Download CIRCULATION - Salisbury Composite High School

Heart & Circulation
Circulation
The human circulatory system
consists of 96,000 km of blood
vessels that transport blood to
each cell in the body. Your entire
blood volume (about 5L) is
pumped every minute.
The circulatory system performs the
following functions:
1. carries oxygen and nutrients to the cells
2. carries carbon dioxide and waste away from
the cells
3. carries hormones to target organs
4. distributes heat throughout the body
5. helps defense of invading micro-organisms
Blood Vessels
Arteries – carry blood away
from the heart. Their thick
walls are composed of three
distinct, elastic layers. Each
time the heart pumps, the
arteries stretch to accommodate
the rush of blood. This is felt in
the neck, or on the wrist as a
pulse.
 Arterioles - are smaller
arteries whose middle layer is
composed of elastic fibers and
smooth muscle. The arterioles
are able to contract and relax,
controlling blood flow to
different parts of the body.

Vasoconstriction –
the narrowing of
blood vessels,
decreasing flow to
the tissues.

Capillaries – are tiny blood
vessels composed of a
single layer of cells. This is
the site of fluid and gas
exchange between the
cells and the body
tissues. Many capillaries
are only as thick in diameter
as one red blood cell
(<0.005 mm). Pressure in
the capillaries is high,
increasing the risk of
rupturing and causing a
bruise.
Venules – larger blood vessels that form as
capillaries merge. The venules are lined with
smooth muscle to ensure blood continues to
flow back towards the heart.
 Veins – larger blood vessels that result as
venules merge, take blood back towards the
heart. Veins also serve as blood reservoirs,
holding up to 65% of the total blood volume.
Blood pressure in the veins is quite low, so the
veins have uni-directional valves that ensure the
one way flow of blood. Skeletal muscles also
help aid venous flow. Venous pressure
increases when skeletal muscles contract and
push on the vein, forcing blood upwards.

Blood Vessels
Problems with blood vessels:

Aneurysm – a bulge or
weakening in the wall of a
blood vessel.

Atherosclerosis –
degeneration of blood
vessels caused by the
accumulation of fat
deposits (plaque) in the
inner wall.

Bruising – rupture of
capillary beds cause
blood to leak into the
extra-cellular space.

Varicose Veins –
damage to the oneway valves in veins
causes blood to pool
and the veins to
bulge.
Circulation

The heart consists of two parallel pumps. The right
connects to blood vessels that circulate blood to
the lungs, for oxygenation, and back to the heart.
This system is called the pulmonary circulatory
system. The second, left hand pump, connects
blood vessels to the body and circulates blood to
the body tissues. This system is called the
systemic circulatory system.
One way blood flow is maintained by unidirectional valves in the heart and in the blood
vessels.
Pulmonary
System
Systemic
System
Closed Circulation

Blood never leaves vessels
Double Circulatory System
-In mammals, birds
and reptiles, the blood
is pumped twice
before returning to its
origin
-Fish, and other lower
organisms pump the
blood only once
Four Chambered Heart

oxygenated and
deoxygenated blood do
not mix in the heart

septum separates the
right and left sides
Heart Chambers

The top chambers
are called atria
(sing. Atrium)

These collect blood
from major veins
and pump it into
the bottom
chambers
Ventricles
Much larger and more muscular than atria
 Pump blood into arteries for distribution
to body (and lungs)

Vessels

Arteries – carry blood away from heart

Veins – carry blood toward heart

Systemic circulation – blood flow to and
from body organs (not lungs)

Pulmonary circulation – blood flow to and
from lungs
Atrioventricular Valves

Separate the atria and ventricles

Atrioventricular
valves have:
– Chordae tendinae
prevent flaps from
everting (opening
backward)
– Papillary muscles to
attach chordae
tendinae to ventricle
wall
The Bicuspid Valve (AV)
Also called the mitral
valve
 On the left side of the
heart
 Has two flaps

Tricuspid Valve (AV)
On the right side
 Has three flaps

Semilunar Valves
At the entrance to the major arteries are
smaller valves with no muscular
attachments
 These have three flaps each and prevent
backflow into the ventricles

Valve movie
http://www.wellesley.edu/Biology/Courses/111/
HeartValves.MOV
 video

Pericardium

Membrane
around heart
which
prevents
friction
between heart
and lungs

Also helps
isolate
infection
Coronary Arteries

The aorta branches and one of the
branches comes back to serve the heart
muscle (myocardium)
Coronary Circulation

These arteries can become blocked
with plaque (cholesterol and calcium
deposits) and clots can occur causing:
– pain: angina pectoris
– Heart muscle death: myocardial
infarction (heart attack)
Coronary Circulation
Risks for Heart Disease
Genetics
 Male
 Smoking
 Obesity
 Diet (saturated fat
and cholesterol)
 Lack of exercise

Heart Beats

Cardiac Muscle: striated, branched

Is myogenic muscle: can contract
without nerve impulse
Heart Beats
 Chemoreceptors
in aorta and carotid
(neck) arteries detect high carbon
dioxide levels in blood (lesser extent
– oxygen is also monitored)

Cranial nerves carry this information to the
heart
Heart Beats
The heart beat is
controlled by the
sympathetic
(stimulating) and
parasympathetic
(relaxing) branches of
the nervous system.
Heart Beats
Tempo is set by the sinoatrial node (SA
node) : the pacemaker
Heart Beats

Electrochemical
impulses from the S.A.
node cause contraction
of atria muscle
Heart Beats

the impulse travels to
another cluster of
nervous tissue – the
Atrioventricular node
(A.V. node)
Heart Beats

The A.V. node sends
impulses through
Purkinje fibers to all
parts of the
ventricles

Ventricles contract
simultaneously
Heart Beats

Heart muscle then ‘rests’ before the cycle
begins again

‘systole’ – phase of heart contraction

‘diastole’ – phase of heart relaxation

‘lub – dub’ – heart sounds caused by
valves slamming shut
Heart Beats

Normal Heart Rate – 80 beats/minute

Bradycardia - < 50 beats/min

Tachycardia - > 100 beats/min
Monitoring Heart Beat
EKG (or ECG) – electrocardiogram
 Uses electrical activity in heart muscle to
diagnose problems

EKG
P wave – depolarization preceding atrial
contraction
 QRS complex – precedes ventricular
 T wave – repolarization of myocardium

Ventricular Fibrillation
Defibrillator

Used to shock hearts
into proper rhythm
Other Abnormal Rhythms

tachycardia
Bradycardia
Blood Flow in the Heart
Heart Technology

stethescope
Heart Technology
Artificial
pacemakers –
use batteries to
produce a
coordinated
signal when
‘real’ pacemaker
malfunctions
Cardiac Catheterization

a thin catheter is inserted into a blood
vessel, usually an artery in the leg or arm,
and passed through the blood vessel to
the heart.

Dye is injected to make the coronary
arteries and other structures visible on Xrays.
Heart Technology

Angioplasty: using a catheter and
‘balloon’ to open up blocked arteries
Heart Technology
Valve Replacement : routinely done to fix
valves scarred by infections, etc.
Heart Technology

Coronary bypass:
heart operation to
use a vein from leg
to bypass blockage
Heart Transplant
 Often
miraculous
results
 Shortage of organs
 Person must take
immunosupressants
for life
Xenotransplants
Dismal failures when whole heart is
transplanted
 Pig arteries and valves have been used for
years
 New genetic research hopes to produce
pigs with human proteins

Artificial Heart

Some success as a bridge to transplant