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:• 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

Last week

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 re-

utilization• 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 oxygenatedblood away from heart

Blood Pressure Changes as Blood Flows through the Cardiovascular System

Take pulse fromarteries 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 useHigh blood pressure

High blood cholesterol levelsHigh-fat diet

Increasing ageObesity

Personal or family history of heart diseaseSmoking

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: • 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 causesBacterial

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?