Transcript Veins
Veins and Arteries Smooth muscle: no striations, uninucleated, spindle shaped cells. Veins and Arteries Arterioles, Venules, and Capillaries The Circulatory System The Circulatory System I. System Overview A. Function: A closed system of dynamic tubes responsible for the transportation of blood to lungs, heart, and body tissues. • There are over 65,000 miles of vessels in your body! The Circulatory System I. System Overview B. System Organs: Blood Vessels Arteries carry blood away from the heart Arterioles smaller branches of arteries Capillaries site of nutrient/gas exchange Venules smaller branches of veins Veins carry blood to the heart Figure 13.6 The Circulatory System II. Anatomy of a Blood Vessel A. Blood vessel walls consist of three layers: 1. Tunica Intima-inner layer • smooth surface • minimizes friction 2. Tunica Media-middle layer • composed of smooth muscle • regulates size of lumen 3. Tunica Adventitia-outer layer • made of collagen fibers • protects and connects Figure 13.17 *The interior of a blood vessel is called the lumen. The Circulatory System III. Characteristics of Arteries A. Large muscular walls • • Controls blood flow by vasoconstriction and vasodilation. Prevents walls from bursting as arteries experience high blood pressure because they are closer to heart. B. Elastic walls • • Allows for vessels to stretch to withstand pressure fluctuations. Allows for blood to flow continuously through artery. The Circulatory System IV. Characteristics of Veins A. Thin walls • Veins experience lower pressure so there is less chance of bursting. B. Adaptations to aid blood return to the heart • • Lumen is large to reduce friction in blood flow. Valves are present in limbs to aid in movement against gravity. The Circulatory System V. Characteristics of Capillaries A. Very thin walls • One cell thick walls allow for easy gas and nutrient exchange. B. Regulates blood flow throughout the body • Sphincters regulate blood entry into capillary beds, increasing or decreasing volume of blood in certain regions. Figure 13.19 The Circulatory System VI. Atherosclerotic Artery Figure 13.A The Circulatory System VI. Varicose Veins