Transcript Circulatory system

S. MORRIS 2006
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What is the circulatory system?

The circulatory system carries blood and dissolved
substances to and from different places in the body.

The Heart has the job of pumping these things around
the body.

The Heart pumps blood and substances around the
body in tubes called blood vessels.

The Heart and blood vessels together make up the
Circulatory System.
Functions of the Circulatory
System
• Transport oxygen to cells
• Transport nutrients from the digestive system to
body cells
• Transport hormones to body cells
• Transport waste from body cells to excretory
organs
• Distribute body heat
Double Circulation
• The heart pumps oxygenated blood to all organs
• Deoxygenated blood is returned to heart
• This deoxygenated blood must be sent to the
lungs to replenish its oxygen content
• Once oxygenated, the blood returns to the heart
again to be pumped to the rest of the body
• This is known as double circulation (blood need
to pass by the heart twice in one cycle)
Double Circulation
• Pulmonary Circulation
– Transports blood to lungs
and back to heart
– Low pressure
• Systemic Circulation
– Pumps blood to rest of body
and back to heart
– Higher pressure
Double Circulation
Rest of
Body
Blood vessels to and from Heart
Aortic arch
Superior
Vena Cava
Pulmonary
artery
Pulmonary
Vein
Inferior
Vena Cava
How does this system work?
pulmonary vein
pulmonary artery
lungs
head & arms
aorta
main vein
Right
Left
liver
digestive system
kidneys
legs
Circulatory System
Our circulatory system is a double circulatory system.
This means it has two parts parts.
Lungs
the right side of
the left side of
the system
the system
deals with
deals with
oxygenated
deoxygenated
blood.
blood.
Body cells
Capillaries of
head and arms
The Heart
•Circulation of Blood
through the Body
Superior vena
cava
•See it in action!Capillaries of
right lungs
Aorta
Pulmonary
vein
Inferior
vena cava
Copyright Pearson Prentice Hall
Pulmonary
artery
Capillaries
of left
lung
Capillaries of
abdominal organs and
legs
The pulmonary circuit consists of the right side of the heart (right
atrium and right ventricle), the pulmonary arteries, which convey
poorly oxygenated blood to the lungs, and the pulmonary veins,
which convey oxygenated blood from the lungs to the left atrium.
The systemic circuit
consists of the chambers
on the left side of the
heart (left atrium and left
ventricle) and all the
named blood vessels
that carry blood to the
tissues (arteries) and all
the named blood vessels
that return the blood
from the tissues (veins)
back to the right atrium
of the heart. The tissue
capillaries are included.
Inferior vena cava
Superior vena
cava
Aorta
The Location of the Heart
• Your heart is
located under your
ribcage and is
tilted to the left
which is why
everyone thinks it is
on the left side of
your body.
The Heart
This is a vein. It brings
blood from the body,
except the lungs.
These are arteries.
They carry blood
away from the heart.
2 atria
2 ventricles
Coronary arteries,
the hearts own
blood supply
The heart has four chambers
now lets look inside the heart
THE ANATOMY
• The heart has 4
chambers
• 2 ventricles (right and
left)
• These are muscular
chambers that move
blood out of the heart’
• The 2 atriums hold the
blood and at the right
moment empty the
blood into the right and
left ventricles
Textbook Pg 133, Fig 8.10 (b)
Valves in
the Heart
Tricuspid Valve
Chordae Tendineae
Semilunar
Valves
Bicuspid
Valve
Chordae Tendineae
• Cords / tendons that are attached to the
tricuspid and bicuspid valves
• Help to prevent the valves from being
turned inside out
The pumping action of the
heart is essential to maintain
blood circulation. It beats
about 75 times per minute.
The amount of blood pumped
from one ventricle per minute
is called the cardiac output.
Coronary arteries
ALBIO9700/2006JK
The Heart
Artery to Lungs
Vein from Head and Body
Right Atrium
valve
Right Ventricle
Artery to Head and Body
Vein from Lungs
Left Atrium
valve
Left Ventricle
Cross section of the Heart
Oxygenated blood leaves
the left ventricle to
circulate through the body
Receives blood
from the venae
cavae
Control the flow
& backflow of
blood
Carries deoxygenated
blood away from the
heart
vena cava
from the
head
Upper left
chamber
Upper
right
chamber
vena cava
from lower
body
Deoxygenated
blood flows into
the pulmonary
arteries
Lower right
chamber
Lower
left
chamber
Receives blood
from the
pulmonary veins
Control the flow &
backflow of blood
Oxygenated
blood flows into
the aorta.
The heart is located left of the body midline posterior to the
sternum in the mediastinum.
But how does it work?
1. Atrial systole stage:
The heart fills with blood
> the atrial wall muscle
contracts
2. The pressure forces the
blood in the atria down
into the ventricles
3. Semilunar valves
prevent blood backflow
4. Ventricular systole stage:
the ventricle thick
muscular wall squeezes
inwards > increasing
pressure pushes the
blood out of the heart
5. Backflow is prevented by
the pressure difference
that pushes the atrioventricular valves shut
But how does it work?
6. The blood rushes
upwards into the aorta &
the pulmonary artery
pushing open the
semilunar valves
7. Ventricular diastole stage:
all the heart muscles
relax > low pressure
blood from the veins flows
into the 2 atria >
Blood moves downwards
into ventricles through the
atrio-ventricular valves >
the atrial muscle
contracts to push the
blood forcefully down into
the ventricles >
8. The cycle begins again
Cardiovascular Diseases
• Diseases of the heart and blood:
–
–
–
–
Coronary heart disease
Hypertension (high BP)
Arteriosclerosis (hardening of arteries)
Atherosclerosis (narrowing of arteries)
Coronary arteries
• A lot of blood pass
through the heart all
the time
• But heart is NOT
nourished by the
blood pass through it
• Coronary arteries
supply oxygen and
nutrients to the heart
Coronary Heart Diseases
• Occur when coronary
arteries become
blocked
• Result: Oxygen and
nutrients cannot be
supplied to the heart
Steps in coronary heart disease
1. Coronary arteries become
blocked when lipids (fat and
cholesterol) carried by the blood
get deposited on the walls of the
arteries, thus making them
narrower
2. This is called atherosclerosis
3. Calcium salts then cover the lipids to form a fibrous
net called atheroma
4. Blood clots (thrombus) may also form
5. Coronary occlusion occurs when the artery is fully
blocked and the supply of blood to the heart is
stopped
6. A heart attack results, as part of the heart dies from
the lack of oxygen
Causes of Heart Diseases
•
•
•
•
•
Fatty diet (high in sodium, cholesterol and saturated fats)
Lack of exercise
Obesity
Smoking
Stress
Mode of Action of the Heart
(i.e. How the heart beats)
• The chambers of the
heart contract and relax in
pairs
• When both atria contract;
ventricles are relaxed
• When ventricles contract,
atria are relaxed
Heartbeat (Cardiac Cycle)
One heartbeat (a cardiac cycle) consists of
two parts:
1. Systole (ventricular contraction)
2. Diastole (ventricular relaxation)
Systole (contraction)
–
–
–
–
Ventricles contract
Blood is forced into the pulmonary artery and aorta
Tricuspid and bicuspid valves are closed
Blood pressure normally rises to120 mmHg
How does the Heart work?
STEP ONE
blood from the
body
blood from
the lungs
The heart beat begins when the
heart muscles relax and blood
flows into the atria.
How does the Heart work?
STEP TWO
The atria then contract and
the valves open to allow blood
into the ventricles.
How does the Heart work?
STEP THREE
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.
Heart sounds
• During systole, “Lup” sound is caused by
backflow of blood against closed tricuspid and
bicuspid valves
• During diastole, “Dup” sound is caused by
backflow of blood against closed semilunar
valves
• Rhythmic “Lup-Dup” sounds results
• Stethoscope can be used to hear the heart beat
Heart action control
Purkyne tissue
ALBIO9700/2006JK
Control of Heartbeat
• The heart has a natural rhythmic
contraction of its own
• Can be also controlled by some nerves
from the brain to increase or decrease the
number of heart beats when necessary.
Pacemaker
• Group of specialized cells found at top
right atrium
• Pacemaker initiates heart beat
• Pacemaker is controlled by nerves from
the brain
• To speed up or slow down heart rate
when necessary
http://www.phschool.com/science/biology_place/biocoach/cardio1/electrical.html
Artificial Pacemaker
• Some heart diseases can cause the heart to
beat irregularly
• Can be corrected by using an artificial (manmade) pacemaker
• Doctors will implant this small electronic device
near the patient’s heart
• It will produce regular pulses of electricity which
stimulates the heart to contract and relax at the
right rate.
Pulse Rate
• The number of times the
heart beats in one minute
• The resting heart beats
approximately 60 to 100
times per minute
• Pulse rate increases
during exercise, and when
one is feeling stressed,
nervous, angry or excited.
Pulse Rate
How many times does your heart beat in :
• One minute? 70
• One day?
100,800
• One week?
705,600
• One month? 21,168,000
• One year?
254,016,000
Pulse Rate of…
• Foetus:
140-150 beats/min
• Newborn baby:
• 3 year old:
130-140
95-100
• 10 year old:
84
• 25 year old:
72
• 50 year old:
76
Blood Pressure
• Blood pressure is around
120/80 mmHg
• Blood pressure is the force of
the blood pushing against the
walls of the arteries each time
the heart beats.
• Blood pressure is at its highest
during systole.
• Blood pressure is lowest when
the heart is at rest, between
beats (diastole)
High Blood Pressure
• Blood pressure of 140/90 or higher is
considered high blood pressure
Who is at risk?
– middle-aged and elderly people
– obese people
– heavy drinker
– Inherited form parents