Transcript Circulatory System

Circulatory System Part 2
Begins
THE BLOOD VESSELS
Let’s talk about blood vessels now. There are three basic types
of blood vessels. The ARTERY, CAPILLARY AND VEIN. Small
arteries are called ARTERIOLES and small veins VENULES.
High
pressure
5.3 kpa
Low
pressure
1.3 kpa
Osmotic pressure 3.3kpa
results from proteins
ARTERY
CAPILLARY
Carries blood
away from the
heart
Connects artery to vein. Site of
O2/nutrient delivery and CO2/waste
pick up from tissues. Large proteins
and RBC don’t pass through
capillary wall.
VEIN
Carries blood
back to the
heart
Blood vessels have a LUMEN. That is the description of the inner
space of the blood vessel tube. Contrary to what you might think,
the lumen is actually smaller in the artery as opposed to the vein
Smooth muscle and connective
layer are much thicker to deal
with high pressure blood
Smooth muscle and connective
layers are thinner and there are
one way valves
1= endothelium layer. Thin
saran-wrap-like innermost
layer
2=tunica intima
3= smooth muscle layer
Tunica media
4= connective tissue layer
Tunica adventitia
5= one way valve
The outer walls of the artery are elastic. This is very important to
allow the artery to stretch during the initial push of blood by the
heart and also to maintain blood pressure even as the heart relaxes.
Smooth muscle
surrounds and
controls the lumen
diameter. Dilation
lowers blood
pressure and
constriction of the
muscles increases
blood pressure.
If it was too thin or rigid, it would be
more prone to burst. An artery such as
this aorta could prove fatal if it
stretches but does not spring back due
to a defect. The aneurysm shown
could burst and kill the patient.
If you were to buy a
hose that you wanted to
last, thick rubber would
be the best choice
because it is elastic to
stretch and spring back
after the pressure.
The blood vessels are kind of like a highway system with cars
that only receive a push-no engines. Imagine you are in a red
blood cell.
Blood flow 1000X faster than capillary speed.
Heart pumps – Pushes you into
artery. It’s like a fast moving
multi-lane highway. ARTERY
Traffic will slow as you branch
onto many different road paths
and encounter more cars less
push and fewer lanes. ARTERIOLE
Many narrower tubes –
slower speed less pressure
Thanks for
the CO2 and
waste?
Traffic slows right down as cars
enter various narrow streets
one at a time and exchange
goods. CAPILLARY
You might think that there would be a huge traffic
jam here in the capillaries since all the blood must
pass through one cell at a time, but....
Money is like oxygen
to us cells. We need
that glucose too
The enormous number of capillaries
does not result in backups, high speeds
or high pressure. Total cross sectional
area of capillaries is much greater than
the arteries supplying them.
That’s a lot of drive through windows. Say can you alert
Mr. Leukocyte for me please.
MATH BREAK
“R” you kiddin’.
Math ain’t no
break!
I carry more blood.
No we
carry
more
blood
If the radius of this
artery lumen is 21 µm,
determine the cross
sectional area.
Cross sectional area of this
arteriole lumen reflects how much
blood is carried. It is determined
by the formula π r 2
Obviously the capillaries carry
more blood, but would it move
slower? If so by how much?
ANSWER
approx
1385 µ m2
The artery leads into this capillary
bed. If each capillary lumen
diameter is 7 µm , (radius 3.5)
determine the cross sectional area of
the capillary.
ANSWER
approx 38.4
µm2
CAPILLARIES 2X
slower
Multiply that by
the number of
capillaries for
total area.
ANSWER 72 x 38.4 =
approx 2765 µm2
MATH BREAK
CONTINUED
If blood moves slower in
the capillary, what
happens to the blood
pressure?
Hello. I
still have a
problem!
Ah come on! Enough
with the math. Lets talk
Monster trucks.
ANSWER
Blood pressure decrease
No. Lower pressure results because there
are many capillaries that attach to the
artery. So both blood velocity and
pressure decrease as the number of
blood vessels attached to the artery
increases. Even though these blood
vessels are smaller, there are many of
them that combined have more space.
Wait a minute.
Ain’t capillaries
smaller than
arterioles? That
means more blood
would have to
move through
them at higher
pressure. That’s
Law of continuity
according to fluid
flow in pipes
Let’s see what happens here in the capillaries. Exchange of nutrients
and waste takes place. The endothelium is only one cell thick so
passage of materials can occur by diffusion.
CAPILLARY FACTS
DIAMETER 7-8 micrometer diameter
RBC must pass through one at a time.
Blood slows down LOW PRESSURE
Capillaries shut off with
precapillary sphincters or
the smooth muscle
contracts narrowing the
lumen.
Only 5-10% of capillaries are blood filled at any given
time, but liver brain kidneys and heart are usually filled.
Substances diffuse through or
use coupled endo/exocytosis
Precapillary
sphincters open
to face-blushing
Pickin’ on my Mc
friend huh?
I’ll engulf you in my
macrophage state
(phagocytosis)
Remember, red
blood cells and
large proteins do
not pass though
the endothelium.
White blood cells,
like our Mr.
Leukocyte, can
squeeze through
the endothelium to
seek and destroy
invaders.
Honk Honk Hey
move it!
Once blood exits the capillaries
it is moving very slowly at low
pressure. Remember, there is
now no push other than the red
blood cells behind you. Your car
has no engine!
If the valves
break, the
blood
backflows and
expands the
veins in the
VARICOSE
VEIN problem
shown below.
The majority of blood collects in the veins and is conducted slowly
back to the heart by one way valves in combination with skeletal
muscle contractions. Notice how the one way valves only allow
the blood to proceed back toward the heart.
William
Harvey
William Harvey in the 1600’s
was the first to develop the
understanding of systemic
circulation. Here you can see
his famous experiment showing
the one way valve operation in
veins of the arm. TRY IT
YOURSELF! Pump up your veins
(exercise) Run your finger along
the vein to the armpit to empty
the vein. Try running your
finger the other way. TRY IT!
One way valve
only permits
blood flow back
to heart
I wrote my
famous tragedies
during this period
William
Shakespeare
Fluids that exit the blood vessels enters the
interstitial fluid between cells. Much of this is
drained by a series of vessels called the lymphatic
system. Lymph vessels look a lot like veins and they
also have one way valves. They feed into lymph
nodes where all the B cells hang out. Eventually the
fluid is returned to the bloodstream
That’s right. I hang most of the time in
the lymph nodes like the groin and
armpit.
Lymphatic
drainage
pattern
DID YOU KNOW?
When we
inhale, the
pressure in
the chest
cavity is
decreased.
This results in
a vacuum that
pulls air into
the lungs.
Veins in this
cavity also are
exposed to
this vacuum.
The vena
cava – both
inferior and
superior, are
exposed to
this vacuum
and pull
blood into
their lumen
spaces
THE MAMMALIAN HEART --- Let’s take a look at me
right
pulmonary
artery
Right
side of
heart
Deoxygenated
blood
Right
pulmonar
y veins
Left
pulmonary
artery
Learn the structures
Left pulmonary
veins
Left
side of
heart
Oxygenated
blood
I function like two hearts in one. My right side pumps deoxygenated blood
to the lungs and my left side pumps blood returned from the lungs to the
rest of the body under high pressure.
The heart and lungs are
located in the thoracic cavity,
protected by the rib cage
I’m about the size of your fist
and I am the most important
muscle in your body.. The
muscles of the heart are
specially designed to contract
yet not ever get tired like
skeletal muscle. These
muscle cells are CARDIAC
MUSCLE CELLS.
CARDIAC CYCLE – That’s a complete sequence of pumping and filling.
0.1
sec
Artrial
systole
Atria contract
0.3
sec
Ventricular
systole
Ventricles contract
Systole- That is
when I contract!
First Atrial
contraction, then
ventricular
contraction.
Diastole- That is when I relax!
This is the time I can provide nourishment, primarily oxygen, to
my muscle cells through the coronary arteries.
Diastole
–during this time
the ventricles refill
with blood
Both
ventricle
and
atrial
diastole
0.4 seconds to
nourish muscle
Coronary arteries
What is my CARDIAC OUTPUT you ask? Two things are
considered
STROKE VOLUME amount of blood
pumped by the left ventricle each
contraction
Average is about 75 mL
At rest = 70 beats per min.
HEART RATE number of beats per minute
Stroke volume x heart rate = 5.25L/min
Cardiac output in resting person is about 5.25 L/min
Circulatory System Part 2
ends