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BIOL 4260 Midterm: HA_SG_Chpt23_Blood_Vessels

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BIOL 4260

Objectives: - Anatomy of blood vessels 1. Describe the structure and function of arteries, veins and capillaries. Blood Vessels Delivery system of dynamic structures that starts and ends at the heart a. Arteries: carry blood away from the heart; oxygenated except for pulmonary circulation and umbilical vessels of a fetus b. Capillaries: contact tissue cells and directly serve cellular needs c. Veins: Carry blood toward the heart Structure of Blood Vessel Walls • Arteries and Veins- tunica intima, tunica media and tunica externa • Lumen- central blood-containing space • Capillaries- endothelium with sparse basal lamina o Tunics • Tunica intima- endothelium lines the lumen of all vessels o In vessels larger than 1 mm a subendothelial connective tissue basement membrane is present • Tunica Media- smooth muscle and sheets of elastin o Smooth muscle vasomotor nerve fibers control vasoconstriction and vasodilation of blood vessels o Bulkiest layer responsible for maintaining blood flow and blood pressure • Tunica Externa (tunica adventitia) o Outermost layer of wall o Composed mostly of loose collagen fibers that protect and reinforce wall and anchor it to surrounding structures o Infiltrated with nerve fibers, lymphatic vessels ▪ Large veins also contain elastic fibers in this layer o Vasa Vasorum: system of tiny blood vessels found in larger vessels ▪ Function to nourish outermost external layer o o 2. Explain how veins differ from arteries. Veins a. Formed when venules converge b. Have thinner walls, larger lumens compared with corresponding arteries c. Blood pressure is lower than in arteries d. Thin tunica media and thick tunica externa consisting of collagen fibers and elastic networks e. Called capacitance networks/ blood reservoirs; contain up to 65% of the blood supply g. Veins= adaptations that ensure return of blood to the heart h. Large diameter lumens offer little resistance i. Valves prevent backflow of blood (most abundant in veins of limbs) j. Venous sinuses= flattened cells with extremely thin walls (Ex: coronary sinuses of the heart and dural sinuses of the brain) 3. Define vasoconstriction and vasodilatation. Mention the receptor that is important to bring about these functions.??? a. Smooth muscle vasomotor nerve fibers control vasoconstriction and vasodilation of blood vessels b. Vasoconstriction is a reduction in the lumen diameter of a blood vessel due to smooth muscle contraction. Vasodilation is a widening of the lumen due to smooth muscle relaxation. Both are regulated by vasomotor nerve fibers of the sympathetic division of the autonomic nervous system. c. 4. Describe the three types of capillaries and parts of the body that they are found. 3 structural types a. Continuous capillaries- abundant in skin and muscles i. Tight junctions connect endothelial cel
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