Circulatory System

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Circulatory System

• Chapter 42

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Diffusion alone is not enough

• Diffusion is insufficient and inefficient over
  distances larger than a few millimeters.
• Circulatory system solves problem by transporting
  materials in bulk throughout the body in
  dissolved or suspended form, so connects aqueous
  environment of body cells to the organs
• where need absorption, gas exchange, waste
  removal

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Where internal transport takes place

• Gastrovascular cavity or circulatory system
• G.C. orgs with few cell layers cnidarians,
  flatworms
• C.S. orgs with many cell layers
• nematodes through chordates
• these rely on blood and blood pressure (so
  some type of heart is present)
• Open circulatory systems hemolymph bathes the
  organs directly (uses cavities called sinuses)
• Closed circulatory systems blood is confined to
  vessels and is separate from cell fluid

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Figure 42.2 Open and closed circulatory systems
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Circulatory system anatomy

• Heart 2 atria that receive blood, 2 ventricles
  that pump it out
• 3 types of blood vessels totaling 100,000 km in
  body
• arteries carry blood away from heart
• veins carry blood toward heart
• capillaries microscopic vessels with thin,
  porous walls (chemical exhange occurs here)
• Heart ? arteries ? arterioles ? capillaries ?
  venules ? veins ? heart

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Figure 42.8 The structure of blood vessels
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Circulatory schemes of vertebrates page 874 (2
chambers, 3 chambers, 4 chambers)
Double loop, some mixing
Double loop, completely separate
Single loop
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• Gill circulation from heart to gills
• Systemic circulation from heart to rest of body
• Pulmocutaneous circulation from heart to to
  capillaries in skin and lungs in amphibians
• Pulmonary circulation from heart to lungs

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Figure 42.0 External gills of a salmon
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Figure 42.4 The mammalian cardiovascular system
an overview
Pumping cycle page 875
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Heart contracts and relaxes in cycle

• Cardiac cycle one complete sequence of pumping
  and filling
• Systole contraction phase of cycle
• Diastole relaxing phase of cycle
• Cardiac output volume per min of blood that
  left ventricle pumps into the systemic circuit
  (depends on heart rate and stroke volume)
• Stroke volume amount of blood pumped by left
  ventricle in each contraction

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Figure 42.6 The cardiac cycle
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Figure 42.5 The mammalian heart a closer look
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Valves

• AV valves between each atrium and ventricle
  anchored by chordae tendinae
• Semilunar valves at two exits of heart, aorta
  (left ventricle) and pulmonary artery (right
  ventricle)
• Valve defects blood flows differently, get
  different heart sounds
• Ex. Murmur hissing of blood back through valve

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Figure 42.7 The control of heart rhythm
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Things that effect heart rate.

• SA node, sets tempo but many physiological cues
  affect it
• two sets of nerves affect heart rate
• hormones (Ex. Epinephrine, adrenal glands,
  increases rate)
• increase in body temp raises heart rate(1o
  C 10 beats/min)
• exercise increases heart rate

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Nodes

• Sinoatrial node (SA node) pacemaker of heart
  located in wall of right atrium near where
  superior vena cava enters heart
• Atrioventricular node (AV node) located in wall
  between right atrium and right ventricle delays
  impulses from SA node slightly, ensures that
  atria empty before ventricles contract

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Movement of Blood through system

• Law of continuity If a pipes diameter changes
  over its length, a fluid will flow through
  narrower segments faster than it flows through
  wider segments.
• If this is the case, why does blood slow as it
  reaches the capillaries and the capillary beds?

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Blood pressure

• Hydrostatic pressure drives fluids through the
  cardiovascular system specifically, blood
  against vessels, so blood pressure
• Systolic pressure heart contracts, blood is
  pumped
• Diastolic pressure when elastic walls of
  arteries snap back during heart resting time
• READ pages 878 to 880 AP lab will cover this.
• Blood pressure is reported as Systolic over
  Diastolic

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Two mechanisms regulate distribution of blood in
capillary beds

• Interior Contraction of the smooth muscle layer
  in wall of arteriole cuts off flow when relax,
  blood flows
• Exterior Precapillary sphincters control flow
  of blood between arterioles and venules

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Figure 42.12 Blood flow in capillary beds
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Read over pages 882-886

• Blood and its structural components
• Stem cells
• Clotting
• Cardiovascular disease

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Lymphatic System

• Returns fluid and blood proteins lost from
  circulatory system to the blood. Drains into the
  circulatory system near the junction of the venae
  cavae with the right atrium.
• Lymph fluid in lymphatic system, pretty much
  like interstitial fluid.
• Lymph vessels have valves, and depend on movement
  of skeletal muscles to squeeze fluid toward the
  heart.
• Lymph nodes clusters of tissue that filter
  lymph and attack invaders. When body is fighting
  infection, the cells multiply and nodes swell.