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					               Exam 4 Review Notes – Chapter 11 – Cardiovascular System

Heart Anatomy & Circulatory System – General
       Closed system – blood is not “loose” in the body, blood remains in blood vessels & heart
       Double system – half the heart pumps deoxygenated blood (right side), the other half pumps oxygenated blood
        (left side) – very efficient system, the two sides don’t mix
       Heart is a double organ/pump:
             o Pulmonary circuit – heart lungs  heart
             o Systemic circuit – heart  body tissues  heart
             o Like a large figure eight, the systemic circuit has more vessels because it has more “ground” to cover
Capillary beds exist within tissues to perform gas exchanges:
       Within lungs, CO2 eliminated, O2 added to blood
       Within body tissues, O2 is absorbed and CO2 is excreted into blood
       Capillaries exist within a millimeter of all tissues
Heart is approx. size of clenched fist, positioned in mediastinum, 2/3 to left of midline, tilted forward
Heart is medial to lungs, superior to diaphragm, anterior to esophagus & descending aorta
Heart surface anatomy:
       Sulci – grooves that indicate boundaries between heart chambers
       Coronary sulcus (between atria & ventricles ) eg., atrioventricular sulcus
       Interventricular sulci (between ventricles)
       Apex – inferior, pointed tip
       Base – superior back end of heart, point of attachment for great vessels (ie., superior vena cava, aorta)
Heart chambers – 4 chambers:
       Atria (2) – superior receiving chambers
            o receive blood from veins
            o auricles are flaps which cover atria on outside of heart
            o right atrium receives deoxygenated blood from systemic circuit through vena cavae (inferior & superior)
                and coronary sinus (part of coronary circulation)
            o left atrium receives oxygenated blood from pulmonary circuit through pulmonary veins
       Ventricles (2) – inferior pumping chambers
            o Send blood to arteries
            o Receives blood from atria
            o Right ventricle receives deoxygenated blood from right atria and pumps to pulmonary circuit through
                pulmonary arteries
            o Left ventricle receives oxygenated blood from left atria and pumps to systemic circuit through aorta
Arteries – away from heart; Veins – towards heart – ALWAYS
Heart septa – internal walls to separate chambers – 2 of them:
    1. Interatrial septum – between atria
    2. Interventricular septum – between ventricles
Heart valves – one-way, direct blood flow passively – blood pushes them open & closed, 2 valves:
    1. Atrioventricular (location name) – between atria and ventricles – cuspid valves
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                Exam 4 Review Notes – Chapter 11 – Cardiovascular System

              Tricuspid – right side
              Bicuspid (mitral valve) – left side
              Like 1-way swinging doors pushed by blood, blood holds the valves shut
              “tri before you bi”
              AV valves are anchored to structures in ventricles by:
                      Chordae tendineae – strong, fibrous strings that prevent cusp inversion into atria
                      Papillary muscles – conical (“hot dog” shaped) extensions of myocardium (muscle) that contract
                        & pull on chordae tendineae to close valves
    2. Semilunar valves – between ventricles and arteries leading from heart, prevent back flow into ventricles, 2
       valves:
            Pulmonary semilunar valve – right side
            Aortic semilunar valve – left
            Have 3 “folds”/cusps
Heart wall – 3 layers – start from the inside and work to the outside
    1. Endocardium – inner lining, consists of endothelium (epithelial, simple squamous), lines chambers, valves,
       septa, & blood vessels – very thin layer
    2. Myocardium – thickest layer – cardiac muscle tissue, very thick in left ventricle which must pump to entire
       systemic circuit, contains inherent rhythmicity (acts like nervous tissue – conduction system, discussed later)
    3. Pericardium – outer layer, breaks down into multiple layers:
            Epicardium – aka, visceral pericardium – inner layer of serous membrane, thin, fibrous, transparent,
               attaches to outside of heart
            Parietal pericardium – outer layer of serous membrane, secretes lubricating pericardial fluid into
               pericardial cavity (space between serous layers)
            Fibrous pericardium – tough, outer, fibrous coat – reinforces serous layers
            Pericardial cavity is between epicardium and parietal pericardium
            Pericardial sac encloses heart & bases of great vessels at base of heart
Heart Physiology
Cardiac cycle – events of one heartbeat:
       Systole – atria contract, ventricles fill, ventricles contract, blood forced into aorta & pulmonary trunk
       Diastole – NO contraction, atria relax & fill, ventricles passively receive blood from the atria (semilunar valves
        close)
Cardiac output (CO) – stroke volume & heart rate
       Stroke volume (SV) is the amount of blood pumped out by ventricle with each heartbeat
       Not all blood in the heart is pumped out
       Cardiac output is the amount of blood pumped out in 1 minute, calculated as CO = SV * heart rate per minute
       Amount of blood returned to heart by veins (venous return) directly impacts SV
       Heart rate (and thus CO) is effected by drugs, hormones, & ions
Blood pressure – pressure exerted by blood on inner walls of blood vessels, measured in arteries where it is higher
       Blood pressure rises & falls within vessels as the heart contracts & relaxes, keeps blood moving

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       High blood pressure can damage vessels, low blood pressure can shut down kidneys
       Systole – contraction of ventricles causes arterial pressure to rise – systolic pressure (SBP) is the maximum
        pressure during contraction
       Diastole – relaxation & refilling of ventricles while semilunar valves are closed, arterial pressure drops as blood
        flows “downstream”, diastolic pressure (DBP) is the minimum pressure just before the next systole
       Average BP 120/80 – although this is now considered borderline high
       Arterial surge in pressure = pulse, pulse rate = heart rate
       Average adult pulse = 60 – 80 BPM
       Blood pressure is measured by constricting a arterial flow (usually brachial artery) - gradually releasing pressure,
        when first pulse sounds can be heard = systolic, when sounds disappear = diastolic
Conduction system of heart
Specialized cardiac muscle tissue within heart acts like nervous tissue – capable of generating & conducting action
potentials (depolarization & repolarization) – this stimulates myocardium contraction, sets heart rhythm
5 components of intrinsic conduction system (from text) – in order of conduction:
    1. Sinoatrial node – pacemaker
            Located in right atrium, spontaneously depolarizes
            activates atrial contraction for both atria
            Origin of heartbeat
            Action potential spreads through myocardium to next node:
    2. Atrioventricular (AV) node
            Located in right atrium in interatrial septum (septum between atria)
            Action potential spreads to:
    3. Atrioventricular bundle (bundle of His):
            Only path between atria & ventricles
            If this is broken, the atria & ventricles beat independently – called C.T. block? (C.T. can’t conduct
               impulse)
            Carries action potential to:
    4. Bundle branches – left & right:
            Located in interventricular septum
            Carries action potential to respective ventricles
            Conduction continues to:
    5. Purkinje fibers:
            Conduction fibers within the myocardium of the ventricles
            directly stimulates ventricles for contraction
electrocardiogram – record of electrical activity of heart muscle (depolarization & repolarization):
       electrodes applied to skin & pick-up electrical activity from heart, depicted by “waves”
       P wave – SA node stimulates atrial depolarization
       QRS complex – ventricular depolarization, more tissue depolarizing creates a bigger wave, occurs prior to
        ventricle contraction, large wave hides atrial repolarization
       T wave – ventricular repolarization
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Heart sounds – caused by closing of heart valves
       AV valves close – prevents blood from flowing backward into atria – “lubb” (systole?)
       Semilunar valves – prevents blood from flowing backwards into ventricles – “dupp”(diastole?)
Any kind of abnormal heart sound is called a heart murmur – some are pathological, some are benign – may indicate a
valve disorder; possible causes include congenital defects, scarring, & backflow
Blood vessel anatomy – 3 types of blood vessels – arteries, veins, & capillaries – typical blood flow:
        Heart artery arterioles capillaries venules veins heart
Entire body (with a few exceptions) is perfused with capillaries
General anatomy of blood vessels – from inside to outside – 3 tunics/coats:
       Tunica intima (interna) – innermost, thin, made of endothelium (simple squamous E.T.) & C.T., continuation of
        endocardium of heart (see discussion of heart layers previously)
       Tunica media – middle, thickest, made of muscle fiber (smooth muscle)
             o Arranged circularly – facilitates vascular spasm (phase 1 of hemostasis)
             o Includes C.T. made up of collagen (protein) & elastic – collagen reacts with platelets during phase 2 of
                hemostasis to become “sticky”
       Tunica externa (adventitia) – outermost layer, toughest, fibrous C.T. sheath, anchors blood vessels to external
        tissues
Arteries – carry blood away from the heart, oxygenation depends on circuit – ALWAYS
       Under the highest pressure, thus have thicker walls – tunica media is thicker (compared to veins)
       Usually carry oxygenated blood (in systemic circuit) – this statement is true because the systemic circuit (SC) is
        larger than the pulmonary circuit (PC), thus SC has MORE arteries
       Pulmonary arteries carry oxygen poor blood, systemic arteries carry oxygen rich blood
       Arterioles are smallest arteries – deliver blood to capillaries – regulate capillary blood flow (smooth muscle in
        arteriole can restrict blood access to capillaries)
Veins – return blood to the heart, oxygenation depends on circuit – ALWAYS
       Under lowest pressure, thus have thinner walls (compared to arteries)
       Wider lumen (opening) and valves in veins traveling against gravity – facilitates blood returning (called “venous
        return”) to heart under lower pressure
       Located more superficially than arteries (safety mechanism) – if injured, bleeding is slower than artery
       Venules – smallest veins, receive blood from capillaries, very close to capillaries in structure
       Overall diameter of veins is larger than comparable arteries to facilitate venous return under lower pressure
Vein valves are passive – they close as blood passes (one way swinging door again!) – not all veins have valves
Tunica intima is approximately the same in arteries & veins
Tunica media is very different: thick in arteries, thin in veins
Venous return – the return of blood through the veins to the heart, accomplished by:
       Valves – in veins that go against gravity (why do I keep hearing “Defying Gravity”?)
       Muscular compression – skeletal muscles “milk” the veins, keeping the blood moving, but the body needs to
        KEEP MOVING

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         Respiratory pump – the thoracic cavity is closed – when a breath is drawn (inhalation), a vacuum is created
          (pressure drops) that sucks blood up into the veins into the chest (venae cavae)
Arterial blood movement is accomplished by pumping of heart
Arteries & veins are for transport only – capillaries are where diffusion in & out of the circulatory system occurs
Capillaries – thinnest walls: tunica intima only (endothelium & C.T.)
         Diffusion of nutrients, ions, wastes, & hormones go in & out
         Some capillaries form beds – blood flow to the capillaries & beds is regulated by arterioles and precapillary
          sphincters within capillary beds:
              o If tissues do not need capillary support (nutrients, ions, waste, ion diffusion), arteriole may contract and
                  blood passes by the capillary bed OR
              o If tissues do not need capillary support, precapillary sphincters close and blood shunts directly past the
                  capillaries to venules
        Property             Arteries               Veins                            capillaries
        Directional flow     Away from heart        Toward heart                     from arterioles to venules
        Pressure level       High pressure          Low pressure
        Flow control         Heart contraction      Valves                           Access allowed by:
                                                    Skeletal muscle compression       Arterioles smooth
                                                    Respiratory pump                   muscles
                                                                                      Precapillary sphincters
        Wall thickness       Thick – tunica media   Thinner – tunica media is thin   Only one layer – tunica
                             is very thick                                           intima – VERY thin to allow
                                                                                     for diffusion
        Oxygenation          Systemic – high        Systemic – low                   Both high & low – depends
                             Pulmonary – low        Pulmonary – high                 on stage of diffusion
        Function             Transportation         Transportation                   Delivery (diffusion)
        Location             Deep                   Superficial                      Throughout tissues
        Outer Diameter       narrower               Wider                            n/a
        Inner lumen          narrower               Wider                            n/a


Special circuit – hepatic portal system:
         Carries venous blood from digestive organs to liver
         All substances absorbed in digestive tract (nutrients, wastes, toxins, etc.) are put through the liver first before
          going to the heart
         Liver stores & converts nutrients, detoxifies blood
         Liver receives arterial blood (ie, oxygenated blood) from hepatic artery
Special circulation – fetal circulation:
         Mom has done the “breathing” and “liver” work for baby (Mom has digested nutrients), so lungs & liver are
          bypassed in fetus (primary difference from adult circulation) – non-functional lungs & digestive tract
         Hepatic portal circulation is bypassed
         Oxygenation of blood comes from placenta – ALL exchanges comes from placenta (nutrients, etc.)

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          Some blood goes to lungs because developing lung tissue needs oxygen
          At time of birth, C.T. closes these special structures
          Following table lists fetal circulation structures in blood flow order from placenta to heart to placenta:
        Circulatory Structure in Fetus      Oxygenation   Function                              “Evolves” after birth
                                            level
        Placental or umbilical vein         High          Return O2 rich blood from             Round ligament of liver -
                                                          placenta to fetus                     C.T. closes structure after
                                                          (has a branch that joins portal       birth
                                                          vein)
        Ductus venosus - Branch of          High          Bypasses liver (hepatic portal        Ligamentum venosum –
        umbilical vein                                    circulation), empties into inferior   C.T. closes structure after
                                                          vena cava                             birth
        Foramen ovale – opening             n/a           Shunts blood from right side of       Fossa ovalis
        between atria                                     heart to left side – bypasses                        st
                                                                                                (closes with 1 breath due
                                                          pulmonary circuit                     to pressure change)
        Ductus arteriosus – opening         n/a           Shunts blood from pulmonary           Ligamentum arteriosum
        between pulmonary trunk &                         artery to aorta – bypasses                           st
                                                                                                (closes with 1 breath due
        aorta                                             pulmonary circuit                     to pressure change)
        Placental or umbilical arteries     Low           Carry blood back to placenta to       Umbilical ligaments –
        (2) – branches off internal iliac                 get re-oxygenated                     C.T. closes structure after
        arteries                                                                                birth


Special circulation – coronary circuit – part of systemic circuit
          Coronary arteries are 1st vessel to branch from aorta (ascending aorta) before the 3 major branches
          Supply myocardium (cardiac muscle tissue) of heart with oxygen
          Drain into right atrium via coronary sinus
          Like any part of systemic circuit, heart has capillaries in its tissues that supply oxygen & nutrients
Special circulation – circle of Willis – supplies oxygen to brain
          Two sources of oxygen from heart: vertebral arteries & internal carotid arteries
          Circle creates a “back-up” system of blood supply if there is a problem on one side, the other side is still
           available




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