Download I. THE HEART

THE CIRCULATORY SYSTEM
All organisms must be able to transport nutrients and wastes. Smaller organisms rely on _diffusion_
for this movement; humans require an organized circulatory system for the movement of substances through the body.
We have a _closed____ circulatory system, which means our blood is _contained in vessels___. The human circulatory
system includes the heart, the blood vessels, and the blood.
I. THE HEART
(pp. 943-946)
The function of the heart is to _pump the blood to the cells of the body________. The heart itself is mostly composed
of _cardiac_____ muscle which forms a thick layer of tissue known as the _myocardium______. Humans have a _4__chambered heart, divided by a _septum____ into right and left sides.
A. Structure
1. Chambers
a. Atria (atrium = singular) _Upper__ chambers of the heart that _receive__ blood.
b. Ventricles - _Lower____ chambers of the heart that _pump____ blood.
2. Valves – Flaps of tissue that keep blood flowing _in one direction_______
to increase pumping efficiency of the heart; prevent _backwash_______________.
a. Tricuspid valve – Valve between _right atrium____ and _right ventricle____
b. Mitral valve – Valve between _left atrium____ and _left ventricle_______
c. Pulmonary valve – Valve between _right ventricle___ and _pulmonary artery________
d. Aortic valve – Valve between _left ventricle____ and _aorta_____
B. Pathway of Blood Through the Heart
_vena cava → right atrium → right ventricle → pulmonary artery → lung → pulmonary vein
→ left atrium → left ventricle → aorta__________________________
THE CIRCULATORY SYSTEM
All organisms must be able to transport nutrients and wastes. Smaller organisms rely on _diffusion_
for this movement; humans require an organized circulatory system for the movement of substances through the body.
We have a _closed____ circulatory system, which means our blood is _contained in vessels___. The human circulatory
system includes the heart, the blood vessels, and the blood.
I. THE HEART
(pp. 943-946)
The function of the heart is to _pump the blood to the cells of the body________. The heart
itself is mostly composed of _cardiac_____ muscle which forms a thick layer of tissue
known as the _myocardium______. Humans have a _4__-chambered heart, divided
by a _septum____ into right and left sides.
A. Structure
1. Chambers
a. Atria (atrium = singular) _Upper__ chambers of the heart that _receive__ blood.
b. Ventricles - _Lower____ chambers of the heart that _pump____ blood.
2. Valves – Flaps of tissue that keep blood flowing _in one direction_______
to increase pumping efficiency of the heart; prevent _backwash_______________.
a. Tricuspid valve – Valve between _right atrium____ and _right ventricle____
b. Mitral valve – Valve between _left atrium____ and _left ventricle_______
c. Pulmonary valve – Valve between _right ventricle___ and _pulmonary artery________
d. Aortic valve – Valve between _left ventricle____ and _aorta_____
B. Pathway of Blood Through the Heart
_vena cava → right atrium → right ventricle → pulmonary artery → lung → pulmonary vein
→ left atrium → left ventricle → aorta__________________________
THE HEART
aorta
aortic valve
atrium (left & right)
bicuspid (mitral) valve
myocardium
pulmonary artery
pulmonary valve
pulmonary vein
septum
tricuspid valve
vena cava
ventricle (left & right)
C. Circulatory Pathways
1. Pulmonary Circulation – The blood entering the right atrium from the body is _low___ in oxygen
and _high___ in carbon dioxide. The flow of blood from the right side of the heart to the _lungs____ and
back to the heart is referred to as _pulmonary__ circulation.
2. Systemic Circulation – The blood entering the left atrium from the lungs is _high____ in O2 and
_low___ in CO2. The flow of blood from the left side of the heart to the _body__ and back to the heart is
referred to as _systemic____ circulation.
D. The Heartbeat
1. Stimulus for Contraction
Although the brain can change the rate & force of contraction, the heart generates and maintains its own beat. There is a
small cluster of cardiac muscle cells in the _right atrium_____ referred to as the _pacemaker_________. They trigger
an _electrical____ impulse that stimulates the contraction of cardiac muscle cells.
2. The Pulse
The powerful contraction of the _left ventricle________ causes a surge of blood to leave through the
_aorta____. This surging action of the blood continues into the _arteries____ that branch off from the
aorta. Each contraction of the left ventricle results in another surge of blood in the arteries leading away
from the heart. This surge can be felt and is known as the _pulse____.