Circulatory System (Post)

7/31/2019 Circulatory System (Post)

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The Circulatory System


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Objectives

Introduce components of blood Understand difference between venous &

arterial blood

Components of each Vessels associated with each

Understand the heart & cardiac cycle

Introduce major (great) vessels of the body Understand concept of lymph


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Components

Heart

Blood vessels

Arteries

Arterioles

Capillaries

Venules

Veins

Blood


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Circulation vs. Cardiovascular vs.

Hematology

Circulation= heart, blood vessels & blood

Cardiovascular (CV)= heart & blood vessels

NOT blood

Vascular= blood vessels (not heart)

Hematology= study of blood (no heart or

blood vessels)


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Functions of the circulatory system

Transport Erythrocytes (red blood cells/RBCs) carry oxygen from lungs, removeCO2 from tissues

Nutrients, hormones etc. all carried by the fluid portion of blood (NOTRBCs)

Metabolic wastes from body tissues delivered to renals

Protection White cells (immune cells)

Antibodies, inflammatory mediators (cytokines), blood clotting factors

Regulation

Constant flow helps to stabilize fluid and fluid ingredient distribution(mixes everything equally)

Buffers pH changes in tissue

Buffers temperature changes


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Heart

4chamber double pump muscle Pumps 5 L/min (2.5+ million liters year)

At roughly 60-70 bpm, heart pumps almost 50 million

times / year

An RBC takes 1 minute to travel from the heart toyour finger or toe and back to the heart!

Roughly size of your fist

Contained within parietal pericardium

2-layer tissue

Outer dense fibrous connective tissue

Inner serous pericardium

Produces serous fluid that surrounds heart proper


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Heart 3 layers form the heart proper (organ within

the parietal pericardium)

Epicardium(visceral pericardium) *Most superficial

Where cardiac vasculature is located

Where you look for the root cause of damage duringmyocardial infarction

Myocardium(muscle layer)

Cardiac muscle cells

Arranged so that during contraction, chambers squeeze in aparticular manner

Thickness reflects amount of force required to pump

Thickestin region of the Left Ventricle *Pushes blood to arteries,hence out to the rest of the body

Thinnestin the atrial walls


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Heart

3 layers form the heart proper (organ withinthe parietal pericardium)

Epicardium (visceral pericardium)

Myocardium (muscle layer)

Endocardium (endotheliumwithin the heart &

blood vessels) *Deepest layer

Inner lining of the heart chambers

Not very porous (acts as a bag to retain blood andprevent leakage between muscle layers)


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Cardiac muscle

Myocardium comprises the most mass ofthe heart

Striated(like skeletal muscle in contractile

protein arrangement)

Each cell is much shorter, and usually more thick as

well

Each cell joined by anintercalated disc ***

An area of cell-cell adhesion, as well as gap

junctions to permit 1 cell to stimulate the

next (forming a chain)

Short and stout muscle cells (spreads the

metabolic load between many cells)


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Intercalated disc

with agap junction


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Cardiac muscle

Cardiac muscle cells have less developed

sarcoplasmic reticulum

Less ability to store calcium than skeletal muscle

Damage is repaired byfibrosis

Cannot regenerate cardiac muscle cells


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Cardiac muscle

NO neural stimulus for contraction

Has pacemaker cells that set off rhythmicdepolarizations (electrical pulses) to trigger yourheartbeat

Known as autorhythmic because your heartdoes not need your brain to tell it to beat

Note: these pacemaker cells are still neuronstheyrelocated WITHIN the heart, and NOT associated withthe CNS (hence no neural stimulus means NO

voluntary/conscious stimulation needed)


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Cardiac muscle Cardiac muscle cells perform Aerobicrespiration

exclusively (Rely on oxygen)

NO anaerobic fermentation (Make their own oxygen for asmall period of time)

If you stop bloodflow to the myocardium, IT

WILL DIE


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Cardiac muscle External heart structure:

Coronary sulcus: divides atria from ventricles

Think: circumferential

Interventricular sulci: divides left & right

ventricles Look for adipose lines


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Cardiac muscle External heart structure:

Various sulci serve as routes for cardiac blood

vessels

Cardiac muscle reliant on cardiac blood vessels for

blood supply (endocardium does not permit fluid orgas exchange within the heart)


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Heart Within the heart proper, 4 chambers & valves

Atria= most superior/cranial chambers

Atrial walls characterized by Pectinate Muscles (gives the look of a

wicker basket)

Interatrial septum = thin, muscular membrane separating left &

right atria Atrioventricular valves separateatriafromventricles

Ventricles = most caudal/inferior

Much more muscular (have to pump blood further)

Characterized by Trabeculae Carneae (NOT pectinate muscles, butsimilar in look)

Semilunar valves (pulmonary & aortic) separate ventricles from

pulmonary & systemic circuits

Valvesmaintain one-way flow of blood through heart


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Papillary muscles: contract

during ventricular contraction. If

you study the image, it might besomewhat confusing. Bear in

mind that the papillary muscles

have to contract to hold the

bicuspid/tricuspid (AV) valves

and prevent them fromprolapsing.

Think of a parachute: without

someone/something pulling downon the parachute, it would flap

around (like a bedsheet or

blanket)not much good when

you think about how much

pressure the ventricles can build.


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Heart Within ventricles endocardium = specialized

formation

Trabeculae carneae: little beams of flesh within

the ventricle to prevent suction

If the inner wall of the ventricle were flat, as theventricle contracted, it would have difficulty opening

up as the two flat surfaces would adhere together


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Heart Conduction

Sinoatrial (SA) node = pacemaker due to cyclicdepolarization of specialized neurons

Located in right atrium, near insertion of SVC

Depolarization spreads across BOTH atria

BOTH atria contract simultaneously

Impulse then passes down to atrioventricular node

(AV node)

Inferior side of the interatrial septum atrioventricular

bundle at most superior end of the interventricular

septum L/R ventricles

In the ventricles, conduction fibers (Purkinje fibers) carry

impulse throughout both ventricles


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Heart Conduction

Systole= ventricular contraction Coupled with smooth muscle contraction in the

arteries = systolic pressure

Diastole= ventricular relaxation


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Heart Conduction Heart sounds: Vascular ascultation

2 distinct sounds: lub=dub

Lub= Atrioventricular valves closing (ventricles

contracting, SYSTOLE)

Dub= aortic & pulmonary valves closing (ventriclesrelaxing, DIASTOLE)


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Heart Rate Control

SA node does not rely on CNS input to initiate thecycle, BUT, the CNS still controls RATE of SA node

depolarization

Heart rate control via ANS

Systoleinnervation via T1-T4 ganglia toincreaseheart

rate (increase rate of SA node depolarizations)

Diastoleinnervation via VAGUS nerve (X)to decrease

heart rate (decrease rate of SA or AV node cycles)

RightVagus nerve (X) innervates SA node

LeftVagus nerve (X) innervates AV node


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Both sympathetic & parasympathetic (Vagus nerve X) innervate the

SA node, but are derived from different regions of the CNS.

Remember that the BOTHVagus (X) nerve fibers branch into the

heart. This image only depicts the left branch of the Vagus (X).


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Blood Total blood volume 5L

Roughly 8-10% total body weight

Thicker viscosity than water (obviouslythere are cells and

proteins in it)

pH 7.35-7.45 (pH homeostasis is vital)

Normally 38C

When you donate blood, 1 unit = 500 ml

(10% total blood volume)

2 component groups:

Formed elements (45% total volume)

Blood plasma (fluid portion)


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Formed Elements of Blood Blood cells

Erythrocytes(red blood cells, RBCs)

Bi-concave - divited in middle

Increases surface area for gas exchange (O2 and CO2)

Permits greater flexibility (allows RBC to flex and squish

through tight capillaries)

7.5 m diameter, 2.5 m thick

No nucleus, no mitochondria

Produce ATP by anaerobic fermentation exclusively

Without nucleus, there is NODNARBCs retain mRNA for

various protein requirements, but are generally born with

everything they need to function


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Hematopoiesis: formation of blood cells

Erythropoiesis: formation of red blood cells, granular leukocytes& platelets

Red bone marrow produces 2.5 million cells/day

Despite the fact that mature RBCs have no nuclei, they do

originate from a cell type that does have a nucleus. During

RBC development or maturation, the nucleus dissolves.


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120 day lifespan

Lifespan reflects number of bends & squishes , hemoglobin

function & lack of a nucleus (cannot repair itself)

Terminated in the spleen & liver

Hemeis either recycled into the red bone marrow, or

processed by liver into bilirubinand excreted in bile

Excess bilirubin in blood =jaundice(yellow skin tone),

indicative ofcholestasis(liver failure) Bilirubin in bile is transferred into the chyme/fecal

material (what makes your poo brown)


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Contain hemoglobin (4 subunit large gas-carrying

protein)

Usually

250-300 billion hemoglobin molecules per RBC

Allows RBC to capture 1000+ trillion oxygen (O2)

molecules

When bound to O2, hemoglobin changes color (diffracts light

differently)

Oxygenated RBC is bright red Deoxygenated RBC is dark purple/red

NOTE: venous blood still has oxygenit just doesnt have as

much as arterial blood


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Leukocytes(white cells)

Larger than RBCs, but fewer in number

Have nuclei, have mitochondria

Motile (can migrate or move by themselves)

Ameboid motility permits extravasation via diapedesis

http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0

Characterized by how they stain

Cannot really see leukocytes without stains

Eosin & hematoxylin

Granular leukocytes

Agranular leukocytes
http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0http://video.google.com/videoplay?docid=-142799799667345732&q=diapedesis&total=1&start=0&num=10&so=0&type=search&plindex=0


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Leukocytes(white cells) Granular leukocytes (_____phils) *theyre all called something-phils

Granules = vesicles of digestive enzymes, reactive oxidants etc.

When attacking an invading pathogen (or autoimmune reaction), willdegranulate or exocytose granular contents

Will also phagocytose foreign particles and fuse granules withthem to kill/digest

Neutrophils: most common granular leukocyte (65% total white cellcount)

first line defenders

Eosinophils: larger than neutrophils (eosinophil = stained by eosin)

Phagocytic white cells for parasite and antibody-mediateddefense

Basophils: most rare leukocyte

Produce histamine (similar to tissue mast cells)

Involved in allergic responses


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Leukocytes (white cells)

Agranular leukocytes (____cytes)

No granulesrelatively clear cytoplasm

Most formed by LEUKOPOIESIS(different than erythrocytes)

Development takes place inlymphoid tissue Lymph nodes, tonsils, spleen & thymus

Lymphocytes: 30-35% total white cell count

B-cellsdifferentiate in BONE MARROW (antibody cells)

T-cellsdifferentiate in THYMUS (killer, helper etc.)

Monocytes: largest cells in the blood (note: same precursor aserythrocyte)

In circulation = monocyte

When in tissue (after extravasation) = macrophage

Phagocytic digesters

Hematopoietic: from same precursor as erythrocytes


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Platelets(not cells per se)

Originate from megakaryocytesin red bone marrow

that fragment into platelets

No nuclei (no DNA) Are capable of extravasation and have ameboid motility

Very short lifespan (5-7 days)

Act to form blood clots by altering their plasma

membrane Releaseserotonin(5-hydroxytryptamine, 5-HT) during clot

formation in order to vasoconstrict in the general vicinity

Also neutralize heparin (an anti-coagulant)


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Megakaryocytesextend a cellular appendage into the blood

stream. The velocity of the blood breaks off the platelets from

this appendage (the laminar flow shears off the platelets from the

megakaryocytes arms).

Figure 18.1


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Blood Plasma Fluid portion of blood (technically the

extracellular matrix of bloodsince blood is a

form of connective tissue)

90% water

Straw/yellowtone due to presence of proteins,various salts, carbohydrates, lipids, amino acids,

vitamins & hormones


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Blood Plasma

Plasma proteins ( 7-9% total plasma ingredients)

Plasmaalbumins(a family of proteins)

60 % total plasma protein content

Produced in liver

Act as carrier/delivery molecules

Influence blood viscosity Influence blood pressure through viscosity

Plasma globulins


Alpha ()&Beta () globulinsproduced in liver Assist in fat/lipid transport throughout the blood

Gamma () globulins produced by lymphoid cells

antibodiesproduced primarily by B-lymphocytes


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Blood Plasma Plasma proteins

Plasma albumins (a family of proteins)

Plasma globulins

Plasmafibrinogen


Largest plasma protein

Produced inliver

Combines with platelet activity to form blood clot


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Blood Plasma vs. Serum

Blood plasma is different than blood serum serum antibodies etc.

Recallfibrinogen

Serum = plasma without fibrinogen

Serum = plasma AFTER a clot (anything involved in clot

formation removed from plasma)

serum = liquid portion after you make cheese from milk

Serum can be harvested by NOT including an anti-

coagulant in a blood draw (allow blood to clot)


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Blood Plasma Proteins

If albumin = 60%, globulin = 35%, fibrinogen =4%

1% of blood protein content = regulatory proteins,

lipoproteins, iron-binding proteins etc.

Recall theENDOCRINEsystem


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Blood vessels Tubular network for blood flow

Blood flow is a closed system (components ofblood do not readily leave the blood vessels)

3 layers to every blood vessel

Tunica externa (adventitia) Most superficial layer of loose connective tissue

Tunica media

Smooth muscle layer

In arteries, tunica media layer has very dense elastic fibers

Tunica interna (endothelium)

Simple squamous epithelial tissue with elastic fibers

Continous with endocardium


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Blood vessels Capillaries

Fluid, nutrient and gas exchange is only possible

across capillaries

Endothelium more loose or porous in a capillary

Over 40 billion capillaries in your body (1800+square kilometers of coverage)

No cell is more than a few m from a capillary

Despite large surface area and extensive network, only

250 ml blood is within the entire capillary network atany one time!

Walls are unique

Simple squamous endothelium


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Blood vessels Capillaries

3 subtypes of capillaries: Continuouscapillary: tight pores between squamous

cells (most common type)

Muscle, lungs, adipose, CNS

Remember that in CNS, this is the basis for the blood-brain barrierincredibly tight capillary network

Fenestratedcapillary: fenestrations = windows/pores

Renals, endocrine organs & GI tract

Wide pores permits fast transfer of gas andnutrients/waste

Covered by a mucoprotein diffusion barrier

Discontinuouscapillary: widest pore size

Bone marrow, liver & spleen

Pores = sinusoids(sinus-like pores)


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Continuous capillary Fenestrated capillary

Note the diameter of the capillary = 1 cell wide


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In discontinuous capillaries,

the endothelial cells do notphysically connect to one

another. These pores are so

wide theyre called sinusoids.

Discontinuous capillaries arerestricted to organs that

process LARGE volumes of

blood

Despite the sinusoidal

space, most blood cells

cannot easily leave the

capillary


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Blood vessels Veins

Carry blood from capillaries BACK to heart From capillaryvenulevein

Very LOW pressure (0.02 psi)

Arteries can hold up to 5 psi (in some areas, even more)

At this low pressure, blood cannot return to the heart

Relies on1-way valves (venous valves) and skeletal musclecontractions to propel blood back to heart

Varicose veins = veins stretched from standing (stretchedveins = pulled valves that dont work correctly

Only find valves in veinsnever in arteries

Low pressure = more volume of blood can befound in the venous network than the arteries


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Low pressure in venous

network due to the fact that

the high arterial pressure

(from heart contraction &arterial recoil) is lost at

the level of the capillary bed

(like trying to blow through

a syringeat the other end,very little gets out).

Low pressure in veins

therefore requires skeletal

muscle contractions topush or milk blood

back to the heart.


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Very Important Fact

Arteries & veins are named for the DIRECTION

in which they carry blood

Artery =blood away from the heart (efferent)

Vein = blood towards the heart (afferent)

The terms: arteries & veins have NOTHING to

do with the amount of oxygen in the blood

To say that arteries carry oxygen-rich blood is

INCORRECT


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Cardiac Blood Flow Recall the heart:

4 chambers Right atrium & ventricle

Left atrium & ventricle

Blood flow TO lungs

Venous blood fromsuperior&inferior vena cava (SVC&IVC) drawn into right atrium

IVC also has input from coronary sinus

Contraction ofR-atrium= blood pumped through

tricuspid /right atrioventricular valve intoR-ventricle Contraction ofR-ventricle= blood pumped into

pulmonary trunk

Bifurcatesintoright/left pulmonary arteriestowardslungs

1

2


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Cardiac Blood Flow Blood flow FROM lungs

L-atriumreceivesoxygenatedblood from lungs via 2Xright/left pulmonary veins

L-atriumcontracts and pumps blood via

bicuspid/mitral or left atrioventricular valve

Valve opening dependent upon L-ventricle RELAXATION

L-ventricle contracts & pumps blood via aortic

semilunar valveinto ascending aorta

3

4


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Note that despite going

over these steps as

separate stages, thesepatterns occur in

PAIRS. The atria open

to draw blood at the

same time. Both atria

contract at the sametime to force blood into

the ventricles. Both

ventricles then contract

at the same time topropel blood towards

thepulmonary artery or

theaorta.

lub

dub

systole

diastole

flo chart


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flow chart

Venous

blood

(body)

Rightatrium

Rightventricle

Pulmonary

trunk / artery

(lungs)

flow chart


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flow chart

Venousblood

(body)

Right

atrium

Right

ventricle

Pulmonarytrunk /artery

(lungs)

Pulmonary

veinLeft

atrium

Left

ventricle

Ascending

aorta

(body)

Flow chart in reality


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Venousblood

(body)

Right

atrium

Right

ventricle

Pulmonarytrunk /artery

(lungs)

Left

atrium

Left

ventricle

Ascendingaorta

(body)

Firstsimultaneous

contraction

Second

simultaneous

contraction



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Venousblood

(body)

Right

atrium

Right

ventricle

Pulmonary

trunk /artery(lungs)

Left

atrium

Leftventricle

Ascending

aorta(body)


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Specialized Circulatory Subsystems

Pulmonary circulation: Blood vessels that transfer blood between heart &

lungs

Blood vessel-way

R-ventricle pulmonary valve pulmonary trunk L/R-

pulmonary arteriespulmonary capillaries (in lungs)

pulmonary veins L-atrium

Note how the coronary circulation begins at the right

ventricleand ends at the left atrium

l d l b


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Coronary circulation: Blood vessels that transfer to myocardium of the

heart

Interesting that the heart, despite pumping so much

blood, hasno myocardial access to that blood otherthan thecoronary circulation

l d l b


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Coronary circulation: Blood route

Ascending aorta aortic/semilunar valve L/R-coronary arteries

Left coronary artery anterior atrioventricular artery anterior region of both ventricles circumflex artery

Circumflex artery L-atrium & L-ventricle

Right coronary artery posterior interventricular sulcus Posterior region of both ventricles

From capillaries in myocardium cardiac veins

Anterior interventricular vein (drains from anterior region ofheart)

Posterior interventricular vein (drains from posterior heart)

Merge into coronary sinus R-atrium


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S i li d Ci l S b


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Systemic circulation: Everything OUTSIDE the pulmonary circulation

Includes the coronary circuit as well

From:

Left ventricle aortic valve ascending aorta

systemic vasculature capillaries (not within the

lungs) venous apparatus right atrium

S i li d Ci l S b


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Portal circulation: vein-capillary-vein Recall portal circulation in the adenohypophysis

(anterior pituitary)

Carries venous blood from hypothalamus into the

capillary bed of the adenohypophysis

Hepatic portal blood circuit

Drains blood from the gastrointestinal viscera via

hepatic portal vein, into the liver (hepatic) system

before emptying into the IVC via the hepatic vein

F l Ci l i


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Fetal Circulation

Fetusreceives maternal oxygen & nutrients

Blood does NOT transfer, only plasma & oxygen

Transition occurs at placenta

Umbilicalcord= between placenta & fetus

Umbilical vein + 2 umbilical arteries

Umbilicalveincarries oxygen-rich blood towards liver

1 branch towardsportal vein

2nd branch anastomizes with interior vena cava viaductus

venosus Maternal blood then enters right atrium

Most will bypass/shunt into the left atrium viaforamen ovale

Additional shunt at ductus arteriosus(between

pulmonary artery & aorta)


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Fetal circulatory system

designed to place maternal

blood into systemic circulation

rather than pulmonary circuit.

Uses 2 shunts to limit

pulmonary circuit:

Foramen ovale

Ductus arteriosus (ductus

Van Botalli)

F t l Ci l ti


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Fetal Circulation fetal collapsed lung

In placenta, lung is filled with fluid Very difficult to draw in blood due to hydrostatic pressure

First breath following parturition:

Expel the fluid within the bronchioles of the lungs

Draw in first breath Establish negative thoracic pressure

Expulsion of fluid from lungs reduces pressure in lungs

Reduction in lung pressure allows blood to more easily enterlungs via pulmonary artery

As right ventricle is permitted to expand (due to reduced resistance),

foramen ovaleis forced shut If you clamp the umbilicus, you also reduce pressure in the IVC

& right atrium

First breath is at least 20-50X more difficult to mount thansubsequent inspirations

F t l Ci l ti


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Fetal Circulation Foramen ovale is therefore the first shunt to close

following parturition fossa ovale when fully closed

Ductus arteriosus closure = more gradual

Usually remains partially open for 6 weeks

Increasing levels of vascular oxygen stimulates arterial smoothmuscle contraction

Ductus remnant atrophies & becomes non-functional(ligamentum arteriosum)

Ductus venosus closure similar to ductus arteriosus

Remnant =ligamentum venosum

Because it remains open, you can cannulate after birth


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F t l Ci l ti


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Fetal Circulation

Fetus pumps blood out of

body (back to placenta) via

UMBILICAL ARTERY

Paired artery exiting from

internal iliac artery Carries metabolic waste,

oxygen-poor blood back to

placenta for exchange

Ci l t ll t l


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Circulatory collaterals

Throughout your circulatory system, there arecollaterals

Pools or supplies of blood that can be mobilizedwhen called for

GI tract retains 50-70% blood volume during rest During high activity/trauma, GI tract innervated by sympathetic

nervous system is triggered to vasoconstrict (provide moreblood for vitals and skeletal muscle)

Within brain: circle of Willis provides a similar function

for the brain Paired carotid arteries, paired vertebral arteries provides at 4

different pathways for arterial blood to enter the brain

Pairs of vessels span many joints

Allows flexion of the joint while maintaining blood flow


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Within the mesenteric vasculature,

all of the capillaries are gated by

precapillary sphincters. Whencalled upon by the sympathetic

nervous system, these sphincters

will constrict the amount of blood

entering the capillary bed,restricting the bloodflow and

permitting more arterial blood to

be shunted to the vitals.


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Follow the Vertebral arteries and the Internal carotid arteries

(not labeled). Note the circle of Willis. Any of the 4 arteries

can feed into the circle of Willis (cerebral arterial circle) and

keep the brain supplied with arterial blood.


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Important note: in following

the major arteries, do not

make the mistakethatcapillary beds are only at

the ends of these arteries.

Along literally the entire

length of many arteries are

branches that provide

arterioles / capillary beds

for practically every tissue

along the way.

Remember that practicallyevery cell in your body is

mere microns (m) from a

capillary bed.

Principle Arteries


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Principle Arteries

Aorta = major systemic artery

Directly from left ventricle =ascending aorta

Right & left coronary arteries are the ONLY branches at this

point

Aortic ARCH

Brachiocepalic trunk

Further branches into right subclavian artery &right

common carotid artery

Next branch = Left common carotid artery

Third branch = Left subclavian artery Following left subclavian artery, aorta proceeds caudally as

thedorsal aorta

Past diaphragm = abdominal aorta

Principle Arteries


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Principle Arteries

Arterial blood from brachiocephalic trunk has a

number of choices

Vertebral artery = towards cranium via transverseforamen of the cervical vertebrae & enters craniumviaforamen magnum

Thyrocervical trunk = destined for thyroid

Internal thoracic artery = destined for thymus,pericardium, sternum & anterior costals

Costovertebral trunk = destined for intercostalmuscles, posterior intercostals & spinal meninges

Subclavian artery = destined for upper appendage


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Principle Arteries


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Principle Arteries

Common carotid arteries will bifurcate into external

and internal carotid arteries External= supplying blood to external cranium

Internal= supplying blood to internal cranium (meninges,brain etc.)

At sight of bifurcation = carotid sinus

Site of pressure sensors (baroreceptors) & chemoreceptors(oxygen & CO2) that feed back into medulla oblongata

respiration center

Remember: internal carotid arteries are not the onlyarteries that deliver blood to the brain

Principle Veins


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Principle Veins

Cranial arterial blood is returned via internalor

external jugular veins

External cranium drained by external jugular vein

Internal cranium (brain via dural venous sinus)

Dural venous sinus is a unique vein: no valves


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Principle Arteries


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Principle Arteries

Towards upper appendage viasubclavian artery

Subclavian artery=axillary artery between 1st rib &

median edge of the humerus

Past medial side of humerus = Brachial artery

Around humerus = anterior & posterior humeralcircumflex arteries

Ring of arteries around brachial muscles

Bifurcates intoradial&ulnar arteries proximal to cubital

fossa Radial= pulse at the wrist


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Principle Veins


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Principle Veins From upper appendage

In order to return arterial blood that has passed out

of the capillary beds throughout the upper

appendage:

Combination ofsuperficial&deep veins

Superficial veins often quite variable in location

Deep veins usually follow arteries

Radial&ulnar veins draw blood from palmar region

Both anastomizeintobrachial vein

Superficial basilic vein draws blood ulnar&medial veins

Eventuallyanastomizewithbrachial vein axillary vein

Superficial cephalic veindraws blood from superficial

radial region of arm


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Appendicular veins (in fact

most veins throughout your

body) are formed after the

arteriesthey are much

more variable due to the

way they develop during

embryonic development.

Superficial & deep veins

drain blood from

cutaneous/integument vs.

muscles vs. bonerespectively.

Principle Veins


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Principle Veins

From upper appendage

Once all upper appendicular veins have

anastomized into axillary vein:

Axillary vein subclavian vein

Receives venous drainage from cranium as well External jugular vein

Internal jugular vein

Whereinternal jugular vein merges/anastomizes with

subclavian vein =brachiocephalic vein

Principle Arteries


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Principle Arteries

Abdominal:

4 branches from the dorsal/descending/abdominal aorta Celiac trunk

Splenic artery (to spleen & stomach)

L-gastric artery (to lesser curvature of the stomachmost cranialportion)

Common hepatic artery Further bifurcates into gastroduodenal artery &proper hepatic

artery

Superior mesenteric artery

Branches throughout mesentery (small intestine, upper 2/3 largeintestine, pancreas)

Left & right renal arteries

Inferior mesenteric artery

Branches throughout distal/terminal mesentery (terminal colon,rectum)


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Principle Arteries


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Principle Arteries

Abdominal:

Mesentery = mes enteric

reflection/fold of the peritoneal cavity

enteric usually infers gastrointestinal

middle of the gastro or intestinal tract Mesenteric artery = artery that branches within the

mesentery

Principle Veins


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Principle Veins

Abdominal veins:

Absorptive viscera do not directly drain into the

inferior vena cava

Absorptive viscera drain into hepatic portal vein

All venous blood from GI tract drains into liver via hepatic portalvein

Liver processes venous blood, then delivers back to inferior vena

cava (cranial to diaphragm) via hepatic vein (NOTE: notthe

hepatic PORTAL vein)

Lower extremities, renals & reproductive organs are theonly organs that directly drain into the IVC


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Principle Arteries


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Principle Arteries

Abdominal:

Note: there are additional accessory arteries that

are important but often variable

Gonadal artery(testicular/ovarian) usually arise from

dorsal aorta Caudal/distal to renal arteries

Variations exist: arise from renal arteries, cranial/proximal

to renal arteries etc.

Principle Arteries


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Principle Arteries

Lower appendage:

Common iliac artery is most distal bifurcation of the

dorsal aorta (marks termination of aorta)

Further branches into:

Internal iliac arteries(L/R) Supplies pelvic organs (reproductive organs, pelvic

diaphragm, urogenital diaphragm, gluteals etc.)

Note: reproductive organs excluding ovaries/testicles

External iliac arteries(L/R)

Once through inguinal ligament =femoral artery

Principle Arteries


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Principle Arteries

Lower appendage:

Femoral artery

Principle Arteries


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Principle Arteries

Lower appendage:

Femoral artery further bifurcates:

Deep femoral artery= supply to the coxal region

Femoral arteryspirals posterior to become popliteal

artery (spans popliteal fossa) Further bifurcates intoanterior&posterior tibial arteries

Principle Veins


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Principle Veins

Similar to the upper limb,

the lower limb drains

through a combination of

deep and superficial

arteries.

Thegreat saphenous vein

(most medial &

superficial) is a common

vein used for coronarybypass surgery.

Circulatory pathophysiology


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Atherosclerosis: scar tissue of the arteries

Recall elasticity of arteries (tunica media)

In cases of exaggerated stretching, the endothelial layer tends to

suffer damage

Circulating immune cells then sense this damage and act to form a

scar Actually start to attack endothelium & place fatty deposits under the

scar

Once scar & fatty deposits begin to calcify = atherosclerotic plaque

Plaque then inhibits/prevents stretch response

Inability for artery to respond to stretch = inability to control bloodpressure (blood pressure usually risesvelocity rises significantly)

Should really be thought of as a chronic inflammation of the

arterial system


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Boundary layer/unstirred layer effect: as the velocity of

the fluid within a tube increases, there is a decrease invelocity at the very edge of that tube Boundary layer immobile (actually an unstirred layer of

fluid)makes it very easy for these plaques and particles tocollect

When these particles collect, the plaque formation can increasefaster

A vicious cycle: formation of initial restriction = increased velocitythrough that region = greater boundary layer = greater ability for plaqueto take hold

Plaque formation can eventually starve flow


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Boundary layer has a fewnon-atherosclerosiseffects as

well: Very middle of the blood column = highest velocity

Edges of the blood column = lowest velocity

In larger vessels (arteries), erythrocytes characteristically

flow sideways (like a frisbee), due to velocity In capillaries, due to small diameter and thus slow flow rate,

erythrocytes take up rouleaux (cylinder/single file) pattern



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Atherosclerosis:scar tissue of the arteries

Note: while this occurs primarily in arteries (due to

stretching), this can occur in veins

Saphenous vein grafts for bypass surgery have been

shown to develop these same atherosclerotic plaquesdespite reduced elasticity in a vein


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Angioplasty: insertion of a balloon into the region of restriction in order to

restore flow. Newer techniques couple a balloon with a stent (wire structure to

hold artery open) that is usually coated with anticoagulants/anti-plaque

chemicals

Lymphatics & Immunity


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y p y

Lymphatic system is very closely related to the

circulatory system

Blood plasma that seeps from the capillary beds is

normally drawn back into the venous blood flow by

diffusion/osmosis Remember that this blood plasma will transfer gasses,

nutrients & metabolic wastes to-from circulation-tissue

15% does not return to venous flow

Must be returned to circulation via lymphatic system

If you do not return this fluid, EDEMA



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y p y

Functions of the lymphatic system

Fat absorption

Intestinal lipid absorption places chylomicrons

(intestinal lipid carrier proteins) into the lymphatic

system rather than the hepatic portal system

Systemic circulation has first-pass access to intestinal

lipids and fat-soluble vitamins (unlike amino acids &

glucose)

Returns interstitial fluid to circulation

Retains lymphocytes (lymph-based cells) for

immunity



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y p y

Drawbacks:

Because the lymphatic system is such a slow

system (low pressure, low fluid velocity), it

takes a great deal of time to get these fluids

back to central circulation 1 drawback: many carcinomic cells will tend to

collect in the lymphatic system if they become

mobile

Slow velocity, low pressure = tendency for these cancerouscells to stay within the lymphatics

If they take up residence in the lymphoid tissues, they will

grow into a tumor



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y p y

Lymphatic capillaries are intertwined

with the vascular capillary bed



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y p y

Lymphaticcapillariesare markedly

similar to veins:

One-way valves & requirement for

skeletal muscle propulsion (skeletal

muscle pump)

Where lymphatics differ from venous

system arises with lymph nodes

Nodes or collections of reticulartissue along the lymphatic vessel tract

Note: lymph does NOT contain

erythrocytes



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y p y

Lymph nodes

usually located

in characteristic

locations along

the lymphnetwork



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y p y

Note how lymph enters the

lymph nodes and permeates

through the reticular tissue

where immature lymphocytes

are located. These immaturelymphocytes then sample the

contents of the lymph and

develop tolerance or attack

postures.


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Recall how lymph

(fluid) is extracellular or

interstitial fluid.

This fluid will be sampled by dendriticcells in the lymph nodes, and presentedto

T-lymphocytes(immature, learning what to kill in the lymph nodes). If these

lymphocytes fail to learn correctly, they are killed. A great number of

lymphocytes are killed, only a very small amount are permitted to leave the lymph

node and fully mature into functional circulating lymphocytes.



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y p y

Lymph drainage is not proportional: rightlymphatic duct only drains from upper right

torsointo right subclavian vein. Thoracic duct

drains the rest of the body.



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y p y

Additional lymphoid organs

In addition to lymph nodes dispersed throughout

lymphatic circulation, there are accessory

lymphoid organs:

Tonsils Thymus

Spleen

Peyers patches throughout thegastrointestinal tract

Your tonsils are NOT


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Your tonsils are NOT

that thing that hangs

down from the back ofyour throat.


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Throughout your digestivetract are Peyers patches.

Essentially lymph nodes

that allows your immune

system to sample what

youve eaten.


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Circulatory System (Post)

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