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The Cardiovascular System

Modified from a PowerPoint created by Cindy Dostal of Hawkeye Community College, content from Essentials of Human Anatomy & Physiology by Elaine N. Marieb

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The Cardiovascular System

A closed system of the heart and blood vessels

The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body

The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

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The Heart

Slide 11.2a

Location

Thorax between the lungs
Pointed apex directed toward left hip

About the size of your fist

Less than 1 lb.

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The Heart

Figure 11.1

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The Heart: Coverings

Slide 11.3

Pericardium – a double serous membrane

Visceral pericardium

Next to heart

Parietal pericardium

Outside layer

Serous fluid fills the space between the layers of pericardium

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The Heart: Heart Wall

Slide 11.4

Three layers

Epicardium

Outside layer
This layer is the parietal pericardium
Connective tissue layer

Myocardium

Middle layer
Mostly cardiac muscle

Endocardium

Inner layer
Endothelium

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External Heart Anatomy

Slide 11.5

Figure 11.2a

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Internal Heart Anatomy

Slide 11.5

Figure 11.2a

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The Heart: Chambers

Slide 11.6

Right and left side act as separate pumps
Four chambers

Atria

Receiving chambers

Right atrium
Left atrium

Ventricles

Discharging chambers

Right ventricle
Left ventricle

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Blood Circulation

Slide 11.7

Figure 11.3

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The Heart: Valves

Slide 11.8

Allow blood to flow in only one direction
Four valves

Atrioventricular valves – between atria and ventricles

Bicuspid valve (left)
Tricuspid valve (right)

Semilunar valves between ventricle and artery

Pulmonary semilunar valve
Aortic semilunar valve

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The Heart: Valves

Slide 11.9

Valves open as blood is pumped through
Held in place by chordae tendineae (“heart strings”)
Close to prevent backflow

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Operation of Heart Valves

Slide 11.10

Figure 11.4

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Valve Pathology

Incompetent valve = backflow and repump
Stenosis = stiff= heart workload increased
May be replaced
Lup Dub Heart Sound

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The Heart: Associated Great Vessels

Slide 11.11

Aorta

Leaves left ventricle

Pulmonary arteries

Leave right ventricle

Vena cava

Enters right atrium

Pulmonary veins (four)

Enter left atrium

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Coronary Circulation

Slide 11.12

Blood in the heart chambers does not nourish the myocardium
The heart has its own nourishing circulatory system

Coronary arteries
Cardiac veins
Blood empties into the right atrium via the coronary sinus

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Cardiac Pathology

Rapid heart beat
= Inadequate blood
= Angina Pectoris

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The Heart: Conduction System

Slide 11.13a

Intrinsic conduction system �(nodal system)

Heart muscle cells contract, without nerve impulses, in a regular, continuous way

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The Heart: Conduction System

Slide 11.13b

Special tissue sets the pace

Sinoatrial node (right atrium)

Pacemaker

Atrioventricular node (junction of r&l atria and ventricles)
Atrioventricular bundle (Bundle of His)
Bundle branches (right and left)
Purkinje fibers

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Heart Contractions

Slide 11.14b

Figure 11.5

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Three formations

P wave: impulse across atria
QRS complex: spread of impulse down septum, around ventricles in Purkinje fibers
T wave: end of electrical activity in ventricles

Electrocardiograms (EKG/ECG)

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Electrocardiograms (EKG/ECG)

Figure 8.15B, C

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Pathology of the Heart

Damage to AV node = release of ventricles from control = slower heart beat
Slower heart beat can lead to fibrillation
Fibrillation = lack of blood flow to the heart
Tachycardia = more than 100 beats/min
Bradychardia = less than 60 beats/min

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The Heart: Cardiac Cycle

Slide 11.16

Atria contract simultaneously
Atria relax, then ventricles contract
Systole = contraction
Diastole = relaxation

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Filling of Heart Chambers – �the Cardiac Cycle

Slide 11.15

Figure 11.6

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The Heart: Cardiac Output

Slide 11.18

Cardiac output (CO)

Amount of blood pumped by each side of the heart in one minute
CO = (heart rate [HR]) x (stroke volume [SV])

Stroke volume

Volume of blood pumped by each ventricle in one contraction

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Cardiac Output

CO = HR x SV
5250 ml/min = 75 beats/min x 70 mls/beat
Norm = 5000 ml/min
Entire blood supply passes through body once per minute.
CO varies with demands of the body.

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Cardiac Output Regulation

Slide 11.19

Figure 11.7

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The Heart: Regulation of Heart Rate

Slide 11.20

Stroke volume usually remains relatively constant

Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction

Changing heart rate is the most common way to change cardiac output

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Regulation of Heart Rate

Slide 11.21

Increased heart rate

Sympathetic nervous system

Crisis
Low blood pressure

Hormones

Epinephrine
Thyroxine

Exercise
Decreased blood volume

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The Heart: Regulation of Heart Rate

Slide 11.22

Decreased heart rate

Parasympathetic nervous system
High blood pressure or blood volume
Decreased venous return
In Congestive Heart Failure the heart is worn out and pumps weakly. Digitalis works to provide a slow, steady, but stronger beat.

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Congestive Heart Failure (CHF)

Decline in pumping efficiency of heart
Inadequate circulation
Progressive, also coronary atherosclerosis, high blood pressure and history of multiple Myocardial Infarctions
Left side fails = pulmonary congestion and suffocation
Right side fails = peripheral congestion and edema

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Blood Vessels: The Vascular System

Slide 11.23

Taking blood to the tissues and back

Arteries
Arterioles
Capillaries
Venules
Veins

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The Vascular System

Slide 11.24

Figure 11.8b

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Blood Vessels: Anatomy

Slide 11.25

Three layers (tunics)

Tunic intima

Endothelium

Tunic media

Smooth muscle
Controlled by sympathetic nervous system

Tunic externa

Mostly fibrous connective tissue

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Differences Between Blood Vessel Types

Slide 11.26

Walls of arteries are the thickest
Lumens of veins are larger
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

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Movement of Blood Through Vessels

Slide 11.27

Most arterial blood is pumped by the heart
Veins use the milking action of muscles to help move blood

Figure 11.9

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Capillary Beds

Slide 11.28a

Capillary beds consist of two types of vessels

Vascular shunt – directly connects an arteriole to a venule

Figure 11.10

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Capillary Beds

Slide 11.28b

True capillaries – exchange vessels

Oxygen and nutrients cross to cells
Carbon dioxide and metabolic waste products cross into blood

Figure 11.10

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Diffusion at Capillary Beds

Slide 11.29

Figure 11.20

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Vital Signs

Arterial pulse
Blood pressure
Repiratory Rate
Body Temperature
All indicate the efficiency of the system

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Pulse

Slide 11.35

Pulse – pressure wave of blood
Monitored at “pressure points” where pulse is easily palpated

Figure 11.16

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Blood Pressure

Slide 11.36

Measurements by health professionals are made on the pressure in large arteries

Systolic – pressure at the peak of ventricular contraction
Diastolic – pressure when ventricles relax

Pressure in blood vessels decreases as the distance away from the heart increases

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Measuring Arterial Blood Pressure

Slide 11.37

Figure 11.18

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Blood Pressure: Effects of Factors

Slide 11.39a

Neural factors

Autonomic nervous system adjustments (sympathetic division)

Renal factors

Regulation by altering blood volume
Renin – hormonal control

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Blood Pressure: Effects of Factors

Slide 11.39b

Temperature

Heat has a vasodilation effect
Cold has a vasoconstricting effect

Chemicals

Various substances can cause increases or decreases

Diet

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Variations in Blood Pressure

Slide 11.41

Human normal range is variable

Normal

140–110 mm Hg systolic
80–75 mm Hg diastolic

Hypotension

Low systolic (below 110 mm HG)
Often associated with illness

Hypertension

High systolic (above 140 mm HG)
Can be dangerous if it is chronic