cardiovascular system

The cardiovascular system

By

Dr: Nassar Ayoub

DVM.PHD Firas hayajneh 1

(Sohage Univers.)

FUNCTIONS OF THE

CARDIOVASCULAR SYSTEM

1. Transport of materials (oxygen , nutrients ,hormones ) throughout the body.

2. it removes metabolic waste products, such ascarbon dioxide, lactic acid, and urea, fromthe tissues.

3. contributes to the actions of the immunesystem by transporting antibodies andleukocytes to areas of infection.

2

FUNCTIONS OF THE

CARDIOVASCULAR SYSTEM

• The cardiovascular system delivers blood to tissues in the same time takes blood away to be reloaded with vital requirements for the cells.

• Components

1. Pump (heart).

2. Vessels.

3

The cardiovascular system

• All tissues are perfused (receive blood),

depending on their function.

• kidneys, only 1% of BW receive 20% (O2),

the GIT receives approximately 27% of the

O2, the skin receives 6 -15% of the blood.

• During exercise blood flow is directed away

from the kidneys and organs of the digestive

system and toward the skeletal and cardiac

muscles.

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The Blood Vessels

• There are three kinds of vessels:

1. Arteries (and arterioles) – carry blood

away from the heart

2. Capillaries – where nutrient and gas

exchange occur

3. Veins (and venules) – carry blood toward

the heart.

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Blood vessels


The Arteries

Arteries and arterioles take blood away

from the heart.

The largest artery is the aorta.

an artery wall has smooth muscle that can

constrict to regulate blood flow and blood

pressure.

Arterioles can constrict or dilate,

changing blood pressure.7

The Capillaries

• Capillaries have one cell thick walls to

allow exchange of gases and nutrients

with tissue fluid.

• Capillary beds are present in all regions

of the body but not all capillary beds are

open at the same time.

8

• Contraction of a sphincter muscle closes off a

bed and blood can flow through an

arteriovenous shunt that bypasses the capillary

bed.

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Anatomy of a capillary bed

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The Veins

• Venules drain blood from capillaries, then join to form veins that take blood to the heart.

• Veins have much less smooth muscle and connective tissue than arteries.

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The Veins• Veins often have valves that prevent

the backward flow of blood whenclosed.

• Veins carry about 70% of the body’sblood and act as a reservoir duringhemorrhage.

• large blood vessels are characterized

by an abundance of collagen fibers

and elastin fibers 12

Heart• Located in the center of the thoracic

cavity.

• The heart is a cone-shaped ( مخروط) ,

muscular organ located between the lungs

behind the sternum.

• The heart muscle forms the myocardium,

with tightly interconnect cells of cardiac

muscle tissue

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Functions of the Heart• Generating blood pressure

• Routing blood

–Heart separates pulmonary and systemic circulations

• Ensuring one-way blood flow

–Heart valves ensure one-way flow

• Regulating blood supply

–Changes in contraction rate and force match blood delivery to changing metabolic needs

Heart• Located in the center of the thoracic

cavity.

• The pericardium is the outer membranous

sac with lubricating fluid produced by the

membranes of the pericardium.is

composed of:

1) Receiving chambers (atria, single atrium)

2) Delivery chambers (ventricles).

3) Valves (forward flow of blood).

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• The heart has four chambers: two upper, thin-walled atria, and two lower, thick-walled ventricles.

• The septum is a wall dividing the two sides of

the heart.

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Pericardium: a double-walled fibrous sac sorrounding

the heart

pericardial fluid produced by the pericardium minimizes

friction of the heart

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The heart

• The wall of the heart has three layers:

1. Epicardium:is the thin membrane on the

external surface of the heart

2. Endocardium: thin delicate layer of cells

lining the chambers of the heart

3. Myocardium: the muscular layer of the heart

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Valvesflexible but tough fibrous tissue

1. Atrioventricular (AV) valves (between theatria and the ventricles):

A. The right AV tricuspid).

B. The left AV (bicuspid, mitral valve).

2. Semilunar valves: separate the ventriclesfrom their associated arteries

I. pulmonary valve is found between the rightventricle and pulmonary artery

II. aortic valve is found between the left ventricle andthe aorta.

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Valves

• both valves are reinforced by chordae tendinae

attached to muscular projections within the

ventricles.

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Heart

• The heart is a cone-shaped ( مخروط) , muscular organ located between the lungs behind the sternum.

• The heart muscle forms the myocardium, with tightly interconnect cells of cardiac muscle tissue.

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The septum is a wall dividing the two sides of the heart.

Atrioventricular valves occur between the atria and ventricles –

1. the tricuspid valve on the right

2. the bicuspid valve on the left.

• lub-dup heart sounds are due to the closing of

the atrioventricular valves, followed by the

closing of the semilunar valves.

• The pumping of the heart sends out blood

under pressure to the arteries.

• Blood pressure is greatest in the aorta; the

wall of the left ventricle is thicker than

that of the right ventricle and pumps

blood to the entire body.

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Passage of Blood Through the Heart

Blood follows this sequence through the heart: superior and inferior vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semi lunar valve → pulmonary trunk and arteries to the lungs → pulmonary veins leaving the lungs → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta → to the body.

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External heart anatomy


Coronary artery circulation


Internal view of the heart



• The pumping of the heart sends outblood under pressure to the arteries.

• Blood pressure is greatest in the aorta;the wall of the left ventricle is thickerthan that of the right ventricle andpumps blood to the entire body.

Path of blood through the heart


The Heart beat

• Each heartbeat is called a cardiac cycle.

• When the heart beats, the two atria contract together, then the two ventricles contract; then the whole heart relaxes.

• Systole is the contraction of heart chambers; diastole is their relaxation.


• The heart sounds, lub-dup, are

due to the closing of the

atrioventricular valves, followed

by the closing of the semilunar

valves.

• Blood pressure then decreases as

the cross-sectional area of arteries

and then arterioles increasesDVM.PHD Firas hayajneh 39

• From the left ventricle (main force)……right

atrium.

• Systolic pressure 120mmHg, diastolic pressure

80mmHg.

• Pulse pressure =120-80=40

Blood pressure

40

• Is determined by:

1. Pressure gradient.

The difference between the beginning pressure

and the pressure at the end.

1. Vascular resistance . Which depends on

Blood viscosity

Vessel length

Vessel radius

Blood flow through vessels

41

Is the driving force for blood flow through the

body’s organs and tissues. (very important):

hypotension:

dizziness and fainting

Hypertension:

Increase cardiac workload

Vascular damage (atherosclerosis) and the

rupture of small vesseles, in arteries of the brain

and heart.

Mean arterial pressure(MAP)

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1. Autonomic nervous system (ANS)

2. Vasoactive substances

3. Venous return

4. Local metabolic activity

Control of mean arterial pressure

(MAP)

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Intrinsic Control of Heartbeat

• The SA (sinoatrial) node, or pacemaker, initiates the heartbeat and causes the atria to contract on average every 0.85 seconds.

• The AV (atrioventricular) node conveys the stimulus and initiates contraction of the ventricles.

• The signal for the ventricles to contract travels from the AV node through the atrioventricular bundle to the smaller Purkinje fibers.

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Electrical activity of the heart

The specialized excitation and electrical

conduction system in the heart consists of:

A. Sinoatrial node

B. Interatrial pathway

C. Internodal pathway

D. Atrioventricular node

E. Bundle of His

F. Bundle branches

G. Purkinje fibers

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Intrinsic Control of Heartbeat

A. The SA (sinoatrial) node, or pacemaker, agroup of cells on the wall of the rightatrium, near the entrance of the superiorvena cava , initiates the heartbeat and causesthe atria to contract on average every 0.85seconds.

• Sympathetic and parasympathetic systeminnervates the SA node.

• Sympathetic nerves cause increase in theheartbeat, parasympathetic cause decrease inthe heart rate. 46

http://en.wikipedia.org/wiki/Superior_vena_cava

Contraction of the heart muscles• The “resting” membrane potential, or pacemaker

potential is -55mv.

1. depolarization due to influx of (Na, Ca). Untillthreshold is reached (-40mv).

2. Action potential happens.

3. Calcium channels close and potasium channelsopen leading to repolarization .

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Nervous system control• Norepinephrine, which stimulates b-adrenergic

receptors, increases the rate of pacemaker

depolarization by increasing the permeability to Na

and Ca ions.

• Parasympathetic stimulation causes a decrease in

heart rate. Acetylcholine, which stimulates muscarinic

receptors, increases the permeability to potassium.

• From the SA node the heart beat spreads to the atria.

(left atrium)

B. interatrial conduction pathway (from the SA node

to the left atrium

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C. internodal conduction pathway: at the baseof the right atrium near the interventricularseptum, transmits the impulse directly to theatrioventricular (AV) node

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• atria and ventricles are separated from eachother by fibrous connective tissue

D. the AV node serves as the only pathwaythrough which the impulse can betransmitted to the ventricles slight delay (0.1sec).

• it allows atria to complete their contractionbefore ventricular contraction begins. Thistiming ensures proper filling of the ventriclesprior to contraction.

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• The AV (atrioventricular) node conveys thestimulus and initiates contraction of theventricles.

E. Bundle of His: impulse spread through theheart , this bundle penetrates the fibroustissue seperating the atria from the ventricles.

F. Purkinje fibers: that extend from the bundlebranches and spread through the

myocardium.

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Conduction system of the heart

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Extrinsic Control of Heartbeat• A cardiac control center in the medulla

oblongata speeds up or slows down theheart rate by way of the autonomic nervoussystem branches: parasympathetic system(slows heart rate) and the sympatheticsystem (increases heart rate).

• Hormones epinephrine and norepinephrinefrom the adrenal medulla also stimulatefaster heart rate.

• parasympathetic system innervates the SA

node and the AV node of the heart by way of

the vagus nerves(decrease HR, which

decreases CO and MAP).

• The sympathetic system innervates most

tissues in the heart including the SA node, AV

node, and ventricular muscle. increase in HR

and increase in the heart contactility.

Autonomic nervous system (ANS)

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• Autonomic nervous activity to the

cardiovascular system is regulated by the

vasomotor center, Located in the lower pons

and the medulla of the brainstem.

Vasomotor center

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1. Baroreceptors (stretch receptors)

Monitor blood pressure in the aorta and carotid

sinuses, respond to stretch or distension of

blood vessels.

2. Chemoreceptors (carotid bodies, aortic

bodies):

Stimulated by hypoxisa and hypercarpnia and

decrease in arterial pH (acidosis)

3. Low pressure receptors: located in the

walls of the atria and pulmonary arteries.

Stimulated by a change in blood column

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• Substances released from many cells and

tissues in the body, including the endothelium

lining blood vessels, endocrine glands to cause

vasoconstriction or inhibit it to cause

vasodilation.

Vasoactive substances

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• Vasoconstrictors: When blood vessels

constrict, the flow of blood is restricted or

decreased (increased BP)

I. Catecholamines(epinephrine and

norepinephrine) from the adrenal medulla.

• Through α1-adrenergic receptors

• The selective α 1-adrenergic receptor

antagonist, prazosin (hypertension )

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I. Angiotensin II (kidney). Act through AT1

receptors on smooth muscles. ACE inhibitors for

the treatment of hypertenision.

II. Vasopressin (antidiuretic hormone), produced in

the hypothalamus. Secreted from the

adenohypophysis. Increases the reabsorption of

water. Act through V1, V2 receptors.

III. Endothelin: produced by vascular endothelium

IV. Thromboxane A2: produced by vascular

endothelium.

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• consistent elevation in blood pressure such that

systolic/diastolic pressures are ≥140/90 mmHg.

• There are several categories of antihypertensive

agents:

1. Diuretics. Decreases plasma volume ( decreases CO

(cardiac outpu, MAP (mean arterial pressure, VR

(venous return)).

2. Sympatholytics. Centrally acting agents affect the

vasomotor center in the brainstem and inhibit

sympathetic discharge, decrease CO, MAP

Pharmacy application

antihypertensive drugs

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3. Vasodilators: hydralazine causes direct

relaxation of arteriolar smooth muscle.

4. Ca++ channel blockers.(Verapamil,

nifedipine.

5. Angiotensin-converting enzyme (ACE)

inhibitors.

6. Angiotensin II receptor antagonists..

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• Vasodilators produced in the human body:

1. Prostacyclin: a metabolite of arachidonic

acid acid

2. Nitric oxide

Vasodilators

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Angina pectoris ( الصدريهالذبحه ).

• symptom of chronic ischemic heart disease. caused by animbalance between the oxygen supply and oxygendemand of the cardiac

muscle.

• Myocardial oxygen demand increases during exertion,exercise, and emotional stress.

• treated with nitroglycerin (vasodilation), which mightdecrease blood pressure.

• Nitroglycerin is administered sublingual.

Pharmacy application

67

Venous return (VR)

• Is the volume of blood that flows from the

systemic veins into the right atrium per minute.

• In a healthy heart CO is equal to VR.

• VEINS serve as blood reservoirs ( The most

distensible vessels in the circulatory system

are the veins).

• veins help to regulate cardiac output (CO).

• under resting conditions, 64% of the blood

volume is contained within these vessels.

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Venous return (VR)

Several factors influence VR, including:

1. Blood volume (hemorhage. Rehydration)

2. Sympathetic stimulation of the veins (vasoconstriction.. Blood pressure.. Blood moves to heart).

3. Skeletal muscle activity (arms , legs), contraction venous pressure venous return)

4. Respiratory activity (inspiration increases VR)

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• Each heartbeat is called a cardiac cycle.

• When the heart beats, the two atria contract together, then the two ventricles contract; then the whole heart relaxes.

• Systole is the contraction of heart chambers; diastole is their relaxation.


The Hear tbeat

How does the Heart work?

blood from

the body

blood from

the lungs

The heart beat begins when

the heart muscles relax

and blood flows into the

atria.

STEP ONE

The atria then contract

and the valves open

to allow blood into the

ventricles.


STEP TWO


The valves close to stop blood

flowing backwards.

The ventricles contract forcing

the blood to leave the heart.

At the same time, the atria are

relaxing and once again filling with

blood.

The cycle then repeats

itself.

STEP THREE

Circuits

•Pulmonary circuit

–The blood pathway between

the right side of the heart, to

the lungs, and back to the left

side of the heart.

•Systemic circuit

–The pathway between the

left and right sides of the

heart.

The Pulmonary Circuit

• The pulmonary circuit begins with the pulmonary trunk from the right ventricle which branches into two pulmonary arteries that take oxygen-poor blood to the lungs.

• In the lungs, oxygen diffuses into the blood, and carbon dioxide diffuses out of the blood to be expelled by the lungs.

• Four pulmonary veins return oxygen-rich blood to the left atrium.

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The Systemic Circuit

• The systemic circuit starts with the aorta carrying O2-rich blood from the left ventricle.

• The aorta branches with an artery going to each specific organ.

• Generally, an artery divides into arterioles and capillaries which then lead to venules.



• The vein that takes blood to the vena cava often has the same name as the artery that delivered blood to the organ.

• In the adult systemic circuit, arteries carry blood that is relatively high in oxygen and relatively low in carbon dioxide, and veins carry blood that is relatively low in oxygen and relatively high in carbon dioxide.

• This is the reverse of the pulmonary circuit.


Conduction system of the heart

• A cardiac control center in the medulla oblongata :

*parasympathetic system (slows heart rate) .

* sympathetic system (increases heart rate)..


Extrinsic Control of Heartbeat


Hormones epinephrine andnorepinephrine from the adrenalmedulla also stimulate faster heart rate

Cardiovascular system diagram


Major arteries and veins of the systemic circuit



• The coronary arteries serve the heart muscle itself; they are the first branch off the aorta.

• Since the coronary arteries are so small, they are easily clogged, leading to heart disease.

• The hepatic portal system carries blood rich in nutrients from digestion in the small intestine to the liver, the organ that monitors the composition of the blood.

Blood Flow in Arteries• Blood pressure due to the pumping of the

heart accounts for the flow of blood in the arteries.

• Systolic pressure is high when the heart expels the blood.

• Diastolic pressure occurs when the heart ventricles are relaxing.

• Both pressures decrease with distance from the left ventricle because blood enters more and more arterioles and arteries.


Blood Flow in Capillaries

Blood moves slowly in capillaries because there are more capillaries than arterioles.

This allows time for substances to be exchanged between the blood and tissues.


Blood Flow in Veins

• Venous blood flow is dependent upon:

1) skeletal muscle contraction,

2) presence of valves in veins, and

3) respiratory movements.

• Compression of veins causes blood to move forward past a valve that then prevents it from returning backward.



• Changes in thoracic and abdominal pressure that occur with breathing also assist in the return of blood.

• Varicose veins develop when the valves of veins become weak.

• Hemorrhoids (piles) are due to varicose veins in the rectum.

• Phlebitis is inflammation of a vein and can lead to a blood clot and possible death if the clot is dislodged and is carried to a pulmonary vessel.

Capillary Exchange

• At the arteriole end of a capillary, watermoves out of the blood due to the forceof blood pressure.

• At the venule end, water moves into theblood due to osmotic pressure of theblood.

• Substances that leave the bloodcontribute to tissue fluid, the fluidbetween the body’s cells.



• In the midsection of the capillary,nutrients diffuse out and wastesdiffuse into the blood.

• Since plasma proteins are too large toreadily pass out of the capillary, tissuefluid tends to contain all componentsof plasma except it has lesser amountsof protein.

• Excess tissue fluid is returned to theblood stream as lymph in lymphaticvessels.

The Electrocardiogram

• An electrocardiogram (ECG) is a

recording of the electrical changes that

occur in the myocardium during a cardiac

cycle.

• Atrial depolarization creates the P wave,

ventricle depolarization creates the QRSwave, and repolarization of the ventricles

produces the T wave.


Electrocardiogram


The ECG provides information

concerning:

1. Relative size of heart chambers

2. Various disturbances of rhythm and electrical conduction

3. Extent and location of ischemic damage to the myocardium

4. Effects of altered electrolyte concentrations

5. Influence of certain drugs (e.g., digitalis and antiarrhythmic drugs)


Pharmacy applicationsantiarrhythmic drugs

• Arrhythmia: Any abnormality of the initiationor propagation of the impulse.

1. Verapamil (Class IV antiarrhythmic drug) is aneffective agent for atrial or supraventriculartachycardia. A Ca++ channel blocker.

2. Procainamide (Class IA antiarrhythmic drug),blockade of the fast Na+ channels

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Cardiac cycle

• the period of time from beginning of oneheart beat to beginning of the next.

• Systole, in which the chambers contract and eject the blood

• Diastole, in which the chambers relax allowing blood to fill them

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• capillary blood flow is not interrupted by this cycle because blood flow to the tissues is continuous, due to the elastic properties of the arterial walls.

• large blood vessels are characterized by an abundance of collagen fibers and elastin fibers

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Cardiac output

• cardiac output (CO):the volume of blood

pumped into the aorta per minute.

• Cardiac output (CO) = heart rate (HR)*stroke

volume (SV).

• At rest (adult)

• CO = 70 beats/min*70 ml/beat = 4900 ml/min

=5 l/min

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Control of heart rate

• the typical average heart rate is about 70beats per minute ( much greater in children).

• Heart rate depends on:

1. Autonomic nervous system influence

2. Catecholamines

3. Body temperature

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1. Autonomic nervous system influence

• sympathetic and parasympathetic systemshave antagonistic effects on the heart.

100

SA node AV node

sympathetic and sympathetic

parasympathetic systems.

Sympathetic stimulation: norepinephren binds to beta

adrenergic receptorrs:1. Increased rate of discharge of the SA node

2. Increased rate of conduction through the AVnode

3. Increased rate of conduction through thebundle of His and the Purkinje fibers


enhanced depolarization

• potassium permeability sodium, calciumpermeability. the inside of the cell becomesless (threshold more rapidly). In this way,action potentials are generated faster andtravel through the conduction pathway more

quickly so that the heart can generate moreheartbeats per minute


Parasympathetic stimulation

• heart rate. Acetylcholine (vagus nerve) bindsto muscarinic receptors and causes thefollowing effects:

1. Decreased rate of discharge of the SA node

2. Decreased rate of conduction through theAV node.


Parasympathetic stimulation

permeability to potassium……SA node (cells are hyperpolarized…a far threshold…greater depolarization is needed.

• Rate of depolarization is reduced.

• at rest parasymathetic nervous system predominates.


2. Catecholamines ( epinephrine and norrepinephrine

Released from From adrenal medulla Increase the heart

rate.

3. Body temperature affects heart rate by altering the

rate of discharge of the SA node.

An increase of 1 F in body temperature results in an

increase in heart rate of about 10 beats per minute.


stroke volume

• The volume of blood pumped from one ventricle of the heart with each beat depends on:

1. Length of diastole

2. Venous return (preload)

3. Contractility of the myocardium

4. Afterload

5. Heart rate


• Diastole: is the period in the cardiac cycle inwhich relaxation of the myocardium andventricular filling take place.

• Venous return: the volume of blood returned to the right atrium per minute.


Cardiovascular Disorders

• Cardiovascular disease (CVD) is the leadingcause of death in Western countries.

• Modern research efforts have improveddiagnosis, treatment, and prevention.

• Major cardiovascular disorders includeatherosclerosis, stroke, heart attack,aneurysm, and hypertension.


Atherosclerosis• Atherosclerosis:arteriosclerotic vascular disease

or ASVD) is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholestrol under the inner lining of arteries.

• The plaque can cause a thrombus (blood clot) to form.

• The thrombus can dislodge as an embolus and lead to thromboembolism.


Stroke, Heart Attack, and Aneurysm

• A cerebrovascular accident, or stroke, results when an embolus lodges in a cerebral blood vessel or a cerebral blood vessel bursts; a portion of the brain dies due to lack of oxygen.

• A myocardial infarction, or heart attack, occurs when a portion of heart muscle dies due to lack of oxygen.



• Partial blockage of a coronary artery causes angina pectoris, or chest pain.

• An aneurysm is a ballooning of a blood vessel, usually in the abdominal aorta or arteries leading to the brain.

• Death results if the aneurysm is in a large vessel and the vessel bursts.

• Atherosclerosis and hypertension weaken blood vessels over time, increasing the risk of aneurysm.

Coronary Bypass Operations

• A coronary bypass operation involves removing a segment of another blood vessel and replacing a clogged coronary artery.

• It may be possible to replace this surgery with gene therapy that stimulates new blood vessels to grow where the heart needs more blood flow.


Coronary bypass operation


Clearing Clogged Arteries

• Angioplasty uses a long tube threaded through an arm or leg vessel to the point where the coronary artery is blocked; inflating the tube forces the vessel open.

• Small metal stents are expanded inside the artery to keep it open.

• Stents are coated with heparin to prevent blood clotting and with chemicals to prevent arterial closing.


Angioplasty


Dissolving Blood Clots

• Medical treatments for dissolving blood clots include use of t-PA (tissue plasminogen activator) that converts plasminogen into plasmin, an enzyme that dissolves blood clots, but can cause brain bleeding.

• Aspirin reduces the stickiness of platelets and reduces clot formation and lowers the risk of heart attack.


Heart Transplants and Artificial Hearts

• Heart transplants are routinely performed but immunosuppressive drugs must be taken thereafter.

• There is a shortage of human organ donors.

• Work is currently underway to improve self-contained artificial hearts, and muscle cell transplants may someday be useful.


Hypertension

• About 20% of Americans suffer from hypertension(high blood pressure).

• Hypertension is present when systolic pressure is 140 or greater or diastolic pressure is 100 or greater; diastolic pressure is emphasized when medical treatment is considered.

• A genetic predisposition for hypertension occurs in those who have a gene that codes for angiotensinogen, a powerful vasoconstrictor.


cardiovascular system

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larger middle layer

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