Transcript The Human cardiovascular system

Open circulation
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This is where blood
does not stay within
vessels.
Low blood pressure
It passes through large
blood spaces called a
sinus/haemocoel and
comes in direct contact
with cells
Eg. insects
The Human cardiovascular system
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Consists of:
Blood
Blood vessels
Heart
As the blood always remains within
vessels it is called a closed circulatory
system.It does not come in direct
contact with body cells
Advantages: higher blood pressure
maintained,faster flow of oxygen &
nutrients
Can be more responsive to change and
direct blood to where it is needed by
constriction & dilation of vessels
Single circulation
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Blood pressure
reduced after flowing
through the tiny
capillaries of the gills
Slow flow to the rest
of the body
Limits rate of delivery
of oxygen and
nutrients to tissues
Limits activity levels
Double Circulation
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The blood passes through the heart
TWICE on each circuit of the body
This means the pressure can be
increased again after the lungs to
ensure faster delivery of materials to
tissues(mammals are active and also
have to maintain body temperature)
Body-heart-lung-heart-body.
Circulation to the lungs is the
PULMONARY CIRCULATION
Circulation to the body is the
SYSTEMIC CIRCULATION at a
higher pressure than pulmonary to
avoid damaging delicate capillaries
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The advantage of double
circulation is to maintain
higher blood pressure in
the circulatory system
In single circulation the
blood only passes through
the heart ONCE on each
circuit
Eg Fish
Disadvantage is lower
blood pressure in systemic
circulation
Blood Vessels
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Arteries(smaller = arterioles)-carry blood
away from the heart
Veins(smaller = venules)-carry blood
back to the heart
Capillaries-tiny,thin walled vessels
connect arteries & veins
Artery Structure
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Arteries transport blood away from the heart
at high pressure to the tissues
The properties of the artery wall adapt it for
its function :
Artery –Structure & function
Artery structure
Endothelium
Property
Function
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Endothelium- the inner lining of the artery
made up of squamous epithelial cells. Flat and
smooth to minimise friction as blood flows.It is
folded and can unfold when the artery stretches
Lumen(blood space)- this is small to maintain
high blood pressure
Artery wall – this is thick & strong as it
contains the protein collagen to withstand the
high blood pressure(120mm Hg or 16 kPa)
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It contains elastic fibres(protein elastin)allows them to give when blood is forced
through them- so more in walls nearer the
heart.
Then they recoil they give the blood an extra
push.This also helps even out blood
flow(though you can still feel a pulse)
Both contain smooth muscle tissue,more as
you get further from the heart. These
muscles can contract,narrowing(constricting)
the arterioles and control blood flow. When
they relax the arteriole dilates.
Vein Structure- vessels that
return blood to the heart
Veins – Structure & function
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Walls thinner – blood pressure much
lower so do not need to be so strong
Thinner layers of collagen,elastic fibres
and smooth muscle.They do not need to
constrict to control flow.
Larger lumen to ease blood flow.
Valves to prevent backflow
Movement of blood through
veins
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The low blood
pressure means it is
harder to return the
blood to the heart(less
push)
Valves ensure there is
no back flow
The valves are semilunar or pocket valves
Movement of blood through
veins
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Many veins run
close to skeletal
muscles.
Contraction of
these muscles
squeezes the
veins and helps
move blood
through them
Blood Pressure
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The pressure of blood pushing against the
walls of the blood vessel.
Mammals have a high blood pressure
This is useful as it maintains a fast flow
of blood through the circulatory system.
Measuring
blood pressure
•A cuff that inflates is wrapped around
your upper arm and kept in place with
Velcro. A tube leads out of the cuff to a
rubber bulb.
•Air is then blown into the cuff and
increasing pressure and tightening is
felt on the upper arm.
•The doctor puts a stethoscope to your
arm and listens to the pulse while the
air is slowly let out again.
•The systolic pressure(Heart
contracting) is measured when the
doctor first hears the pulse.
•This sound will slowly become more
distant and finally disappear.
•The diastolic pressure(heart
relaxing)is measured from the moment
the doctor is unable to hear the sound
of the pulse.
•The blood pressure is measured in
terms of millimetres of mercury
(mmHg).
Blood pressure changes in the circulatory
system.
Blood Pressure Changes
during circulation
1.
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4.
Pressure is highest in the aorta having just been
pumped out of the left side of the heart
Pressure varies during a heart beat(systolic)
when it is higher and during heart
relaxation(diastolic) when it is lower. This
change in pressure can be felt as a pulse
As blood moves further from the heart the
pressure drops- due to friction (peripheral
resistance) with the walls of the vessels. Pulse
also disappears due to evening of flow
Largest drop occurs in the arterioles due to
increase in area of wall touching the blood.
Changes in blood pressure
5. Passing through the narrow capillaries sees a further
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7.
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drop in pressure. Also caused by loss of tissue fluid
from the capillaries
Venous blood is low in pressure normally about 5 mm
Hg
Blood returns to the right side of the heart and is
pumped to the lungs by the right ventricle.Thinner
walls than left side so lower pressure(again surges in
the pressure are seen)
Again pressure drops while passing through the lung
arterioles & capillaries and stays low until returning to
the left side of the heart.
Capillary structure
Capillary – Structure & Function
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Connect arterioles to venules
Take blood as close as
possible to all cells in the
body – red blood cell may be
as little as 1μm from a cell
Allowing rapid transfer of
materials between cells &
blood
Tiny size allows this- 7μm
diameter
Similar size to red blood cells
which must squeeze
through-slows flow so
oxygen can be exchanged
presses them close to the
capillary wall
Capillary – Structure & Function
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Walls of capillaries are only made up of a
single layer of endothelial cells – very thin for
fast and easy diffusion
Cells have gaps between them making them
leaky- tissue fluid seeps out into the cells
Comparison of blood vessels
Feature
Function
Wall thickness
Wall composition
Inner lining
Shape
Lumen
Valves
Blood pressure
Artery
Vein
Capillary
Plasma & Tissue Fluid
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The liquid part of the blood is plasma it
carries the blood cells and many dissolved
materials
Tissue Fluid
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As blood flows through the capillaries fluid
leaks out into the spaces around your
cells(one sixth of your body!!)
This is TISSUE FLUID-it surrounds our cells
and allows exchange of materials-will contain
O2,nutrients etc
Identical to plasma except does not contain
red blood cells,though some white cells can
squeeze out
Contains less proteins as these are too
large to pass out
Factors controlling movement of
tissue fluid
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Blood pressure: (hydrostatic pressure)
forces fluid out at the arteriole end of the
capillary bed
Osmotic pressure (solute pressure) :
returns fluid to the blood at the venule
end
Overall net flow OUT into the tissues
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Arterial end
Effective HP = 4.3-1.1 = 3.2kPa(out)
Effective SP = -3.3-(-1.3) = -2kPa(in)
Overall effective blood P = 3.2-2=1.2 kPa
Fluid pushed out
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Venule end
Effective HP = 1.6-1.1=0.5 kPa(out)
Effective SP =-3.3-(-1.3)=-2kPa(in)
Overall effective blood P= 0.5 -2 = -1.5 kPa
Fluid pushed back into capillary
Arteriole end
Venule end
4.3
-3.3
1.6
1.1
-1.3
1.1
Net outflow 1.2kPa
Hydrostatic pressure
-3.3
-1.3
Net inflow -1.5kPa
solute pressure
(water potential)
The Lymphatic system
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About 90% of fluid that
leaks from the
capillaries returns to
them
10% does not - and
must be drained away
by lymph vessels
These vessels form the
lymphatic system
The Lymphatic system
Lymph Vessels
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Tiny,dead end vessels
which are found in
almost all tissues
Fluid enters them
through tiny valves
This fluid is called
lymph and is virtually
identical to tissue fluid
Lymph vessels
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The tiny valves allow large
proteins to enter the
lymph(cannot enter the
blood capillary)
With out them protein
would build up in your tissue
fluid causing oedema
(Water leaving your blood
causing swelling of tissues)
And death within 24 hours
Lymph
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In some parts of the
body the lymph has
differences:
Small intestine
lymph will contain high
amounts of lipids after
a meal
The villi contain a
lymph vessel(a
lacteal),which absorbs
digested fats
Lymph
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Tissue fluid and lymph in the
liver has high concentrations of
proteins.
Lymph is moved through the
vessels very slowly(100cm³/h –
blood 80cm³/sec!)
Contraction of skeletal muscles
help this and
also the vessels have smooth
muscle in their walls which
contracts to squeeze lymph
along
Lymph eventually drains back
into the blood in the subclavian
veins
Lymph
Nodes
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Found at intervals in the lymphatic system
Involved in protection from disease
Microbes are filtered from the lymph as it
passes through the lymph nodes by white blood
cells - lymphocytes
Comparison of blood,tissue fluid and lymph
Feature
Proteins
Fats
Glucose
Amino acids
Oxygen
Carbon dioxide
Cells
Blood plasma
Tissue fluid
lymph
The cardiac cycle
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The heart beats on average 70bpm
The cardiac cycle is the events that take
place in one heart beat.
The cardiac cycle
1.
Atrial systole(0.1s)
Heart full of blood .
Atria walls contract,
blood pushed through
the AV valves into the
ventricles.Valves in
the vena cava and
pulmonary vein
prevent backflow.
2. Ventricular systole(0.3s)
Thick ventricle muscle walls
contract.This produces a
higher pressure.Blood is
forced into the PA and
aorta, through the semilunar
valves which are forced
open.
 Papillary muscles also
contract to pull on the
tendons, stopping the closed
AV valve flaps turning inside
out.
3.Ventricular diastole
Ventricle and atrial
muscles are relaxed.
heart begins to fill with
blood starting in the
atria . Blood pressure
in the aorta and
pulmonary artery shuts
the semi lunar valves
Heart valves
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Semilunar valve
Consists of 3
pockets in half
moon shape
Blood flowing
through pushes
past the pockets
When it tries to
return it will fill
the pockets
closing the valve.
Pressure changes in the heart during the cardiac cycle
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Atria contract (atrial systole)
ventricular systole begins. When
pressure in the ventricle exceeds
pressure in the atria AV valves
shut.
Ventricular systole,rapid increase
in pressure as ventricles contract
Pressure in ventricle exceeds that
in aorta, semilunar valves open.
Maximum systolic
pressure,ventricles now start to
relax
Pressure in ventricles drops below
aorta.SL valves shut
Wave of contraction running down
aorta raises pressure
Ventricular diastole starts
Blood starts to refill the atria
increasing pressure
When pressure exceeds ventricle,
AV valves open and blood flows
into the ventricles
(a) Atrial systole (b) ventricular systole
Control of Heart beat
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Cardiac(heart)muscle contracts by itself. It
does not need a nerve supply(only muscle in the
body that does this)
It is said to be MYOGENIC- if cardiac muscle
cells are cultured-they will beat with their own
rhythm
Muscles that need a nerve impulse sent to them
to cause contraction are called NEUROGENIC
Control of heart beat
The Pacemaker
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The heart beat is initiated by a patch of tissue in
the wall of the right atrium
Called the SINOATRIAL NODE(SAN)- naturally
beats at 70 bpm
This sets the rhythm for the heart so is called
the pacemaker
It starts a wave of electrical activity- which
spreads across the atria-causing them to
contract
The ATRIOVENTRICULAR
NODE(AVN)
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The electrical wave cannot spread straight to
the ventricles
There is a band of non conducting fibres
between the atria and ventricles
Electrical wave has to first go to the AVN and
then down the SEPTUM in the BUNDLE OF
HIS and then in PURKYNE TISSUE.to the
ventricles
It then spreads UP the ventricle walls from the
base,causing them to contract
Why does this happen?
Changing the heart rate
Left alone the heart rate would be 70 bpm
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Why would this be a problem?
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Heart rate can be slowed or increased
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By nerves from the cardiovascular centre of the
brain to the SAN
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Stimulating the sympathetic nerve speeds up the
heart rate(neurotransmitter – noradrenaline)
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Stimulating the parasympathetic(vagus) nerve
slows the heart rate(neurotransmitter - acetyl
choline)
2. By the hormone ADRENALINE secreted by the
adrenal glands,to heart in the blood -this speeds up
heart rate
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Cardiac muscle
Cardiac Muscle Structure
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Consists of cylindrical branching fibres
Form a 3D structure
Very well supplied with mitochondria and
blood capillaries(from coronary artery)
Cells joined by special intercalated discs,pass
the electrical wave rapidly between cells,helped
by the branching-so they all contract almost at
once
Long refractory period(time when muscle will
not contract),means it has a recovery time so it
can continue beating without tiring
Electrocardiogram
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Electrodes are placed
over the opposite sides
of the heart
The electrical potentials
generated are measured
Shows the wave of
electrical activity passing
through the heart
ECG graph
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The ECG graph shows a
plot of voltage against
time
P wave atria contracting
QRS wave ventricles
contracting
T wave recovery of the
ventricles
Diagnosis using ECG
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Abnormal ECG trace can identify:
Myocardial infarction (heart attack)
Fibrillation (atrial or ventricular)
Ventricular hypertrophy (increase in
muscle thickness)
Heart block (problems with the
movement of the electrical signals
between parts of the heart)
Arrhythmia(irregular heart beat)
bradycardia and tachycardia
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Heart muscle
respires fatty acids
This can only be
aerobic
Any lack of oxygen
will cause cells to
die leading to a
heart attack
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Fibrillation
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No regular heart rhythm
So no cardiac output
Patient will lose consciousness and life threatened
Defibrillation passes a large voltage through the
heart,stopping it and allowing pacemaker to restart in
natural rhythm
Heart Sounds
Heart murmurs
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Abnormal heart
sounds
Can be due to leaking
valves, thickened or
abnormal valves
Often “innocent
murmurs” common in
childhood with no
danger to health