BIOL 22000 Lecture Notes - Lecture 7: Deep Vein Thrombosis, Lymphocyte, Erythropoietin

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Chapter 7 The Cardiovascular System
7.1 Anatomy of the Cardiovascular System
The cardiovascular system consists of a muscular, four-chambered heart, blood vessels,
and blood
The vasculature consists of arteries, capillaries, and veins
THE HEART
The heart is a four-chambered
structure
The heart is composed of two pumps
o The right side accepts
deoxygenated blood
returning from the body and
moves it to the lungs
This constitutes the
first pump
(pulmonary
circulation)
o The left side receives
oxygenated blood from the
lungs
Forces it out to the
body through the
aorta (systemic
circulation)
The atria are thin walled structures
where blood is received from either
the venae cavae (deoxygenated blood entering the right
heart) or the pulmonary veins (oxygenated blood entering
the left heart)
o The atria contract to push blood into the ventricles
o After the ventricles fill, they contract to send blood to
the lungs and the systemic circulation
o Ventricles are far more muscular than the atria,
allowing for more powerful contractions
The atria are separated from the ventricles by the
atrioventricular valves
o Note: The vasculature consists of arteries, capillaries, and veins
o These valves allow the pump to create the pressure within the ventricles necessary
to propel the blood forward within the circulation, also preventing backflow of
blood
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The valve between the right atrium and the right ventricle is known as the tricuspid
valve (three leaflets)
The valve between the left atrium and the left ventricle is known as the mitral or
bicuspid valve (two leaflets)
The valve that separates the right ventricle from the pulmonary circulation is known as
the pulmonary valve
The valve that separates the left ventricle from the aorta (systemic circulation) is known
as the aortic valve
MNEMONIC
o Atrioventricular valves: LAB RAT
o Left Atrium = Bicuspid
o Right Atrium = Tricuspid
The left heart is more muscular than the right heart
o Left heart pumps blood into the systemic circulation
o Blood leaving the left heart must travel a considerable distance so that blood
pressure can be maintained as far away as the feet
Electric Conduction of the Heart
The rhythmic contraction of cardiac muscle travels through a pathway formed by four
electrically excitable structures
o The sinoatrial (SA) node, the atrioventricular (AV) node, the bundle of His (AV
bundle) and its branches, and the Purkinje fibers
Impulse initiation occurs at the SA node, which generates 60100 signals per minute
without requiring any neural input
o Located in the wall of the right atrium
o As the depolarization wave spreads from the SA node, it causes the two atria to
contract simultaneously
o Most ventricular filling is passive (that
is, blood moves from the atria to the
ventricles based solely on ventricular
relaxation), atrial systole (contraction)
results in an increase in atrial pressure
that forces a little more blood into the
ventricles
o This additional volume of blood is called
the atrial kick and accounts for about 5
30 percent of cardiac output
Next, the signal reaches the AV node, which sits
at the junction of the atria and ventricles
o The signal is delayed here to allow for
the ventricles to fill completely before
they contract
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The signal then travels down the bundle of His and its branches, embedded in the
interventricular septum (wall), and to the Purkinje fibers, which distribute the
electrical signal through the ventricular muscle
o The muscle cells are connected by intercalated discs, which contain many gap
junctions directly connecting the cytoplasm of adjacent cells, allowing
coordinated ventricular contraction
The circulatory system is under autonomic control
o The autonomic division, which consists of the sympathetic (“fight-or-flight”) and
parasympathetic (“rest-and-digest”) branches
o Sympathetic signals speed up the heart rate and increase the contractility of
cardiac muscle
o Parasympathetic signals, provided by the vagus nerve, slow it down
Contraction
Each heartbeat is composed of two phases, systole and diastole
o During systole, ventricular contraction and closure of the AV valves occurs and
blood is pumped out of the ventricles
o During diastole, the heart is relaxed, the semilunar valves are closed, and blood
from the atria fills the ventricles
Contraction of the ventricular muscle generates a higher pressure during systole, and
during relaxation the pressure decrease
The wall of the large arteries is elastic, starch to receive blood from the heart, allows the
vessels to maintain sufficient pressure while the ventricular muscles are relaxed
Cardiac output, the total blood volume pumped by a ventricle in a minute
o The two ventricles are connected by one series, so the volume for each one is the
same
Cardiac output (CO) is the product of heart rate (HR, beats per minute) and stroke
volume (SV, volume of blood pumped per beat)
o CO = HR × SV
THE VASCULATURE
The three major types of vessels are arteries, veins, and capillaries
Blood travels away from the heart in arteries
o The largest
o Major arteries, such as the coronary, common carotid, and renal arteries, divide
the blood flow from the aorta toward different peripheral tissues
Arteries branch into arterioles, which ultimately lead to capillaries that perfuse the
tissues
On the venous side of a capillary network, the capillaries join into venules (a very small
vein), which join to form veins
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Document Summary

7. 1 anatomy of the cardiovascular system: the cardiovascular system consists of a muscular, four-chambered heart, blood vessels, and blood, the vasculature consists of arteries, capillaries, and veins. 30 percent of cardiac output: next, the signal reaches the av node, which sits at the junction of the atria and ventricles, the signal is delayed here to allow for the ventricles to fill completely before they contract. In the cross section of blood vessels: same types of cells comprise the different vessels" surface, arteries have much more smooth muscle than veins. In the hepatic portal system, blood leaving capillary beds in the walls of the gut passes through the hepatic portal vein before reaching the capillary beds in the liver. In the hypophyseal portal system, blood leaving capillary beds in the hypothalamus travels to a capillary bed in the anterior pituitary to allow for paracrine secretion of releasing hormones.

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