Blood Flow Images

8/2/2019 Blood Flow Images

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Arteries

AWAY

Branch

Typically oxygenated.


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Capillaries

Smallest.

Most abundant.

How many??

Why?

Exchange


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Veins

TOWARDS

Converge.

Typically deoxygenated.


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3 Layers of the Vascular Wall

Tunica interna

Tunica media

Tunica externa.


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Tunica Interna/Intima

Lining.

Endothelium.

Supported by loose CT.

Only layer in capillaries.


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Tunica Media

Primarily smooth muscle plus elastic fibers.

Most prominent layer in arteries.


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Tunica Media

Smooth muscle tone

Regulated by:

Metabolites

Hormones

Sympathetic vasomotor

neurons.


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Vasomotor neurons constantly release NE onto TM smooth

muscle. What does the NE do?

Why have a constant release?


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Increased NE release by a vasomotor neuron causes:

Tunica media smooth muscle tone to:

Vessel diameter to:

Resistance to blood flow in the vessel to:

Blood flow thru the vessel to:


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This gentleman has fatty plaques in his lower

leg arteries.

How do you think they affect blood flow?

How does that relate to his facial

expression?

His doctor recommends that the sympatheticnerves to those arteries be cut.

Why?


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Tunica Externa/Adventitia

Primarily collagen

Function?

Most prominent

layer in veins


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Elastic Arteries

Aorta and major branches.

Act as AUXILIARY PUMPS.


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Regional distribution

Significant layer

Muscular Arteries
http://www.vetmed.wsu.edu/VAn308/_vti_bin/shtml.dll/muscular.htm/map


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Smallest.

May or may not have an externa.

Highly innervated by vasomotor neurons.

Arterioles


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Regulation of blood pressure and flow.

Easy to change the diameter.How would you do it?

Why would you want to?

Arterioles


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Capillaries

Smallest.

Thin walls

Billions

Function?

Almost everywhere.

C i ill i


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Continuous capillaries

Most common and least permeable.

No endothelial holes

Intercellular clefts.

Abundant in

F t t d ill i


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Fenestrated capillaries

Endothelial holes

Intercellular clefts

Found in

Si id l ill i


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Sinusoidal capillaries.

Most permeable and least common.

Big endothelial holes

Intercellular clefts.

Can have macrophages in theirlining. Why?

Found in


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Why are capillaries organized into beds?

What tissues will have high densities of capillary beds?

Wh t d ill hi t d ?


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What determines whether the

sphincters are open or closed?

What do precapillary sphincters do?

Vascular shunt vs.

True capillaries

If i


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If you were running,

1. Precapillary sphincters in your biceps femoris would

2. Precapillary sphincters in your large intestine would


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Veins

All 3 tunics.

TE is the largest.

Thin walls

Large lumens.

Low resistance

High compliance


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Veins

Smooth muscle toneprevents too muchdistention.

Capacitance vessels/Bloodreservoirs.

65%


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Veins

Low pressure vessels.

Contain valves.

What do they do?

Where are they needed?


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Venous Sinuses

Thin-walled veins made of endothelium only.


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Blood Flow

Volume per time.

Flow thru systemic circuit = cardiac output.

Flow to individual organs varies.

How is this achieved?


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Blood Pressure

Force per unit area exerted on

the vessel wall by blood.

Millimeters of mercury (mmHg).

All vessels


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Resistance

Opposition to flow

Measure of friction.

Peripheral resistance.

Direction!


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While this guy is running,

- the resistance of the arterioles

of his quadriceps needs to

- the resistance of arterioles inhis colon needs to


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Sources of Resistance

Blood viscosity.

Total vessel length.

Vessel radius.


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Viscosity

Viscosity resistance.

Can you drink one of these with

a straw?

What makes it challenging?


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What are the major contributors to blood

viscosity?

Does viscosity change often in a healthyperson?

An increase in plasma EPO will cause

resistance to


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Total Vessel Length

Length resistance.

Does total vessel length change in a normal person?


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Which tube has greater intrinsic resistance?

A B

As total vessel length increases, resistance will

As total vessel length decreases, blood flow will


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Vessel Radius

(1/radius4

) resistance

Does vessel radius change in a normal healthy


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Does vessel radius change in a normal healthyperson?

Which vessels?

How is the change achieved?


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Which tube has the greater intrinsic resistance?

What layer of the vessel wall has the greatest effect on

vessel resistance?

a. Interna

b. Media

c. Externa

A B


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Resistance (length)(viscosity)

(radius)4

Whi h t b h th LEAST i t ?


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Which tube has the LEAST resistance?

Which tube has the GREATEST resistance?


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FLOW PRESSURE GRADIENTRESISTANCE


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As resistance decreases, flow will

As the pressure gradient increases, flow will

Which does the heart influence more: pressure

gradient or resistance?

Bl d P


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Blood Pressure

Why do all blood vessels have a BP?

Which vessel do we usually care about?

Where is systemic BP the highest?

Where is systemic BP the lowest?


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Arterial Blood Pressure Model


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What would happen to AP if the amount of blood

pumped into the arteries increased?

Thus, arterial pressure varies directly with


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What would happen to AP if the resistance in the

arterioles went up?



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What would happen to AP if there was more blood

in the entire system?


Systolic Blood Pressure


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Systolic Blood Pressure

Diastolic Blood Pressure


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Diastolic Blood Pressure


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P l


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What creates it?

How/Where do you measure it?

Whats its relationship to heart rate?

Pulse

Pulse Pressure


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Pulse Pressure

Change in arterial pressure caused by ventricular

systole.

Varies directly with

PP = SBPDBP.

Mean Arterial Pressure (MAP)


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Arterial BP fluctuates. Why?

MAP is the pressure driving blood flow.

MAP is a weighted average of SBP and DBP.



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MAP = DBP + SBP

MAP = DBP + PP


Capillary Blood Pressure


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Capillary Blood Pressure

Low BP.

Why is this good? (Think about the structure of a

capillary.)

Venous Blood Pressure


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Venous Blood Pressure

Even lower BP.

Very small gradient.

What is responsible for venous return?


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What is responsible for venous return?

Remaining force imparted by ventricular systole.

Gravity.

Skeletal muscle pump.

Respiratory pump.

Venomotor action.


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Skeletal Muscle Pump


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Skeletal Muscle Pump

Deep InspirationRespiratory Pump


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Thoracic volume will

Pressure in thoracic cavity will

Blood flow into thoracic veins and

towards the heart will

Deep InspirationRespiratory Pump

Pressure in thoracic veins will

Venomotor Tone


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Venomotor Tone

An increase in sympathetic activity causes:

NE release on the TM of medium/large veins to

Venous pressure to

Venous return to

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Blood Flow Images