Heart

Heart

CIRCULATORY SYSTEMFUNCTIONS:

Transport (nutrients, wastes, oxygen, CO2, hormones)

Immunity (leukocytes, antibodies)

Temperature regulation (when you are cold, blood vessels constrict; when hot, they dilate)

Penile erection

COMPONENTS OF CIRCULATORY SYSTEM

Heart

Blood

Blood vessels (arteries, capillaries, veins)

Lymph vessels and nodes

THE HEART

The heart is the simplest organ in the body. It does only one thing: pumps blood. It beats 42 million times a year. It’s about the size of your clenched fist. Some of you have big fists, some have smaller fists.Its location is deep to the sternum. Take your left fist and place it on the sternum, then angle the bottom of your wrist to the left. When you say the Pledge of Allegiance, your hand is not over your heart. It’s not on the left, it’s in the center.

Location of the Heart in the Thorax

Figure 18.2

Layers of tissues

around the heart:

Pericardium

Heart muscle

PERICARDIUM

Surrounds the heart (like a heart in baggie).

The function is to lubricate the heart, so as it beats, it won’t rub against anything.The pericardium is divided into two layers with a space between them filled with fluid:PARIETAL PERICARDIUM

PERICARDIAL CAVITY

VISCERAL PERICARDIUM

PARIETAL PERICARDIUM

This is actually the outermost layer of thoracic cavity. Two layers:

SEROUS LAYER (simple squamous epithelium). Watery fluid.

FIBROUS LAYER (moderately dense fibrous connective tissue)

VISCERAL PERICARDIUM (aka EPICARDIUM)

Outermost layer of heart.

It also has two layers:

– SEROUS LAYER

– FIBROUS LAYER

Layers of tissues

around the heart:

Pericardium

Heart muscle

Structure of the Heart – Coverings

Figure 18.3

MYOCARDIUM

The heart muscle itself (myocardium) is made of what tissue?

Cardiac muscle.

ENDOCARDIUM

The lining on the inside of the heart. Has two layers:

ENDOTHELIUM (simple squamous epithelium that provides a smooth surface for the blood to pass by)

Loose fibrous connective tissue (deep to the endothelium)

PERICARDITIS

Inflamed outer layer of heart.

Fluid accumulates in pericardial cavity, putting pressure on heart improper beat

Pericarditis can be caused by damage to the blood vessels blood leaks into pericardial cavity pressure improper beat.

Pericarditis can lead to pericardial friction rub, adhesions, and additional excess fluid in the pericardial cavity.

PERICARDITISCARDIAC TAMPONADE: In severe cases of pericarditis, or if there is a stab wound to the heart wall that causes fluid to exude into the pericardial cavity.

The excess fluid compresses the heart and diminishes the heart’s ability to pump.

Treatment is to stick a needle in the cavity and drain the fluid.

ENDOCARDITIS

More serious:

Bacteria enter bloodstream (dental procedures, IV drug abuse, catheter) damage to lining and valves blood clots.

Those who already have damaged heart valves need prophylactic antibiotics.

THE HEART IS TWO PUMPS: LEFT AND RIGHT

LEFT PUMP:From lungs to bodyRIGHT PUMP: From body to lungs

The Pulmonary and Systemic Circuits

Figure 18.1

Heart Chambers• Each pump has two types of chambers:

ATRIUM and VENTRICLE

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve

Bicuspid valve

Blood FlowDeoxygenated blood from body enters the RA through the superior and inferior vena cava.It pours through the TRICUSPID (RIGHT AV) VALVE into the right ventricle.Right atrium contracts, pushes blood into the right ventricle ventricle expands, then contracts with force. To prevent the blood from going back up into the atrium, need a valve.

VALVES

Valves are like a swinging door that can only open one direction. But you can push against this door, since it’s only tissue. But if you tie a rope to the doorknob, it won’t be able to go the wrong way. Rope = CHORDAE TENDONAE, which is attached to pieces of myocardium called PAPILLARY MUSCLES.The contraction pulls on the chordae tendonae to close the valves, preventing a PROLAPSED VALVE (turned inside out).

Figure 18.9a

Valves

Function of the Atrioventricular Valves

Figure 18.9b

Heart Valves – Valve Structure

Figure 18.8a

What is an artery?

An artery is a vessel that carries blood AWAY from the heart. It does not matter if it is oxygenated or deoxygenated blood.

A vein is a vessel that carries blood TOWARD the heart. It does not matter if it is oxygenated or deoxygenated blood.

Blood Flow• With the ventricular contraction, blood can go only one

way: into the PULMONARY ARTERY (one of the few arteries with deoxy blood).

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve

Bicuspid valve

• When the ventricles relax, the PULMONARY SEMILUNAR VALVE close to prevent blood from going from the pulmonary artery back into the right ventricle.

.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve

Bicuspid valve

Pulmonary semilunar valve

Function of the Semilunar Valves

Figure 18.10a, b

Blood Flow

When the ventricles relax, the PULMONARY SEMILUNAR VALVE closes to prevent blood from going from the pulmonary artery back into the right ventricle. Do the semilunar valves have a chordae tendonae? No; the blood is not being forced back (with a contraction), it just falls back with gravity, so there’s not as much pressure.

• Blood then goes into lungs, gets oxygenated, and returns on the left side through the PULMONARY VEINS (one of the few veins with oxy blood), into the LEFT ATRIUM.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve

Bicuspid valve


Lungs

• From the LEFT ATRIUM, it goes through the MITRAL VALVE (BICUSPID VALVE) into the LEFT VENTRICLE(there are also chordae tendonae here), which contracts.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve

Bicuspid valve (Mitral)


• Therefore, the left ventricle is the chamber which is responsible for generating the largest pressure upon contraction.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve



• The blood then goes past the AORTIC SEMILUNAR VALVE, into the AORTA, and back to the body.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve


Aortic semilunar valve


Body

The semilunar valves are located between the ventricles and the great arteries.

VALVES

CHORDAE TENDONAE

PAPILLARY MUSCLES

TRICUSPID VALVE

MITRAL VALVE (BICUSPID VALVE)

PULMONARY SEMILUNAR VALVE

AORTIC SEMILUNAR VALVE

SUMMARY OF BLOOD FLOW

Deoxy blood sup/inf vena cava R atrium tricuspid valve R ventricle pulmonary semilunar valve pulmonary artery lungs pulmonary veins Left atrium mitral (bicuspid) valve Left ventricle aortic semilunar valve aorta rest of body.

Heart Chambers

Figure 18.5b

Heart Chambers

Figure 18.5e

Inferior View of the Heart

Figure 18.5d

Apex

Right atrium

Interventricular Interventricular septumseptum

Left atrium

Right ventricle

Left ventricle

Atrial Atrial septumseptum

Mitral Mitral (bicuspid) (bicuspid) valvevalve

Cordae Cordae tendonaetendonae

Papillary Papillary musclesmuscles

Aortic Aortic semilunar semilunar valvevalve

Mitral Valve Stenosis • If there is stenosis (blockage) of the mitral valve, where

will the blood back up into?

• Answer: the pulmonary circulation.

LA

LV

IVC

Pulmonary artery

Aorta

Pulmonary vein

SVC

RA

RV

Tricuspid valve


Aortic semilunar valve


Body

Lungs

HEART BEATS

The pressure of blood against blood vessel walls is called blood pressure.Blood pressure is recorded systole over diastole. Normal resting blood pressure is said to be 120/80. When blood pressure is too high, it is called HYPERTENSION.The sound your heart makes when it is beating is the sound of the blood hitting the valves after they are closed.The heart normally beats at a rate of 60-80 beats per minute. A faster or slower heart rate is an indication of a problem.

HEART BEATS

The left and right ventricles contract at the same time = SYSTOLE.

When the ventricles are relaxed = DIASTOLE.

At which stage do the atria contract? Diastole.

HEART BEATS

SYSTOLE: Ventricles contract

Atria relax

DIASTOLE:Ventricles relax

Atria contract

HEART BEATS

Start of Systole: Closing of valves (tricuspid and mitral) causes blood to hit the valves, making a sound. Systole of the ventricle means that this chamber is contracting.

End of Systole: Closing of semilunar aortic and pulmonary valves causes blood to hit the valves, making a sound

HEART BEATS

Lub-Dub is the sound of the blood hitting the closed valves.

Start of Systole: Closing of the large valves (tricuspid and mitral) = “LUB” sound from blood hitting them.

End of Systole: Closing of semilunar valves (aortic and pulmonary)= “DUB” sound (“Dub”) from blood hitting them.

Heart Sounds

Figure 18.11

Valve Problems

HEART MURMUR If the valve leaks, it doesn’t close all the way

“Lub-squirt”

Most murmurs are benign; fairly common, esp. in babies and some adults.

Valve Problems• PROLAPSED VALVE is more serious. • Mitral valve is most likely to prolapse because it pumped

the hardest. See how much thicker the left ventricle is? Mitral Valve Prolapse is the most common heart valve disorder. Might need artificial valve.

What controls the heart beat?There is a small region in the right atrium = SA NODE (Sino-atrium node) = pacemaker of the heart. Its job is to speed up or slow down the heart rate as needed.

SA node sends an electrical signal (action potential) to the AV NODE (atrio-ventricular node) atrium contraction pauses signal transmitted to both ventricles sends the action potential to all parts of the heart so it can contract.

SA and AV Nodes

Conducting System

Figure 18.12

PLAYPLAY Intrinsic Conduction System

Heart Beats

• The heart does not need a nerve to stimulate it to contract; rather, specialized heart cells can spontaneously start an action potential that spreads to depolarize the rest of the cardiac muscle cells.

• First the Sinoatrial (SA) node starts an action potential which causes the atria to depolarize.

• This depolarization will then reach the AV node at the bottom portion of the right atrium and there is a delay here because these cells are so small in diameter.

• Another delay in the transmission of the depolarization at the bundle of His (AV bundle) because these special heart cells travel through the atrioventricular septum which is non-conductive fibrous connective tissue.

• Next, the depolarizing event travels through the left and right bundle branches, found in the interventricular septum, to finally arrive at the Purkinje fibers in the lateral walls of the myocardium of the ventricles.

Conducting System

Figure 18.12

PLAYPLAY Intrinsic Conduction System

Impulse Pathway

• SA node• AV node• Bundle of His (conduction

slows down here because this area is fibrous connective tissue, not muscle cells. This gives the atria time to contract before the ventricles

• Right and left bundle branches on the IV septum

• Purkinje fibers on the lateral wall of the ventricles…now they contract

http://www.phschool.com/science/biology_place/biocoach/cardio1/electrical.html

EKG

Problems

ARRHYTHMIA

Problem with the SA or AV node improper heart beat.

Treatment is medicines or a pacemaker.

Ventricular Fibrillation

FIBRILLATION is when the heart beat is not really present…it just vibrates. A heart in fibrillation does not contract rhythmically; it just quivers without pumping blood. It needs an electric shock from a defibrillator. This machine is never used when someone’s heart is beating with a lub-dub sound, even if it is irregular, because it can cause the heart to stop. Whatever caused the fibrillation in the first place is not treated, so it may not work, but it’s worth a try! Most large public facilities have them. There are three on this campus. Disneyland has one every 100 yards.

THE HEART NEEDS ITS OWN BLOOD/O2

The endocardium gets plenty of O2 from the blood cells that touch this layer as they travel through the heart, but the oxygen does not diffuse all the way into the myocardium, which is a deeper layer.


Therefore, the myocardium needs its own blood supply by CORONARY ARTERIES and VEINS.

They are on the surface of the heart, and there are four of them.

The more you exercise, the more branches of these arteries are formed between themselves, and the better the blood supply to the heart.


When blood vessels fuse together where they meet it is said that they ANASTOMOSE.

This is a safety mechanism that allows blood to get through if one of the vessels gets clogged.


If one of the four coronary arteries becomes clogged, ISCHEMIA (lack of oxygen) to part of the heart muscle will result.

This is a painful condition, and the pain of it is called ANGINA (heart pain).

If nothing is done immediately to increase the blood flow, the myocardial tissue can die; this condition is called a HEART ATTACK.

Coronary Bypass

People who have an angina attack can take nitroglycerine as a tablet under the tongue that dissolves quickly.

This medicine will dilate the blood vessels.

Weird ER Story

A 28-year old male was brought into the ER after an attempted suicide. The man had swallowed several nitroglycerine pills and a fifth of vodka.

When asked about the bruises about his head and chest he said that they were from him ramming himself into the wall in an attempt to make the nitroglycerine explode.

Coronary Bypass

When a person has their first angina attack, the doctor will order an ANGIOGRAM to look for a narrowing in an artery, especially in one of the coronary arteries.

Coronary Bypass

If a coronary artery is found to have a severe blockage, they can do a CORONARY BYPASS.

In this procedure, the doctor takes another blood vessel graft (from the greater saphenous vein in the thigh) and sews it in around the blockage.

For double or triple bypasses, that’s how many vessels are affected.

Blood Supply to the Heart

Figure 18.14

R. Coronary artery L. Coronary

artery

Anterior interventricular artery (posterior interventricular artery is on the back side)

Circumflex artery

TERMS

ANGINA: heart pain, usually caused from not enough oxygen to the myocardium (ischemia)

ISCHEMIA: lack of blood/oxygen

MYOCARDIAL INFARCTION: heart attack from blood clot in coronary artery, causing ischemia, which causes angina

HEART ATTACK

Not enough blood to the heart’s myocardium layer MILD ISCHEMIA severe pain: ANGINA (angina pectoris)

Treatment is nitroglycerine to open arteries

Complete blockage not enough O2 to that area = SEVERE ISCHEMIA that part of heart muscle dies = MYOCARDIAL INFARCTION. Heart muscle never regenerates. If a large area dies, person will die.

HEART ATTACKWhat are symptoms of a heart attack? Chest pain, pain down left arm, shortness of breath, nausea, tight pressure in chest. A common symptom is death. 50% of first heart attacks are fatal within 2 hours. If a person receives good treatment in the first 2 hours, they are more likely to survive. About ¾ million people die each year from heart attacks.A drug that can stop heart attacks in progress by dissolving clots is t-PA (also used to prevent clots that cause strokes)Angioplasty is a surgical procedure to clean out a clogged artery.A beta blocker is a drug that slows down the heart rateAspirin reduces blood clot formationNitroglycerine dilates the coronary arteries so more blood can get in.

Fun Fact

If a person takes an aspirin once a day to prevent clots or a heart attack, they should take it at NIGHT.

Aspirin has a half life of 24 hours, so its effect is strongest in the morning.

Most heart attacks occur in the morning!

Bayer has new Quick Release crystals that dissolve faster in your mouth.

Heart Medicines

t-PA (dissolves blood clots)

Beta-blockers (slows heart rate)

Aspirin (prevents blood clots)

Nitroglycerine (dilates coronary arteries)

CIRCULATORY DISEASE CONDITIONS

The leading cause of untimely death in the Western countries of the world is cardiovascular disease.There are several hereditary factors that influence whether a person will get cardiovascular disease: 1. family history of heart attack2. gender (males are high risk)3. race/ethnicity (African Americans high risk)

CIRCULATORY DISEASE CONDITIONS

Whether or not you have a hereditary factor, there are some things you can do to prevent heart disease with diet and exercise. Included in this is knowing your cholesterol level, lowering your LDL intake, use olive and canola oil rather than butter/cream. Some studies also suggest that antioxidant vitamins (A, E, and C) may help, but remember that too much vitamin A and E cause a lot more harm to the liver than good to the circulation.

Causes of High Blood Pressure

ARTERIOSCLEROSIS (hardening of the arteries): caused by a build-up of calcium deposits in the artery wall; artery cannot expand with blood surges. Tends to be hereditary.

The blood vessel becomes hard like a rock; it can’t expand or contract, causes increase in blood pressure.

Diet and exercise don’t help this much. Both arteriosclerosis and atherosclerosis cause high blood pressure.

Areteriosclerosis

Causes of High Blood Pressure

ATHEROSCLEROSIS (The most common form of arteriosclerosis; a build-up of fat in the arteries): caused from eating fatty food narrowing of artery Spasm shut or blood clot.

Atherosclerosis

EMBOLISM

When fat builds up in a lump in one place, it is called a PLAQUE. It causes the lumen to narrow, restricting blood flow. If this fatty plaque breaks off and travels in the bloodstream, it is now called an EMBOLISM. An embolism can also be made of blood instead of fat.

How a thrombus becomes embolism

If a platelet catches on a piece of this fat, it can start a blood clot (thrombus).

If a piece of the clot (thrombus) breaks off and enters the circulation, it is now called an embolism, it can lodge in a smaller blood vessel and block the oxygen to all the tissue past that point, and the tissue dies.

A thrombus can become an embolism

A thrombus is made of BLOOD. It is a blood clot that is located on the inside wall of a blood vessel (usually a vein but not always) and it has not moved anywhere (yet).An embolism can be made of FAT or BLOOD. It is either a build up of fat in a vessel (usually an artery but not always) that has broken off a piece or a blood clot (usually in a vein but not always) that has broken off a piece. It travels and gets lodged in a smaller vessel somewhere.

Blockage of blood vessel

If the embolism lodges in the coronary arteries myocardial infarct (Heart attack).

If the embolism lodges in an artery in the brain stroke

If the embolism lodges in the lungs pulmonary embolism

Pulmonary Embolism

ANGIOGRAM

An ANGIOGRAM is a procedure to inject dye into the arteries and x-ray to see if there is narrowing (sclerosis) of a vessel. This can be done anywhere in the body that is of interest, but frequently it is done to check the coronary arteries.

Angiogram

ANGIOGRAM

If an artery is too narrow, an ANGIOPLASTY can be performed to open it up. This involves sticking a balloon into the artery and inflating it, causing the vessel to enlarge a little to increase blood flow. This can be done anywhere in the body, but is frequently done in coronary arteries.

Angioplasty

CORONARY BYPASS

For a coronary artery that has become extremely narrow from plaques, you can do a CORONARY BYPASS.Take another blood vessel graft (superficial vein from thigh) and go around the blockage. For double or triple bypasses, that’s how many vessels are affected. People who exercise have the same number of heart attacks as those who don’t, but they tend to survive them.

VENTRICULAR FIBRILLATION

Even a small clot can be a problem. If it happens to enter the interior of the heart and lodge in the wall of the atrium, it can block the conduction of the signal of the AV node VENTRICULAR FIBRILLATION.

ANEURYSM

High blood pressure is due to high pressure of blood against the walls of the blood vessels; the blood vessels compensate by developing a thicker wall. The vessels can no longer expand during systole, so the vessel gets thicker and thicker, and the blood pressure goes up more. If the blood pressure gets too high, an ANEURYSM can form, which is a weakening in the wall of the blood vessel, causing it to expand like a balloon.

ANEURYSM

Thus, an aneurysm is a sac-like outpouching of an artery. If it ruptures, it’s very dangerous. The aorta is the first artery that leaves the heart. It is under high pressure, so it is susceptible to rupture; you’ll be dead in three heart beats. Can also get aneurysms in the brain that cause stroke. Aneurysms have no symptoms.

Predictors of Heart Attack

High Blood Pressure

High Cholesterol

Large Waist Size


Normal blood pressure is 120/80. Pre-hypertension is 120 to 139 (systolic) and/or 80 to 89 (diastolic). Hypertension – also known as high blood pressure -- is 140 or higher (systolic) and 90 or higher (diastolic). One in three adults in the U.S. has high blood pressure or pre-hypertension.

Predictors of Heart Attack:Cholesterol levels you DON’T want

Total cholesterol higher than of 200 mg/dL.

HDL ("good" cholesterol) lower than 50 mg/dL (females) or 40 mg/dL (males).

LDL (“bad” cholesterol) higher than 100Unless you have other major risk factors, like diabetes, you want your LDL closer to 70.

Triglycerides of greater than 150 mg/dL.


FEMALES: waist size more than 35 inches

MALES: waist size more than 40 inches

Measure around your belly button.

If patients lose even 1 inch off their waist, there are improvements in all the other heart health numbers

If they gain even 1 inch, there is a worsening in those numbers. It's a much better indicator of heart health than weight.

Other Heart Conditions

Congestive Heart failureProgressive weakening of the heartBlood backs up into lungs (may cough up blood)Cannot meet the body’s demands for oxygenated blood

Hypertrophic cardiomyopathyCongenital condition where the walls of the left ventricle are so thick that the lumen is too small to hold much blood.

Disorders of Conduction

Ventricular fibrillation Rapid, random firing of electrical impulses in the ventricles of the AV node

Atrial fibrillation Rapid, random firing of electrical impulses of the SA node

Most Common Heart Problems

ATHEROSCLEROSIS

VENTRICULAR FIBRILLATION

Congestive heart failure

Hypertrophic cardiomyopathy

EMBRYONIC DEVELOPMENT OF THE HEART

The heart is the most common site for congenital defects (those one is born with).

During fetal life, the mother provides the oxygen and nutrients through the placenta. If there is a problem with the baby’s heart, it is not a problem until birth, although it can be detected by ultrasound.


• The earliest heart chambers

Figure 18.16a, b

The Heart Throughout Life

Figure 18.16c–e


At 28 days (two weeks after a woman misses her period), the human heart first starts to beat and pump blood in the embryo (at the start of the fourth week).

You have to stop smoking and drinking before you get pregnant. By the time you know you’re pregnant, it’s too late for the baby’s heart.

Fetal Heart

Where is the fetus getting the oxygen during the nine months in the womb?

The mother, not the lungs.

So there’s no sense in sending half of the body’s blood to the lungs for oxygen.

FORAMEN OVALE

The lung tissue needs some oxygenated blood, but only a little. Therefore, there is an opening from the right to the left atrium called the FORAMEN OVALE which shunts blood from the right to the left side of the heart to bypass the lungs.There is a foramen ovale in the skull and another one in the heart. The foramen ovale in the heart normally closes shortly after birth, and is then called the FOSSA OVALIS.A ‘blue baby” has low oxygen levels in the blood that may be due to failure of the foramen ovale to close at birth.

Foramen Ovale

DUCTUS ARTERIOSIS

Another shunt: between the pulmonary artery and the aortic arch so that most of the blood bypasses the immature lungs Therefore, there are two shunts to take blood away from the lungs. When the ductus arteriosis closes off at birth, it is called the ligametum arteriosum

Figure 18.5b

Changes at Birth

At birth, there is an immediate change. Half of the blood needs to go to the lungs.

At the first breath, a flap closes over the foramen ovale, and a muscle around the ductus arteriosis constricts, causing instant closing, and seals shut permanently.

Patent Foramen OvaleWhen a baby has not started walking, it doesn’t need as much oxygen, so a patent (open) foramen ovale might not be noticed until they start to walk and run at age 2-3.

However, every time the baby cries, it might turn blue.

A patent foramen ovale can be surgically closed by going through the blood vessels without cutting into the heart tissue.

A patent foramen ovale in an adult is just a tiny opening and can be heard as a heart murmur.

Heart Deformities

You can also have a patent ductus arteriosis.

More significant problems: interventricular septal defect (between right and left ventricle).

Requires open heart surgery.

Congenital Heart Defects

Figure 18.17a, b

Artificial Heart

• If heart is totally deformed, need transplant.

The Heart in Adulthood and Old Age

Age-related changesHardening and thickening of valve cusps

Decline in cardiac reserveSympathetic control over heart is less efficient

Less severe in the physically active

Fibrosis of cardiac muscle tissue Lowers the amount of blood the heart can pump

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