Physiology Exam 3 Lecture 9B [The Vascular System and Blood Flow: Cabeza]

Most of your blood is in _____ circulation

systemic

mostly in the veinous side

Characteristics of systemic circulation

Operating pressure is high

Response to increase CO2 = Dilate

Resistance to flow = variable

Length of vessels = long

Vessel compliance = variable

Characteristics of pulmonary circulation

Operating pressure is low

Response to increase CO2 = Little effect

Resistance to flow = low

Length of vessels = short

Vessel compliance = very high

Both arteries and veins contain a tough outer layer called the

Tunica adventitia (connective tissue that holds everything together)

Arteries have a _____ muscle layer and Veins have a ____ muscle layer

Thick, thin

Muscle layer (Tunica media) is all

Circular smooth muscle

no longitudinal smooth muscle in Blood vessels

Elastic and white fibrous tissue

Gives elasticity to blood vessels allowing them to stretch

Innermost layer of blood vessels

Tunica intima (endothelium)

layer of cells

Anatomy difference between veins and arteries

veins have unidirectional valves (only in the majory veins)

Arteries do not have valves

No exchange of gases, nutrients, or wastes takes place at the

Major vessels.

Major vessels have their arterioles and capillaries to provide them with necessary blood

All exchange of gases, nutrients, and wastes takes place at the

Capillaries

The terminal arteriole is the

blood vessel leading up into the capillary

Only one cell thick (only the endothelium)

Blood enters the capillary bed through a structure called the _____ and then this structure spreads out into a bunch of capillaries

metarteriole

There are _____ that regulate if the capillary is open or closed

Sphincters

Blood enters the capillary through the arterial side goes through the capillary and then returns to the veinous side for flow

Yes, yes it does

In a closed capillary

Sphincters constrict

greatly reduced flow into capillaries

mainly goes through metarteriole to throughfare channel and then back into venous side

Capillaries do not have ______ muscle

smooth muscles

All capillaries are _____ cell thick, containing only the ____

one, endothelium

Being only one cell thick allows for

exchange of materials easier and faster

Conducting arteries are ______ and help maintain pressure

compliant

Vessel expands when you pump blood into it and then squeezes on the blood due to its

elastic properties

(its not contracting it is elastic)

Veins are _____ complaint than the arteries and operate at lower pressure

more

Because of the property of veins being more compliant than arteries is the reason why

blood is more on the venous side than artery side of the body

Veins operate under ___ pressure

low

Veins travel between

major muscle masses

as muscle contracts it squeezes veins

Veins are very compliant, have valves, and along with muscle contraction they help insure

unidirectional flow

SUMMARY: The pulmonary circulation has ___ of the blood, is extremely ____, is short, and operates at lower pressure

10%, compliant

SUMMARY: The systemic circulation has __ of the blood, is ______ in compliant, is long, and operates at higher pressures

90%, variable

SUMMARY: All blood vessels contain a

smooth muscle layer and a 1 cell thick endothelium

SUMMARY: Exchange of all materials takes place on at

Capillaries

SUMMARY: Artery compliance is important for

blood pressure

SUMMARY: Major veins have ________ to ensure flow towards the heart at low pressure

one way valves

Ohms Law for fluid flow

Q = Blood flow

Blood flow = driving pressure divided by the resistance

The bigger the driving pressure we get _____ blood flow

more

The higher the resistance

Blood flow goes down

The resistance for the flow of blood depends on the

blood vessel anatomy

Serial resistance

Rt > largest single resistance

total resistance is higher than the highest resistance of any given part. Because its additive

Parallel resistance

Rt < smallest single resistance

Total resistance is always lower than the lowest resistance of any given part

In the circulatory system most of the systems are

Parallel

Because we want low resistance

Circulatory system through the digestive tract going to the liver

Portal system

Branch of capillaries that reform and then reforms a whole bunch of different capillaries in another organ

Thus GI system has higher resistance due to this portal system

The renal system is also

A portal type system

Poiseuille's law

Relates how different factors relate to resistance

n = viscosity

r= radius

L= Length

ΔP = difference in pressure

π = 3.14

BREAKING DOWN POISEUILLE: Length (L)

The longer the length of a blood vessel the more resistance

BREAKING DOWN POISEUILLE: Viscosity (n)

The more viscous the higher resistance

NOTE:

Viscosity is how thick a liquid is. So it makes since that the thicker it is the more resistance

BREAKING DOWN POISEUILLE: radius (r)

The higher the r value the lower the resistance.

r is to the 4th power in the equation meaning that when you chance it it has a major effect on resistance.

NOTE:

If something is ever in the denominator it has an inverse relationship. Thus decrease r = increase Resistance

Poiseuille's law is important

because it is by regulating the diameter of the arterioles that we can have a large effect on blood flow through a given capillary. The state of the precapillary sphincters plays the major role in regulating blood flow through a capillary bed

The pulsatile blood pressure is maintained by the

major arteries because of their compliance and muscular layers

From the terminal arterioles all the way back to the heart pressure is

steadily falling with only about 20 mm/Hg of pressure driving blood back to the heart

The largest fall in blood pressure occurs at the

arterioles. Because these have the highest resistance. These are the major resistance vessels that help to maintain the general or systemic blood pressure

The most resistant vessels are the

Arterioles

Pulse pressure is

the difference in pressure experienced by the major arteries between systole and diastole:

Pp = Psys - Pdias

120 mmHg - 70mmHg = 50 mmHg

The mean arterial pressure

MAP = Pdias + 1/3 (Pp)

70 mmHg + 17 mmHg = 87 mmHg

As you get older your Blood vessels get

Harder

As vessels get stiffer they

are less compliant

Systolic pressure goes up

Disystolic pressure goes down

MAP =

CO * TPR (total peripheral resistance)

LaPlace's Law

Tension = Pressure x radius

Therefore, the larger a blood vessel is the more tension will be experienced on the wall of the vessel for the same pressure

Aneurisms occur in ______

larger vessels, never at capillary beds

Although capillaries are very small their combined

cross section is very large

Because of the large cross section of capillaries

blood flow through a capillary bed is slower than in the arteriole or venule associated with it

Blood is slowest through

capillaries

Why is blood slowest through capillaries

To allow for exchange

SUMMARY: Flow of blood follows Ohm's law such that flow is proportional to

pressure differences along the blood vessel and inversely proportional to the resistance of the blood vessel

SUMMARY: Overal resistance in one vessel is just the sum

of the resistance of the parts of the blood vessel

SUMMARY: Overall resistance to a vessel that splits into 2 vessels is the product of resistance of each vessel divided by the sum of the resistance. Thus

the resistance of such vessels is always less than the component resistance

SUMMARY: The resistance of a vessel is proportional to 1 over the radius raised to the 4th power. Because of this

small changes to the radius of a blood vessel leads to large changes in resistances and the flow of blood

SUMMARY: The pressure experienced by the walls of a blood vessel are proportional to the radius. Therefore

larger vessels have more tension on their walls and it is only larger vessels that experience the formation of aneurism

SUMMARY: Blood flow through the capillaries is the slowest because

of their large cross sectional area

The net filtration pressure for fluid inside and outside a capillary is

NFP = Pressure (out) - Pressure (in)

Hydrostatic pressure is

Always pushing out (pushing pressure)

The pressure that the heart is generating

Oncotic pressure

Pulling force

A form of osmotic pressure (oncotic pressure is osmotic pressure due to proteins)

You can think of hydrostatic pressures as the pressure water itself exerts when

squeezed

Oncotic pressures are

the attraction of water by dissolved proteins

Hydrostatic pressure always ___ water away, while oncotic pressure always ___ water toward them

Push, Pull

Starling-Landis Equilibrium is

Because the capillary hydrostatic pressure is changing as the blood moves through a capillary we need to calculate the NFR at both the

arteriole side of the capillary and at the venule side of the capillary

Measuring both sides of the capillary bed gives us an idea about how the arteriole and venule sides behave and whether there is

an overall net pressure driving fluid in or out of the capillary

At most capillaries there is a net pressure of

1-2 mmHg driving fluid out into the interstitial space

NFR =

K (Hout + Oncotic out) - ( Hin + Oncotic in)

K is a factor determined by how leaky the capillary is

Since there is normally a net pressure driving fluid out of the capillaries we must do something with this fluid or it will

build up in the tissues and there will be a decrease in blood volume occurring at most capillaries being perfused with blood

SUMMARY: Net filtration is determined by pressures driving

fluid out of a capillary minus pressures driving fluid into the capillary

SUMMARY: The rate of Net filtration is determined by

the leakiness of the capillary (K)

SUMMARY: Hydrostatic pressures

push fluid away

SUMMARY: Oncotic pressures

Pull fluid towards them

SUMMARY: At most capillaries there is a net pressure of

1-2 mm/Hg driving fluid out

Lymphatic vessels are found

throughout the tissue

Lymphatic vessels function by

having button-like junctions that act as pores

Valves that allow lymph flow to go in one direction

Usually run next to veins so that muscles can help pump the fluid back to the heart

The lymphatic vessels connect to

nodes which are part of the immune system

The lymphatic vessels drain their fluid

into the subclavian trunks of the venous system so that the fluid can return to the heart and the circulation

SUMMARY: Lymphatic vessels have blind ends with ______ valves that allow fluid into the vessels

button

SUMMARY: Lymphatic vessels have valves and run along

side veins to help move fluid towards the heart

SUMMARY: The fluid of the lymphatic system re-enters the circulation at

the subclavian veins

KEY TERM: Pulmonary circulation

blood circulation from the right heart to the lungs

KEY TERM: Systemic circulation

blood circulation from the left heart to every part of the body except the lungs

KEY TERM: Arterioles

major resistance vessels of the circulatory system which account for the overall blood pressure

KEY TERM: Endothelium

the one cell thick inner lining of all blood vessels which also form the capillaries

KEY TERM: Precapillary sphincters

the annular smooth muscle cells that surround the precapillary arterioles and regulate blood flow into the capillary

KEY TERM: Vascular shunt

The vessel through a capillary bed that allows some blood to flow through the bed even when the capillary bed is closed

KEY TERM: Compliance

the ability a blood vessel to stretch and take on a larger volume of blood at a given change in pressure

KEY TERM: Muscle pumps

a structural feature of veins and lymphatic vessels that travel between major muscle groups such as that when the muscle contract they squeeze the vessels and move fluid towards the heart due to the presence of of valves on the vessel

KEY TERM: Ohm's law

The relation between pressure, resistance, and flow.

Flow = Pressure difference/vascular resistance