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The Circulatory system

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The Circulatory system Powered By Docstoc
					Honors Anatomy & Physiology
Mrs. McMahon

THE CIRCULATORY SYSTEM
CIRCULATORY SYSTEM DEFINED

I.    Circulatory System Introduction
     A.    Circulatory System Defined
          1.    The system that supplies our cells‟ transportation
                needs
          2.    This system is extremely effective in meeting the needs
                of substances in the blood
          3.    Important structural components:
               a.   Heart
               b.   Blood vessels
LOCATION AND SIZE OF THE HEART

II.    The Heart
      A.    Location, size and position
           1.   The heart is located between the lungs in the lower
                portion of the mediastinum
           2.   About 2/3 of the mass of the heart is to the left of the
                center line
           3.   The heart is roughly the shape and size of a closed fist
           4.   It is positioned in the thoracic cavity between the
                sternum (front) and the thoracic vertebrae (back)
POSITION OF THE HEART
   5.    The apex (bottom point) lies on the diaphragm, pointing
         toward the left
   6.    Pressure on the sternum compresses/squeezes the
         heart
        a.   Rhythmic compression in this way can maintain blood
             flow during cardiac arrest
        b.   This, combined with artificial respirations, is known as
             CPR (cardiopulmonary resuscitation)
CHAMBERS OF THE HEART
 B.    Anatomy
      1.    Heart Chambers
           a.       The heart contains 4 hollow chambers
           b.       The 2 upper chambers are atria and the 2 lower
                    chambers are ventricles
           c.       Atria are smaller than ventricles
                i.      Atrial walls are thinner and less muscular
                ii.     Atria are often called “receiving chambers” because
                        blood enters the heart through veins that open into
                        these atria
CHAMBERS OF THE HEART (CONT’D)
     d.       Eventually blood is pumped from the heart into arteries
              that exit from ventricles
          i.      Therefore, they are sometimes called “discharging
                  chambers”
     e.       Each heart chamber is named for its location
          i.      Right and Left Atria
          ii.     Right and Left Ventricle
     f.       The wall of each chamber is composed of cardiac
              muscle tissue called myocardium
     g.       The atria are separated by the inter-atrial septum
     h.       The ventricles are separated by the inter-ventricular
              septum
CHAMBERS OF THE HEART (CONT’D)
     i.       Each chamber is lined by a thin layer of smooth tissue
              called endocardium
          i.      Inflammation of this lining is called endocarditis
          ii.     If inflamed, the lining can become rough and abrasive
                  for passing red blood cells
     j.       Blood flowing over a rough surface is subject to clotting
              and thrombosis may occur
          i.      Endocarditis or injuries to blood vessel walls often
                  cause the release of platelet factors
          ii.     The result is often the formation of a fatal blood clot
COVERING OF THE HEART
   2.        Pericardium
        a.      This is the covering of the heart
        b.      It consists of 2 layers of fibrous tissue with a small
                space between
        c.      Visceral pericardium (aka epicardium) – inner layer
        d.      Parietal pericardium – outer layer
        e.      A thin film of pericardial fluid moistens the space
                between the heart and the pericardial sac
        f.      If the pericardium becomes inflamed, pericarditis results
AV VALVES OF THE HEART
   3.    Heart valves
        a.   Atrioventricular (AV) valves separate the atrial chambers
             above and the ventricles below
        b.   Bicuspid valve – AV valve separating left atrium and
             ventricle
        c.   Tricuspid valve – AV valve that separates right atrium
             and ventricle
        d.   The AV valves prevent backflow of the blood into the
             atria when ventricles contract
        e.   Strong, stringlike chordae tendinae attach AV valves to
             the heart walls
SL VALVES OF THE HEART
     f.   Semilunar (SL) valves are located between the ventricles
          and the large arteries that carry blood away
     g.   Like the atria, ventricles contract together, so the SL
          valves open and close together
     h.   The pulmonary semilunar valve allows blood to flow from
          the right ventricle to the lungs, but not back
     i.   The aortic semilunar valve allows blood to flow out of the
          left ventricle into the aorta, but not back
ACTIONS OF THE HEART
 C.    Heart Action
      1.    The heart serves as a muscular pumping device for
            distributing blood to all parts of the body
           a.   Systole – heart contraction
           b.   Diastole – heart relaxation
      2.    When the heart beats, the atria contract first
           a.   This atrial systole forces blood into the ventricles
      3.    Once filled, the ventricles contract
           a.   This ventricular systole forces blood out of the heart
      4.    The direction of blood flow must be directed and
            controlled
      5.    The AV and SL valves make this happen
SOUNDS OF THE HEART
 D.    Heart Sounds
      1.    The heart sounds are rhythmical and repetitive and are
            often described as “lub dup”
      2.    The „lub‟ is caused by closure of AV valves as ventricles
            contract (systole)
           a.   This closure prevents blood from rushing back into the atria
                during ventricular contraction
           b.   The „lub‟, 1st sound, is longer and lower in pitch
      3.    The „dup‟ is caused by closure of SL valves when
            ventricles relax (diastole)
           a.   The pause between „lub‟ and „dup‟ is shorter than between
                „dup‟ and next „lub‟
CONTRACTIONS OF THE HEART
 E.   Blood Flow Through the Heart
      1.   The heart acts as 2 separate pumps
      2.   The right atrium and ventricle perform a task quite
           different from the left atrium and ventricle
      3.   When the heart “beats,” atria contract simultaneously
           a.   This is called atrial systole
      4.   The ventricles fill and contract simultaneously
           a.   This is called ventricular systole
      5.   Even though right and left atria and right and left
           ventricles contract together, the right and left sides still
           act as separate pumps
PATH OF BLOOD FLOW THROUGH THE HEART
   6.   Blood enters the right atrium through 2 large veins
        called the superior and inferior vena cava
        a.   The entering blood is oxygen-poor
        b.   After entering the right atrium, blood is pumped through the
             tricuspid (right AV) valve into the right ventricle
        c.   When the ventricles contract, blood in the right ventricle is
             pumped through the pulmonary SL valve into pulmonary
             artery
        d.   From here, blood goes to the lungs where O2 is added and
             CO2 is lost
PATH OF BLOOD (CONT’D)
    7.   Oxygen-rich blood returns to the left atrium through the
         4 pulmonary veins
         a.   It then passes through the biscuspid (L AV) Valve into the
              left ventricle
         b.   When ventricles contract, blood is forced through the aortic
              SL valve into the aorta
         c.   From here, it is distributed to the rest of the body
TYPES OF CIRCULATION
   8.   The 2 sides of the heart pump through separate
        „circulations‟
        a.   Pulmonary Circulation – movement of blood from right
             ventricle to the lungs
        b.   Systemic Circulation – movement of blood from left
             ventricle throughout the body as a whole
BLOOD FLOW TO THE HEART
 F.   Blood Supply to the Heart
      1.   To sustain life, the heart must pump blood on a regular,
           ongoing basis
      2.   As a result, the heart muscle requires a constant
           supply of blood with nutrients and O2 to function
           a.   Coronary Circulation – delivery of good blood to the heart
                and bad blood back to venous system
      3.   Blood flows into the heart by way of two small blood
           vessels
           a.   Right and left coronary arteries
BLOCKAGE IN CORONARY ARTERIES
     b.   Coronary arteries are the first branches of the aorta
     c.   In both coronary thrombosis and coronary embolism, a
          blood clot plugs a coronary artery
     d.   Deprived of oxygen, heart muscle cells die  myocardial
          infarction (MI)
           i.  MI is a common cause of death during middle and late
               adulthood
           ii. Recovery is possible if the amount of tissue death is small
               enough that undamaged muscle can still pump
     e.   Angina pectoris – pain caused when myocardium is
          deprived of oxygen
           i.  It is often a warning that coronary artery is blocked and no
               longer functioning correctly
CORONARY BYPASS SURGERY
        f.   Coronary bypass surgery is a frequent treatment for
             severely blocked coronary arteries
             i.  Veins are “harvested” or removed from other areas of the
                 body
             ii. They are used to bypass partial blockages in coronary
                 arteries


   4.   After blood passes through capillaries in the
        myocardium, it flows into cardiac veins which empty
        into the coronary sinus and finally the right atrium
THE CARDIAC CYCLE
 G.   Cardiac Cycle
      1.   Cardiac Cycle – each complete heartbeat
           a.   Includes atrial and ventricular systole and diastole
           b.   Each cycle takes about 0.8 seconds to complete
           c.   This is if the heart is beating at an average rate of ~72
                beats per minute
      2.   Stroke Volume – volume of blood ejected from
           ventricles during each beat
      3.   Cardiac Output – volume of blood pumped by one
           ventricle per minute
           a.   This averages about 5 L in a normal, resting adult
CARDIAC MUSCLE CELLS
 H.   Conduction System of the Heart
      1.   Cardiac muscle fibers must be coordinated by electrical
           impulses to be effective
      2.   Although cardiac muscle rate is controlled by
           autonomic nerve signals, the heart has its own built-in
           conduction system for coordinating contractions during
           the cardiac cycle
CARDIAC MUSCLE CONDUCTION
   3.   All cardiac muscle fibers in each region of the heart are
        electronically linked together
        a.   Intercalated disks are electrical connectors within muscle
             fibers
        b.   They join muscle fibers into a single conducting unit
             powerful enough to send impulses straight through the
             heart wall
   4.   Atria and ventricles contract simultaneously because
        they are electrically linked
IMPULSE GENERATORS IN THE HEART
   5.   Four structures embedded in the heart wall generate
        specialized impulses to specific locations within the
        heart
        a.   They ensure the atria and ventricles contract effificiently
        b.   They are:
              i.   Sinoatrial node – aka SA node / pacemaker
              ii.  Atrioventricular node – aka AV node
              iii. AV bundle – aka Bundle of His
              iv.  Purkinje fibers
        c.   Impulse conduction normally starts in the SA node
             (pacemaker)
        d.   Then it spreads in all directions through the atria causing
             atrial fibers to contract
CONTROLLING THE PACE OF THE HEART
     e.   When impulses reach AV node, it relays them through the
          Bundle of His and Purkinje fibers to the ventricles, causing
          them to contract
     f.   Therefore, normally a ventricular beat follows each atrial
          beat
           i.  Endocarditis or MI can damage the conduction system and
               disrupt the heart rhythm
           ii. An example if „heart block‟ when impulses are blocked
               from getting through to the ventricles, slowing the pace of
               the heart drastically
     g.   Physicians may treat this by implanting an artificial
          pacemaker
           i.  An electrical device that stimulates regular ventricular
               systole
DEFINING AN ELECTROCARDIOGRAM
 I.   Electrocardiogram
      1.   Electrocradiogram is commonly known as ECG
      2.   It is the graphic record of the heart‟s electrical activity
      3.   A normal ECG has 3 distinctive waves
           a.   P wave
           b.   QRS complex
           c.   T wave
      4.   Depolarization – electrical activity that triggers
           contraction of heart muscles
      5.   Repolariziation – begins just before relaxation phase of
           cardiac muscle activity
WAVES OF AN ELECTROCARDIOGRAM
   6.   In a normal ECG, the small P wave occurs with
        depolarization of the ventricles
   7.   The QRS complex occurs as a result of depolarization
        of the ventricles
   8.   The T wave results from electrical activity generated by
        repolarization of the ventricles
   9.   Changes in an ECG are indicative of MI or heart
        disease
ECG IMAGES




ECG video
ECG Video 2
 MAIN BLOOD VESSEL TYPES
III.        Blood Vessels
       A.        Types of Blood Vessels
            1.         Artery – vessel carrying blood away from the heart
                  a.     The largest artery in the body is the aorta
                  b.     Arteries subdivide and become progressively smaller
                         arterioles
                  c.     Arterioles control the flow into microscopic exchange
                         vessels called capillaries
            2.         Capillary Beds – location of the exchange of nutrients
                       and respiratory gases
                  a.     Blood is drained from the capillary beds and enters the
                         small venules
MAIN BLOOD VESSEL FLOW
       3.   Venules – each join with other venules and increase in
            size becoming veins
            a.   The largest veins are the superior and inferior vena cava

  B.   Main Blood Vessel Flow Summary
       1. Arteries carry blood away from heart toward capillaries
       2. Veins carry blood toward the heart away from capillaries
       3. Capillaries carry blood from tiny arterioles into tiny
          venules
       4. The aorta carries blood out of the left ventricle of the
          heart
       5. Venae cavae return blood to the right atrium after
          systemic circulation
MAIN BLOOD VESSEL STRUCTURE
 C.   Blood Vessel Structure
      1.   Both arteries and veins consists of three layers (coats)
           a.   Tunica adventitia – outer layer made of connective tissue
                fibers, which reinforce the wall to keep it from bursting
                under pressure
           b.   Tunica media – middle layer of smooth muscle tissue and
                elastic fibrous tissue, which is much thicker in arteries than
                in veins
           c.   Tunica intima – single layer of squamous epithelial cells
                called endothelium, lining the inner surface of the entire
                circulatory system
BLOOD VESSEL STRUCTURE (CONT’D)
   2.   Microscopic capillaries have one single layer
        a.   Capillaries are extremely thin and not visible to the naked
             eye
        b.   Their membranes have only the tunica intima layer which
             allows substances such as glucose, oxygen, and wastes to
             easily pass through
        c.   Precapillary sphincters control the entrances to capillaries
             and determine into which capillary blood will flow
MAIN BLOOD VESSEL FUNCTION
 D.   Blood Vessel Function
      1.   Arteries and Arterioles:
           a.   Distribute blood from the heart to capillaries all throughout
                the body
           b.   Help to maintain arteriole blood pressure at a normal level
                by constriciting and dilating
      2.   Veins and Venules:
           a.   Collect blood from capillaries and return it to the heart
           b.   Serve as blood reservoirs because they can expand to hold
                a larger volume of blood or constrict to hold a smaller
                volume
      3.   Capillaries:
           a.   Function as exchange vessels
SYSTEMIC CIRCULATION
III.        Circulation
       A.        Systemic Circulation –
            1.     The left ventricle pumps blood into the aorta
            2.     From there, it flows into arteries that carry it into
                   tissues and organs of the body
            3.     Within each structure, blood moves from arteries to
                   arterioles to capillaries (where exchange occurs)
            4.     Next, blood flows out of each organ through venules
                   and veins
            5.     Eventually, blood drains into the inferior and superior
                   vena cava
            6.     These veins return blood to the right atrium to
                   complete the cycle
PULMONARY CIRCULATION
 B.   Pulmonary Circulation –
      1.   In order for blood to come full circle and reach back to
           the left ventricle, it must first go through pulmonary
           circulation
      2.   Venous blood moves from the right atrium into the right
           ventricle
      3.   From here it goes to the pulmonary artery for transport
           to lung arterioles and capillaries (where exchange
           occurs)
      4.   Oxygenated blood then flows back through lung
           venules into 4 pulmonary veins and returns to the left
           atrium of the heart
      5.   From here, it enters the left ventricle to begin systemic
           circulation again
HEPATIC PORTAL CIRCULATION
 C.   Hepatic Portal Circulation –
      1.   Veins from the spleen, stomach, pancreas, gallbladder,
           and intestines do not pour directly into the inferior vena
           cava, instead they send their blood through to the liver
           through the hepatic portal vein
      2.   Blood then passes through the liver before reentering
           the regular venous system returning to the heart
      3.   In this process, blood passes through an additional
           capillary bed in the liver
           a.   This allows for the liver to store excess glucose from food,
                providing the blood leaving the liver with a normal blood
                glucose concentration
           b.   Liver cells also remove and detoxify poisonous substances
                that may be present in the blood
FETAL CIRCULATION
 D.   Fetal Circulation
      1.   Circulation in the body before birth differs from
           circulation after birth because the fetus must secure
           oxygen and food from maternal blood instead of from
           its own lungs and digestive organs
      2.   Three specialized blood vessels (within the umbilical
           cord) must carry the fetal blood to the placenta, where
           exchange occurs, and then return it to the fetal body
           a.   2 small umbilical arteries
           b.   1 larger umbilical vein
      3.   In fetal circulation, arteries carry oxygen-poor blood
           while veins carry oxygen-rich blood
FETAL CIRCULATION (CONT’D)
    4.   Ductus venosus – a continuation of the umbilical vein
         which serves as a shunt, allowing most blood from the
         placenta to bypass the under-developed fetal liver and
         empty directly into the inferior vena cava
    5.   Two other structures allow most blood to bypass the
         developing lungs, which remiain collapsed until birth
         a.   Foramen ovale – shunts blood from the right atrium directly
              into the left atrium
         b.   Ductus arteriosus – connects the aorta and pulmonary
              artery
    6.   When a newborn takes its first deep breaths, the
         circulatory system is subject to increased pressure, and
         these structures collapse and become non-functional
BLOOD PRESSURE
IV.        Blood Pressure
      A.        The force exerted on your blood vessel wall as
                blood flows through the body
           1.         When the heart contracts it sends a surge of blood
                      through the blood vessels and pressure increases
                 a.     This is called systolic pressure
           2.         Between each beat (contraction), the heart relaxes
                 a.     This is called diastolic pressure
      B.        Blood pressure is written as a fraction
           1.         Systolic is the numerator (top) and diastolic is the
                      denominator (bottom)
           2.         It is recorded in millimeters of mercury (mm Hg)
FACTORS IMPACTING BLOOD PRESSURE
C.   Several factors impact blood pressure
     1.   Blood volume – direct relationship with BP
          a.   Higher blood volume = higher blood pressure
          b.   The diameter of arteries plays an important role in determining
               blood volume
     2.   Strength of heart contractions – direct relationship with BP
          a.   Stronger contraction = higher blood pressure
     3.   Heart rate – direct relationship with BP
          a.   Faster heart rate = higher blood pressure
          b.   However, if stroke volume decreases as ventricles are contracting
               faster, they have less time to fill so they are pumping less blood
          c.   This demonstrates an inverse relationship
     4.   Blood viscosity – direct relationship with BP
          a.   Less viscosity (thickness) = lower blood pressure
NORMAL BLOOD PRESSURE
 D.   Normal Blood Pressure
      1.   Normal blood pressure is said to be 120/80 mm Hg,
           but new guidelines are saying this is the high end of
           normal
      2.   New US guidelines say the risk of cardiovascular
           disease begins at 115/75 mm Hg
      3.   The normal for 17 year old females is 111/66
      4.   The normal for 17 year old males is 118/67
      5.   Hypotension – 90/60 and below
      6.   Hypertension – 140/90 and above
ALTERING BLOOD PRESSURE
 E.   Foods that Influence Blood Pressure
      1.   “Yes” foods – apples, avocado, bananas, broccoli, fish,
           grapes, oats, orange juice, water
      2.   “No” foods – high salt foods, medium salt foods,
           saturated fat, hydrogenated oils, partially hydrogenated
           vegetables oils
 F.   Blood Pressure Lowering Tactics
      1.   Stop smoking
      2.   Reduce weight
      3.   Reduce salt and protein intake
      4.   No caffeine
      5.   Suffificent rest / no oversleeping
     PULSE

V.        Pulse
     A.        When taking a pulse, you feel an artery expanding
               and then recoiling alternately
     B.        A pulse can be detected best at certain pulse points
          1.         In the head and neck:
                a.     In front of the ear over the superficial temporal artery
                b.     On the neck over the common carotid artery
                c.     Below the corner of the mouth over the facial artery
PULSE POINTS
   2.   In the upper limb:
        a.   In the armpit over the axillary artery
        b.   At the bend of the elbow along the medial side over the
             brachial artery
        c.   On the wrist over the radial artery
   3.   In the lower limb:
        a.   In the groin over the femoral artery
        b.   Behind the knee over the popliteal artery
        c.   On the front surface of the foot over the dorsalis pedis
             artery

				
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