Transcript Blood Vessels PowerPoint

Bell Work
1. What is the difference between a vein and an
artery?
2. What is blood pressure?
3. What is cardiac output?
4. What is resistance?
5. What does the word constriction mean?
6. What do the prefixes hypo- and hyper- mean?
Blood Vessels, Blood Pressure
and Capillary Beds
Oh my.
Blood Vessels
• When it comes to blood, your body is a giant closed
system with heart as the pump.
• To complete this huge circulatory task of delivering
blood to all the body parts, the body has several
types of blood vessels.
• Blood is propelled from the heart into large arteries,
which gradually branch into smaller arteries.
• Branching off of arteries are arterioles, which feed
capillaries.
• Capillaries drain into venules, which empty into veins
which return the blood to the heart.
Anatomy of Blood Vessels
• Blood vessels are composed of three layers or
tunics
– Tunica intima – the inner layer that is
composed of endothelium that form a
smooth, slick surface.
– Tunica media – the bulky middle layer that is
composed of mainly smooth muscle and
elastic tissue.
– Tunica externa – the outer layer that is
composed of fibrous connective tissue that
supports and protects the vessels
Differences in blood vessels
• Arteries are thicker, especially in the tunica
medula, so it can withstand the forces coming
from the heart
• Veins are thinner due to decrease pressure but
larger veins need valves to prevent backflow and
muscle activity to help “squeeze” the blood back
to the heart
• Capillaries are usually only one cell thick (just the
tunica intima layer) to promote gas and nutrient
exchange.
More about capillaries
• They are intricate branching networks of thin blood
vessels at the end of arteries
• This area is also known as a capillary bed
• The flow from the arteriole to the venule is known
as microcirculation.
• They are composed of two types of vessels, the
vascular shunt (directly connects arteriole and
venule) and the true capillaries (exchange vessels,
where various materials can flow into and out of
the cells and bloodstream.)
• True capillaries (and thus exchanges) can be “turned
off” by the body by using precapillary sphincters
Use page 361 to draw and label
the various type of blood vessels.
The four different routes for exchange
• Direct diffusion – can occur if materials are lipid
soluble. In this case they can pass straight
through the plasma membrane
• Vesicle transportation – lipid insoluble materials
enter into tiny capsules called vesicles and can to
transported in (endocytosis) or out (exocytosis)
• Limited passage through intercellular clefts (gaps
in the plasma membrane)
• Fenestrated capillaries – an oval pore (opening)
known as a fenestra that is covered with a thin
permeable membrane
Fluid Movement
•
•
•
•
Fluid movement depends on two pressures
Blood Pressure – tends to force fluid outward
Osmotic Pressure – tends to draw fluids in
As a rule, blood pressure is higher at the arterial
end of the capillary bed and osmotic pressure is
higher at the veneous end.
• The result is fluids move out at the beginning of
the capillary bed and are reclaimed at the end.
Use page 380 (especially picture b
and c) to draw a summary of the
different type of capillary transport
mechanisms
What is Blood Pressure
• The pressure the blood exerts against the
walls of the blood vessels
• It is also the force that keeps the blood
circulating continuously between heart beats
• It moves from areas of high pressure to low
pressure
Measuring Blood Pressure
• Systolic Pressure – the pressure in the arteries
at the peak of ventricular contraction (top
number)
• Diastolic Pressure – the pressure when the
ventricles are relaxing (bottom number)
What effects blood pressure?
• It is related to
– Cardiac output – the amount of blood
pumped out of the left ventricle per minute
– Peripheral resistance – the amount of
friction encountered by the blood as it flows
through the blood vessels
What can change these?
• Neural factors – autonomic nervous system
changes that causes vasoconstriction (narrowing
of the blood vessels) and increase blood pressure
• Renal factors that involve the kidneys – the
kidneys can alter the blood volume. Less volume
means less pressure.
• Temperature – cold temperature causes
vasocontriction while heat causes vasodilation
• Chemicals
• Diet
Variations in Blood Pressure
• Hypotension – low blood pressure, usually a good
thing
• Orthostatic hypotension – results from an aging
sympathetic nervous system and its slower
reaction times, it causes older individuals to free
dizzy or fainting when quickly rising from a
reclined or seated position
• Hypertension – high blood pressure, higher
pressures strain the heart and weaken it over
time
• http://www.youtube.com/watch?v=Q530H1W
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