Cardiovascular System - faculty.sxu.edufaculty.sxu.edu/dlc1/humanweb19/Cardiovascular System.pdf · 3/7/2019 1 HEART AND BLOOD VESSELS CARDIOVASCULAR SYSTEM • POINTS TO PONDER •What

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H E AR T AN D B L O O D V E S S E L S

CARDIOVASCULAR

SYSTEM

POINTS TO PONDER

• What are the functions of the cardiovascular system?

• What is the anatomy of the heart? Of blood vessels, such as veins and arteries?

• How is the heart beat regulated?

• What is blood pressure?

• What are common cardiovascular diseases and how might you prevent them?

SYSTEM COMPONENTS &

FUNCTIONS

• System overview

• Components

• Heart – pumps blood

• Blood vessels – blood flows through these

• Functions

• Circulation

• Performs exchanges

• Oxygen and nutrients are brought to cells

• Waste products are removed

• Kidneys, liver, lungs, intestines

WHAT IS THE CARDIOVASCULAR

SYSTEM?

• It includes the heart and blood vessels.

• It brings nutrients to cells and helps get rid of wastes.

• Blood is refreshed in the lung, kidneys, intestine, and liver.

• Lymphatic vessels help this system by collecting excess fluid surrounding tissues and returning it to the cardiovascular system.

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WHAT ARE THE FUNCTIONS OF THE

CARDIOVASCULAR SYSTEM?

1. Transport: oxygen, carbon dioxide and

other wastes products, nutrients, and

horomones

2. Protection: cells of the immune system

are transported to help protect the

body from infection

3. Regulation: maintain homeostasis of a

variety of the body’s conditions

ARTERIES AND ARTERIOLES

• Arteries carry blood away from the heart.

• Their walls have 3 layers.

• Thin inner epithelium

• Thick smooth muscle layer

• Outer connective tissue

• Arterioles are small arteries that

regulate blood pressure.

ARTERIES AND ARTERIOLES

• The strong walls of an artery give it support when blood enters under

pressure;

• The elastic tissue allows an artery to

expand to absorb the pressure.

• The constriction or dilation of arterioles

controls blood pressure.

CAPILLARIES

• Microscopic vessels between arterioles and

venules

• Made of one layer of epithelial tissue

• Form beds of vessels where exchange

with body cells occurs

• Combined large surface area

Figure 5.2 Structure of a capillary bed.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

a.

v.

v. = vein; a. = artery

valve

blood

flow

blood

flow

connective

tissue

artery

arteriole

capillary bed

arteriovenous

shunt

vein

venule

smooth muscle

endothelium

elastic tissue

precapillary

sphincter

(left): © Ed Reschke; (right): © Biophoto Associates/Photo Researchers

Blood Vessels VEINS AND VENULES

• Venules are small veins that receive blood

from the capillaries.

• Venule and vein walls have 3 layers. • Thin inner epithelium • Thick smooth muscle layer

• Outer connective tissue

• Veins carry blood toward the heart.

• Veins that carry blood against gravity have

valves to keep blood flowing toward the

heart.

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TYPES OF BLOOD VESSELS

vein artery

capillary


arteriovenous

shunt

vein

venule

arteriole

artery

connective

tissue

v.=vein; a.=artery

blood

flow

valve

blood

flow

smooth muscle

endothelium

elastic tissue

precapillary

sphincter

v.

a.

(left): © Ed Reschke

Figure 5.2 Structure of a capillary bed.

HOW CAN YOU TELL THE DIFFERENCE BETWEEN AN ARTERY AND VEIN?


• The Capillaries: exchange • Arterioles branch into capillaries.

• The capillaries have walls that are only one cell

thick and allow exchange of substances with tissue fluid.

• Not all capillary beds are open at the same time.

• Contraction of a precapillary sphincter muscle

closes off the bed and then blood flows through an arteriovenous shunt, bypassing the capillary

bed, going directly into a venule.

arteriovenous

shunt


• The Veins: To the Heart

• Venules drain into veins that return blood to the heart.

• Veins have much less smooth

muscle and connective tissue than arteries.

• Veins often have valves that prevent the backward flow of

blood due to gravity when closed.

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THE HEART

• Located behind and

slightly left of the

breastbone(sternum)

• Cone-shaped • Points slightly left

• Has 4 chambers • 2 atria (sing. = atrium)

• 2 ventricles

THE HEART

• Muscular

• Myocardium = cardiac muscle tissue

• Lies inside a fibrous

pericardium

ANATOMY OF THE HEART

• Large, muscular organ consisting of mostly cardiac tissue called the myocardium

• Surrounded by a sac called the pericardium

• Consists of 2 sides, right and left, separated by a septum

• Consists of 4 chambers: 2 atria and 2 ventricles

• 2 sets of valves: semilunar valves and atrioventricular valves (AV valves)

• Valves produce the “lub” and “dub” sounds of the heartbeat

EXTERNAL ANATOMY OF THE HEART

left subclavian artery

left common carotid artery

brachiocephalic artery

superior vena cava

aorta

left pulmonary artery

pulmonary trunk

left pulmonary veins

right pulmonary artery

right pulmonary veins

left atrium

left cardiac vein

right atrium

right coronary artery

left ventricle

right ventricle

left anterior descending

coronary artery

inferior vena cava

apex

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INTERNAL ANATOMY OF THE HEART left subclavian artery

left common carotid artery

brachiocephalic artery

superior vena cava

aorta

left pulmonary artery

pulmonary trunk

left pulmonary veins

right pulmonary artery

right pulmonary veins

semilunar valve

left atrium

right atrium

atrioventricular

(bicuspid) valve

atrioventricular

(tricuspid) valve

chordae tendineae

papillary muscles

right ventricle

septum

left ventricle

inferior vena cava

a.

THE HEART

• Right and left atria empty into the right and left

ventricles respectively.

• Atrioventricular valves occur between the atria and ventricles

• Semilunar valves occur between the ventricles and the attached arteries.

• Chordae tendinae strengthen atrioventricular valves.

• Intercalated disks contain gap junctions and desmosomes which join neighboring fibers together

and make sure that cardiac fibers contract simultaneously.

THE HEART

CORONARY CIRCULATION

• Myocardium receives

oxygen and nutrients

from the coronary

arteries.

• Right coronary artery

• Left coronary artery

• Circumflex artery

• Left anterior desending

artery

THE STRUCTURE OF THE VESSELS AND HEART

MATCH THEIR FUNCTIONS

• The left ventricle is much more muscular

than the right ventricle because it must

pump blood to the entire body.

• The arteries are more muscular than veins to

withstand the higher pressure exerted on

them.

• The veins have a thinner wall and a larger

center to contain blood.

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VISUALIZING BLOOD FLOW THROUGH THE HEART

Figure 5.4 The heart is a double pump.

PASSAGE OF BLOOD THROUGH

THE HEART

• From the body through the heart

• Superior and inferior vena cava, right atrium, right ventricle, pulmonary arteries to the lungs.

• From the lungs

• Blood goes back to the heart via pulmonary veins, left atrium, left ventricle, and then to the

body through the aorta.

• Oxygen-poor blood never mixes with

oxygen-rich blood!

HOW DOES THE HEARTBEAT OCCUR?

• During systole, the atria contract together followed by the ventricles contracting together.

• This is followed by diastole, a rest phase, when the chambers relax.

• This cardiac cycle, or heartbeat, occurs 70 times/minute on average.

THE HEART

• Each heartbeat is called a cardiac cycle.

• Systole refers to the contraction of heart

chambers

• Diastole refers to their relaxation.

• Heart sounds, lub-dub

• Due to the closing of the atrioventricular valves

• Followed by the closing of the semilunar valves.

WHAT IS THE CARDIAC CYCLE?

Figure 5.5 The stages of the cardiac cycle.

bicuspid valve aortic semilunar valve semilunar

valves close

(“dup”)

superior

vena cava semilunar

valves

pulmonary

trunk

aorta

right

atrium

right

ventricle

a.

aorta

b.

atrioventricular (AV)

valves close

(“lub”)

d. pulmonary

trunk

c.

right

atrium

inferior

vena cava

left

atrium

left

ventricle

represents

contraction

d: © Biophoto Associates/ Photo Researchers

HEARTBEAT IS CONTROLLED

• Internal Control of Heartbeat

• Sinoatrial (SA) node (pacemaker) initiates the beat and causes the atria to contract.

• Atrioventricular (AV) 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.

• These impulses travel between gap junctions at

intercalated disks.

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VISUALIZING THE GAP JUNCTIONS AT

THE INTERCALATED DISKS

gap junction

Figure 5.4b The heart is a double pump.

5.3 The Heart is a Double Pump

HEARTBEAT IS CONTROLLED

• External Control of Heartbeat

• Cardiac control center in the

medulla oblongata regulates the heartbeat by way of the parasympathetic nervous system

(slows heart rate)

• The sympathetic nervous system (increases heart rate) systems.

• Hormones of the adrenal medulla also stimulate the heart.

ELECTROCARDIOGRAM

• Electrocardiogram (ECG) is a recording of

the electrical changes that occur in the

myocardium during a cardiac cycle.

• ECG pattern

• P wave signals the atria are about to contract when stimulated by the SA node;

• QRS complex signals contraction of the ventricles;

• Recovery of the ventricles produces the T wave.

• ECG can also detect various types of abnor-

malities, including ventricular fibrillation.

ELECTROCARDIOGRAM WHAT DOES A NORMAL ECG LOOK LIKE?

SA node

AV node

branches of

atrioventricular

bundle

Purkinje fibers

a.

b. Normal ECG

P

Q

T

S

R

b: © Ed Reschke

Figure 5.6a-b An electrical signal

pathway through the heart.

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FEATURES OF THE

CARDIOVASCULAR SYSTEM

• Pulse Rate Equals Heart Rate

• The surge of blood entering the arteries following a heartbeat causes their elastic walls to stretch

and then recoil. This is felt as a pulse.

• The pulse rate of the radial or carotid artery

indicates the heart rate.

• Blood Flow Is Regulated

• Beating of the heart is necessary for homeostasis because it creates the pressure that propels

blood in the arteries and the arterioles

FEATURES OF THE


• Blood Pressure Moves Blood in Arteries

• Blood pressure is the pressure of blood against the wall of a blood vessel.

• Usually measured in the brachial artery of the arm with a sphygmomanometer

• Higher number is the systolic pressure and the lower number is the diastolic pressure

• Normal blood pressure is less than 120/80.

• High blood pressure is called hypertension and low blood pressure hypotension.

Figure 5.7 Sphygmomanometers measure blood pressure.

What is blood pressure? BLOOD PRESSURE READINGS

• Systolic

• The top number, which is also the higher of the

two numbers, measures the pressure in the arteries when the heart beats (when the heart

muscle contracts).

• Diastolic

• The bottom number, which is also the lower of the two numbers, measures the pressure in the

arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood).

Am. Heart Assoc. values 2012

FEATURES OF THE


• When the left

ventricle contracts,

a surge of blood

flows through the

arteries.

• BP is highest in the

aorta

• BP is lowest in the superior and inferior

vena cavae.

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49

BLOOD FLOW

• Blood Flow Is Slow in the

Capillaries

• Blood moves slowly in capillaries because there

are more capillaries than arterioles.

• Slow pace allows time for exchanges between capillary blood and tissue

cells.

What is important about blood flow?

Figure 5.8 Blood velocity and

pressure in the blood vessels.

Rela

tiv

e m

ag

nitu

de

total

cross-sectional

area of

vessels

velocity

blood

pressure

arteries arterioles capillaries venules veins

Blood flow (starting from heart)

BLOOD FLOW

• Blood Flow in Veins

Returns Blood to Heart

• Venous return is dependent upon skeletal

muscle contraction, the presence of valves in veins, and respiratory

movements.

• Once blood has

moved past a valve it closes preventing backward return.

TWO CARDIOVASCULAR PATHWAYS

• Blood flows in two circuits:

• Pulmonary

• Systemic circuits

• The Pulmonary Circuit: Exchange of Gases

• Pulmonary arteries take blood from the right

ventricle to the lungs

• Carbon dioxide is given off

• Oxygen is picked up

• Pulmonary veins return it to the left atrium.

• Pulmonary arteries carry oxygen-poor blood while pulmonary veins carry oxygen-rich blood.

TWO CARDIOVASCULAR PATHWAYS

• The Systemic Circuit: Exchanges with Tissue

Fluid

• Aorta is largest artery in the systemic circuit

• Receives blood from the heart

• Superior and inferior venae cavae

• Trace the Path of Blood – see following figure

Ascending Aorta

Descending Aorta

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BLOOD FLOW

55 56

FIG. 5.11

THE HEART’S BLOOD SUPPLY:

CORONARY CIRCULATION

• There are small coronary arteries that supply

the heart.

• They are separate from the systemic and

pulmonary pathways of the body.

HEPATIC PORTAL SYSTEM

• Hepatic Portal System: Specialized for Blood

Filtration

• Drains blood from the capillary beds of the digestive tract to a capillary bed in the liver

• Purifies blood of toxins and pathogens

• Blood returns via hepatic vein to inferior vena cava

HEPATIC PORTAL SYSTEM

• A system that brings amino acid- and glucose-rich blood from the digestive tract to the liver.

• The liver synthesizes blood proteins and stores the glucose as glycogen.

• The liver also plays a role in purifying blood from the digestive tract.

• Finally, the blood will return to the heart via the inferior vena cava.

EXCHANGE AT THE CAPILLARIES

• Movement of fluid through the capillary wall

controlled by

• Osmotic pressure

• Blood pressure control

• Arterial End

• Blood pressure is higher than osmotic pressure

and water exits capillary

• Venule End

• Osmotic pressure is greater than blood pressure, and water tends to move into capillary

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61

Exchange at the capillary beds is primarily a

result of osmotic and blood pressure


from heart

Arterial End

Blood pressure is higher

than osmotic pressure.

Net pressure out.

water

oxygen amino

acids

Tissue Fluid

glucose carbon

dioxide

wastes

arteriole smooth

muscle fiber blood pressure

osmotic pressure

plasma

protein

Venous End

Osmotic pressure is higher

than blood pressure.

Net pressure in.

venule

to heart

salt

water

Figure 5.12 The movement of solutes in a capillary bed. 62

Exchange at the capillaries

• Lymphatic capillary beds lie alongside

capillary beds.

• When lymphatic capillaries take up excess

fluid it becomes lymph.

• Lymph returns to the cardiovascular veins in

the chest.

• Precapillary sphincters can shut down a blood

capillary, and blood then flows through the

shunt.


• Excess tissue fluid left behind in capillary beds is

collected by lymphatic vessels. This fluid is called lymph and is returned to the venous blood in the

shoulder region.

64


Figure 5.13 Interaction of lymphatic and capillary beds.


venule lymphatic

duct

blood

capillary

lymphatic

capillary

tissue

cells

arteriole

65

Cardiovascular Disease

Cardiovascular disease (CVD) is the most

common cause of death in the Western

world.

5.7 Cardiovascular Disorders

DISORDERS OF THE BLOOD VESSELS

• Hypertension/high blood pressure

• Atherosclerosis

• Stroke

• Heart attack

• Aneurysm

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CARDIOVASCULAR DISORDERS

• Disorders of the Blood Vessels

• High Blood Pressure (Hypertension)

• Can lead to heart disease

• Best defense against hypertension is a life-style that lowers the risk of hypertension

• Often seen in individuals with atherosclerosis, an

accumulation of plaque in the linings of arteries.

• These clots can dislodge and lodge in a small

blood vessel, forming a thromboembolism, which is life-threatening.

HYPERTENSION

• High blood pressure results when blood moves through vessels at a rate higher than normal, often due to arterial plaque.

• 120/80 mmHg is considered prehypertensive.

• It is a silent killer because there are few symptoms.

• It can lead to a heart attack, stroke, or kidney failure.

ATHEROSCLEROSIS

• It is a build up of plaque in blood vessels.

• Plaque that is stationary is called a thrombus, and an embolus when it detaches and can move to distant sites.

• It is associated with a stroke, heart attack, and aneurysm.

5.7 Cardiovascular Disorders

Figure 5B Coronary arteries and plaque.

Atherosclerosis

coronary artery ulceration

lumen of vessel

atherosclerotic

plaque cholesterol

crystals

fat


© Biophoto Associates/Photo Researchers


• Stroke, Heart Attack, and Aneurysm

• Stroke

• Blood clot lodges in a cerebral blood vessel or a cerebral blood vessel bursts, and a portion of

the brain dies.

• Heart attack

• Blood clot lodges in a coronary blood vessel

• Aneurysm • Ballooning of a blood vessel

• If a major blood vessel like the aorta bursts,

death is likely

STROKE

• A stroke is also known as a cerebrovascular accident (CVA).

• It usually occurs when a cranial artery is blocked or bursts.

• Part of the brain dies dues to lack of oxygen.

• Symptoms may include numbness of hands or face, difficulty speaking, and inability to see in one eye.

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HEART ATTACK

• A heart attack is also known as a myocardial infarction (MI).

• Part of the heart dies due to lack of oxygen.

• It can begin with angina pectoris, a pain that radiates down the left arm due to a blockage of a coronary artery.

ANGINA

• Chest pain or discomfort caused when your

heart muscle doesn't get enough oxygen-

rich blood.

• Usually happens because one or more of

the coronary arteries is narrowed or

blocked, also called ischemia.

• Symptom of an underlying heart problem

ANGINA

• Symptoms

• May feel like pressure or squeezing in your chest.

• The discomfort also can occur in your shoulders, arms, neck, jaw, or back.

• Angina pain may even feel like indigestion.

• Treatments • Lifestyle changes • Medicines – vasodilators (nitroglycerine) • Cardiac procedures

• Cardiac Rehab

ANEURYSM

• It is a ballooning of a blood vessel.

• Atherosclerosis and hypertension can

weaken a vessel and cause ballooning.

• The most commonly affected is the

abdominal artery or the arteries leading to

the brain.


• Angina pectoris.

• Blockage of a coronary artery

• Dissolving Blood Clots

• t-PA drug dissolves clots

• Aspirin reduces chance of clots

• Treating Clogged Arteries

• Coronary bypass operation

• Angioplasty

• Gene therapy has also been used to grow new

blood vessels

Treatments for blood vessel disorders

• Treating clogged arteries

• Bypass surgery: usually a vein from the leg is taken and used to bypass a clogged artery

• Stents: wire mesh cylinder inserted into a clogged artery to hold it open

• Angioplasty: a tube with a balloon is inserted into the clogged area and the balloon is then inflated to open the vessel

• A stent and angioplasty may be used in combination

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TREATMENTS FOR ATHEROSCLEROTIC

PLAQUE IN CORONARY ARTERIES DISORDERS OF THE HEART AND

ITS TREATMENT

• Disorders

• Heart failure is when the heart no longer

pumps properly.

• Treatments

• Left ventricular assist device (LVAD)

• Heart transplant either natural or artificial


• Heart Failure

• Heart no longer pumps as it should

• Implantation of a cardioverter-defibrillator senses

fast or slow heart beat


• Heart Transplants

• Routinely performed but there is a shortage of human hearts

• Left ventricular assist device

(LVAD), implanted in the abdomen,

• Alternative to a heart transplant.

• Work still goes forward on an artificial heart.

83 Figure 5.15 An artificial heart.

Artificial Heart


replacement

heart

photograph of

artificial heart

wireless

energy-

transfer

system

rechargeable

internal

battery

external

battery

pack

internal

controller

external

wireless

driver

(right): Courtesy SynCardia Systems, Inc.

CARDIOVASCULAR DISEASE PREVENTION

• Preventable risk factors include:

• use of tobacco products.

• drug and alcohol abuse.

• obesity and a sedentary lifestyle.

• poor diet.

• stress.

• poor dental hygiene.

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HOMEOSTASIS

• All body systems work together to maintain homeostasis.

• How Body Systems Work Together

• The cardiovascular system delivers oxygen and nutrients

to, and takes away metabolic wastes from, the tissue fluid that surrounds cells.

• The lymphatic system returns tissue fluid to the

bloodstream.

• The muscular system makes essential contributions to body movement.

• In the skeletal system, bones contribute calcium ions, which are important to blood clotting.

• The urinary system regulates acid-base and water-salt

balance of blood and tissue fluid.

Documents

Cardiovascular System - faculty.sxu.edufaculty.sxu.edu/dlc1/humanweb19/Cardiovascular System.pdf · 3/7/2019 1 HEART AND BLOOD VESSELS CARDIOVASCULAR SYSTEM • POINTS TO PONDER •What