Exercise 21

Blood Vessels & Circulation

Portland Community CollegeBI 232

Blood vessels• Arteries transport

blood away from the heart.

• Deliver blood to capillary beds where gas and nutrient exchange occurs.

• Veins transport blood toward the heart.

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Martinipg. 711

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Artery and VeinHistology

• Walls have 3 layers:• Tunica intima• Tunica media• Tunica externa

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Tunica Intima

• Is the innermost layer near the lumen• Includes:

• The endothelial lining• Connective tissue layer

• Internal Elastic Membrane: In arteries, is a thick layer of elastic fibers in the outer margin of the tunica intima

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Tunica Media

• Is the middle layer• Contains concentric sheets of smooth

muscle in loose connective tissue• Binds to inner and outer layers

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Tunica Externa (aka: Tunica Adventitia)• Is outer layer• Contains connective tissue sheath• Anchors vessel to adjacent tissues• In arteries:

• Contain collagen• Elastic fibers

• In veins:• Contain elastic fibers• Smooth muscle cells

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Arteries

• Carry blood away from the heart.• Pulmonary arteries: The pulmonary trunk

and its branches; leave the right ventricle of the heart and contain deoxygenated blood.

• Systemic arteries: The aorta and its branches; leave the left ventricle of the heart and contain oxygenated blood.

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Elastic Arteries• Also called conducting arteries, these are the

largest arteries• Tunica media has many elastic fibers and few

muscle cells• Elasticity evens out pulse force • Examples:

• Pulmonary trunk• Aorta• Common carotid arteries• Subclavian arteries• Common iliac arteries

10n = smooth muscle cellTA = tunica adventitia

TI = tunica intimaTM = tunica media

el = elastic fibersend = endothelial cells

Aorta

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Muscular Arteries

• Also called distribution arteries, are medium-sized (most arteries)

• Tunica media has many muscle cells• Examples:

• External carotid arteries• Brachial arteries• Femoral arteries

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Muscular Arteries

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Arterioles

• The smallest branches of arteries• Feed into capillaries• Have little or no tunica externa• Have thin or incomplete tunica media

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Arteriole

end = endothelial cell nucleus

n = smooth muscle nucleus

rbc = red blood cells

end = endothelial cell nucleusn = smooth muscle nucleusrbc = red blood cells

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Veins

• Carry blood to the heart• Are larger in diameter than arteries• Have thinner walls • Contain valves

• Folds of tunica intima that prevent blood from flowing backward

• Venules: The smallest veins that carry blood away from the capillaries

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Veins

• Medium-sized veins:• Thin tunica media and few smooth muscle cells• Tunica externa with longitudinal bundles of

elastic fibers• Large veins:

• Have all 3 tunica layers• Thick tunica externa• Thin tunica media

• Example: Inferior and Superior vena cava

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Venous Valve in Medium Vein

ad = adipose tissueTA = tunica adventitiaTM = tunica mediav = valve

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Large Vein

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Arteries Vs. Veins

• Arteries and veins run side-by-side• Arteries have thicker walls and higher

blood pressure• Collapsed artery has small, round lumen• Vein has a large, flat lumen

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Vein

Artery

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Capillaries• The smallest vessels • Structure: Simple squamous epithelium tube

• Lumen side has a thin basal lamina• No tunica media, No tunica externa

• Location of exchange between blood and interstitial fluid.• Gasses and chemicals diffuse across their walls

• Types: • Continuous• Fenestrated

• Sinusoids

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Continuous Capillaries• Have complete endothelial lining (most

common type of capillary)• Permit diffusion of:

• Water• Small solutes• Lipid-soluble materials

• Prevent diffusion of:• Blood cells• Plasma proteins

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Continuous Capillary

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Continuous Capillaries

Simple squamous epithelium

RBCBasal lamina

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Fenestrated Capillaries

• Have pores in endothelial lining• Permit rapid exchange of water and larger

solutes between plasma and interstitial fluid• Are found in:

• Choroid plexus• Endocrine organs• Kidneys• Intestinal tract

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Fenestrated Capillary

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FenestratedCapillary

Fenestrations

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Sinusoids

• Modified, extremely leaky, fenestrated capillaries

• Found in locales where large stuff needs to exit/enter the bloodstream.• Liver• Spleen• Bone marrow• Endocrine organs

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Sinusoid

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Hepatic Sinusoid

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Vasa Vasorum• “Vessels of Vessels”• Small arteries and

veins in the walls of large arteries and veins

• Supply cells of tunica media and tunica externa

Aorta

Vasa Vasorum

Activity 21.1

• View prepared slides of arteries and veins• Be able to ID layers under the microscope.

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Ascending Aorta

Aortic Arch

Right Coronary A.

Left Coronary A.

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AorticArch External carotid

Internal Carotid

R. Vertebral

Common Carotid

Brachiocephalic Trunk

R. Axillary a.

R.Subclavian a. L.Subclavian a.

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Brachiocephalic Trunk

Left Common Carotid

L..Subclavian

R.Subclavian

Right Common Carotid

Vertebral

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External carotid

Internal Carotid

Vertebral

Circle of Willis

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Axillary Artery

R. Axillary a.

Brachial a.

Radial a. Ulnar a.

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Circle of Willis

R. Vertebral L. Vertebral

Basilar

Internal Carotid (cut)Anterior cerebral

Anterior communicating

Middle cerebral

Posterior cerebral

Posterior communicating

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Middle cerebral

Posterior cerebral

Anterior cerebral

Internal Carotid

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AbdominalAorta Celiac Trunk

Superior Mesenteric

Gonadal

Renal A.

Inferior MesentericCommon Iliac

External IliacInternal Iliac

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Renal a.

Spleen

Splenic a.

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Abdominal Aorta

Celiac Trunk

Common HepaticLeft Gastric

Splenic

Inferior Mesenteric

Superior Mesenteric

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Thigh

External Iliac

Femoral

Deep Femoral

Anterior Posterior

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LowerLeg

Femoral

Popliteal

Anterior tibial

Posterior tibial

Fibular

Dorsalis Pedis

Fibular

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Petrosal sinus

Superior Sagittal sinus

Transverse SinusStraight sinus

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Superior Sagittal sinus

Petrosal sinus

Straight sinus

Cavernous sinus

Transverse sinus

Sigmoid sinus

Vertebral Vein

Internal Jugular

External Jugular

Subclavian vein

BrachiocephalicRightLeft

Superior Vena Cava

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Azygos Hemiazygos

BrachiocephalicRight Left Subclavian vein

Axillary vein

Cephalic vein

Brachial vein

Basilic vein

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Axillary vein Cephalic vein

Basilic veinBrachial vein

Median Cubital vein Radial vein

Ulnar vein

Basilic vein

Cephalic vein

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Hepatic veins

Renal veinInferior Vena Cava

Common iliac vein

External iliac vein

Internal iliac vein

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Femoral

Deep Femoral

Great Saphenous

Small Saphenous

Small Saphenous

Popliteal

Posterior Tibial

Fibular

Anterior Tibial

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Anterior Tibial

Small Saphenous

Great Saphenous

PoplitealSmall Saphenous

Femoral

Anterior Tibial

Posterior Tibial

Fibular

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Inferior Vena Cava

Hepatic veins

Hepatic Portal vein

Inferior Mesenteric

Superior Mesenteric

Splenic vein

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The End