Transcript Circulatory System

Circulatory System
Chapter 37-1
The Circulatory System
We need oxygen to live!
 Blood brings air to our cells so oxygen can
be absorbed and used to produce energy
for the cell
 The circulatory system transports blood
throughout the body and back
 The CS consists of the heart, a series of
blood vessels, and the blood that flows
through them
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The Heart
The heart is approximately the size of a
clenched fist.
 It is made almost entirely of muscle.
 Myocardium: thick layer of muscle which
produces powerful contractions to pump
blood through the circulatory system.
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The Heart
Useless facts…
 The heart is the strongest muscle in the
human body
 The heart pumps about 72 times a minute
on average
 Each pump pushes 70ml of blood
 In one year, a heart pumps enough blood
to fill up an olympic-size swimming pool!
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Figure 37-3 The Structures of the Heart
Section 37-1
The Heart
Superior Vena Cava
Large vein that brings oxygen-poor blood from the
upper part of the body to the right atrium
Aorta
Brings oxygen-rich blood from the left
ventricle to the rest of the body
Pulmonary Arteries
Bring oxygen-poor blood
to the lungs
Pulmonary Veins
Bring oxygen-rich blood from each
of the lungs to the left atrium
Left Atrium
Pulmonary Valve
Prevents blood from flowing
back into the right ventricle
after it has entered the
pulmonary artery
Right Atrium
Tricuspid Valve
Prevents blood from flowing
back into the right atrium after it
has entered the right ventricle
Aortic Valve
Prevents blood from flowing
back into the left ventricle
after it has entered the aorta
Mitral Valve
Prevents blood from flowing back
into the left atrium after it has
entered the left ventricle
Left Ventricle
Inferior Vena Cava
Vein that brings oxygen-poor
blood from the lower part of
the body to the right atrium
Septum
Right Ventricle
The Heart
The heart can be divided into four
chambers
 Atrium: upper chambers which receive
blood (enters)
 Ventricle: The lower chambers which
pump blood out of the heart (exits)
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Circulation
Think of the heart as two separate pumps.
 Pulmonary circulation: Right side of heart
that pumps blood from the heart to the
lungs
 Systemic circulation: Left side of heart that
pumps blood oxygen-rich blood to the rest
of the body

Capillaries of head and arms
Superior vena
cava
Pulmonary vein
Capillaries of right
lung
Aorta
Pulmonary artery
Capillaries of left
lung
Inferior vena
cava
Capillaries of abdominal
organs and legs
Circulation
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5.
Oxygen-poor blood enters heart through
right atrium.
Valve (connective tissue that opens &
closes) opens so blood froms from R
atrium to R ventricle.
R ventricle pumps blood to lungs
Lungs replenish blood with oxygen
Oxygen-rich blood then flows to L atrium
Circulation
6.
7.
8.
9.
10.
Valve opens and oxygen-rich blood flows
from L atrium to L ventricle
L ventricle pumps blood to the body
Body absorbs oxygen
Oxygen-poor blood goes back to the
heart
Cycle starts over!
Circulation
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Atriums contract first (by sinoatrial node)
Contraction of atrium by SA triggers the
ventricles to contract (atrioventricular node or
AV)
Together, these two nerves serve as the
pacemaker.
Remember sympathetic and parasympathetic?
During exercise, sympathetic increases heart
rate (can go up to 200bpm) and
parasympathetic decreases it
Blood Vessels
Aorta: Large blood vessel where blood first
leaves the L ventricle
 Arteries: carry oxygen rich blood
 They have thick walls to withstand the
pressure of bloodflow
 Think of arteries as the superhighways of
the CS
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Blood Vessels
Capillaries: Narrow tubes where body
absorbs oxygen and nutrients are
exchanged
 Can be as narrow as one cell wide
 Think of capillaries as side streets and
alleys
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Blood Vessels
Veins: Blood vessels that return blood to
the heart
 Thinner than arteries
 Larger veins have valves to prevent
backflow
 Muscular contractions help push blood
through veins
 Otherwise, blood pools and vericose veins
result
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Vein
Artery
Endothelium
Arteriole
Capillary
Venule
Connective
tissue
Connective
tissue
Smooth
muscle
Endothelium
Smooth
muscle
Endothelium
Valve
Blood Pressure
Heart produces pressure when it pumps.
 The pressure allows blood to flow
throughout the body
 If pressure is too low, oxygen can’t get to
body
 If pressure is too high, heart has to work
harder, damaging the CS
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Blood Pressure
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BP is measured by systolic & diastolic pressures
Systolic is the blood pressure when a ventricle
contracts
Diastolic is the blood pressure when a ventricle
relaxes
Normal BP is 120/80
Atherosclerosis, a hardening of the arteries due
to fat is a major cause of HBP and heart disease
Result is heart attack or stroke