Blood VesselsBlood Vessels

Types of Blood VesselsTypes of Blood Vessels

Artery – carries blood away from the Artery – carries blood away from the heartheart

Vein – A vessel that carries blood Vein – A vessel that carries blood towards the hearttowards the heart

Capillaries – microscopic vessels that Capillaries – microscopic vessels that carry blood from small arteries to small carry blood from small arteries to small viens viens

The The Pathway Pathway

of of BloodBlood

ArteryArtery

ArterioleArteriole

CappillaryCappillary

VenuoleVenuole

VeinVein

Blood Vessel StructureBlood Vessel Structure

Tunica Intima (endothelium) Tunica Intima (endothelium)

Tunica Media (smooth muscle; elastic Tunica Media (smooth muscle; elastic connective tissue)connective tissue)

Tunica Adventitia (fibrous type of Tunica Adventitia (fibrous type of vessel connective tissue) vessel connective tissue)

ArteriesArteries Tunica Intima – Smooth lining Tunica Intima – Smooth lining

Tunica Media – Allows constriction and Tunica Media – Allows constriction and dilation of vessels; thicker than in dilation of vessels; thicker than in veins; muscle innervated by veins; muscle innervated by autonomic fibers autonomic fibers

Tunica Adventitia – Provides flexible Tunica Adventitia – Provides flexible support that resists collapse or injury; support that resists collapse or injury; thicker than in veins; thinner than thicker than in veins; thinner than tunica media tunica media

VeinsVeins Tunica Intima – Smooth lining with semi-Tunica Intima – Smooth lining with semi-

lunar valves to ensure one way blood flowlunar valves to ensure one way blood flow

Tunica Media – Allows constriction and Tunica Media – Allows constriction and dilation of vessels; thinner than in arteries; dilation of vessels; thinner than in arteries; muscle innervated by autonomic fibersmuscle innervated by autonomic fibers

Tunica Adventitia – Provides flexible Tunica Adventitia – Provides flexible support that resists collapse or injury; support that resists collapse or injury; thinner than in arteries; thicker than thinner than in arteries; thicker than tunica mediatunica media

CappillariesCappillaries

Tunica Intima – Makes up the entire Tunica Intima – Makes up the entire wall of the capillary; thinness permits wall of the capillary; thinness permits transport across vessel walltransport across vessel wall

Tunica Media – Absent Tunica Media – Absent

Tunica Adventitia – Absent Tunica Adventitia – Absent

Micrograph of Blood Vessel Micrograph of Blood Vessel StructureStructure

This light This light micrograph of a micrograph of a cross section of cross section of tissue contains tissue contains an artery (left) an artery (left) and a vein and a vein (right). Note the (right). Note the prominence of prominence of the smooth the smooth muscle (tunica muscle (tunica media) in the media) in the artery compared artery compared to the vein to the vein

Function of CapillariesFunction of Capillaries Most important vessels functionallyMost important vessels functionally

Very tiny (on average, only 1mm long)Very tiny (on average, only 1mm long)

According to one estimate, 1 cubic cm of According to one estimate, 1 cubic cm of muscle tissue contains more than 100,000 muscle tissue contains more than 100,000 capillariescapillaries

Primary exchange vesselsPrimary exchange vessels

The small size and large number ensures The small size and large number ensures slow blood flowslow blood flow

MicrocirculationMicrocirculation

Function of Arteries Function of Arteries

Arteries serve mainly as “distributors,” Arteries serve mainly as “distributors,” carrying blood to the arterioles, which carrying blood to the arterioles, which then carry blood to the capillariesthen carry blood to the capillaries

Arterioles are important in maintaining Arterioles are important in maintaining normal blood pressure and circulation normal blood pressure and circulation (resistance vessels)(resistance vessels)

Precapillary sphincters function as valves Precapillary sphincters function as valves regulating blood flow into the capillariesregulating blood flow into the capillaries

Function of VeinsFunction of Veins

Function both as collectors and reservoir Function both as collectors and reservoir vessels (ability to hold blood)vessels (ability to hold blood)

Capacitance -- Great ability to strech, Capacitance -- Great ability to strech, therefore, they can hold large amounts therefore, they can hold large amounts of blood with almost no change in blood of blood with almost no change in blood pressurepressure

Valves maintain the one way flow of Valves maintain the one way flow of bloodblood

The reservoir The reservoir function of function of

veinsveins

Pooled blood is Pooled blood is moved toward the moved toward the

heart as valves heart as valves are forced open are forced open by pressure from by pressure from volume of blood volume of blood

from below. from below. Closure of valves Closure of valves

prevents prevents backflow. backflow.

Circulatory RoutesCirculatory Routes

Systemic Circulation – blood is Systemic Circulation – blood is pumped from the left side of the pumped from the left side of the heart to all the tissues of the bodyheart to all the tissues of the body

Pulmonary Circulation – blood is Pulmonary Circulation – blood is pumped from the right side of the pumped from the right side of the heart to the gas exchange tissues of heart to the gas exchange tissues of the lungsthe lungs

Blood Flow Through the Blood Flow Through the Circulatory SystemCirculatory System

Main Arteries Main Arteries

of the Bodyof the Body

The AortaThe Aorta

Arteries of the Head and NeckArteries of the Head and Neck

ArteriesArteries

at the at the

Base of Base of the Brainthe Brain

Major Arteries of the Upper Major Arteries of the Upper ExtremityExtremity

Major Arteries Major Arteries

of the of the

Loser ExtremityLoser Extremity

General Principles About General Principles About VeinsVeins

Veins branch into vessels of increasing Veins branch into vessels of increasing sizesize

Vessels vary considerable in size and Vessels vary considerable in size and location from person to personlocation from person to person

Veins found deep in the body are called Veins found deep in the body are called deep veins and those found near the deep veins and those found near the surface are called superficial veinssurface are called superficial veins

Major Veins Major Veins

of theof the

BodyBody

Major Veins of the Head and Major Veins of the Head and NeckNeck

Major Major Veins of Veins of

the Upper the Upper ExtremityExtremity

Principal Veins of the ThoraxPrincipal Veins of the Thorax

Inferior Vena Cava and its Inferior Vena Cava and its Abdominopelvic TributariesAbdominopelvic Tributaries

Disorders of the Cardiovascular Disorders of the Cardiovascular SystemSystem

Mitral Valve ProlapseMitral Valve Prolapse

Coronary BypassCoronary Bypass

Partial Blockage of Artery in Partial Blockage of Artery in AtherosclerosisAtherosclerosis

Balloon AngioplastyBalloon Angioplasty

Varicose VeinsVaricose Veins