Cardiovascular System - Blood Chapter 17 - PowerPoint PPT Presentation

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Title: Cardiovascular System - Blood Chapter 17


1
Cardiovascular System - BloodChapter 17
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  • Blood
  • - the only fluid tissue
  • Average adult has approximately 5L of blood
  • Composed of formed elements and plasma
  • Formed elements are cells and cell fragments
  • Plasma is liquid portion of blood
  • Hematocrit separating blood by centrifugation
    into its formed elements and liquid components
  • Erythrocytes (red blood cells) 45
  • Plasma nearly 55
  • Other cells and platelets less than 1

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  • Functions of blood
  • 1. Distribution
  • A. delivery system for oxygen from the lungs and
    nutrients from the digestive system to all body
    cells.
  • B. Transporting metabolic waste products from
    cells to elimination sites.
  • C. Transporting hormones from endocrine glands
    to target organs.
  • 2. Regulation
  • A. Helps maintain proper body temperature and
    distributes heat throughout the body.
  • B. Maintains proper pH in body tissues.
  • C. Maintains adequate fluid volume in the
    circulatory system.

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  • 3. Protection
  • A. Preventing blood loss.
  • B. Prevents infection with antibodies and
    leukocytes (white blood cells).
  • Plasma
  • Straw-colored sticky fluid that makes-up about
    55 of blood volume.
  • 90 water
  • Also contains over 100 dissolved solutes
    including nutrients, gases, hormones, waste
    products, ions, and plasma proteins.
  • Plasma proteins are most abundant solutes and are
    mostly produced by the liver
  • They are not taken up by cells
  • Maintain osmotic pressure of fluids, help to
    carry some nutrients, serve as clotting factors,
    etc.
  • Contents constantly adjusted to help maintain
    homeostasis.

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  • Formed Elements
  • 1. Erythrocytes Red Blood Cells (RBCs)
  • Anucleate biconcave discs
  • Extremely small size and shape result in huge
    surface area
  • Filled (97) with hemoglobin the oxygen
    carrying molecule
  • Composed of four polypeptide (protein) chains
    each arranged around a heme group that contains
    an iron atom
  • Each molecule of hemoglobin can carry four
    molecules of oxygen
  • Oxyhemoglobin when combined with oxygen

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  • Lack mitochondria and thus do not use any oxygen
  • Useful lifespan is 100-120 days 100 million
    die/minute
  • Production of erythrocytes
  • General blood cell formation is hematopoiesis or
    hemopoiesis
  • Occurs in red bone marrow
  • All formed elements arise from hemocytoblasts,
    but they develop differently in response to
    specific hormones and growth factors.
  • Erythrocytes are first released into the blood
    stream as reticulocytes (count these to estimate
    RBC production)
  • Balance is maintained within narrow limits as too
    few lead to tissue hypoxia while too many make
    the blood too viscous.
  • Erythropoietin is the primary hormone (from liver
    and kidneys) that stimulates RBC production in
    response to low oxygen delivery to tissues
  • Iron and B-complex vitamins required

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  • Disorders due to erythrocytes
  • A. Anemias
  • - when blood has abnormally low oxygen-carrying
    capacity
  • - hemorrhagic, hemolytic, aplastic,
    iron-deficiency, pernicious, abnormal hemoglobin
    (thalassemias and sickle-cell)
  • B. Polycythemia
  • - abnormal excess of RBCs leading to thick
    blood
  • 2. Leukocytes White blood cells (WBCs)
  • - only formed elements that are complete cells
  • - vary with health
  • - crucial in fighting disease
  • - can leave circulatory system (diapedesis),
    move by ameboid movement, and use chemotaxis
    to find areas of tissue damage or
    infection.

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  • - two main types
  • - Granulocytes have specialized granules in
    them
  • - phagocytes
  • - Agranulocytes lack these granules
  • - Lymphocytes most are located in the lymph
    tissues
  • - key to immunity
  • - T lymphocytes attack virus-infected cells
    and tumor cells directly
  • - B lymphocytes produce antibodies
  • - Monocytes macrophages present w/ chronic
    infections
  • Disorders due to Leukocytes
  • A. Leukemias cancerous condition in which WBCs
    proliferate and suppress or impair normal bone
    marrow infection
  • B. Mononucleosis viral disease

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  • 3. Platelets
  • - cell fragments that function in blood clotting
  • - stick to damaged blood vessels and form a
    temporary plug
  • - release several clotting factors

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  • Hemostasis
  • Stoppage of bleeding
  • Three steps
  • Vascular spasms
  • - constriction of the damaged blood vessel
  • Platelet Plug Formation
  • - platelets swell, form spiked processes, and
    become sticky
  • - stick to exposed fibers of the damaged vessel
    and begin to release clotting factor chemicals
  • 3. Coagulation blood clotting
  • - Prothrombin activator is formed from certain
    plasma proteins and calcium
  • - Prothrombin activator transforms prothrombin
    to the active enzyme thrombin

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  • - thrombin catalyzes fibrinogen into insoluble
    fibrin strands which form the structural basis
    for the clot
  • Fibrinolysis removes unneeded clots after
    healing
  • - cleans out the many small clots that form when
    they shouldnt form

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  • Disorders of Hemostasis
  • 1. Thromboembolytic conditions
  • - a clot that forms in an unbroken blood vessel
    is a thrombus
  • - if a thrombus breaks loose and moves within
    the bloodstream it is an embolus
  • - cause trouble when they get to a blood vessel
    that is too small for them to pass through and
    they block blood flow
  • - caused by conditions which roughen the blood
    vessel endothelium or by slow blood flow
  • - aspirin and heparin can decrease risk
  • 2. Bleeding disorders
  • - when the normal clotting procedure is
    interfered with
  • - Platelet deficiency causes spontaneous
    bleeding from small blood vessels throughout the
    body
  • - caused by problems in the bone marrow

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  • - Impaired liver function can cause excessive
    bleeding because many of the clotting factors
    are produced by the liver
  • - Hemophilias genetic bleeding disorders
  • - often sex-linked and more common in males
  • - treat with injections of the missing factor
  • Transfusions
  • when blood loss is severe whole blood
    transfusions are given
  • Human Blood Groups
  • Genetically determined
  • Result from certain antigens (proteins) on the
    surface of RBCs
  • ABO and Rh blood groups cause strong transfusion
    reactions and are always matched in transfusions
  • Agglutination (clumping) of RBCs occurs when
    RBCs with the wrong antigen are transfused into
    another person

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  • - when blood types are mixed incorrectly
    antibodies in the recipient plasma cause
    agglutination of the donated RBCs
  • - Transfusion reactions can block small blood
    vessels, cause fevers, chills, nausea, vomiting,
    and in severe cases renal failure which can be
    lethal
  • - Rh factor is another antigen on the RBCs
  • indicates the presence of the antigen

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  • Erythroblastosis fetalis is a special case which
    is similar to a transfusion reaction.
  • - can happen when an Rh- woman has a second Rh
    child.

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THE HEART
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  • The Heart
  • Located in the mediastinum of the thoracic
    cavity.
  • About the size of your fist
  • Surrounded by the double-layered pericardium
    which helps protect it and anchors it to other
    structures
  • Pericardial space between the layers allows the
    heart free movement
  • Layers of the heart wall
  • - epicardium inner layer of the pericardium
    which is tightly attached to outer layer of the
    heart
  • - myocardium composed of cardiac muscle which
    actually does the contracting of the heart
  • - made of branching fibers which spread the
    impulse between them
  • - intercalated discs allow flow of ions from
    fiber to fiber

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  • - endocardium inner covering of the heart
    chambers
  • Chambers of the heart
  • 1. Atria receiving chambers
  • - receive the returning blood from the body
    circulation
  • - relatively small and thin-walled
  • - Right Atrium
  • - receives blood from the systemic circulation
  • - superior vena cava (precava) from tissues
    above diaphragm
  • - inferior vena cava (postcava) from tissues
    below diaphragm
  • - coronary sinus collects blood draining from
    the myocardium itself
  • - Left Atrium
  • - receives blood from the pulmonary circulation
    via the pulmonary veins

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  • 2. Ventricles discharging chambers
  • - compose most of the mass of the heart
  • - walls much thicker and more muscular than the
    atria
  • - Right Ventricle pumps blood to pulmonary
    trunk which branches into the pulmonary arteries
    to the lungs
  • - Left Ventricle pumps blood to the systemic
    circulation through the aorta
  • 3. Valves of the heart
  • - unidirectional flaps that impede backflow of
    blood
  • - open and close due to blood pressure
    differences on their two sides
  • A. Atrioventricular valves control flow between
    the atria and the ventricles
  • - chordae tendinae anchor the valve flaps to
    the ventricles and keep the flaps from reversing
    up into the atria when the ventricles contract

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  • - when ventricles are relaxed these valves are
    open and blood can flow into the ventricles
  • B. Semilunar valves
  • - prevent backflow of blood into the ventricles
    when the ventricles relax
  • - leaking valves are not always severely
    handicapping
  • Blood Flow Through the Heart
  • - heart acts as a double pump system to two
    distinct circuits
  • - Right side is the pulmonary circuit
  • - receives oxygen-poor blood and carbon
    dioxide-rich blood
  • - enters right atrium which pumps it through
    the tricuspid valve (rt. Atrioventricular
    valve) to the right ventricle which pumps
    blood through the pulmonary semilunar valve
    to the lungs where gas exchange takes place

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  • - Left side is the systemic circuit pump
  • - left atrium receives oxygen-rich blood from
    the pulmonary vein and pumps it through the
    bicuspid valve (left atrioventricular
    valve) to the left ventricle which pumps blood
    through the aortic semilunar valve to the aorta
    which branches to all parts of the body
  • - left ventricle is the largest and strongest
    chamber due to work load

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Blood flow through Heart
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  • Blood supply to the heart
  • - blood that flows through the heart chambers
    supplies very little of the needs of the heart
  • - the two main coronary arteries branch off of
    the aorta as it leaves the heart.
  • - heart attacks (myocardial infarctions) are
    caused by occlusion of a coronary artery
  • - heart muscle requires 5 of the bodys blood
    supply
  • - venous blood returns through the coronary sinus
    which dumps into the right atrium

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Coordination of Heart Beat
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  • Heart Beat
  • cardiac muscle contraction will occur
    spontaneously (autorhythmic)
  • Normally is under nervous system control
  • Intrinsic cardiac conduction system is a network
    of noncontractile cardiac fibers which initiate
    and distribute impulses throughout the heart
  • Sinoatrial node located in the right atrial wall
    is the normal pacemaker of the heart
  • Internodal pathway carries the impulse to the
    atrioventricular node located in the septum
    between the two atria causes a slight
    hesitation in the impulse which allows the atria
    to contract before the ventricles do
  • Next to the atrioventricular bundle (bundle of
    His) which branches into the Purkinje fibers
    which carry the impulse throughout the ventricles.

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  • - arrhythmias are irregular heart rhythms caused
    by defects in the conduction system
  • nervous system control speeds heart rate in
    response to increased body needs for blood
  • Electrocardiogram (ECG or EKG) is a graphic
    recording of the electrical changes in the heart
    during a contraction
  • P wave caused by depolarization of atria
  • QRS complex depolarization of ventricles
  • T wave ventricular repolarization

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  • Cardiac Cycle
  • Systole contraction of the heart chambers
  • Diastole relaxation of the heart chambers
  • Heart sounds are the sounds of heart valves
    operating
  • Heart murmurs are when the blood is not moving
    smoothly through the heart or is moving
    incorrectly through the valves
  • Cardiac output
  • function of heart rate and stroke volume
  • 75/min. x 70 ml/beat 5252 ml/min
    (5.25L)
  • Affected by many factors

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  • Blood Vessels
  • - except for smallest capillaries all blood
    vessel walls are composed of three layers
    surrounding the lumen of the vessel

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  • 1. Tunica intima
  • - innermost layer which is in contact with the
    blood
  • - composed of simple squamous epithelium with
    closely fitting cells which form a slick surface
    with little friction on the blood
  • 2. Tunica media
  • - layer of circular muscles
  • - controlled by sympathetic division of the
    autonomic nervous system
  • - vasoconstriction contraction of these
    muscles decreases vessel diameter
  • - vasodilation relaxation increases vessel
    diameter
  • - very important in control of blood pressure
  • 3. Tunica adventitia
  • - tough outer layer that protects the blood
    vessel and helps to anchor it to surrounding
    tissues

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  • Arteries
  • Blood vessels which carry blood away from the
    heart
  • Thick walls with small lumens
  • Elastic arteries are the large arteries near the
    heart
  • Elastin in walls allows them to stretch out and
    push back against the blood to maintain pressure
    between pulses
  • Muscular arteries distribute blood to all parts
    of the body
  • Arterioles are smallest arteries which control
    blood flow into the capillary beds

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  • Capillaries
  • - smallest blood vessels in which exchange takes
    place between the blood and tissues
  • - walls are one cell thick
  • - some have continuous walls others have pores
    that allow materials through
  • - capillary beds are alternately filled with
    blood or by-passed depending on the opening or
    closing of precapillary sphincters

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  • Veins
  • - capillaries fuse to form venules which begin to
    carry blood back to the heart
  • - venules fuse to form veins
  • - thinner walls and more open lumens than
    arteries
  • - normally contain about 65 of total blood
    volume
  • - because blood in veins is under low pressure
    they often contain valves to control the backflow
    of blood
  • - varicose veins are caused by stretching of the
    veins above these valves
  • - blood is often moved through veins by
    contraction of surrounding skeletal muscles

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  • Blood Flow, Blood Pressure, and Resistance
  • - blood must continuously flow to all body
    tissues to perform its vital functions
  • - Blood flow actual volume of blood flowing
    through an organ or the entire circulation in a
    given amount of time
  • - in totality cardiac output but varies
    within certain organs at different times
  • - Blood Pressure force per unit area on the
    wall of a blood vessel by the blood contained
    within it
  • - Resistance opposition to blood flow through a
    vessel a measure of the friction on the blood.
    Affected by three main factors
  • 1. blood viscosity internal resistance to flow
  • 2. total blood vessel length longer vessels
    create greater resistance
  • 3. blood vessel diameter most important factor
    in controlling peripheral resistance constantly
    changing

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  • Blood Pressure
  • - normally measured in large systemic arteries
  • - affected by amount of blood entering the
    arteries and the amount leaving the arteries at
    any time

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  • - because blood entering varies with the heart
    beat while blood leaving is essentially constant
    the pressure is felt as a pulse

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  • - Systolic pressure pressure peak caused by the
    contraction of the left ventricle
  • - Diastolic pressure lowest pressure when the
    ventricles are relaxed and the elastic arteries
    are recoiling from the pulse
  • - pressure decreases the further you get from the
    heart
  • - low pressure in most capillaries is desirable
  • - blood pressure in veins is too low to keep
    blood flowing so muscle contractions in
    surrounding tissues move the blood
  • - blood pressure is an overall function of
    cardiac output, peripheral resistance, and blood
    volume
  • - changes in any one of these will be
    compensated for to maintain constant pressure
  • - blood pressure is measured using a
    sphygmomanometer which is used to cut-off blood
    flow and then allow flow to slowly return

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  • - blood pressure is measured using a
    sphygmomanometer which is used to cut-off blood
    flow and then allow flow to slowly return
  • - systolic pressure is read when blood flow
    returns through the artery
  • - diastolic pressure is read when no further
    resistance is being offered to blood flow

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  • Fetal Circulation
  • - mother and childs blood does not mix, but is
    in close proximity at placenta
  • - chorionic villi from the chorion surrounding
    the embryo/fetus penetrate into the uterine
    lining
  • - blood vessels in the umbilical cord belong to
    fetal circulation
  • - within the circulation of the fetus several
    things are different than in the adult
  • 1. Ductus arteriosus redirects blood from lungs
    to aorta
  • 2. Ductus venosus returns blood from umbilical
    cord to fetus
  • 3. Umbilical arteries branch from internal
    iliac arteries (in legs) to umbilical cord and
    placenta
  • 4. Foramen ovale allows blood to flow from
    right atrium to left atrium instead of right
    ventricle (decreases blood going to fetal lungs)
  • - all of these must close at birth

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  • Diseases and disorders of the Cardiovascular
    System
  • 1. Hypotension low blood pressure
  • 2. Hypertension high blood pressure
  • - common in obese people due to greater total
    length of blood vessels
  • - chronic hypertension is often a result of
    increased peripheral resistance
  • - often caused by atherosclerosis
  • - primary hypertension has no discernable cause
    but is affected by diet, obesity, age, race,
    heredity, stress, smoking

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  • 3. Circulatory Shock
  • - most often caused by blood loss
  • 4. Heart attack
  • - caused by blockage of the coronary arteries
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