Lecture 19 - Vessels and Circulation

7/27/2019 Lecture 19 - Vessels and Circulation

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Vessels and Circulation


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Some embryology

first

There are at first sixpairs of aorticarches

In fish these areconnected to thegills

They undergo atransformation inmammals Birds use the right

arch of the fourth pair Mammals use the

left arch of thefour th pair
http://upload.wikimedia.org/wikipedia/commons/f/f7/Gray472.png


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Ventral (anterior)

view

Full set of arches develops,

but not all present at

the same time; (before

transformation)

Transformation :

4th through 7th

weeks: some persist,

some atrophy
http://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.png


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R

ight common carotid a ------------------------------.

Right subclavian a. --------------------------

Brachiocephalic trunk-----------------------------------

4th arches become:

Left side: aortic arch

Right side: brachiocephalic trunk
http://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.png


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What the aortic

arches become

Right common

carotid a ---------------------------.

Right subclavian a. ---------------------------

Brachiocephalic trunk-------------------------------
http://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.pnghttp://upload.wikimedia.org/wikipedia/commons/8/84/Gray473.png


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3 Major types of

blood vessels

Body

RA

RV

Lungs

LA

LV

Boby

1.Arteries

2.Capillaries

3.Veins

Arteries carry blood awayfrom the heart

-branch, diverge or forkVeins carry blood towardthe heart

-join, merge, converge


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General characteristics of vessels

Three layers (except for the smallest)

1. Tunica intima - AKA intima

2. Tunica mediasmooth muscle

3. Tunica externa - AKA adventitia

Lumen is the central blood filled space


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Intima is endothelium (simple squamous epithelium) May have subendothelial layer if 1mm or larger

Tunica media: layers of circular smooth muscles Lamina (layers) of elastin and collagen internal and external

Thicker in arteries than veins (maintain blood pressure)

Smooth muscle

contraction:

vasoconstriction

Smooth muscle

relaxation:

vasodilation

Sympatheticvasomotor

nerves of

autonomic

nervous system

regulate


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Adventitia (t. externa) longitudinally running

collagen and elastin for strength and recoil


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Arteries Carry blood away from the heart

From big to small, these are the categories:1. Elastic

2. Muscular

3. Arter io les(then these to capillaries)

Pressure diminishes along the route

1. Elast ic arteries: act as condui ts 2.5-1 cm diameter

Expand with surge

of blood from heart

Recoil and continue

the propagation of blood

Elastin is thick in media:

dampens the surge of blood

pressure

Aorta and i ts branches


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Arteries continued

2. Musculararteries: act as

distr ibut ingarteries

Middle sized .3mm-1cm

Changes diameter todifferentially regulate flow

to organs as needed

Internal as well as

external elastic lamina Most of what we see as

arteries

Tunica media larger in proportion

to the lumen, thus muscular


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Arteries continued

3. Arter ioles Smallest: .3mm-10um

Only larger ones have all 3layers

Regulated 2 ways: Locally in the tissues

Sympathetic control

Systemic blood pressure (theBP we measure) can be

regulated through them Send blood into capillaries

Tunica media has only a few

layers of smooth muscle cells


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Capillaries

Heart to arteries to capillaries to veins to heart

Capillaries are smallest 8-10um

Just big enough for single file erythrocytes

Composed of: single layer of endothelial cells surroundedby basement membrane

Universal function Oxygen and nutrient delivery to tissues

CO2 and nitrogenous waste (protein break-down product)removal

Some also have tissue specific functions


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Capillaries

Theres a capillary bed in almost all tissues


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Capillary permeability

Direct diffusion through endothelial cell

membranes

Only O2 and CO2

Other molecules by various other methods

Blood brain barrier: complete tight junctions

Selective transport of necessary molecules

Lipid soluble agents (like anesthetics) get

through, as do O2 and CO2


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Veins

Pressure has been lowered so capillariescan tolerate

With lower pressure, walls (of veins) can

be thinner From smallest to large:

Capillaries to postcapillary venules to venules toveins

Veins are larger than arteries, plus

Tunica externa is thicker

There is less elastin


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Special features of veins

Valves

Prevent backflow

Most abundant in legs (where

blood has to travel againstgravity) Muscular contraction

Aids the return of blood to heart in

conjunction with valves

Mechanical issues

(really good to know)


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Exercise helpscirculation

(because

muscles

contract andsqueeze blood

back to the

heart)


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Vascular anastomoses

Vessels communicating with each other Veins have more than arteries

Form alternative pathways or collateral channels

Protect organs from being supplied by just oneroute Poor anastomoses & therefore vulnerable: central

artery of retina, kidneys, spleen, bone diaphyses

Vasa vasorum Means vessels of the vessels

Blood supply to vessel itself

Smallest vessels dont need


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Vascular System

(Blood vessels of the body)

Two circulations

Systemic

Pulmonary

Arteries and veins usually run together

Often nerves run with them

Sometimes the systems do not have bilateralsymmetry

In head and limbs, most are bilaterally symmetrical


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Pulmonary Circulation

Pulmonary trunk branches Right and left pulmonary arteries

Division into lobar arteries 3 on right

2 on left

Smaller and smaller arterioles, into capillaries surrounding alveoli Gas exchange

Pulmonary system pressure is only 1/6 of systemic blood pressure


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Pulmonary Circulation

After gas exchange blood enters venules

Larger and larger into Superior and Inferior

Pulmonary veins

Four Pulmonary Veins empty into left atrium


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In lungs


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Systemic Circulation

Oxygenated blood to body

Leaves LV through Ascending Aorta

Only branches are the 2 coronary arteries to the heart

Aortic Arch has three arteries branching from it:1. Brachiocephalic trunk, has 2 branches:

Right common carotid a. Right subclavian a.

2. Left common carotid a.

3. Left subclavian a.

Ligamentum arteriosumconnecting to pulmonary a.

remember aortic arches


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Descending aorta

Thoracic aorta

at T12 becomes

abdominal aorta

Abdominal aorta

ends at L4

branching into:

R & L commoniliac arteries


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Commoncarotids branch: Internal carotids

External carotids

Subclavian: 3branches Vertebral

arteries

Thyrocerical

trunk Costocervical

trunk


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Head and neck

Common carotids justlateral to trachea: feel At larynx divides into

internal & external

External carotid:supplies headexternal to brain andorbit Feel superficial

temporal a.

Middle meningeal:

vulnerable (branch ofmaxillary)

Internal carotid Supply orbits and

most of cerebrum


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Internal carotid a.

Enters skullthrough carotid

canal

Gives off:

Ophthalmic artery

Then divides into

anterior and middle

cerebral arteries(see next slides):

together they supply

80% o f cerebrum


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Angiogram


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Middle cerebral

arteries run throughlateral fissures

Anterior cerebralarteries of each

side, throughanteriorcommunicatingartery, anastomose

(an anastomosis is a union)

arteriogram


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R and L vertebral arteries* (from subclavians) Ascend through vertebral foramina of C6-C1

transverse processes

Through foramen magnum into skull

Join to form one Basilar artery*

*

*

*

*


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Basilar artery: branches Divides into posterior cerebral arteries

Posterior communicating arteries connect tomiddle cerebral arteries

CIRCLE OF WILLIS(now called cerebral arterial circle)

Note how it loops

around pituitary

gland & optic chiasm


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Upper limb

Subclavian runslaterally onto 1st rib,under clavicle

Enters axilla asaxillary artery Sends branches

Continues asbrachial artery inupper arm

Splits into radial &ulnararteries

See hand supply

Feel brachial & radial puls es


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overview


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overview


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Thorax

Anterior intercostalsbranch off Internalthoracic*(branch ofsubclavian)

Posterior

intercostals branchoff Thoracic aorta

Intercostal arteries,veins and nervesrun just UNDERtheribs

Small bronchial

arteries supply the

lung structures

*

A t i t th bd


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Arteries to the abdomen

Arise from the abdominal aorta

At rest, arterial blood is here!

Three single midline branches supply the digestive tube1. Celiac trunk2. Superior mesenteric artery

3. Inferior mesenteric artery

1.

2.

3.


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1. Celiac trunk: divides into 3 right away: left gastric,splenic & common hepatic (see pic; the latter isthe only which goes off to the right)

2. Superior mesenteric supplies most of intestines

1.

2.

Definition of mesenteries: double layered sheets of peritoneum

that support most organs in the abdominopelvic cavity


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3. Inferior mesenteric supplies distal half of

large intestine

2.

3.

1.

Know what these terms mean: phrenic, gastric, hepatic, renal, colic

(The 1, 2 and 3 are branches of the abdominal aorta)

A t i t th bd


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Arteries to the abdomen

Paired branches off the abdominal aorta

supply adrenal glands, kidneys, gonadsand abdominal body wall

supp ly

diaphragm

3.

supp ly

adrenals

to kidney


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Abdominal aortabranches into

Common iliacs atL4; these branchinto Internal iliacs to

pelvic organs,

perineum,buttocks, medialthighs

External iliacs: to

rest of lower limbs


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External iliac

passes under

inguinal ligamentbecoming Femoral

artery

At back of knee

femoral becomes

popliteal artery,

and branches

Feel dorslis pedis &

posterior tibial


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review


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review


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review


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Systemic Veins

3 major vessels enter Right Atrium: SVC (superior vena cava)

IVC (inferior vena cava)

Coronary sinus Many veins are very superficial (unlike

arteries)

Venous plexuses (networks of anastomosesand parallel veins) are very common

Head and hepatic portal systems are unusual


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Dural sinuses

Drain the veins of

the brain Cavernous sinuses

Carotid arteries andsome cranial nerves

run within them Dangerous if trauma

Come together assigmoid sinus

becomes InternalJugularvein Exits skull throughjugular foramen

Internal jugular veins


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Internal jugular veins Drain most of blood from brain

Run lateral to internal then common carotid

At base of neck joins subclavian v. to form brachiocephalic v.

External jugulars drain some of scalp & face

Vein


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Vein

overview

Azygos system

drains the thorax:

Note that unlike the arteries, the veinshave a brachiocephalic on the right

and left sides


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Deep veins of

upper limbs followarteries, most ofthem double toone artery

Superficial veins:see pic

Blood drawn frommedian cubitalvein in antecubitalfossa

(look at)

Tributaries of IVC: note asymmetry


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Tributaries of IVC: note asymmetry Left gonadal and suprarenal veins drain into left renal

vein

On right they drain directly into IVC Right and left hepatic veins enter superior part of IVC

Hepatic portal system


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Hepatic portal system Picks up digested nutrients from stomach & intestines and delivers them

to liver for processing and storage Storage of nutrients

Detoxification of toxins, drugs, etc.

Two capillary beds Route: artery to capillaries of gut to hepat ic po rtal veinto livers

capillaries to hepatic vein to IVC

Dont confuse hepat ic veinwith hepat ic porta l vein


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Kind of confusing

Superior mesenteric

and splenic veins jointo form hepatic

portal vein, which

goes up into liver

Inferior mesenteric

empties into the

splenic vein*

*

(same info with different pic)


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Hepatic portal system Picks up digested nutrients from stomach & intestines

and delivers them to liver for processing and storage Storage of nutrients

Detoxification of toxins, drugs, etc.

Two capillary beds

Route: artery to capillaries of gut to hepatic portalveinto livers capillaries to hepatic vein to IVC

( p )

Tributaries of hepatic

portal vein:

-superior mesenteric vein-splenic vein-inferior mesenteric vein


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Leg veins


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Leg veins Names similar to

arteries

Femoral becomesexternal iliac after

crossing under

inguinal ligament

External iliac joins

with internal iliac to

form common iliacvein

_________used for grafting in coronary

artery bypass grafts: is the

longest vein in the body

Fetal


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Fetal

Circulation

The one umbilicalvein brings bloodwhich has been tothe placenta foroxygenation (by gasdiffusion from momsblood)

The pair of umbilicalarteries (branchesfrom babys internaliliac arteries) carryblood to placenta to

pick up oxygen andnutrients

Fetal heart startsbeating at 21 dayspost conception


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Some Diseases

Atherosclerotic cardiovascular disease Cerebrovascular disease affects brain, strokes

Coronary artery disease (CAD) arteries of heart

Peripheral vascular disease (PVD) arterial

Affecting veins Chronic venous insufficiency venous = veins

Deep venous thrombosis (DVT)

Aneurysms Portal hypertension

Hypertension

Lecture 19 - Vessels and Circulation

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