomotor nerve fibres of the ans.