BIOL 240M Chapter Notes - Chapter 42: Superior Vena Cava, Pulmonary Artery, Pulmonary Vein

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6 Feb 2017

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II. Coordinated cycles of heart contraction drive double circulation in mammals
a. Mammalian Circulation
i. Organization of mammalian cardiovascular system
1. Pulmonary Circuit
a. Right ventricle pumps blood to the lungs via
pulmonary arteries
b. Blood flows through capillary beds in the left and
right lungs
c. Oxygen-rich blood returns to lungs via
pulmonary veins to left atrium of the heart
d. Pumps down to left ventricle which pumps into
systemic circuit
2. Systemic Circuit
a. The blood leaves the left ventricle via the aorta,
which conveys blood to arteries leading
throughout the body
i. First branches go to the coronary arteries
to supply blood to the heart
b. Branches then lead to capillary beds in the head
and arms
c. Aorta descends through abdomen supplying
oxygen-rich blood through capillary beds in
abdominal organs and legs
d. All blood returns to the heart from the head,
neck, and forelimbs through the superior vena
e. All other blood comes from the inferior vena
f. Both vena cava conjoin to empty their blood into
the right atrium
b. The Mammalian Heart: A Closer Look
i. Atria have relatively thin walls and serve as collection
chambers from lungs and the body/brain
ii. Ventricles are thicker and contract much more forcefully
(especially left ventricle)
iii. One Complete cardiac cycle of pumping and filling
1. Systole contraction phase of the cycle
2. Diastole relaxation phase of the cycle
3. Cardiac output volume of blood each ventricle pumps
per minute (5L/min)
a. Heart rate rate of contraction
i. 60-100 bpm
b. Stroke volume amount of blood pumped by a
ventricle in a single contraction
i. Average 70 mL
iv. Valves Prevent Backflow in the Heart
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