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Circulation
The Heart and Blood Vessels
What is the function of the
circulatory system?
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consists of a muscular pump and
two circulatory loops
one loop delivers blood to the
body,
one delivers blood to the lungs
Functions of the blood:
• transports oxygen to the body cells
• transports nutrients from the digestive system
to body cells
• transports hormones to body cells
• transports wastes from the body cells to
excretory organs
• distributes body heat
• helps to maintain a constant pH in tissue fluids
• prevents infections
Blood is supplied to three separate
sections of the body. They are the
systemic system, the pulmonary
system and the coronary system.
Systemic system
• carries blood throughout the body (except
the heart and lungs)
• brings nutrients and oxygen to the body
tissues
• removes carbon dioxide and other wastes
Pulmonary System
• carries blood from the right side of the
heart to the lungs where carbon dioxide is
eliminated and oxygen is picked up
• blood returns to the left side of the heart
where it is distributed via the systemic
system
Coronary system
• provides blood to the heart
• http://www.youtube.com/watch?v=Lqhv
mUEdOYY&feature=related
• http://www.youtube.com/watch?v=nx-XRC_1nQ&p=426FEBCEBDD42DD1&playnext=1&inde
x=12
• http://www.youtube.com/watch?v=oHg5ZvrI4N
Y
The Blood Vessels
• there are three major divisions of blood
vessels:
The arteries (carry blood away
from the heart to body tissues)
• thick muscular walls with three distinct layers
of tissue
• stretch to accommodate blood rushing in
• blood flows due to the elasticity of the artery
walls
• arteries of various sizes (large to medium to
small) branch the entire body
• the largest artery is the aorta, found in the heart
• smaller sized arteries are called arterioles whose
diameter is regulated by nerves
• arterioles branch into capillaries
Capillaries (form an extensive
exchange system)
• have thin walls through which nutrients and wastes can
pass
• provide a site of exchange between the blood and the
tissue fluid surrounding the cells of the body
• permeable to many substances: O2, CO2, water soluble
ions, vitamins and some proteins
• oxygen diffuses from the blood through the capillary
walls to the surrounding tissue, and carbon dioxide and
other wastes move in the opposite direction
• work through the processes of endocytosis, exocytosis,
osmosis and diffusion
• one cell layer thick – easy to destroy (high blood
pressure can burst a capillary, even a bruise is evidence
of ruptured capillaries)
Remember the alveoli?
Veins (carry blood back to the
heart)
• capillaries merge and form venules, which then merge
into veins
• walls are thinner and weaker than the walls of arteries
• the pressure of blood is less than it is in the arteries so
veins need valves to move the blood back to the heart
• contractions of the skeletal muscles surrounding the
veins also aid in the pushing of blood back to the heart
• veins start off small and converge with other veins,
forming larger and larger vessels
• the largest veins are the superior and inferior vena cava
found in the heart
http://defiant.corban.edu/jjohnson/Pages/BioII/42/CirculationNotes.html
All blood vessels are capable of
changing in diameter depending on a
situation:
• vasoconstriction is the narrowing of blood
vessels due to the contraction of smooth muscle
fibres in the arterioles.
– for example, when we turn white in fright, skin blood
vessels constrict so that more blood is supplied to the
muscles
• vasodilation is the widening of blood vessels
resulting in more blood entering the tissue area,
caused by a relaxation of the muscle fibres in the
blood vessels
– for example, blushing is a vasodilation of skin blood
vessels
Dissection
• http://www.zerobio.com/videos/sheep_he
art_anatomy.html
• http://www.zerobio.com/videos/dissect_s
heepheart1.html
The Heart
• the heart is a muscular pump in the chest
cavity
• it is the workhorse of the circulatory
system propelling blood through 80, 000
km of blood vessels
• each day the heart beats 100, 000 times,
adjusting its rate to meet the needs of the
body
Human hearts have four chambers
– Composed of two thin
walled atria and two
thick walled ventricles
– The atria act as holding
chambers for blood
entering the heart from
the systemic or
pulmonary circulatory
systems
– Ventricles are stronger
and more muscular,
they pump blood to the
tissues in the body
http://www.wvhsta.org/summer_2003/biomed/teachers/Anatomy1/anatomy2/index_anat
omy.htm
Layers of Heart tissue
Layers of Heart Tissue
•
•
•
Pericardium – a thin closed sac surrounding
the heart and the bases of the vessels that enter
and leave the heart. It is filled with a clear
slippery fluid that reduces friction caused by
heart contractions
Myocardium – the middle layer, it is the
thickest part of the wall and is composed
mostly of cardiac muscle cells
Endocardium – inner layer that forms the
lining of the heart chambers
The flow of blood
• each side of the heart is a separate pump
with the right side pumping blood to the
lungs (pulmonary circulation), and the left
side pumping blood to the body (systemic
circulation).
http://www.pbs.org/wgbh/nova/heart/heartmap.html
Orientation of the heart
• Drawings of the heart will show the left
side of the heart on the right side of the
diagram, and the right side on the left.
WHY IS THIS?
– This is what your heart would look like if you
were looking directly at your own heart. It is
like a photograph of your heart
The Course that Blood Takes
• blood that is low in O2 enters the right side of
the heart through the superior and inferior vena
cavae (plural of cava)
– these veins empty directly into the right atrium, the
top chamber on the right side of the heart
• blood is pumped from the right atrium into the
right ventricle which is the lower chamber on
the right side of the heart
• when the right ventricle is full, the muscles in its
wall contract forcing blood into the pulmonary
arteries which lead to the lungs
• blood whose oxygen supply has been restored
(from the lungs) flows back to the heart via the
pulmonary veins
• the pulmonary veins empty directly into the left
atrium, the upper chamber on the left side of the
heart
• the blood is pumped from the left atrium to the
left ventricle
• when the left ventricle is full, its thick muscular
walls contract, propelling blood into the aorta
• the aorta carries oxygenated blood away from
the heart delivering it to the cells and tissues of
the body
• both atria fill simultaneously, then contract, bringing
blood to the ventricles.
• Both ventricles fill simultaneously pumping blood to the
pulmonary and systemic systems
• Flow of blood animation:
• https://www.youtube.com/watch?v=TMdKp2zHgog
The Valves of the Heart
http://www.lifeisnow.com/MyHeart/Anatomy.aspx
Atrioventricular Valves (A-V
valves)
• the valves between the atria and ventricles on
the left and right sides of the heart
• consists of two or there flaps of tissue that are
anchored to the inner walls of the ventricles by
the chordae tendinae
• the A-V valve on the right side of the heart,
between the right ventricle and atrium is called
the tricuspid valve (has three flaps of tissue)
• the A-V valve on the left side of the heart is
called the bicuspid valve (has two flaps of
tissue)
Semilunar Valves
• found at the areas in which blood vessels
attach to the ventricles (at the pulmonary
artery and aorta)
• consists of three semicircular flaps of
tissue (resemble half moons)
• both types of valves are one way valves
which open when blood pressure builds
on one side and close when blood
pressure increases on the other
– when the ventricles contract, blood forces the
semilunar valves to open forcing the blood to
rush out of the ventricles into the arteries
(aorta and pulmonary artery)
– the semilunar valves then close, preventing
blood from flowing back to the ventricles
– the A-V valves function in the same way
Nervous Control of the Heart
• cardiac muscle is able to contract without
nervous stimulation
• called myogenic muscle
• a heart that is removed from the body will
continue to beat over a short period of
time
• http://www.youtube.com/watch?v=iKntqy
nkoFICouple Married 72 Years Dies
Holding Hands
The SA node (sino-atrial node)
• the hearts tempo is set by a bundle of specialized
nerve and muscle fibres located where the vena
cava enters the right atrium
• acts as a pacemaker setting the rate of the heart
at about 70 beats per minute
• nerve impulses go from the SA node to the other
muscle cells by modified muscle tissue
– contractions originate in the atria and travel to a
second node, the atrioventricular node (A-V node)
The A-V node
• passes nerve impulses
along special tracts
through the dividing
septum
– the muscle that
divides the left and
right sides of the heart
http://hrspatients.org/patients/the_normal_heart/electrical_system.asp
The Bundle of His and
Perkinje Fibres
• splits into two trunks part way down the
septum
• at the lower portion of the venticle, one bundle
turns up along the outside wall of the left
ventricle and branches out
• the other bundle turns up the outside wall of the
right ventricle
• these bundles branch out into Perkinje Fibres
– Perkinje Fibres pass into muscle cells and cause
contraction of the ventricles
– Electrical System
animation:http://www.nhlbi.nih.gov/health/healthtopics/topics/hhw/electrical.html
Autonomic Nerves
• nerves that we cannot control
• two autonomic nerves from the brain affect heart
rate
– Vagus Nerve – an inhibitory nerve that causes the
heart rate to decreases
• this is a parasympathetic nerve that operates in times of
relaxation
– Augmentor Nerve – an excitatory nerve that causes
the heart rate to increase
• this is a sympathetic nerve that operates in times of stress
(eg. An adrenaline rush)
Heart Sounds
• the sound that we hear when listening to the
heart is caused by the closing of the valves
• the lubb sound is caused by the closing of the
AV valves
• the dub sound is caused by the closing of the
semilunar valves
• the left and right AV valves and the two
semilunar valves do not close at the same time
• Heart in action:
http://www.nhlbi.nih.gov/health/healthtopics/topics/hhw/electrical.html
http://www.bostonscientific.com/templatedata/imports/HTML/CRM/heart/heart_signals.html
• a heart murmur is caused by faulty heart
valves which permit the backflow of
blood into the heart
– the AV valves must withstand much pressure
and are susceptible to defects
– heart murmur patients will compensate for
the increased blood in the ventricle by
increasing the heart rate and strength of each
contraction
Heart Beat Impairments
• tachycardia – heart beats more that 100
times per minute due to increased
exercise, some drugs or severe angina
• brachycardia – the heart beats slower than
normal
The Electrocardiogram
• measures the
electrical activity of
the heart
– changes in the
electrical activity of
the heart can reveal
normal or abnormal
occurrences of the
cardiac system
– see figure 8.8 on page
275
• the electrocardiograph
can be interpreted on the
basis of three waves
– P wave – measures atrial
contraction
– QRS wave – measures
ventricular contraction
– T wave – signals that the
ventricles have recovered
from their contraction.
• A stress test is an
electrocardiograph of a
persons response to
exercise
– Indicates the heart working
in a stressful situation
Cardiac Output
• is the total volume of blood pumped by the ventricle per
minute
• product of heart rate (HR) and stroke volume (SV)
• The stroke volume at rest in the standing position
averages between 60 and 80 ml of blood in most adults.
• Thus at a resting heart rate of 80 beats per minute the
resting cardiac output will vary between 4.8 and 6.4 L
per min.
• The cardiac output of Olympic medal winners in cross
country skiing increased 8 times above resting cardiac
output to approximately 40 liters for one minute of
maximal work with an accompanied stroke volume of
210 ml per beat.
• As a result of increased training, the crosscountry skier exhibits a greater stroke volume
(240) compared to untrained (110), trained (150),
and highly trained (210) individuals during
exercise.
• Why do athletes typically have lower heart
rates and cardiac output?
• If I have a low heart rate, does that necessarily
mean that I am physically fit?
Blood Pressure
• blood pressure of the brachial artery (major
artery of the arm) is measured with a device
called a sphygmomanometer
– shuts off the flow of blood to the brachial artery by
increasing air in the cuff around the arm
– two readings are given when reading blood pressure:
• systolic pressure – read at the point where a heart beat
sound is heard after the cuff is slowly drained of air as the
blood flows back into the brachial artery during ventricular
contraction
• diastolic pressure – measured when the sound disappears as
blood is flowing into the brachial artery and the ventricles
relax
• blood pressure is read systolic/diastolic
• normal pressure is 120 mm Hg systolic/ 80 mm
Hg diastolic
• blood pressure is not the same in all arteries, the
further away from the heart you are, the lower
the blood pressure
• Factors that affect blood pressure:
– Cardiac output – the greater the cardiac output, the
greater the blood pressure
– Arteriolar resistance – vasoconstriction increases blood
pressure, vasodilation decreases blood pressure
The Lymphatic System
• Lymph is a fluid that is found outside the
capillaries
– most often lymph contains some small proteins that
have leaked out of the capillary walls
• The lymphatic system is a network of vessels
that operate in an open ended system (similar to
the circulatory system)
– it returns excess proteins of the ECF to the circulatory
system
– it is key in maintaining osmotic pressure in the tissues
and surroundings, and preventing tissue swelling
• Lymph nodes are enlarged areas on the
lymph vessels that contain white blood
cells to filter bacteria from the lymph
– they filter damaged cells and debris from the
lymph
– found throughout the body
– mononucleosis infects the lymph nodes in
your neck region
• edema (tissue swelling) occurs if the lymphatic system
fails to remove excess fluids from the tissues
Examples of edema:
Obstructed veins (varicose veins)
Localized edema – occurs around injuries
Malnutrition (starvation)
Kidney Damage
Elephantiasis – filaria worm block the lymph nodes
that usually drain the leg and the leg swells literally
to the size of an elephant’s leg. (Can also affect the
scrotum of males causing it to enlarge so much in
some cases that a man must carry his scrotum in a
wheelbarrow to move it about).
Diseases and Disorders of the
Circulatory System
Angina
• pain that is felt when
oxygen supply to the
myocardium is reduced
• pains appear in the
center of the chest and
spread to the neck,
upper back and left arm
• caused by stress or CO
exposure
• a symptom of a heart
attack
http://www.supplementnews.org/angina/
Diseases and Disorders of the
Circulatory System
Myocardial Infarction (heart attack)
• caused by thrombosis (blockage of a coronary
artery or blood clot)
• blood flow is restricted to the heart cutting off
the supply of oxygen and nutrients
• usually occur when the arteries are already
narrowed
• severity depends on the amount of damage to
the heart
Treatment for Heart Attack:
• proper diet and exercise
• doses of aspirin can reduce the
chances of having a heart
attack
• blood clot dissolving agents
reduce damage to heart tissue
(streptokinase, TPA tissue
plasminogen activator)
• coronary bypass surgery
• cleaning clogged blood vessels
with a catheter (balloon
angioplasty)
• lasers to burn away plaque in
artery walls
http://heart.health.ivillage.com/bypasssurgery/bypasssurgery7.cfm
Diseases and Disorders of the
Circulatory System
Atherosclerosis
• a buildup of fat
covered by mineral
plaque deposits on
the arteries
• blood clots can
build up around
these deposits
Diseases and Disorders of the
Circulatory System
Varicose Veins
• occur when the valves
in the veins are not
functioning properly
and gravity carries the
blood down the legs
where pooling occurs
• surface veins bulge and
become larger
• caused by genetics and
lifestyle
http://www.vintage3.com/servcesSurgery.htm
Diseases and Disorders of the
Circulatory System
Hypertension
• also called high
blood pressure
• caused by heredity,
stress, poor diet,
high salt intake and
by disorders of
other organ systems
• more common in
men than in women
Diseases and Disorders of the
Circulatory System
Heart Murmur
•
caused by faulty heart
valves
Stroke
•
caused by the blood being
restricted from a certain part
of the brain, or a blood
vessel bursting in the brain
Heart Problems:
http://www.bostonscientific.com/te
mplatedata/imports/HTML/CRM/h
eart/cardiovascular.html
http://www.heartzine.com/heart-disease/188-Stroke.html