1.2- The Cardiovascular System

7/27/2019 1.2- The Cardiovascular System

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Topic 1~Maintenance of the body~

1.2The cardiovascularsystem

SARINI BINTI AHMAD WAKID


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Circulatory system consist of:

i) Cardiovascular system

Heart: four-chambered pump

Blood vessels: arteries, arterioles, capillaries, venules, and veins.

ii) Lymphatic system

Lymphatic vessels, lymphoid tissues, lymphatic organs (spleen,thymus, tonsils, lymph nodes)

Overview


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The heartHEART ANATOMY

HEART PHYSIOLOGY

BLOOD FLOW AND BLOOD PRESSURE


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The heart.

The pump that moves blood around

the body.

Located behind the sternum and ribs.

Myocardium: interior wall of the heart,

consist of cardiac muscle.

Cardiac muscles are myogenic;

contract and relax without receiving

signals from neurones. The impulse to

contract originates within the heart

itself.

The heart


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Pericardium: a thick doubled

membranous sac that support and

protect the heart. Secretes

pericardial fluid.

The heart


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Septum separates the left and rightside of the heart.

The heart consist of right and left

atrium, and right and left ventricles.

The thickness of the wall of atrium,

right ventricle and left ventricle

differs, depending on the task of

each chamber.

Coronary arteries supply all the

food and nutrients needed by the

heart.

The heart

The structure of the heart


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Right atrium:

Receives deoxygenated blood from

the two vena cava.

Left atrium:

Receives oxygenated blood from

pulmonary veins.

Atrium has thin wall receives blood

at low pressure.

Needs to put relatively little pressure

to move the blood into ventricles.

The heart


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Right ventricle:Filled with deoxygenated blood from

right atrium.

Ventricles have thicker walls and contractmuch more forcefully than atrium.

It produce the pressure needed to force

the blood out into the pulmonary arteries.

The heart


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Left ventricle:Filled with oxygenated blood from left

atrium.

Left ventricle has thicker wall than right

ventricle contract more forcefully to:

1) force the blood out into the aorta and

around the body.

2) overcome the elastic recoil of thearteries.

However, the volume of blood enters both

ventricles are the same.

The heart


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The valves:Made of flaps of connective tissue.

Two types:

1) atrioventricular valve2) semilunar valve.

The heart


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1) Atrioventricular valve (av valve):

Other name:

1) tricuspid valve (separate rightatrium and right ventricle).

2) bicuspid/mitral valve (separate

left atrium and left ventricle).

anchored by strong fibers(tendinous cords/chordaetendinae) attached to papillarymuscles prevent them fromturning inside out.when ventricle contract avvalves closed prevent backflowof blood into the atria.

The heart


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2) Semilunar valve:

In between ventricle and blood

vessel:1) aortic semilunar valve - left

ventricle and aorta.

2) pulmonary semilunar valve -

right ventricle and pulmonary

artery.

Pushed open by the pressure

generated during ventriclescontraction.Closed when ventricles relax,pressure in the aorta close thevalve.

The heart


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The sounds of a heart beat:

Lub created by the recoil of blood

against the closed AV valve.

Dup created by the recoil of blood

against the closed semilunar valves.

The heart


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Cardiac cycle


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When heart contracts it pumps blood.

When heart relaxes blood fill in the chambers.

Cardiac cycle:

One complete sequence of pumping and filling the heart.

In adult at rest, 1 cardiac cycle = 0.8 second.

Only 0.1 second of each cardiac cycle, atria is contract.

The other 0.7 second - atria are relaxed and are filling with blood returningvia the veins.

Cardiac cycle:

Relaxation phase diastole.

Contraction phase systole.

Cardiac cycle


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1) During diastole:relaxation phase - atria and ventricles in diastole.

0.4 sec.

- blood returning from the large veins flows into atria and ventricles.

2) During atrial systole:atrial contract, ventricle relax .

0.1 sec.

- forces all blood remaining in the atria into the ventricles.

3) During ventricular systole:

ventricle contract, atrial relax.

0.3 sec.

- pumps blood into the large arteries through the semilunar valve.

Cardiac cycle


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Cardiac cycle

Systole and diastole during cardiac cycle


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Cardiac cycle

Changes in the heart during cardiac cycle


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Cardiac output


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Cardiac output:

Volume of blood each ventricle pumps per minute.

Cardiac output depends on:

1) Stroke volume (amount of blood pumped by a ventricle in a single

contraction).

~ average stroke volume = 70mL.

2) Heart rate (no of heart beats per minute).

~ normal resting heart rate = 72 beats per minute.

~ controlled by intrinsic and extrinsic conduction of the heart.

Cardiac output


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Intrinsic conduction of the heart.

~ Some cardiac muscle are autorhythmic contrax and relax without

signal from the nervous system.

~ Nodal tissue, which has both muscular and nervous characteristics, is a

unique type of cardiac muscle located in two regions of the heart.

Cardiac output


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~ The SA (sinoatrial) node

(pacemaker) is located in the

wall of the right atrium; the AV

node is located in the base of

the right atrium very near theseptum.

~ Nodal tissue generates

electrical impulses which spread

rapidly within heart tissue, thus

sets the rate and timing at

which all cardiac muscle

contracts.

Cardiac output


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The AVN pass the impulsesonto the bundle of His , which

conduct the impulses to the

muscle fibres in the right and

left ventricles walls.

Impulses pass down the

Purkyne fibres - the right and

left ventricles contract.

Blood is squeezed into the

arteries.

Cardiac output


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After contracting, the heartmuscle cells dissipate the

electrical impulse and prepare

to receive the next impulse.

Cardiac muscle relax for a

period blood fills the atria.

Cardiac output


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Extrinsic conduction of the heart.

1) Sympathetic and parasympathetic nerves.

~ Helps to regulate the heart tempo - speed up or slow down.

~ e.g.: when we walk sympathetic nerves increase the heart rate to

provide additional oxygen needed by the muscle.

~ e.g.: when we relax parasympathetic nerves decrease the heart

rate conserve the energy used.

Cardiac output


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2) Hormones adrenaline and noradrenaline.

~ Secreted into the blood can also influence the heart rate.

~ e.g. hormone is produced in situations of excited, anger, nervous or

scared increase the heart rate.

3) Body temperature.

~ e.g.: when we have fever increase of 1 oC raises the heart beat by

about 10 beats per minute.

4) Substances and drugs.

~e.g.: nicotine and caffeine cause an increased in heart rate.

Cardiac output


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Cardiac output = 72 x 70 = 5040 5 L/min.

Equal to the total volume of blood in the human body.

Heavy exercise = cardiac output increase five fold.

Cardiac output

"Blood." Encyclopedia Britannica . Chicago:

EncyclopediaBritannica, 1973.

"The body of an adultmale contains aboutfive litres of blood,

that of a woman or achild less."

5 L


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Electrocardiogram (ECG or EKG):

Detect and record electrical impulses generated by SA node.

Consists of a P wave, a QRS complex, and a T wave.

The ECG records the electrical activity that results when the heartmuscle cells in the atria and ventricles contract.

Electrocardiogram


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Consists of:

P wave:

Caused by contraction of the atria - time

of atrial systole.

QRS complex:

The main peak of the heartbeat, caused

by contraction of the ventricles - time of

ventricular systole.

T wave:

Caused by relaxation of the ventricles

during diastole.

Electrocardiogram


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Blood pressure


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Contraction of a heart ventricles

generate blood pressure causes the

blood to flow away from the heart.

Pressure in artery is higher as

compared to vein.

Blood pressure is highest in the aorta

and lowest in the venae cavae.

Blood pressure


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Stretches and recoil of elastic wall maintain the blood pressure and

blood flow through out the cardiac cycle.

Once they reach smaller blood vessel resistant increase dissipates

much of the pressure generated by the heart.When blood reach capillary, the lumen is even narrower, but the

number of capillary is enormous pressure will not increase.

Blood travels 500 times slower in the capillary (about 0.1 cm/sec) thanin the aorta (48 cm/sec).

Blood pressure


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Systolic pressure:

Highest blood pressure during

ventricular systole.

Diastolic pressure:

Pressure when elastic wall recoil

during ventricular relax.

Blood pressure


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Pulse is the rhythmic bulging of

the artery walls with each

heartbeat.

The surge of blood entering thearteries causes their elastic walls

to stretch, but then they almost

immediately recoil.

This alternating expansion and

recoil of an arterial wall can be

felt as a pulse in any artery that

runs close to the bodys surface.

Blood pressure


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Measuring the blood pressure:

Blood pressure


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Regulation of blood pressure:

1) Oscillation in arterial blood pressure during each cardiac cycle.

2) Change of state of smooth muscle in artery walls (trigger by nervous

and hormones responses):a) vasoconstriction:

smooth muscle contract arteries becomes narrower increasing the

blood pressure flow in the arteries.

b) vasodilation:

smooth muscle relax arteries become wider decreasing the blood

pressure flow in the arteries.

Blood pressure


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Regulation of blood pressure always coupled with cardiac output.

e.g.: during exercise vasodilation of arteries increase flow of blood

to the muscle - decrease of blood pressure in body as a whole

cardiac output increase maintaining blood pressure and blood flow.

Blood pressure


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Blood flow


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Blood flow (F) is directly proportional to the difference in blood

pressure (P) between two points in the circulation

If P increases, blood flow speeds up

If P decreases blood flow declines

Blood flow is inversely proportional to resistance (R)

If R increases, blood flow decreases

R is more important than P in influencing local blood pressure

Blood flow


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Blood resistance


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Opposition to blood flow.

A measure of the amount of friction blood encounters as it passes

through the vessels.

Referred to as peripheral resistance (PR).

Blood resistance


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Three important source of resistance:

Blood viscosity internal resistance to flow that exists in all fluid;

related to thickness of a fluid. The greater the viscosity, the less

easily molecules slide past one another, the more difficult it is tokeep the fluid moving.

Total blood vessel length the longer the vessel, the greater the

resistance.Blood vessel diameter the smaller the tube, the greater the

friction. Fatty plaques from atherosclerosis cause turbulent blood

flow and increase resistance due to turbulence.

Blood resistance


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The blood vessels

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Blood vessels

Structure of artery, capillary and vein.


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Structure of blood vessels:

1) Tunica intima:

~Innermost layer of vessels.

~One layer of endothelial cells /

endothelium.

2) Tunica media:

~Middle layer of vessels.

~Smooth muscle + elastic tissue.

Blood vessels

3) Tunica adventitia:

~Outermost layer of blood vessel.

~Mainly composed of connective tissue.

Structure of artery, capillary and vein.


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Arteries and veins:highway carrying heavy traffic.

Capillary:

narrow town street. Place for exchange of substance.

All blood vessels are interconnected between one another.

Working within one circulatory system.

Arrangement of blood vessels:

Blood vessels

aorta arter y arteriole capillar y venule vein Venacava


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Arteries:

Carry high-pressure surge of blood away from the heart towards the

cells.

Carry oxygenated blood except:

~ Pulmonary artery.

~ Umbilical artery.

Arteries

Histology of artery and vein.


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Their walls contain a lot of elastic fibres can stretch to accommodatethe greater volume of blood without being damaged.

Aorta have more elastic fibres to increased elasticity - helps to

accommodate blood pumped at high pressure by the heart + maintain

blood pressure when the heart relaxes between contractions.

Between surge elastic fibres return to their original length squeeze

the blood blood move in a continuous flow.

Blood pressure in artery fall as arteries are further away from the heart.

The smaller the lumen, the harder blood can flow through it - arterioles

have more muscle tissue that will contract or relax to control the blood

flow regulate the amount of blood arrive at each organ.

Arteries


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Capillaries:Fine networks of tiny tubes that links the arterioles and venules.

The smallest blood vessels (diameter only slightly greater than RBC).

Therefore, slow speed of blood flow more opportunity for diffusion to

occur.

Vessels that spread throughout the tissues of the body - substance can

diffuse between cells and the blood quickly.

Only certain capillaries are open at any given time.

Precapillary sphincters control the blood flow through a capillary bed

constriction will closes the capillary bed blood flow through

arteriovenous shunt.

Capillaries


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Walls consist of one very thin cell:Consist of only endothelium.

No elastic fibres + smooth muscle + connective tissues.

Facilitates the exchange of substances between the blood in capillaries

and cells, e.g:

1) Oxygen + food molecules diffuse out from capillary into cells.

2) Carbon dioxide + waste diffuse from cells into capillary.

Blood flowing to capillary is under very much low pressure.

Blood entering capillary network oxygenated.

Blood leaving capillary network deoxygenated.

Capillaries


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Veins:Carry blood back to the heart.

Carry deoxygenated blood except:

~ Pulmonary vein.

~ Umbilical vein.

Veins

Histology of artery and vein.


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Two veins carry the returning blood to the heart:~ Inferior vena cava lower parts of body

~ Superior vena cava upper parts of the body

Veins bring blood back to the heart under low pressure and velocity.

Their walls are thin (less elastic walls, smooth muscles and connective

tissues), thus vessels are thinner and less strong then arteries blood

visible in them under the living skin.

Vein can hold a large volume of blood (blood reservoir). More than half

of the bodys blood is in the veins at any 1 time.

Veins


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With relatively low pressure in veins, blood is returned to the heart

through1) Semilunar valves.

Formed from infoldings of the inner wall of the vein. Prevent

backflow of blood and maintain unidirectional flow of blood in the

vessels.

Valve opened by pressure from behind, closed with pressure from in

front.

Veins

Semilunar valve of vein


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2) Contraction of muscle.Many of larger veins are situated

between the large blocks of the

body (arms and legs).

Contraction of muscles will squeeze

the veins.

Veins

Large muscle between vein


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Arteries vs capillaries vs veins

Blood pressure, velocity and total area of arteries, capillaries and veins.

C bl d l


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Common blood vessels


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The cardiovascular

pathway


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The cardiovascular pathway

Double-closed circulation system in human.


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Human have two circulations:1) Pulmonary circulation.

Deoxygenated blood flows from the right side

of the heart to the lungs (diffusion of O2

into

the blood and CO 2 out of the blood) and then

back (oxygenated blood) to the left side of

the heart.

Blood pumps to lungs via pulmonary arteries.

Blood returns to heart via pulmonary veins.

The pathway?



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2) Systemic circulation.Oxygenated blood from the left side of the

heart is then pumped around the rest of the

body and back (deoxygenated blood) to the

right side of the heart.

Blood pumps to body tissues via aorta.

Blood returns to heart via superior and

inferior venae cavae.

The pathway?



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Benefit of double circulation:1) Oxygenated blood is delivered at high pressure to reach the respiring

tissues.

2) Oxygenated blood is unmixed by deoxgynated blood.



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* Coronary circulation *Myocardium receives oxygen and nutrients

from the coronary arteries, remove wastes

through cardiac veins.

Coronary arteries the first branches off

the aorta. Lie on the exterior surface of the

heart, divide into arterioles. Coronary

capillary beds join to form venules, join to

form cardiac veins, then empty into the

right atrium.


1.2- The Cardiovascular System

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