Transcript AP_Bio_Laboratory_files/Lab #10 Blood Pressure Intro

AP Biology
Lab #10
Physiology of the
Circulatory
System
Blood pressure is a measurement
of the force applied to the walls of the
arteries as the heart pumps blood
throughout the body. Blood pressure
is determined by the strength of
contraction, amount of blood pumped
into the arteries, the viscosity of the
blood, and the size and flexibility of
the arteries.
fluids exert
force against
surfaces they
come in
contact with
hydrostatic
pressure
fluids flow
from high
pressure to
areas of low
pressure
fluids flow
faster in
narrower
pipes…
than
wider pipes
BUT -even
though
capillaries are
than
arteries; we
have more
capillaries
smaller
Therefore:
greater crosssectional area
of capillaries
Therefore,
fluids flow
faster in
arteries than
capillaries
This is a good
thing, b/c gas
exchange can
take place in
the
capillaries
Blood exerts
a pressure
against the
wall of the
vessel in
which it is
flowing.
Tissue cell
Capillary
Red
blood
cell
Net fluid
movement out
Net fluid
movement in
15 m
At the arterial end of a
capillary, blood pressure is
greater than osmotic pressure,
and fluid flows out of the
capillary into the interstitial fluid.
At the venule end of a capillary, blood
pressure is less than osmotic pressure,
and fluid flows from the interstitial fluid into
the capillary.
Direction of
blood flow
Blood pressure
Osmotic pressure
Pressure
Capillary
INTERSTITIAL FLUID
Inward flow
Outward flow
Arterial end of capillary
Figure 42.14
Venule end
• One type of cardiovascular disease,
atherosclerosis
– Is caused by the buildup of cholesterol within arteries
Connective
tissue
Smooth muscle
Plaque
Endothelium
(a) Normal artery
50 µm
(b) Partly clogged artery
Figure 42.18a, b
250 µm
140 or below
is a normal
systolic
reading
90 or below
is a normal
diastolic
reading
Cuff is wrapped
around the
upper arm &
inflated until the
pressure closes
the brachial
artery
*No blood can
flow
the cuff,
now
past
Pressure
from cuff is
higher than
pressure in
the artery
Stethoscope
used to listen
for the sound
of blood
flowing below
the cuff
If artery is
closed, no
blood
flowing… no
sound.
Cuff is
loosened
until the
blood can
flow freely
through the
artery
You will hear
the sound of
blood
pulsing into
the artery
Pressure
from blood is
now greater
than the
pressure
from the cuff
Cuff is
loosened
until the
blood can
flow freely
through the
artery
Sound below
the cuff will
disappear,
pressure
remaining in
the artery
when heart is
relaxed.
Range
depends on
heredity,
gender,
environment
Range
depends on
heredity,
gender,
environment
•All blood vessels
•Arteries
have thicker
walls
–To
accommod
ate the high
pressure of
blood
pumped
from the
heart
–Are built of similar tissues
–Have three similar layers
Artery
Vein
Basement
membrane
Endothelium
100 µm
Valve
Endothelium
Smooth
muscle
Connective
tissue
Endothelium
Smooth
muscle
Capillary
Connective
tissue
Artery
Vein
Venule
Figure 42.9
Arteriole
• In the thinner-walled veins
– Blood flows back to the heart mainly as a result of
muscle action
Direction of blood flow
in vein (toward heart)
Valve (open)
Skeletal muscle
Valve (closed)
Figure 42.10