ANP 2 Ch 19 - Blood Vessels

Blood vessels

Delivery system of dynamic structures that

begins and ends at heart

Arteries

carry blood away from heart, mostly oxygenated blood

- Pulmonary arteries

- Umbilical vessels of fetus

What arteries are the exceptions that do not carry oxygenated blood?

Capillaries

contact tissue cells; directly serve

cellular needs (connect arteries to veins)

Veins

carry blood toward heart

Lumen

Central blood-containing space

1. Tuna intima

2. Tuna media

3. Tunica externa

What are the three wall layers in arteries and veins?

Tuna intima

Blood vessel wall made of endothelium and is in contact with blood

Endothelium

Capillaries are made up of _______________ with sparse basal lamina

Elasticity

__________- of arteries determines diastolic pressure

Capillary bed

interwoven network of capillaries between arterioles and venules

1. elastic arteries

2. muscular arteries

3. arterioles

3 types of arteries

Elastic Arteries

Large thick-walled arteries with elastin in tunics

Aorta and its major branches

What is an example of an elastic artery?

Muscular arteries

Arteries that deliver blood to body organs

- thick tunica media, more smooth muscle

They have a large lumen

Why do elastic arteries have very low resistance?

Vasoconstriction

Muscular arteries are especially active in ________________

Arterioles

The smallest arteries that lead to capillary beds

Capillary beds

Arterioles control flow into ___________________ by vasodilation & vasoconstriction

only one

How many RBCs can pass through a capillary's diameter at once?

cartilage, epithelia, cornea and lens of eye

Only 4 tissues in the body that do not have capillaries

Gases, nutrients, wastes, hormones

A large function of capillaries is to exchange what between blood and interstitial fluid?

1. Continuous capillaries

2. Fenestrated capillaries

3. Sinusoid capillaries (sinusoids)

What are the 3 structural types of capillaries?

Continuous capillaries

Capillaries that are abundant in skin and muscles

Tight junctions

Continuous capillaries have _____________ to connect endothelial cells

Intercellular clefts

allow passage of fluids and small solutes into continuous capillaries

Continuous capillaries

Form the blood-brian barrier

Tight junctions complete & there are no lefts

How are continuous capillaries in the brain unique?

Fenestrated Capillaries

Capillaries that are more permeable than continuous capillaries and function in absorption or filtrate formation

Fenestrations

Pores/windows on some endothelial cells of fenestrated capillaries

Small intestines & kidneys

Where are fenestrated capillaries likely to be found?

Sinusoid capillaries

Very permeable capillaries that have few tight junctions, larger intercellular clefts, fenestrations, large lumens, and an incomplete basement membrane

Slowly

Does blood flow slowly or fast though sinusoid capillaries?

Where new cells enter circulation

-liver

-bone marrow

-spleen

Where are sinusoid capillaries usually found?

1. Microcirculation

2. Vascular shunt

3. Precapillary sphincters

4. True capillaries

What are the 4 main parts of a capillary bed?

Capillary beds

Pathways between a terminal arteriole and a post capillary venue

Microcirculation

Interwoven networks of capillaries between arterioles and venules

Vascular shunt

central

pathway (thoroughfare

channel)- Directly connects terminal

arteriole and postcapillary venule

Precapillary sphincters

regulate blood flow into true capillaries - decide where the blood flows to

True capillaries

Branch off metarteriole in a capillary bed

No

Does every organ get the same blood supply all the time?

1. Venules

2. Veins

What are the 2 vessel types of the venous system?

Venules

Vessels formed when capillary beds unite

Pericytes

Venules are made up of endothelium and a few _______________________

Veins

Vessels formed when venules converge

Veins have thinner walls and larger lumens

How are veins different than their corresponding arteries?

Lower than arteries

Is the blood pressure in veins lower or higher than the blood pressure in arteries?

Veins

_________ absorb volume without affecting blood pressure

capacitance vessels

the term for veins because they have the ability to stretch. they have a large diameter and are more distensible to hold more blood. this reduces stress on the heart.

65% of blood supply

How much of the blood supply do veins contain?

resistance

Arteries are _____________ vessels because they squeeze

And create resistance to flow

1. Large diameter lumens

2. Venous valves

What adaptations do veins have to ensure blood returns to heart, despite low blood pressure?

Large-diameter lumens

Part of veins that offer little resistance to blood flow to ensure blood goes back to the heart

Venous valves

Part of veins that prevent backflow of blood to make sure it reaches the heart

Blood flow

Volume of blood flowing through vessel, organ, or entire circulation in given period

ml/min

Blood flow is measured in ______________, similar to cardiac output

When the body is at rest

When is blood flow relatively constant?

Blood flow is based on needs

Why does blood flow vary widely between individual organs?

Blood pressure (BP)

Force per unit area exerted on wall of blood

vessel by blood

mm Hg

What unit is blood pressure expressed in?

systemic arterial BP

Measure of BP in large arteries near the heart

(Blood) pressure gradient

Provides a driving force that keeps blood moving from higher to lower areas

It's at the same height as our heart, gravity

Why do we use brachial artery for BP?

Resistance (peripheral resistance)

opposition to flow; the amount of friction blood

encounters with vessel walls, generally in peripheral (systemic) circulation

- Blood viscosity

- Total blood vessel length

- Blood vessel diameter

What are the three important sources of resistance in peripheral circulation?

Blood viscosity & blood vessel length

What two factors that affect peripheral resistance remain relatively constant?

Blood viscosity

The "stickiness" of blood due to formed elements and plasma proteins - flowiness

Increased viscosity = increased resistance

How does increased viscosity of blood affect resistance?

Dehydration

What can cause increased blood viscosity?

Blood vessel length

The factor least likely to change that affects resistance

Longer vessel = greater resistance encountered

How does Blood vessel length affect resistance?

3 miles

If you add 1 lb of fat, how much more blood vessel length do you add?

increased weight = increased blood

vessel length = increased resistance = slower blood flow

How does gaining weight affect resistance and blood flow?

Blood vessel diameter

Factor that has the greatest influence on resistance - frequent changes alter peripheral

resistance

Vasoconstriction increases resistance

How does vasoconstriction affect resistance?

Vasodilation decreases resistance

How does vasodilation affect resistance?

atherosclerosis

Fatty plaque buildup from what disease will increase resistance?

F is directly proportional to ∆P

How is blood flow (F) related to blood pressure gradient (∆P)?

blood flow speeds up

If blood pressure gradient (∆P) increases, what happens to blood flow?

Blood flow inversely proportional to peripheral resistance

How is blood flow (F) related to peripheral resistance (R)?

blood flow decreases

If resistance (R) increases, what happens to blood flow?

F = ∆P/R

What is the formula for blood flow?

R more important; easily changed by altering blood vessel diameter

What factor is more important at determining blood flow, ∆P or R? Why?

Pumping action of heart

Generates blood flow in the body

When blood flow is opposed by resistance

When does pressure of blood result in the body?

Systemic pressure

- Is highest in the aorta

- Declines throughout the length of the pathway

0 mm Hg

What is systemic pressure in the right atrium?

in arterioles

- Point at which arteries are dividing, takes awhile to get through

Where does the steepest drop in systemic blood pressure occur in the body? Why here?

arterial blood pressure

Measure of the pressure exerted by the blood as it flows through the arteries close to the heart

– Elasticity (compliance or distensibility)

– Volume of blood forced into them at any time

What two factors of arteries near the heart effects arterial blood pressure?

Comes in intervals

What does it mean that arterial blood pressure near the heart is pulsatile?

Systolic pressure

pressure exerted in aorta during ventricular contraction

120 mm Hg

Average Systolic pressure in an adult

Diastolic pressure

lowest level of aortic pressure (when ventricles are relaxed, reflects the recoil of aorta)

Pulse pressure

difference between systolic and diastolic pressure

Mean arterial pressure (MAP)

pressure that propels blood to tissues

Decline

Do Pulse pressure and MAP both increase or decline with

increasing distance from heart?

MAP = diastolic pressure + 1/3 pulse pressure

What is the formula for mean arterial pressure (MAP)?

- Blood Pressure: 120/80 mmHg

•PP = SP - DP = 40 mmHg •

MAP = 80 + (40)/3

= 80 + 13.33= 93.33 mmHg

What is a typical MAP if you have a blood pressure of 120/80 mmHg?

from 17 to 35 mm Hg

What is the range of capillary blood pressure?