Circulatory SystemCirculatory System

Chapter 37-1Chapter 37-1

The Circulatory SystemThe Circulatory System

We need oxygen to live!We need oxygen to live!Blood brings air to our cells so oxygen can Blood brings air to our cells so oxygen can

be absorbed and used to produce energy be absorbed and used to produce energy for the cellfor the cell

The circulatory system transports blood The circulatory system transports blood throughout the body and backthroughout the body and back

The CS consists of the heart, a series of The CS consists of the heart, a series of blood vessels, and the blood that flows blood vessels, and the blood that flows through themthrough them

The HeartThe Heart

The heart is approximately the size of a The heart is approximately the size of a clenched fist.clenched fist.

It is made almost entirely of muscle.It is made almost entirely of muscle.Myocardium: thick layer of muscle which Myocardium: thick layer of muscle which

produces powerful contractions to pump produces powerful contractions to pump blood through the circulatory system.blood through the circulatory system.

The HeartThe Heart

Useless facts…Useless facts…The heart is the strongest muscle in the The heart is the strongest muscle in the

human bodyhuman bodyThe heart pumps about 72 times a minute The heart pumps about 72 times a minute

on averageon averageEach pump pushes 70ml of bloodEach pump pushes 70ml of blood In one year, a heart pumps enough blood In one year, a heart pumps enough blood

to fill up an olympic-size swimming pool!to fill up an olympic-size swimming pool!

Section 37-1

Figure 37-3 The Structures of the Heart

Right Ventricle

Right Atrium

Left Atrium

Inferior Vena CavaVein that brings oxygen-poor blood from the lower part of the body to the right atrium

Tricuspid ValvePrevents blood from flowing back into the right atrium after it has entered the right ventricle

Pulmonary ValvePrevents blood from flowing back into the right ventricle after it has entered the pulmonary artery

Pulmonary VeinsBring oxygen-rich blood from each of the lungs to the left atrium

Superior Vena CavaLarge vein that brings oxygen-poor blood from the upper part of the body to the right atrium

AortaBrings oxygen-rich blood from the left ventricle to the rest of the body

Pulmonary ArteriesBring oxygen-poor blood to the lungs

Aortic ValvePrevents blood from flowing back into the left ventricle after it has entered the aorta

Mitral ValvePrevents blood from flowing back into the left atrium after it has entered the left ventricle

Left Ventricle

Septum

The HeartThe Heart

The HeartThe Heart

The heart can be divided into four The heart can be divided into four chamberschambers

Atrium: upper chambers which receive Atrium: upper chambers which receive blood (enters)blood (enters)

Ventricle: The lower chambers which Ventricle: The lower chambers which pump blood out of the heart (exits)pump blood out of the heart (exits)

CirculationCirculation

Think of the heart as two separate pumps.Think of the heart as two separate pumps.Pulmonary circulation: Right side of heart Pulmonary circulation: Right side of heart

that pumps blood from the heart to the that pumps blood from the heart to the lungslungs

Systemic circulation: Left side of heart that Systemic circulation: Left side of heart that pumps blood oxygen-rich blood to the rest pumps blood oxygen-rich blood to the rest of the bodyof the body

Capillaries of head and arms

Capillaries of abdominal organs and legs

Inferior vena cava

Pulmonary vein

Capillaries of right lung

Superior vena cava Aorta Pulmonary artery

Capillaries of left lung

CirculationCirculation

1.1. Oxygen-poor blood enters heart through Oxygen-poor blood enters heart through right atrium.right atrium.

2.2. ValveValve (connective tissue that opens & (connective tissue that opens & closes) opens so blood froms from R closes) opens so blood froms from R atrium to R ventricle.atrium to R ventricle.

3.3. R ventricle pumps blood to lungsR ventricle pumps blood to lungs

4.4. Lungs replenish blood with oxygenLungs replenish blood with oxygen

5.5. Oxygen-rich blood then flows to L atriumOxygen-rich blood then flows to L atrium

CirculationCirculation

6.6. Valve opens and oxygen-rich blood flows Valve opens and oxygen-rich blood flows from L atrium to L ventriclefrom L atrium to L ventricle

7.7. L ventricle pumps blood to the bodyL ventricle pumps blood to the body

8.8. Body absorbs oxygenBody absorbs oxygen

9.9. Oxygen-poor blood goes back to the Oxygen-poor blood goes back to the heartheart

10.10. Cycle starts over!Cycle starts over!

CirculationCirculation

Atriums contract first (by sinoatrial node)Atriums contract first (by sinoatrial node) Contraction of atrium by SA triggers the Contraction of atrium by SA triggers the

ventricles to contract (atrioventricular node or ventricles to contract (atrioventricular node or AV)AV)

Together, these two nerves serve as the Together, these two nerves serve as the pacemakerpacemaker..

Remember sympathetic and parasympathetic?Remember sympathetic and parasympathetic? During exercise, sympathetic increases heart During exercise, sympathetic increases heart

rate (can go up to 200bpm) and parasympathetic rate (can go up to 200bpm) and parasympathetic decreases itdecreases it

Blood VesselsBlood Vessels

Aorta: Large blood vessel where blood first Aorta: Large blood vessel where blood first leaves the L ventricleleaves the L ventricle

Arteries: carry oxygen rich bloodArteries: carry oxygen rich bloodThey have thick walls to withstand the They have thick walls to withstand the

pressure of bloodflowpressure of bloodflowThink of arteries as the superhighways of Think of arteries as the superhighways of

the CSthe CS

Blood VesselsBlood Vessels

Capillaries: Narrow tubes where body Capillaries: Narrow tubes where body absorbs oxygen and nutrients are absorbs oxygen and nutrients are exchangedexchanged

Can be as narrow as one cell wideCan be as narrow as one cell wideThink of capillaries as side streets and Think of capillaries as side streets and

alleysalleys

Blood VesselsBlood Vessels

Veins: Blood vessels that return blood to Veins: Blood vessels that return blood to the heartthe heart

Thinner than arteriesThinner than arteriesLarger veins have valves to prevent Larger veins have valves to prevent

backflowbackflowMuscular contractions help push blood Muscular contractions help push blood

through veinsthrough veinsOtherwise, blood pools and vericose veins Otherwise, blood pools and vericose veins

resultresult

Capillary

Connective tissue

Connective tissue

Smooth muscle

Smooth muscle

Endothelium

Endothelium

Valve

Venule

Endothelium

Arteriole

VeinArtery

Blood PressureBlood Pressure

Heart produces pressure when it pumps.Heart produces pressure when it pumps.The pressure allows blood to flow The pressure allows blood to flow

throughout the bodythroughout the body If pressure is too low, oxygen can’t get to If pressure is too low, oxygen can’t get to

bodybody If pressure is too high, heart has to work If pressure is too high, heart has to work

harder, damaging the CSharder, damaging the CS

Blood PressureBlood Pressure

BP is measured by systolic & diastolic pressuresBP is measured by systolic & diastolic pressures Systolic is the blood pressure when a ventricle Systolic is the blood pressure when a ventricle

contractscontracts Diastolic is the blood pressure when a ventricle Diastolic is the blood pressure when a ventricle

relaxesrelaxes Normal BP is 120/80Normal BP is 120/80 Atherosclerosis, a hardening of the arteries due Atherosclerosis, a hardening of the arteries due

to fat is a major cause of HBP and heart diseaseto fat is a major cause of HBP and heart disease Result is heart attack or stroke Result is heart attack or stroke