Veins arteries online

Copyright © 2011 Pearson Education, Inc.

Overview

Structure:

Arteries

Veins

Capillaries


Blood Vessels

• Transport blood

• Arteries: carry blood away from the heart

• Usually ↑ O2

• Pulmonary circulation exception

• Veins: carry blood toward the heart

• Usually ↓ O2

• Capillaries: contact tissue directly

Copyright © 2011 Pearson Education, Inc. Figure 18.2

Large veins

Arteriovenousanastomosis

Postcapillaryvenule

SinusoidArterioles

Muscular arteries

Elastic arteries

Small veins

Capillaries(exchange vessels)

sphincter

Venous system Arterial systemHeart


BLOOD VESSEL STRUCTURE

Tunics (extera, media, intima)


Structure of Blood Vessel Walls

• Arteries and veins

1. Tunica intima

2. Tunica media

3. Tunica externa

• Lumen

• Central space, contains blood

• Capillaries

• Endothelium with basal layer

Copyright © 2011 Pearson Education, Inc. Figure 18.1b

Tunica media(smooth muscle andelastic fibers)

Tunica externa(collagen fibers)

LumenArtery

LumenVein

Internal elastic lamina

External elastic lamina

Valve

(b)

Endothelial cellsBasement membrane

Capillarynetwork

Capillary

Tunica intima• Endothelium• Subendothelial layer


Tunics

• Tunica intima

• Endothelium

• lines the lumen

• Subentothelial layer

• In larger vessels (>1 mm)

EndotheliumSubendothelial layer


Tunics

• Tunica media

• Smooth muscle

• Controls:

• Vasoconstriction

• Vasodilation

Smooth muscle


Tunics

• Tunica externa

• Outer most layer

• Collagen fibers reinforce

• Large vessels have vasa vasorum

• “vessels to the vessels”

Tunica externa


TYPES OF ARTERIES

Elastic, Muscular and Arterioles


Elastic (Conducting) Arteries

• Largest thick-walled arteries

• Aorta / major branches

• elastin in all tunics

• Blood directly from heart

• Resist high pressure

• Large volume

• Large lumen = low-resistance


Muscular (Distributing) Arteries

• Distal to elastic arteries

• Deliver blood to organs

• Have thick tunica media

• smooth muscle

• Vasoconstriction

• Vasodilation


Arterioles

• Smallest arteries

• Lead to capillary beds

• Control of flow w/

• vasodilation and vasoconstriction

Copyright © 2011 Pearson Education, Inc. Table 18.1 (1 of 2)


Capillaries

• Smallest blood vessels

• thin tunica intima

• one cell thick

• Only one RBC wide

• Pericytes support and control permeability


CAPILLARIES


Capillaries

• Location-

• all tissues except for:

• cartilage, epithelia, cornea and lens of eye

• Functions-

• Exchange:

• gases, nutrients, wastes, hormones, etc.

Copyright © 2011 Pearson Education, Inc. Figure 18.2

Large veins(capacitancevessels)

Arteriovenousanastomosis

Postcapillaryvenule

SinusoidArterioles

Muscular arteries

Elastic arteries

Small veins(capacitancevessels)

Capillaries(exchange vessels)

Venous system Arterial systemHeart


Capillaries

• Three structural types

1. Continuous capillaries

2. Fenestrated capillaries

3. Sinusoidal capillaries


Continuous Capillaries

• Location:

• skin & muscles

• Cells connected with tight junctions

• Clefts allow passage

• Blood-brain barrier

• ↑ Tight junctions

• Limits passage

Copyright © 2011 Pearson Education, Inc. Figure 18.3a

Red bloodcell in lumen

IntercellularcleftEndothelialcell

Endothelialnucleus

Tight junction Pinocytoticvesicles

Pericyte

Basementmembrane

(a) Continuous capillary. Least permeable, and most common (e.g., skin, muscle).


Fenestrated Capillaries

• Endothelial cells contain pores “fenestrations”

• Function:

• Absorption / Filtration

• Location:

• small intestines, endocrine glands, and kidneys

Copyright © 2011 Pearson Education, Inc. Figure 18.3b


Intercellularcleft

Fenestrations(pores)

Endothelialcell

EndothelialnucleusBasement membrane

Tight junction

Pinocytoticvesicles

(b) Fenestrated capillary. Large fenestrations (pores) increase permeability. Occurs in special locations (e.g., kidney, small intestine).


Sinusoidal Capillaries

• Larger intercellular clefts

• Function:

• Passage of large molecules and blood cells

• Location:

• liver, bone marrow, spleen

Copyright © 2011 Pearson Education, Inc. Figure 18.3c

Nucleus ofendothelialcell


Endothelialcell

Tight junction

Incompletebasementmembrane

Largeintercellularcleft

(c) Sinusoidal capillary. Most permeable. Occurs in special locations (e.g., liver, bone marrow, spleen).


Capillary Beds

• Networks connecting arterioles and venules

• Sphincters control flow into capillaries


Venules & Anastomosis

• Venules (smallest vein)

• Form from capillary beds

• “Postcapillary venules”

• Anastomosis

• Alternative connections between arteries and veins


Veins

• Return blood flow to heart

• Converging venules

• larger lumens w/ thin walls

• ↓ blood pressure

• Blood reservoirs

• contain ~65% of blood supply


Veins

• Adaptations to ensure blood return

1. Low resistance

• Large lumen

2. Valves

• Prevent backflow

• in limbs

• Venous sinuses: flattened veins

• Ex. Coronary sinus

Copyright © 2011 Pearson Education, Inc. Figure 18.1a

Artery

Vein

(a)


Arteries Veins

Delivery Blood pumped into single systemic artery—the aorta

Blood returns via superior and interior venae cavae and the coronary sinus

Location Deep, and protected by tissues Both deep and superficial

Pathways Fairly distinct Numerous interconnections

Supply/drainage Predictable supply Usually similar to arteries, except dural sinuses and hepatic portal circulation

Differences Between Arteries and Veins

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Veins arteries online

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