Exercise 21

Blood Vessels & Circulation

Portland Community CollegeBI 232

Blood vessels

• Conduits that carry oxygen and nutrients to cells and remove wastes

• 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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General Circulatory Patterns

• Two main circuits:• Pulmonary circulation: Blood goes from the heart to

the lungs and returns to the heart. The pulmonary trunk and its branches; leave the right ventricle of the heart and contain deoxygenated blood.

• Systemic Circulation: Blood goes from the heart to rest of the body. The aorta and its branches; leave the left ventricle of the heart and contain oxygenated blood.

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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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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

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n = smooth muscle cellTA = tunica adventitia

TI = tunica intimaTM = tunica media

el = elastic fibersend = endothelial cells

Aorta

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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

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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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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

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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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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

Descending aorta

• Thoracic aorta: above the diaphragm• Includes the intercostal

arteries which run between the ribs

• Abdominal aorta: below the diaphragm

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Axillary Artery

R. Axillary a.

Brachial a.

Radial a. Ulnar a.

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External carotid

Internal Carotid

Vertebral

Circle of Willis

Arteries of the head and neck

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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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Abdominal Aorta

Celiac Trunk

Common HepaticLeft Gastric

Splenic

Inferior Mesenteric

Superior Mesenteric

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Renal a.

Spleen

Splenic a.

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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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Axillary vein Cephalic vein

Basilic veinBrachial vein

Median Cubital vein Radial vein

Ulnar vein

Basilic vein

Cephalic vein

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Azygos Hemiazygos

Brachiocephalic

Right Left Subclavian vein

Axillary vein

Cephalic vein

Brachial vein

Basilic vein

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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

Brachiocephalic

RightLeft

Superior Vena Cava

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Anterior Tibial

Small Saphenous

Great Saphenous

Popliteal

Small Saphenous

Femoral

Anterior Tibial

Posterior Tibial

Fibular

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Femoral

Deep Femoral

Great Saphenous

Small Saphenous

Small Saphenous

Popliteal

Posterior Tibial

Fibular

Anterior Tibial

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Hepatic veins

Renal veinInferior Vena Cava

Common iliac vein

External iliac vein

Internal iliac vein

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Inferior Vena Cava

Hepatic veins

Hepatic Portal vein

Inferior Mesenteric

Superior Mesenteric

Splenic vein

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Hepatic Portal Circulation

• Veins that flow into the liver before returning to the heart

• Blood from digestive organs and spleen travel to capillaries of the liver.

• The liver processes the blood before sending it through the hepatic vein.

• Blood then travels to the inferior Vena Cava

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Thoracic Veins

• Intercostal veins which drain the intercostal muscles

• Azygos and hemiazygos veins which drain blood from the thoracic region

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Fetal Circulation

• Lungs of fetus are non functional.

• Oxygen and nutrients move from the maternal side of the placenta to the fetal bloodstream and CO2 and wastes moves from the fetal blood to the placenta

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Fetal Circulation

• Blood flow• From the umbilical

cord blood travels through the ductus venosus which shunts the blood to the inferior vena cava

• From the VC blood travels to the right atrium of the heart

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Fetal Circulation

• Blood can then move either to the right ventricle or through a hole in the right atrium called the foramen ovale (bypass route)

• Blood in the right ventricle moves into the pulmonary trunk where another shunt vessel, the ductus arteriosus carries blood to the aortic arch, bypassing the lungs.

• Closing to the foramen ovale leaves the fossa ovalis which we learned about in the heart lab.

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Blood Pressure• Maintenance of bp is important

for the health of the heart and proper functioning of various organs

• The force exerted by blood on the walls of blood vessels.

• A function of the pumping action of the heart and the resistance to flow as blood moves through the blood vessels.

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Blood Pressure

• In large elastic arteries, the BP fluctuates between a max. and min. value

• Systolic pressure is the maximum pressure exerted on bv walls.

• Diastolic pressure is the minimum level

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Blood Pressure

• Measured in units called millimeters of mercury (mmHg)

• If the pressure in a bv is 95mm Hg, it means that the force exerted by the blood will cause a column of mercury to rise 95mm

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Blood Pressure Cuffs

• BP cuffs come in different sizes.

• Be sure to choose the one that is appropriate for the patient

Large Adult

Infant

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Measuring Blood Pressure

• Most cuffs are marked with an O or an arrow. This should be placed near the artery.

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Measuring Blood Pressure

• Place the BP cuff snugly on the patient's arm.

• Check to make sure you have found the artery.

• Line the mark on the cuff up with the artery

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Measuring Blood Pressure

• Stethoscope: Note how the ear pieces slant slightly in one direction.

• Make sure the ear pieces on the stethoscope are point away from you when you put them on.

• Place stethoscope on the artery, tucked slightly under the cuff

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Measuring Blood Pressure

• The cuff should be placed at the level of the heart.

• The patients arm (or leg) should be completely relaxed.• Resting on the

table or in their lab is helpful

WRONG TECHNIQUE

CORRECT TECHNIQUE

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Inflate the Cuff

• A Grasp the bulb so that your thumb can easily access the valve.

• Turn the valve to the right to tighten it and pump up the cuff, turn it to the left to loosen it and deflate the cuff.

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Measuring Blood Pressure

• Pump up the cuff until the sphygmomanometer reads 180 to 200.

• Loosen the valve to let a little of the air out. • Listen for the first heartbeat, that is the top

number (systolic BP)• Continue to listen until there are no more

heartbeats. The last beat you hear is the bottom number (diastolic BP)

• Let the air all the way out and remove the cuff.

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Video Demonstration for Measuring Blood Pressure

• http://www.uams.edu/csc/programs/orientation/bloodPressure/TakingBP1.mov

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Normal Blood Pressure• Reference:

• August 2004, National Heart Lung and Blood Institute – Diseases and Conditions Index

• http://www.nhlbi.nih.gov/health/dci/Diseases/Hbp/HBP_WhatIs.html

• For adults 18 and older who: • Are not on medicine for high blood pressure

• Are not having a short-term serious illness

• Do not have other conditions such as diabetes and kidney disease

• Systolic BP: Less than 120• Diastolic BP: Less than 80

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Pre-Hypertension

• Systolic BP: between 120-139• Diastolic BP: between 80-89

• Examples: 118/82, 128/89, or 130/86

• If your blood pressure is in the pre-hypertension range, it is more likely that you will end up with high blood pressure unless you take action to prevent it.

• Note: When systolic and diastolic blood pressures fall into different categories, the higher category should be used to classify blood pressure level.

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Hypertension

• Stage 1

• Systolic BP: between 140-159

• Diastolic BP: between 90-99

• Stage 2

• Systolic BP: 160 or higher

• Diastolic BP: 100 or higher

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Hypotension

• Hypotension is a subnormal arterial pressure. • There is not enough pressure to adequately perfuse

the tissues. • There is usually a mean arterial pressure (MAP)

below 60 mmHg. • MAP= diastolic + 1/3(systolic-diastolic)

Example: BP= 120/70 MAP= 70 + 1/3(120-70)= 86.6

• People who are chronically hypertensive may feel symptoms of hypotension if their mean arterial pressure drops by 40 mmHg, even if the absolute value is still over 60.

Pulse

• The rhythmic expansion and recoil of the arteries is known as the pulse.

• Can be found in various locations

• Diminish in smaller arteries and are absent in capillaries and veins

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Pulse

Carotid Pulse

Radial Pulse

Brachial Pulse

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Pulse

Dorsalis Pedis Pulse

Posterior Tibial Pulse

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The End