Chapter 21 – Blood Vessels

Objectives Distinguish among the types of blood vessels based on their structure and function, and

describe how and where fluid and dissolved materials enter and leave the cardiovascular system.

Explain the mechanisms that regulate blood flow through vessels, describe the factors that influence blood pressure, and discuss the mechanisms that regulate movement of fluids between capillaries and interstitial spaces.

Explain the cardiovascular system’s homeostatic response to vessels and hemorrhaging, and identify the principal blood vessels and functional characteristics of the special circulation to the brain, heart, and lungs.

Describe the three general functional patterns seen in the pulmonary and systemic circuits of the cardiovascular system.

Identify the major arteries and veins of the pulmonary circuit. Identify the major arteries and veins of the systemic circuit. Identify the differences between fetal and adult circulation patterns, and describe the

changes in the patterns of blood flow that occur at birth. Discuss the effects of aging on the cardiovascular system. Give examples of interactions between the cardiovascular system and each of the organ

systems.

Structure of WallsComposed of 3 layers (tunics):

Tunica intimao In intimate contact

with the lumen Tunica media

o Vasoconstriction Tunica adventitia

o Composed of collagen fibers

Differences in Walls

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Arterial System Arteries transport blood from the heart Heart (blood not always oxygenated, e.g., pulm.

a.) Elastic arteries

o Thick-walled, near heart, internal elastic layer

Muscular arterieso Distributing, thickest media

Arterioleso Tunica-single layer smooth muscle

Capillaries Walls –

o tunica intima only Types

o Continuouso Fenestratedo Sinusoidal

Form capillary beds

Pathway--70,000 Miles Left ventricle Arteries Arterioles Capillaries Venules Veins Right atrium

Venous System Blood carried to the heart Not always deoxygenateded, eg. pulmonary

vein Venules

o Formed when capillaries uniteo Postcapillary venules

Veins Walls thinner and lumens larger

than those of arteries Venous valves

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Valves in the Venous System

Varicose Veins Veins become dilated due to incompetent

valves (blood pools) Factors:

o Heredityo Obesityo Pregnancy

Varicosities of the anal canal = hemorrhoids

AtherosclerosisAorta and coronary arteries most affected1. Damage to intima (chemicals, virus, stress)2. Injured tissue releases growth factors3. Sequesters and oxidizes LDLs4. Attracts monocytes to the area5. Monocytes migrate beneath intima6. Monocytes → macrophages → foam cells7. Other molecules congregate → plaques

Overview of Cardiovascular PhysiologyPressure in Capillary

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Fetal Circulation

Cardiovascular Adaptation Vascular Supply to Special Regions

o Through organs with separate mechanisms to control blood flow Brain Heart Lungs

Cardiovascular Adaptation Blood Flow to the Brain

o Is top priorityo Brain has high oxygen demando When peripheral vessels constrict, cerebral vessels dilate, normalizing blood flow

Cardiovascular Adaptation Stroke

o Also called cerebrovascular accident (CVA)o Blockage or rupture in a cerebral artery

Hemorrhagic stroke

Ischemic stroke

o Stops blood flow

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Cardiovascular Adaptationo Blood Flow to the Heart

o Through coronary arteries o Oxygen demand increases with activityo Lactic acid and low O2 levelso Dilate coronary vesselso Increase coronary blood flowo Epinephrine

Dilates coronary vessels Increases heart rate Strengthens contractions

Cardiovascular Adaptationo Heart Attack

o A blockage of coronary blood flowo Can cause

Angina (chest pain) Tissue damage Heart failure Death

Cardiovascular Adaptationo Blood Flow to the Lungs

o Regulated by O2 levels in alveoli High O2 content

Vessels dilate Low O2 content

Vessels constrict

The Pulmonary Circuito Deoxygenated blood arrives at heart from systemic circuit:

o Passes through right atrium and right ventricleo Enters pulmonary trunk

o At the lungs:o CO2 is removedo O2 is added

o Oxygenated blood:o Returns to the heart o Is distributed to systemic circuit

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The Pulmonary Circuito Pulmonary Vessels

o Pulmonary arterieso Carry deoxygenated blood

Pulmonary trunk: branches to left and

right pulmonary arteries Pulmonary arteries:

branch into pulmonary arterioles

Pulmonary arterioles: branch into capillary

networks that surround alveoli

The Pulmonary Circuito Pulmonary Vessels

o Pulmonary veinso Carry oxygenated blood

Capillary networks around alveoli:

join to form venules Venules:

join to form four pulmonary veins Pulmonary veins:

empty into left atrium

The Systemic Circuito Contains 84% of blood volume

o Supplies entire bodyo Except for pulmonary circuit

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The Systemic CircuitSystemic Arteries

Blood moves from left ventricleo Into ascending aorta

Coronary arterieso Branch from aortic sinus

The Systemic Circuit The Aorta

o The ascending aorta Rises from the left ventricle Curves to form aortic arch

Turns downward to become descending aorta

The Systemic CircuitThe Systemic Circuit

Branches of the Aortic Archo Deliver blood to head and neck

Brachiocephalic trunk Left common carotid artery Left subclavian artery

The Systemic Circuit The Subclavian Arteries

o Leaving the thoracic cavity Become axillary artery in arm And brachial artery distally

The Systemic Circuit

The Brachial Arteryo Divides at coronoid fossa of humerus

Into radial artery and ulnar artery: fuse at wrist to form:

o superficial and deep palmar arches

o which supply digital arteries

The Sy

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stemic Circuit The Common Carotid Arteries

o Each common carotid divides into External carotid artery - supplies blood

to structures of the neck, lower jaw, and face

Internal carotid artery - enters skull and delivers blood to brain

The Sys

temic CircuitThe Systemic Circuit The Descending Aorta

o Thoracic aorta o Abdominal aorta

The Systemic CircuitThe Systemic Circuit

Abdominal Aorta Divides at terminal segment of the aorta into:

o Left common iliac arteryo Right common iliac arteryo Unpaired branches:

Celiac trunk Splenic artery Gastric artery Hepatic artery Superior mesenteric artery Inferior mesenteric artery

o Paired branches: Renal arteries Gonadal arteries

The Sys

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temic Circuit Arteries of the Pelvis and Lower Limbs

o Femoral artery deep femoral artery Becomes popliteal artery Posterior to knee

Branches to form:o posterior and anterior tibial

arterieso posterior gives rise to fibular

artery

Th

e Systemic CircuitSystemic Veins

Complementary Arteries and Veinso Run side by sideo Branching patterns of peripheral veins are

more variable In neck and limbs

o One set of arteries (deep)o Two sets of veins (one deep, one

superficial) Venous system controls body temperature

The Systemic Circuitmic Circuit The Superior Vena Cava (SVC)

o Receives blood from the tissues and organs of

Head Neck

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Chest Shoulders Upper limbs

The Systemic Circuit Superficial Veins of the Head

o Converge to formo Temporal, facial, and maxillary veins:

temporal and maxillary veins: drain to external jugular

vein facial vein:

drains to internal jugular vein

Veins of the Hando Digital veinso Empty into superficial and deep palmar

veinso Which interconnect to form palmar

venous arches Superficial arch empties into:

cephalic vein median antebrachial vein basilic vein median cubital vein

Deep palmar veins drain into: radial and ulnar veins which fuse above elbow to

form brachial vein Circuit

The Brachial Vein o Merges with basilic vein o To become axillary vein

Cephalic vein joins axillary vein: to form subclavian vein merges with external and internal jugular veins:

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o to form brachiocephalic vein

o which enters thoracic cavity

Veins of the Thoracic Cavityo Brachiocephalic vein receives blood

from Vertebral vein Internal thoracic vein

The Left and Right Brachiocephalic Veins

Merge to form the superior vena cava (SVC)

The Inferior Vena Cava (IVC)o Collects blood from organs inferior to the diaphragm

Veins of the Foot

o Capillaries of the sole Drain into a network of plantar veins Which supply the plantar venous arch

Drains into deep veins of leg: o anterior tibial veino posterior tibial veino fibular vein

all three join to become popliteal vein

The Dorsal Venous Arch

o Collects blood from Superior surface of foot Digital veins

o Drains into two superficial veins Great saphenous vein: drains into femoral vein Small saphenous vein: drains into popliteal vein

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The Popliteal Vein o Becomes the femoral vein

Before entering abdominal wall, receives blood from: great saphenous vein deep femoral vein femoral circumflex vein

Inside the pelvic cavity: becomes the external iliac vein

The External Iliac Veins

o Are joined by internal iliac veins To form right and left

common iliac veins the right and left

common iliac veins o merge to

form the inferior vena cava

Major Tributaries of the Abdominal Inferior

Vena Cava o Lumbar veinso Gonadal veinso Hepatic veinso Renal veinso Suprarenal veinso Phrenic veins

The Hepatic Portal System

o Connects two capillary bedso Delivers nutrient-laden blood

From capillaries of digestive organs To liver sinusoids for processing

Tributaries of the Hepatic Portal Vein

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Inferior mesenteric vein: drains part of large intestine Splenic vein: drains spleen, part of stomach, and pancreas Superior mesenteric vein: drains part of stomach, small intestine, and part of large

intestine Left and right gastric veins: drain part of stomach Cystic vein: drains gallbladder

Blood Processed in Liver

o After processing in liver sinusoids (exchange vessels), blood collects in hepatic veins and empties into inferior vena cava

Embryonic lungs and digestive tract nonfunctional Respiratory functions and nutrition provided by placenta

Aging and the Cardiovascular System

Cardiovascular capabilities decline with age Age-related changes occur in

o Bloodo Heart o Blood vessels

Aging and the Cardiovascular System

Three Age-Related Changes in Bloodo Decreased hematocrito Peripheral blockage by blood clot (thrombus)o Pooling of blood in legs

Due to venous valve deterioration

Aging and the Cardiovascular System

Five Age-Related Changes in the Hearto Reduced maximum cardiac outputo Changes in nodal and conducting cellso Reduced elasticity of cardiac (fibrous) skeletono Progressive atherosclerosiso Replacement of damaged cardiac muscle cells by scar tissue

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Aging and the Cardiovascular System

Three Age-Related Changes in Blood Vesselso Arteries become less elastic

Pressure change can cause aneurysmo Calcium deposits on vessel walls

Can cause stroke or infarctiono Thrombi can form

At atherosclerotic plaques

CV System Linked to All Systems

There are many categories of cardiovascular disorderso Disorders mayo Affect all cells and systemso Be structural or functionalo Result from disease or trauma

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