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Circulation: The Heart
and Blood Vessels
Chapter 7
Be Not Still, My Beating Heart!
 Heart: most durable muscle
 Sudden cardiac arrest treatment:
• Cardiopulmonary resuscitation (CPR)
• Automated external defibrillator (AED)
7.1 The Cardiovascular System:
Moving Blood through the Body
Focus: The cardiovascular system
is built to rapidly transport blood to
every living cell in the body.
The Heart and Blood Vessels Make up
the Cardiovascular System
 Cardiovascular system
• Heart – main pumping organ
• Blood vessels types:
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Arteries
Arterioles
Capillaries
Capillary beds
Venules
Veins
The Heart and Blood Vessels Make Up
the Cardiovascular System
Animation: Major human blood vessels
The Cardiovascular System Helps
Maintain Favorable Operating Conditions
Blood Circulation Is Essential to Maintain
Homeostasis
 Major role in homeostasis
• brings oxygen, nutrients, and hormones to cells
• removes waste products from cells and excess
heat
The Cardiovascular System Is Linked to
the Lymphatic System
 Lymphatic system:
• Pick up excess extracellular fluid and usable
substances
• Return them to the cardiovascular system
7.2 The Heart: A Double Pump
Focus: In a lifetime of 70 years, the human
heart beats some 2.5 billion times.
This durable pump is the centerpiece of the
cardiovascular system.
The Heart
Located in the center of your chest
 Composed of myocardium
• Cardiac muscular middle layer
 Protected by the pericardium
• Outermost layer
 Smooth lining of endocardium
• Inner layer
The Heart Is Divided into Right and
Left Halves
KNOW THIS DIAGRAM!
Animation: The human heart
The Heart Has Two Halves and Four Chambers
 Septum: thick wall divides heart in half
 Chambers of the heart:
• Left and Right Atrium
• Left and Right Ventricle
 Valves:
• Atrioventricular:
• Tricuspid (right side) and bicuspid (left side)
• Semilunar
 Coronary arteries: branch off of the aorta
• Delivers blood & oxygen to the heart
The Heart Is Divided into Right and
Left Halves
The Heart Itself Is Served by Coronary
Arteries and Veins
In a Heartbeat, the Heart’s Chambers
Contract, Then Relax
 Heartbeat: one cycle of contraction and
relaxation of the heart chambers
 Cardiac cycle
• Systole: contraction
• Diastole: period of time when the heart fills with
blood after systole
• Relaxation
• “Lub-dup” sound
 Cardiac output
• Every 60 seconds ~5 liters/ventricle
The Heart Beats in a Sequence Called the
Cardiac Cycle
Animation: Cardiac cycle
7.3 The Two Circuits of Blood
Flow
Focus: Each half of the heart pumps blood.
The two side-by-side pumps are the basis of
two cardiovascular circuits through the body,
each with its own set of arteries, arterioles,
capillaries, venules, and veins.
In the Pulmonary Circuit, Blood Picks Up
Oxygen in the Lungs
 Pulmonary Circuit:
• Carries oxygen-depleted blood away from the
heart, to the lungs, and returns oxygenated blood
back to the heart.
• Lungs and heart only
• Pulmonary arteries: deoxygenated blood to
lungs
• Pulmonary veins: oxygenated blood to heart
Each Half of the Heart Pumps Blood in a
Different Circuit
In the Systemic Circuit, Blood Travels to
and from Tissues
 Systemic circuit
• Oxygenated blood pumped by left side of heart
moves through body and returns to left atrium
• Heart and the rest of the body
 Aorta
• Main vessel out of the left ventricle
• Major arteries branch off this
 Superior vena cava
• Main route of blood from head to heart
 Inferior vena cava
• Major route of blood from lower body to heart
Each Half of the Heart Pumps Blood in a
Different Circuit
Animation: Human blood circulation
Blood from the Digestive Tract Detours
to the Liver for Filtration.
7.4 How Cardiac Muscle Contracts
Focus: Unlike skeletal muscle,
which contracts only when orders
arrive from the nervous system,
cardiac muscle contracts—and
the heart beats– spontaneously.
Electrical Signals from “Pacemaker”
Cells Drive the Heart’s Contractions
 Cardiac muscle have:
• Intercalated discs: communication junctions
between cardiac muscle cells
• Ensures rapid electrical conduction through heart
 Cardiac conduction system: independent of
the nervous system
• Sinoatrial (SA) node: cardiac pacemaker
• Atrioventricular (AV) node:
Intercalated Discs Form Communication
Junctions between Cardiac Muscle Cells
The Cardiac Conduction System
Animation: Cardiac conduction
7.5 Blood Pressure
Focus: Heart contractions
generate blood pressure, which
changes as blood moves through
the cardiovascular system.
Blood Exerts Pressure against the Walls
of Blood Vessels
 Blood pressure: fluid pressure that blood exerts
against vessel walls
 Systolic (ventricular contraction) and diastolic
pressure (ventricular relaxation):
• Normal: 120/80
 Hypertension
• Chronically elevated blood pressure
 Hypotension
• Abnormally low blood pressure
Animation: Measuring blood pressure
Cholesterol types
 High Density Lipoproteins (HDL)
• remove cholesterol from within arteries
• transport it back to the liver for excretion or reutilization
• they are seen as "good" lipoproteins
 Low Density Lipoproteins (LDL)
• carry cholesterol in the blood and around the
body, for use by cells
• commonly referred to as "bad cholesterol" due to
the link between high LDL levels and
cardiovascular disease
Blood Pressure Values (mm of Hg)
A Variety of Factors May Cause
Hypertension
Is this you?
7.6 Structure and Functions of
Blood Vessels
Focus: As with all body parts, structure
is key to the functions of blood vessels.
All our vessels transport blood, but
there are important differences in how
different kinds manage blood flow and
blood pressure.
Arteries Are Large Blood Pipelines
 Outer layer:
• Mainly collagen
 Middle layer:
• Smooth muscle and elastin
 Innermost layer:
• Thin sheet of endothelium
Carries oxygenated
blood away from heart
Blood Pressure Changes as Blood Flows
through the Cardiovascular System
Take pulse from
arteries
because of the
strong pressure
Arterioles Are Control Points for Blood Flow
 Wall built of smooth muscle rings over elastic
tissue
• Dilates when smooth muscle relaxes
• Constricts when smooth muscle contracts
 Offer more resistance to blood flow than other
vessels do
Capillaries Are Specialized for Diffusion
 Thinnest wall of any blood vessel!
• Single layer of flat endothelium
 Site of diffusion of gases, nutrients, and wastes
 Extensive!
• 62,000 miles long
 Blood pressure drops slowly as blood flows through
Venules and Veins Return Blood to the Heart
 Venules
• Function somewhat like capillaries
 Veins
• Large diameters and low-resistance transport of
blood back to the heart
• Outer layer of connective tissue
• Middle layer of smooth muscle and elastic fibers
• Inner layer of endothelium
• Valves prevent backflow of blood
• varicose veins: valves don’t function properly
Contracting Skeletal Muscles Can
Increase Fluid Pressure in a Vein
Animation: Vein function
Animation: Vessel anatomy
Vessels Help Control Blood Pressure
 Medulla
• Monitors resting blood pressure
• Vasodilation
• Vasoconstriction
 Baroreceptor reflex
• Keeps blood pressure within normal limits in the
face of sudden changes
• Baroreceptors found in the carotid arteries in the
neck and in the arch of the aorta
7.7 Capillaries: Where Blood
Exchanges Substances with
Tissues
Focus: Blood enters the systemic
circulation moving swiftly in the aorta,
but this speed has to slow in order for
substances to move into and out of the
bloodstream.
A Vast Network of Capillaries Brings
Blood Close to Nearly All Body Cells
 40 billion capillaries
 Every cell is a diffusible distance away from a
capillary
 Blood flow is slowest in the capillaries
Many Substances Enter and Leave
Capillaries by Diffusion
 Diffusion of fluids and solutes across the
porous capillary walls
• Blood flows through the capillaries very slowly to
allow this exchange
Some of the Substances Pass through
Pores in Capillary Walls
 Fluid movement in capillaries:
• Bulk flow
• Role of lymphatic vessels
• Captures excess fluid from circulatory system
 Help maintain blood pressure
Animation: Capillary forces
Blood in Capillaries Flows Onward to Venules
 Capillaries branch into capillary beds
 Precapillary sphincter
• Ring of smooth muscle
• Regulates the flow of blood into the capillary
7.8 Cardiovascular Disease
Major Risk Factors for
Cardiovascular Disease
Arteries Can Clog or Weaken
 Atherosclerosis
• fatty material collects along the walls of arteries.
This fatty material thickens, hardens (forms
calcium deposits), and may eventually block the
arteries.
• All adults should keep their LDL ("bad") cholesterol
levels below 130-160 mg/dL.
Plaques and Blood Clots May Clog Arteries
Risk factors for atherosclerosis include:
Diabetes
Heavy alcohol use
High blood pressure
High blood cholesterol levels
High-fat diet
Increasing age
Obesity
Personal or family history of heart disease
Smoking
Arteries Can Clog or Weaken
 Coronary arteries
• Narrow and vulnerable to clogging by plaques
• Angina pectoris
• medical term for chest pain or discomfort due to
coronary heart disease
• “Plaque-busting” drugs: statins
• Ways to repair coronary blockage:
• Coronary bypass
• Laser angioplasty
• Balloon angioplasty
• Aneurysm
Heart Damage Can Lead to Heart Attack
and Heart Failure
 Heart attack
• Damage or death to cardiac muscle
• Warning signs:
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Chest discomfort
Discomfort in other areas of the upper body
Shortness of breath
cold sweat, nausea, or light-headedness
• Risk factors
 Heart Failure
• Weak heart and ineffective pump
Arrhythmias Are Abnormal Heart
Rhythms
 Electrocardiogram (ECG)
• Recording of the electrical activity of the cardiac
cycle
 Arrhythmias: irregular heart rhythms
• Bradycardia: slower than normal heart rate
• Tachycardia: faster than normal heart rate
• Ventricular fibrillation: rapid, erratic electrical
impulses
Animation: Examples of ECGs
7.9 Infections, Cancer, and Heart
Defects
Focus: Infections may seriously
damage the heart.
 Myocarditis: is an inflammation of the
myocardium, the middle layer of the heart wall
 various causes
Bacterial
Alcohol abuse
Drug abuse
Heart Damage May Be a Complication of
Lyme Disease
Is There Such a Thing as Heart Cancer?
 Rarely the first site for cancer
 Can be a secondary site
 Chemotherapy and/or radiation can damage the
heart and blood vessels
Inborn Heart Defects Are Fairly Common
 “Blue babies”
 Heart does not pump blood efficiently
 How is the problem corrected?