Blood Vessels and the Mammalian Heart
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Transcript of 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• 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
Structure of Blood Vessels
Structure of Blood Vessels
Mechanisms to Counteract Low Venous Pressure
• There are valves in some veins to stop backflow
• Skeletal muscle pump– Muscles press against
thin-walled veins
Atherosclerosis• Video
The Pulmonary and Systemic Circuits
Figure 18.1
The Mammalian Heart
• Pulmonary circuit: carries blood to and from the lungs
• Systemic circuit: carries blood to and from the body
Heart Chambers
Figure 18.5b
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.
Heart Chambers
Figure 18.5e
Blood Flow Through the Heart
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)