anatomie en fyslilogie

• Exchanges ultimately occur at the cellular level by crossing the plasma membrane
• Diffusion time


  Proportional to the square of the distance
• In most animals, cells exchange materials with the environment via a fluid-filled circulatory system
• Circulatory system


  • Has a circulatory fluid
  • Has a set of interconnecting vessels
  • Has a muscular pump, the heart
• Open circulatory system


  No distinction between blood and interstitial fluid, this general body fluid is called hemolymph
• Closed circulatory system


  The cardiovascular system in humans and other vertebrates
• Main types of blood vessels

  • Arteries
  • Veins
  • Capillaries
• Blood flow is one way in these vessels
• Blood flow in the cardiovascular system

  Blood enters the heart through an atrium and is pumped out through a ventricle
• Arteries and veins are distinguished by the direction of blood flow, not by O2 content
• The mammalian cardiovascular system meets the body's continuous demand for O2 and release of CO2
• Cardiac cycle


  The heart contracts and relaxes in a rhythmic cycle
• Systole


  The contraction, or pumping, phase
• Diastole


  The relaxation, or filling, phase
• Heart rate


  The number of beats per minute
• Stroke volume


  The amount of blood pumped in a single contraction
• Cardiac output


  The volume of blood pumped into the systemic circulation per minute
• Heart valves


  • Atrioventricular (AV) valves
  • Semilunar valves
• Sinoatrial (SA) node


  The pacemaker that sets the rate and timing of cardiac muscle contraction
• Cardiac conduction system


  Impulses from the SA node travel to the AV node, then to the Purkinje fibers that make the ventricles contract
• Endothelium


  The epithelial layer that lines blood vessels
• The endothelium is smooth and minimizes resistance
• Blood pressure


  Flows from high to low
• Blood flow velocity is slowest in the capillary beds
• Lymphatic system


  Returns fluid that leaks out from the capillary beds
• Systolic pressure


  The pressure in the arteries during ventricular systole
• Diastolic pressure


  The pressure in the arteries during diastole
• Pulse


  The rhythmic bulging of artery walls with each heartbeat
• Blood pressure is determined by cardiac output and peripheral resistance
• Lymph


  Fluid that reenters the circulation directly at the venous end of the capillary bed and indirectly through the lymphatic system
• Lymphatic system


  • Drains into veins in the neck
  • Valves in lymph vessels prevent the backflow of fluid
• Lymph nodes


  Organs that filter lymph and play an important role in the body's defense
• Systolic pressure


  The pressure in the arteries during ventricular systole; it is the highest pressure in the arteries
• Diastolic pressure


  The pressure in the arteries during diastole; it is lower than systolic pressure
• Blood pressure reading: 120/70 (of a 20 year old)
• Vasoconstriction


  The contraction of smooth muscle in arteriole walls; it increases blood pressure
• Vasodilation


  The relaxation of smooth muscles in the arterioles; it causes blood pressure to fall
• Nitric oxide (a gas) is a major inducer of vasodilation
• The peptide endothelin is an important inducer of vasoconstriction
• Fainting is caused by inadequate blood flow to the head