Circulation

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Circulation

• Chapter 34

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Outline

• Open versus Closed Circulatory Systems
• Transport in Vertebrates
• Transport in Humans
• Heartbeat
• Vascular Pathways
• Blood Pressure
• Cardiovascular Disorders
• Blood Components
• Blood Clotting

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Transport in Invertebrates

• Invertebrates Without a Circulatory System
• Each cell can independently exchange gases and
  rid itself of wastes.

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Open or Closed Invertebrate Circulation

• Two types of circulatory fluids
• Blood - contained within blood vessels.
• Hemolymph - flows into hemocoel.
• Open Circulatory System
• Heart pumps hemolymph via vessels into tissue
  spaces.
• Closed Circulatory System
• Blood pumped by the heart into a system of blood
  vessels.

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Open Circulatory System
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Closed Circulatory System
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Transport in Vertebrates

• All vertebrates have a closed, cardiovascular
  system.
• Atria receive blood and ventricles pump blood out
  through blood vesicles.
• Arteries - Carry blood away from heart.
• Arterioles
• Capillaries - Exchange materials with tissue
  fluid.
• Veins - Return blood to heart.
• Venules

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Comparison of Circulatory Pathways

• Fish - Blood flows in single loop.
• Single atrium and single ventricle.
• Amphibians - Blood flows in double loop.
• Two atria with single ventricle.
• Other vertebrates - Blood flows in a double loop.
• Heart divided by septum into separate sides.

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Circulatory Circuits
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Transport in Humans

• Human Heart
• Fist-sized, cone-shaped, muscular organ.
• Myocardium composed largely of cardiac tissue.
• Lies within sac (pericardium).

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External Heart Anatomy
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Transport in Humans

• Septum separates halves.
• Four chambers
• Two upper, thin atria.
• Two lower, thick ventricles.
• Atrioventricular valves
• Tricuspid
• Bicuspid
• Semilunar valves
• Pulmonary
• Aortic

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Internal Heart Anatomy
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Transport in Humans

• Blood must go through lungs to pass from the
  right side to the left side of the heart.
• Right side of heart pumps blood to the pulmonary
  circuit.
• Left side of the heart pumps blood to the
  systemic circuit.
• Oxygen-poor blood never mixes with oxygen-rich
  blood.

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Heartbeat

• Systole - Contraction of heart chambers.
• Diastole - Relaxation of heart chambers.
• Pulse - Wave effect that passes down the walls of
  arterial blood vessels when aorta expands and
  then recoils following ventricular systole.

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Heartbeat

• Rhythmic contraction due to cardiac conduction
  system.
• Sinoatrial node (SA) keeps the heartbeat regular.
• Atrioventricular node (AV) signals ventricles to
  contract.
• Purkinje Fibers

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Heartbeat

• Electrocardiogram (ECG) is a recording of the
  electrical changes that occur in myocardium
  during a cardiac cycle.
• When SA node triggers an impulse, the atrial
  fibers produce an electrical charge (P wave).
• P wave indicates atria are about to contract.

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Conduction System of the Heart
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Vascular Pathways

• Human cardiovascular system includes two major
  circular pathways
• Pulmonary Circuit
• Takes oxygen-poor blood to the lungs and returns
  oxygen-rich blood to the heart.
• Systemic Circuit
• Takes blood throughout the body from the aorta to
  the vena cava.

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Blood Pressure

• Systolic Pressure results from blood forced into
  the arteries during ventricular systole.
• Diastolic Pressure is the pressure in the
  arteries during during ventricular diastole.
• Blood pressure normally measured with a
  sphygmomanometer on the brachial artery.
• Systolic/Diastolic

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Velocity and Blood Pressure
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Blood Pressure

• The beat of the heart supplies pressure that
  keeps blood moving in the arteries.
• Skeletal muscle contraction pushes blood in the
  veins toward the heart.

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Cardiovascular Disorders

• Hypertension - High blood pressure.
• Atherosclerosis - Accumulation of fatty materials
  in inner linings of arteries.
• Stroke - Cranial arteriole bursts or is blocked
  by an embolus.
• Heart attack - Myocardial infarction. Coronary
  artery becomes partially blocked.
• Angina pectoris - Squeezing sensation.

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Coronary Arteries and Plaque
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Blood - A Transport Medium

• Homeostasis Functions
• Transports substances to and from capillaries for
  exchange with tissue fluid.
• Guards against pathogen invasion.
• Regulates body temperature
• Clots preventing blood loss

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Plasma

• Plasma contains many types of molecules including
  nutrients, wastes, salts, and proteins.
• Buffer blood.
• Maintain osmotic pressure.
• Proteins involved in clotting.

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Red Blood Cells

• Small, biconcave disks that, at maturity, lack a
  nucleus and contain hemoglobin.
• Hemoglobin contains four globin protein chains,
  each associated with an iron-containing group.
• Manufactured continuously in bone marrow of
  skull, ribs, vertebrae, and ends of long bones.

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White Blood Cells

• Usually larger than red blood cells, contain a
  nucleus, and lack hemoglobin.
• Inflammatory Response
• Neutrophils enter tissue fluid and phagocytize
  foreign material.
• Lymphocytes help fight infection.
• T Cells attack infected cells.
• Antigens cause body to produce antibodies.

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Platelets

• Platelets result from fragmentation of
  megakaryocytes.
• Involved in coagulation.
• Blood clot consists of platelets and red blood
  cells entangled within fibrin threads.

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Blood Clotting
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Capillary Exchange

• Oxygen and nutrients exit a capillary near the
  arterial end.
• Carbon dioxide and waste molecules enter a
  capillary near the venous end.

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Capillary Exchange
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Review

• Open versus Closed Circulatory Systems
• Transport in Vertebrates
• Transport in Humans
• Heartbeat
• Vascular Pathways
• Blood Pressure
• Cardiovascular Disorders
• Blood Components
• Blood Clotting

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