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1 Maria immaculata iwo, sf, itb

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• The heart is located in the thoracic cavity between the lungs,within the mediastinum.

• It is a hollow, cone-shaped, muscular organ, about thesize of a fist.

• The base (the widest part) of the heart is superior to itsapex (the pointed tip), which rests on the diaphragm.

• lso, the heart is on a slant! the base is directed toward theright shoulder, and the ape" points to the left hip.

• The base is deep to the second rib, and the ape" is at thelevel of the fifth intercostal space.

maria immaculata iwo, sf itb

2010

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$ s the heart pumps the blood through thepulmonary and systemic vessels, it performsthese functions&

1. eeps 2-poor blood separate from 2-richblood!

2. eeps the blood flowing in one direction blood flows away from and then bac to theheart in each circuit!

3. creates blood pressure, which moves theblood through the circuits!

. regulates the blood supply based on thecurrent needs of the body


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• The right side of the heart

pumps blood throughvessels of the pulmonary

circuit. • The le!t side of the heart pumps blood through

vessels of the systemiccircuit.

• 0as e"change occurs as

blood passes through lung(pulmonary) capillaries.

•

0as e"change and nutrient- for-waste e"change occuras blood passes throughtissue (systemic)capillaries.

In this illustration, red vesselscarry O2 -rich blood, and blue

-

The heart is called dou"le pump.

- ulmonary circuit

- %ystemic circuit

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#all o! the $eart

The wall of the heart consists of three layers.

• an outer & epicardium or visceral pericardium• a middle& myocardium thic is composed of cardiac

muscle tissue.

• an inner & endocardium

• 3"ternal to the epicardium is the dou"le-la%ered parietal pericardium, composed of an inner serousmembrane and an outer fibrous membrane.

$ The pericardial ca&it%, lies between the epicardium andparietal pericardium containing pericardial fluid

$ 4luid secreted by the serous membranes reduces friction,enabling the heart to move freely within the pericardial sac.


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nterior view of e"terior heart anatomy

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'ham"ers and &al&es o! the heart

The heart has four hollow chambers

$ The upper (superior)& 7 thin-walled chambers, the left and right atria, which receive blood

returning to the heart.

7 tria send blood into the ad8acent ventricles.

$ The lower (in!erior), 7 thic-walled chambers are the left and right &entricles, which

pump blood into the arteries leaving the heart.

7 the left ventricle has a thicer wall than the right ventricle!

7 the right ventricle pumps blood to the lungs, which are nearby.

7 The left ventricle pumps blood to all the other parts of the body.

• Internally, the atria are separated by the interatrial septum, andthe ventricles are separated by the inter&entricular septum.

Therefore, the heart has a left and a right side.


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$ The heart has * valves& 7 two atrio&entricular valves 7 two semilunar &al&es.

*he Atrio&entricular &al&es

• The valves prevent a bacflow of blood from the ventricles intothe atria during systole - the contraction phase of the heart

cycle.• The cusps have thin cords, the chordae tendineae, that

anchor them to papillary muscles on the walls of the ventriclesand prevent the valve cusps from being forced into the atriaduring contraction.

♦ The tricuspid a&-&al&e, has three flaps or cusps andoccurs between the right atrium and ventricle.

♦ The mitral or "icuspid a&-&al&e has only two cusps,and occurs between the left atrium and ventricle.


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*he semilunar &al&es

♦ the pulmonar% semilunar &al&e located at the base of the pulmonary artery

♦ the aortic semilunar &al&e

located at the base of the aorta

They each have three cusps

revent the bacflow of blood from the arteriesinto the ventricles during diastole - therelaxation phase of the heart cycle.


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Internal heart anatomy

Semilunar &al&e

Bicuspid (mitral) &al&e (A+ &al&e)

*ricuspid &al&e (A+ &al&e)

Intraventricular septum

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'oronar% 'ircuit

9ardiac muscle fibers and the other types of cells in the wall of theheart are not nourished by the blood in the chambers!

Instead ,

these cells receive nutrients and rid themselves of wastes atcapillaries embedded in the heart wall.

coronar% arteries,the left and right coronary arteries, branch from the aorta 8ustbeyond the aortic semilunar valve.

$ 3ach of these arteries branchesthen rebranches encircled by

small arterial blood vessels capillary bed in the heart thecoronary veins (specifically called cardiac &eins).

$ The cardiac veins enter a coronary sinus,

$ The coronary sinus enters the right ventricle.


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'oronar% 'ircuit isorders

$ :eart diseases are especially associated with atherosclerosis, adegenerative disorder of arterial walls.

4irst, soft masses of fatty materials, particularly cholesterol, accumulate in the arterial wall. 4urther changes result inplaue, protrusions that interfere with blood flow.

If the coronary artery is partiall% occluded (bloced) by atherosclerosis,the individual may suffer from ischemic heart disease.

the person e"periences insufficiency during e"ercise or stress.

This may lead to angina pectoris, chest pain that is oftenaccompanied by a radiating pain in the left arm.

The blood may clot in an unbroen blood vessel, particularly if pla;ue ispresent throm"oem"olism is present when a blood clot breasaway from its place of origin and is carried to a new location.

Thromboembolism leads to heart attacs when the embolus blocs acoronary artery and a portion of the heart dies due to lac of o"ygen.

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The physiology of the heart pertains to its pumping actionthat is, the heart"eat.

It is estimated that the heart beats two and-a-half billiontimes in a lifetime, continuously recycling some + liters (=) ofblood to eep us alive.

In this section, we will consider what causes the heartbeat,what it consists of, and its consequences.


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'onduction S%stem o! the $eart

♦ The conduction s%stem o! the heart is a route ofspecialized cardiac muscle fibers that initiate andstimulate contraction of the atria and ventricles.

♦ The conduction system is said to be intrinsic , meaningthat the heart beats automatically without the need fore"ternal nervous stimulation.

♦ The conduction system coordinates the contraction ofthe atria and ventricles, so that the heart is an effectivepump.

♦ Without this conduction system, the atria and ventricleswould contract at different rates.


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*he SA node is called the pacemaer "ecause it usuall% eepsthe heart"eat regular.


'onduction S%stem o! the $eart

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/odal s%stem,intrinsic conductings%stem 'omponents

Sinoatrial (S-A) /ode (pacemaer )

Atrio&entricular node

(A-+ node)A-+ "undle

(Bundle o! $is)

right and le!t "undle

"ranches down, the branches

give rise to enlargedurine !i"ers


Sinoatrial(SA) node

(A+) node

A+ "undle

Le!t "undle"ranch

ight "undle"ranch

urine

!i"ers

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• n area other than the % node can become thepacemaer when it develops a rate of contraction that is

faster than the % node. This site, called an ectopic pacemaer , may cause

an e"tra beat, if it operates only occasionally, or itcan even pace the heart for a while.

$ 9affeine and nicotine are two substances that canstimulate an ectopic pacemaer .

rate of !ewer than 0 heartbeats per minute is called

"rad%cardia, and more than 166 heartbeats per minute is

called tach%cardia.

nother type of arrhythmia is !i"rillation, in which the heart

beats rapidly but the contractions are uncoordinated.

heart "loc maria immaculata iwo, sf itb

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$ Impulse transmission

through the conductionsystem generatedelectrical currents thatcan be detected on thebody>s surface.

$ graph that records theelectrical activity of themyocardium duringa cardiac cycle is calledan electrocardiogram,or 4'5.

n 390 consists of aset of waves&

• the wa&e,

• a 6S complex,

•

a * wa&e.

4lectrocardiogram (4'5)

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$ -#a&e

7 Indicates atrial depolarization.$

The spread of the impulse from the %- node through the twoatria.

$ the atria are going to be in systole and that the atrial myocardium

is about to contract.

$ 6S-#a&e or 'omplex 7 ?epresents &entricular depolarization

7 the spread of the electrical impulse through the ventricles.

7 %hortly after the @?% wave begins, the ventricles undergocontraction.

$ *-#a&e

7 Indicates ventricular repolarization maria immaculata iwo, sf itb

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'ardiac '%cle and $eart Sounds

• cardiac c%cle includes all the events that occur during oneheartbeat.

• n average, the heart beats about 70 times a minute,although a normal adult heart rate can vary from /6 to 166

beats per minute.• The right and left sides of the heart beat independentl% of

one another, but actually, they contract together.

4irst the two atria contract simultaneously! then the two

ventricles contract together.• The term s%stole refers to contraction of heart muscle, and

the term diastole refers to rela"ation of heart muscle.

•

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three phases of the cardiac cycle

hase 18 Atrial S%stole.

hase 28 +entricular S%stole.

hase 38 Atrial and +entricular iastole.


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hase 18 Atrial S%stole.

- Time 6.1+ sec.-

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hase 28 +entricular S%stole.

- Time 6.#6 sec.-

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hase 38 Atrial and +entricular iastole.

- Time 6.*6 sec.-

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#1maria immaculata iwo, sf itb

hase 18 atrial s%stole hase 38 atrial 9 &entricular diastole

hase 28 &entricular s%stole

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#2

$eart Sounds

$ heartbeat produces the familiar C=DB-

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$eart murmurs,

• which are clicing or swishing sounds heard after theClub,E are often due to ine!!ecti&e &al&es.

$ These lea% &al&es allow blood to pass bac into the

atria after the atrioventricular valves have closed, or bacinto the ventricles after the semilunar valves haveclosed.

7 trained physician or health professional can diagnose heartmurmurs from their sound and timing.

7 It is possible to replace the defective valve with an artificialvalve.


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'ardiac

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$eart ate

$ cardioregulator% center in the medulla oblongata of the brain

can alter the heart rate by way of the autonomic ner&ouss%stem (A/S)

7 aras%mpathetic motor impulses conducted by the vagusnerve cause the heart rate to slow,

7 S%mpathetic motor impulses conducted by sympathetic motor

fibers cause the heart rate to increase.

$ The cardioregulatory center is under the influence of thecere"rum and the h%pothalamus.

7 when we !eel anxious,

$ the sympathetic motor nerves are activated, and theadrenal medulla releases the hormones norepinephrineand epinephrine.

The result is an increase in heart"eat rate.


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Stroe +olume

$ %A - which is the amount of blood that leaves a ventricle,depends on the strength of contraction.

$ The degree of contraction depends on

7 the blood electrolyte concentration 7 the activity of the autonomic system.


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+enous eturn

Aenous return is the amount of blood entering the heart byway of the vena cava (right side of heart) or pulmonaryveins (left side of heart).

ny event that decreases or increases the &olume or speed of blood entering the heart will affect the strength of

contractioncalled Starling=s Law.

$ slow heart rate allows more time !or the &entricles to!ill and therefore increases the strength o! contraction.

$ low &enous return, as might happen if there is blood

loss, decreases the strength o! contraction.

7 4xercise increases the strength of contraction becauseseletal muscle contraction puts pressure on the veins andspeeds &enous return.


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egulation o! "loodpressure and &olume

Bottom: When the blood sodium (Na) levelis low, a low blood pressure causesthe kidneys to secrete renin. Reninleads to the secretion ofaldosterone from the adrenalcortex. Aldosterone causes the

kidneys to reabsorb Na, and waterfollows, so that blood volume andpressure return to normal.

Top: When the blood Na is hih, a hih

blood volume causes the heart tosecrete atrial natriuretic hormone(AN!). AN! causes the kidneys toexcrete Na, and water follows. "heblood volume and pressure returnto normal.

Documents

2016 02 12&19 03_Heart