560
UNIT FOUR
Superior
vena cava
Systemic
capillaries
Tissue cells
Systemic
capillaries
Tissue cells
Pulmonary
artery
Pulmonary
veins
Alveolus
Alveolus
Left atrium
Mitral valve
Aortic valve
Left ventricle
Right atrium
Tricuspid valve
Pulmonary valve
Inferior vena cava
Right ventricle
Aorta
Alveolar
capillaries
Alveolar
capillaries
O
2
CO
2
O
2
O
2
CO
2
CO
2
O
2
CO
2
FIGURE 15.10
The right ventricle forces
blood to the lungs, whereas the left ventricle
forces blood to all other body parts. (Structures
are not drawn to scale.)
They provide f rm attachments For the heart valves and For
muscle f bers and prevent the outlets oF the atria and ven-
tricles From dilating during contraction. The Fibrous rings,
together with other masses oF dense connective tissue in the
portion oF the septum between the ventricles (interventricular
septum), constitute the
skeleton of the heart
(f g. 15.9).
Path of Blood Through the Heart
Blood low in oxygen and high in carbon dioxide enters the
right atrium through the venae cavae and the coronary sinus.
As the right atrial wall contracts, the blood passes through
the right atrioventricular orif ce and enters the chamber oF
the right ventricle
(f
g. 15.10)
.
PRACTICE
8
Which blood vessels carry blood into the right atrium?
9
Where does blood go after it leaves the right ventricle?
10
Which blood vessels carry blood into the left atrium?
11
What prevents blood from F
owing back into the ventricles when
they relax?
Skeleton of the Heart
Rings oF dense connective tissue surround the pulmonary
trunk and aorta at their proximal ends. These rings are con-
tinuous with others that encircle the atrioventricular orif ces.
TABLE
15.2
|
Valves of the Heart
Valve
Location
Function
Tricuspid valve
Right atrioventricular oriĀ±
ce
Prevents blood from moving from right ventricle into right atrium during ventricular contraction
Pulmonary valve
Entrance to pulmonary trunk
Prevents blood from moving from pulmonary trunk into right ventricle during ventricular relaxation
Mitral valve
Left atrioventricular oriĀ±
ce
Prevents blood from moving from left ventricle into left atrium during ventricular contraction
Aortic valve
Entrance to aorta
Prevents blood from moving from aorta into left ventricle during ventricular relaxation
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