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Blood Vessels and the Mammalian Heart

Blood Vessels and the Mammalian Heart. Types of Blood Vessels. Arteries – carry blood away from the heart Capillaries – smallest blood vessels Site of exchange between blood and tissues Veins – carry blood toward the heart. Blood Vessel Structure.

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Blood Vessels and the Mammalian Heart

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  1. Blood Vessels and the Mammalian Heart

  2. Types of Blood Vessels • Arteries – carry blood away from the heart • Capillaries – smallest blood vessels • Site of exchange between blood and tissues • Veins – carry blood toward the heart

  3. Blood Vessel Structure • Artery: strong walls to withstand high pressure. Middle layers made of muscle fibres and connective tissue • Arteriole: middle layers made of elastic fibres and smooth muscle • Capillary: composed of a single layer of cells • Venule: walls of smooth muscle • Vein: thinner middle layers with one-way valves

  4. Structure of Blood Vessels

  5. Structure of Blood Vessels

  6. Mechanisms to Counteract Low Venous Pressure • There are valves in some veins to stop backflow • Skeletal muscle pump • Muscles press against thin-walled veins

  7. Atherosclerosis • Video

  8. The Pulmonary and Systemic Circuits Figure 18.1

  9. The Mammalian Heart • Pulmonary circuit: carries blood to and from the lungs • Systemic circuit: carries blood to and from the body

  10. Heart Chambers Figure 18.5b

  11. The Mammalian Heart • The four chambered heart contains two upper chambers called atria, and two lower chambers called ventricles • The atria pump blood into the ventricles, then from there is pumped out to the body • The chamber alternately contract (pumping blood) and relax (filling with blood) in a rhythmic cycle called the cardiac cycle.

  12. Heart Chambers Figure 18.5e

  13. Blood Flow Through the Heart

  14. Interior Valves • Four valves in the heart prevent backflow of the blood • Atrioventricular (AV) Valves: located between each atrium and ventricle are forced closed during ventricle contraction (also known as tricuspid valves) • Semilunar valves: located at the top of the aorta (exit of left ventricle) and pulmonary artery (exit of right ventricle) are forced open during ventricle contraction and close during relaxation of ventricles (also known as bicuspid valves)

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