The Cardiovascular System Copyright The McGraw-Hill Companies,
Inc. Permission required for reproduction or display.
Slide 2
Anatomy of the Heart oHeart functions: Keeps O 2 -poor blood
separate from O 2 -rich blood Keeps the blood flowing in one
direction Creates blood pressure Regulates the blood supply
Slide 3
Anatomy of the Heart oThe Wall and Coverings of the Heart
Pericardium Two-layered serous membrane that encloses the heart
Myocardium Thickest part of heart wall Made of cardiac muscle
Endocardium Inner layer of heart Pericardial fluid Reduces friction
as the heart beats The coverings of the heart: Protect the heart
Confine it to its location Prevent it from overfilling
Slide 4
Fig 12.2
Slide 5
Anatomy of the Heart oChambers of the Heart Right atrium
Receives O 2 -poor blood Vessels that empty into right atrium:
Superior vena cava Inferior vena cava Coronary sinus Venous blood
leaves right atrium through the an atrioventricular (AV) valve
(tricuspid) Directs the flow of blood Prevents backflow Has three
cusps Right ventricle Chordae tendineae Fibrous cords connected to
the tricuspid valve Blood passes through the pulmonary semilunar
valve into the pulmonary trunk
Slide 6
Anatomy of the Heart Left atrium Receives O 2 -rich blood Blood
enters atrium through 4 pulmonary veins Blood leaves left atrium
through an AV valve (bicuspid or mitral) Left ventricle Forms the
apex of the heart Blood leaves the left ventricle through the
aortic semilunar valve and enters the aorta
Slide 7
Fig 12.3
Slide 8
Anatomy of the Heart oOperation of the Heart Valves AV valves
Normally open When ventricle contracts AV valves shut Semilunar
valves Normally closed Contraction of ventricles forces valves
open
Slide 9
Anatomy of the Heart oHeart Sounds First sound, lub Heard when
ventricles begin to contract AV valves close Lasts longer and has a
lower pitch Second sound, dup When ventricles relax Semilunar
valves close Heart murmurs Due to ineffective, leaky valves Valves
do not close properly Allows blood to backflow into atria or
ventricles after valves have closed
Slide 10
Anatomy of the Heart oCoronary Circulation Heart cells are not
nourished by the blood in the chambers The left and right coronary
arteries branch from the aorta Coronary arteries branch numerous
times Heart is encircled by small blood vessels After blood passes
through cardiac capillaries it enters the cardiac veins Cardiac
veins enter the coronary sinus Coronary sinus enters the right
atrium
Slide 11
Fig 12.4
Slide 12
Physiology of the Heart oConduction System of the Heart
Initiates and stimulates contraction of the atria and ventricles Is
intrinsic does not require nervous stimulation Coordinates
contraction of atria and ventricles
Slide 13
Physiology of the Heart Nodal Tissue Has muscular and nervous
characteristics SA (sinoatrial) node upper posterior wall of the
right atrium Initiates the heartbeat Sends out an excitation
impulse every 0.85 seconds Pacemaker of the heart AV
(atrioventricular) node base of the right atrium Signals the
ventricles to contract Atrioventricular bundle (AV bundle) Purkinje
fibers
Slide 14
Fig 12.5
Slide 15
Physiology of the Heart Artificial pacemaker may be implanted
if the SA node fails to work properly Heart block slow beating of
the heart due to a damaged AV node Ectopic pacemaker An area other
than the SA node that can become the pacemaker May cause an extra
beat Caffeine and nicotine can stimulate an ectopic pacemaker
Electrocardiogram Electrolyte changes within the myocardium can be
detected by electrical recording devices Helps a physician detect
and diagnose the cause of an irregular heartbeat (arrhythmias)
Slide 16
Physiology of the Heart Cardiac Cycle All events that occur
during one heartbeat Systole contraction of heart muscle Diastole
relaxation of heart muscle Three phases of the cardiac cycle: Phase
1: Atrial Systole Both atria are in systole Ventricles are in
diastole Both AV valves are open The semilunar valves are closed
Phase 2: Ventricular Systole Both ventricles are in systole The
atria are in diastole Semilunar valves are forced open Both AV
valves are closed Phase 3: Atrial and Ventricular Diastole Both
atria and both ventricles are in diastole Both AV valves are open
The semilunar valves are closed
Slide 17
Fig 12.6
Slide 18
Physiology of the Heart Cardiac Output (CO) Volume of blood
pumped out of a ventricle in one minute Average CO is 5,250
ml/minute Dependent on two factors: Heart rate Beats per minute Can
be altered by the autonomic nervous system Temperature affects the
heart rate Proper electrolytes are needed to keep the heart rate
regular Stroke volume Amount of blood pumped by a ventricle each
time it contracts Depends on the strength of contraction Influenced
by blood electrolyte concentration and the activity of the
autonomic nervous system Venous return and difference in blood
pressure also affect the strength of contraction
Slide 19
Fig 12.7
Slide 20
Anatomy of Blood Vessels oVessels function to: Transport blood
and its contents Carry out gas exchange Regulate blood pressure
Direct blood flow oArteries and Arterioles
Slide 21
Anatomy of Blood Vessels oArteries and Arterioles Transport
blood away from the heart Thick, strong walls composed of: Tunica
interna - endothelium Tunica media smooth muscle and elastic fibers
Tunica externa outer connective tissue layer Elasticity allows an
artery to expand and recoil Arterioles are small arteries
Constriction and dilation affect blood distribution and blood
pressure Autonomic nervous system regulates the number of
arterioles that are contracted
Slide 22
Anatomy of Blood Vessels oCapillaries Microscopic blood vessels
One layer of endothelial cells Site of nutrient and gas exchange
Not all capillary beds are in use at the same time Most have a
shunt Precapillary sphincters control the entrance of blood into
capillaries
Slide 23
Fig 12.9
Slide 24
Anatomy of Blood Vessels oVeins and Venules Return blood to the
heart Venules Drain blood from the capillaries Join together to
form veins Vein walls are thinner than arterial walls Valves in
veins prevent backward flow of blood Varicose veins and phlebitis
Varicose veins Abnormal and irregular dilations in superficial
veins Hemorrhoids are varicose veins in the rectum Develop when the
valves of the veins become weak Phlebitis Inflammation of a vein
Thromboembolism can occur
Slide 25
Fig 12.8
Slide 26
Physiology of Circulation oVelocity of Blood Flow Slowest in
capillaries Cross-sectional area is at its maximum Allows time for
gas and nutrient exchange Blood flow increases as venules combine
to form veins Velocity of blood returning to the heart is low
compared to that of blood leaving the heart
Slide 27
Fig 12.10
Slide 28
Physiology of Circulation oBlood Pressure The force of blood
against blood vessel walls Highest in the aorta Decreases with
distance from left ventricle and is lowest in the venae cavae
Fluctuates between systolic blood pressure and diastolic blood
pressure Mean arterial blood pressure Pressure in the arterial
system averaged over time Equals cardiac output x peripheral
resistance Increasing CO increases MABP Peripheral resistance is
the resistance to flow between blood and the walls of a blood
vessel The smaller the blood vessel or the longer the blood vessel
the greater the resistance The greater the resistance the higher
the blood pressure
Slide 29
Fig 12.11
Slide 30
Physiology of Circulation Blood pressure and cardiac output The
faster the heart rate the greater the cardiac output As cardiac
output increases, blood pressure increases The larger the stroke
volume, the greater the blood pressure Stroke volume and heart rate
increase blood pressure only if the venous return is adequate
Slide 31
Physiology of Circulation Venous return depends on: A blood
pressure difference The skeletal muscle pump and the respiratory
pump Contraction of skeletal muscles compress the walls of veins
causing blood to move past a valve During inhalation, thoracic
pressure falls and abdominal pressure rises and blood will flow
from an area of higher pressure to an area of lower pressure Total
blood volume If blood volume decreases, blood pressure falls If
blood volume increases, blood pressure rises
Slide 32
Fig 12.12
Slide 33
Physiology of Circulation Blood pressure and peripheral
resistance Neural regulation of peripheral resistance Vasomotor
center regulates vasoconstriction Also causes blood to be shunted
from one area of the body to another Hormonal regulation of
peripheral resistance Epinephrine and norepinephrine increase heart
rate and constrict arterioles Renin-angiotensin-aldosterone system
Angiotensin II constricts the arterioles Aldosterone causes the
reabsorption of sodium and water in the kidneys Antidiuretic
hormone causes the reabsorption of water and vasoconstriction
Atrial natriuretic hormone inhibits renin and aldosterone
secretion
Slide 34
Fig 12.13
Slide 35
Physiology of Circulation Evaluating circulation Pulse
Alternating expansion and recoil of arterial walls Can be felt in
superficial arteries (pulse points) Radial artery Common carotid
Pulse rate normally indicates the rate of the heartbeat Fig
12.14
Slide 36
Physiology of Circulation Blood pressure Usually measured in
brachial artery Sphygmomanometer is an instrument that records
pressure changes The blood pressure cuff is inflated until no blood
flows through the artery Korotkoff sounds produced when the
pressure in the cuff is released and blood begins to hit the
arterial walls Systolic pressure When sounds end diastolic pressure
is recorded Fig 12.15
Slide 37
Physiology of Circulation Normal blood pressure is 120/80
Higher number is systolic pressure pressure recorded when the left
ventricle contracts Lower number is diastolic pressure pressure
recorded when the left ventricle relaxes Hypertension is high blood
pressure When the systolic pressure is 140 or greater When the
diastolic pressure is 90 or greater
Slide 38
Circulatory Routes oPulmonary circuit Blood from the body
collects in the right atrium Blood moves into the right ventricle
Right ventricle pumps blood into the pulmonary trunk Blood flows
into the pulmonary capillaries in the lungs Blood flows from the
lungs through the pulmonary veins and into the left atrium
Slide 39
Circulatory Routes oCongestive Heart Failure Damaged left side
of the heart fails to pump adequate blood Blood backs up in the
pulmonary circuit Pulmonary blood vessels have become congested
Causes pulmonary edema Indicated by shortness of breath, fatigue,
and a constant cough Treatment Diuretics increase urinary output
Digoxin increases the hearts contractile force Dilators relax blood
vessels
Slide 40
Circulatory Routes oSystemic circuit Includes all other
arteries and veins of the body Aorta and venae cavae are the major
pathways for blood in the systemic circuit Aorta is the largest
artery Superior and inferior venae cavae are the largest veins
Begins in the left ventricle The left ventricle pumps blood into
the aorta Branches from the aorta go to the major body regions and
organs
Slide 41
Circulatory Routes Table 12.1
Slide 42
Fig 12.16
Slide 43
Circulatory Routes Table 12.2
Slide 44
Fig 12.17
Slide 45
Circulatory Routes oSpecial Systemic Circulations Hepatic
Portal System Carries venous blood from the stomach, intestines,
and other organs to the liver Capillaries of the digestive tract
empty into the superior mesenteric and the splenic veins Superior
mesenteric and splenic vein join to form the hepatic portal vein
Gastric veins empty into the hepatic portal vein Nutrients and
wastes diffuse into liver cells The hepatic veins drain the liver
and enter the inferior vena cava
Slide 46
Fig 12.18
Slide 47
Circulatory Routes Hypothalamus-Hypophyseal Portal System Blood
Supply to the Brain Anterior and posterior cerebral arteries and
the carotid arteries supply the brain with arterial blood Cerebral
arterial circle (circle of Willis) The blood vessels form a circle
Provides alternate routes for supplying arterial blood to the brain
Equalizes blood pressure in the brains blood supply
Slide 48
Fig 12.19
Slide 49
Circulatory Routes Fetal Circulation Four circulatory features
not present in adult circulation Foramen ovale Ductus arteriosus
Umbilical arteries Ductus venosus Related to the fact that the
fetus does not use its lungs Path of blood in the fetus From the
right atrium Most blood enters the left atrium via the foramen
ovale Blood that has entered the right ventricle and then the
pulmonary trunk is shunted to the aorta through the ductus
arteriosus Exchange between maternal and fetal blood occurs at the
placenta Blood in the umbilical arteries is oxygen poor Blood in
the umbilical veins is oxygen rich Enters the ductus venosus The
ductus venosus then joins with the inferior vena cava
Slide 50
Fig 12.20
Slide 51
Effects of Aging oHeart Grows larger with age In many
middle-aged people, heart is covered by a layer of fat Number of
collagenous fibers in the endocardium increases Valves become
thicker and more rigid The myocardium loses contractile power and
ability to relax Resting heart rate decrease
Slide 52
Effects of Aging oArteries Atherosclerosis and arteriosclerosis
are common Chances of coronary thrombosis and heart attack increase
Occurrence of varicose veins increases Thromboembolism Pulmonary
embolism
Slide 53
Homeostasis oMaintaining blood composition, pH, and temperature
Growth factors regulate the manufacture of formed elements in the
red bone marrow The digestive system absorbs nutrients into the
blood The lungs and kidneys remove metabolic wastes from the blood
The kidneys help maintain the pH of blood The blood distributes
heat Blood vessels in the skin dilate or constrict in response to
changing temperatures
Slide 54
Homeostasis oMaintaining blood pressure Sensory receptors
within the aortic arch detect a decrease in blood pressure The
lymphatic system collects excess tissue fluid, which helps regulate
blood volume and pressure The endocrine and nervous systems work
together to regulate blood pressure Venous return is aided by the
muscular and respiratory systems
