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Chapter 19 - Part I

The Cardiovascular System:

Blood Vessels

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The Right Hose for the Job

Commercial hoses are a lot like blood vessels, they come in:

different diameters, lengths, materials (e.g. rubber)

basic vinyl p radial cord reinforced

Types:

sprinkler hose - flat, ground surface,fine spray along length of hose

car radiator hose - durable, large volume delivery in short circuit

refrigerator icemaker hose - small, reinforced foropressure

fire hose - long, flexible, high volume delivery underopressure

soaker (drip) hose - round, buried, leaks uniformly along length

of hose at a desired rateSource: http://farm3.static.flickr.com/2209/2414305343_1849e1cb52.jpg?v=0

Hose (aneurysm) bubble

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Blood Vessels: Overview

Perfusion - fluid passage through vessels of a organ

blood is carried in a closed systemby a series of vessels

beginning & ending at heart

Vessel types:

1. arteries - carry blood away from heart

diverge/branch into smaller vessels

2. capillaries - gas, nutrients, & waste exchange

blood > interstitial spaces > adjacent tissue cells

3. veins - carry blood towards heart

join/converge into larger vessels

Source: http://www.merck.com/media/mmhe2/figures/MMHE_03_020_03_eps.gif

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Interconnections

All body fluids derived from blood plasma (e.g. CSF,

interstitial fluid) are returned to blood circulation

Process:

1 plasma fluid - forced out of

blood capillaries becominginterstitial fluid

2 interstitial fluid - enters lymphatic

capillaries to become lymph

3 lymphatic vessels - return lymph

fluid to venous circulation

3

2

1

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Blood Vessels: Generalized Structure

1. tunica interna

2. tunica media

3. tunica externa

Arteries & veins have three different layers (tunics)

Capillaries - primarily

endothelium, some with

sparsebasal lamina

Lumen - central opening in all blood vessels

surrounded by tunics in arteries & veins

determines vessel internal diameter (ID) &perfusion rate

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Tunics

Tunica intima (tunica interna):

1. endothelial layer- lines lumen of all blood vessels

smooth uninterrupted inner surface allows q friction (o flow)

2. subendothelial layer-basement membrane & connective tissue

supporting endothelium in vessels > 1 mm

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Tunics (cont)

Tunica media (bulk of vessel):

1. lamina (elastic fiber) layer

2. smooth muscle layer

regulated by sympathetic

nervous system vasomotorfibers & hormones

controls lumen ID

1. vasodilation - smooth muscle relaxation

2. vasoconstriction - smooth muscle contraction

Normal VasoconstrictedVasodilated

Diameter changes

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Tunics (cont)

Tunica externa (tunica adventitia):

1. loose collagen fibers - protect,

reinforce, & anchor vessels

2. nerves - control smooth muscle

3. elastic fibers (larger veins)

4. lymphatic vessels

vasa vasorum (vessel-of-vessels) - tiny system of vessels

found in larger veins & arteries

feeds external layers

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Blood Vessels

Types & route:

elastic arteries (largest)

muscular arteries (large)

arteriolescapillaries

venules

veins (larger)

vena cavae (largest)

To tissues from heart

From tissues to heart

Blood exchange w/ tissues

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Elastic (Conducting) Arteries

Conducting arteries - large ID,

thick-walled, found near heart

aorta & major aortic branches

large lumen allows low-resistance

blood conduction

elastin is found in all tunics

withstands & smoothes out large

blood pressure fluctuations

1. allows forarterial expansion &

subsequent recoil (avoids bursting)

2. permits continuous blood flow

throughout body

D + T = Total size

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Muscular (Distributing) Arteries

Muscular arteries - size varies,

distal to elastic arteries

thick tunica media with more

smooth muscle & less elastic

tissue

active in vasoconstriction

less distension than elastic arteries

deliversblood to each body organ

makes up most of named arteries

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Arterioles

Arterioles - smallest arteries

leading into capillary beds larger ones have all 3 tunics

mostly smooth muscle layer aroundendothelium

controls capillary bed blood flow viavasodilatation & vasoconstriction

adjusts local blood flow respondingto:

1. neural stimulation

2.blood hormone changes

3. chemical changes mm = 1 x 10-3mQm (micron) = 1 x 10-6 m