Circulation

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Circulation
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Circulatory System

• Necessary for large animals
• Cant use diffusion
• System must have close connection with tissues
• Capillaries are microscopic blood vessels
• They form an intricate network among the tissue
  cells
• No substance has to diffuse far to enter or leave
  a cell

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Circulatory System
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Circulatory Systems

• Most animals have a separate circulatory system
• Open circulatory system-
• Invertebrates
• A heart pumps blood through open-ended vessels
  into spaces between cells
• Diffuse directly from blood into body cells
• No distinction between blood and interstitial
  fluid

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Open Circulatory System
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Closed Circulatory System

• Blood is confined to the vessels so there is a
  difference between it and interstitial fluid
• Most vertebrates have this cardiovascular system
• 3 kinds of vessels
• Arteries- away from heart
• Veins- return blood to heart
• Capillaries- between arteries and veins in organs

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Closed Circulatory System
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The Human Heart

• About the size of a clenched fist
• Made of mostly cardiac muscle tissue
• Atria- Collect blood returning to the heart and
  transport to ventricles
• Ventricles- pump blood to all other bodily organs
• Walls of left ventricle stronger for increased
  pump pressure
• Valves regulate direction of blood flow

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The Human Heart
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Circulation

• Right ventricle (1) pumps blood to lungs through
  two pulmonary arteries (2).
• Blood flows through capillaries (3) in the lungs,
  lets off CO2 and gets O2
• Blood flows back to the left atrium (4) through
  pulmonary artery
• Blood flows from left atrium to left ventricle
  (5)
• Blood leaves ventricle through aorta (6)

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Circulation

• Large arteries branch from the and lead to head
  and arms (7)and to the abdominal cavity and legs
  (8)
• Oxygen-poor blood is pumped back into the
  superior vena cava(9)from the arms and the
  inferior vena cava (10) from the legs
• The two large veins dump their blood back into
  the right atrium (11)
• Process starts all over again

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Structure of Blood Vessels

• Capillaries-
• Very thin walls, a single layer of epithelial
  cells
• Very smooth
• Arteries and veins
• Very think walls
• have smooth muscle and connective tissue to
  regulate flow by constricting
• Larger vessels have muscle to withstand surges
• Connective tissue allows flex and recoil
• Valves in veins prevent the backflow of blood

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Structure of Blood Vessels
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The Heart Muscle

• Passively fills with blood and actively contracts
• Diastole
• Blood flows from the veins into the heart
  chambers
• Systole
• The atria briefly contract and fill the
  ventricles with blood
• Then the ventricles contract and propel blood out

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• An electrocardiogram (ECG) is a recording of
  electrical changes in the skin resulting from the
  electrical signals in the heart
• Control centers in the brain adjust heart rate to
  body needs

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Arterial Blockage
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Blood Pressure

• The force that blood exerts against the walls of
  blood vessels
• Created by the heart
• Main force driving blood from the heart to the
  arteries
• Depends on cardiac output and resistance to blood
  flow by the arterioles
• Highest in arteries, then drops by the time it
  reaches the veins

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Blood Pressure
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Movement in the Veins

• In the veins, blood is no longer propelled by the
  heart
• Veins are in between skeletal muscles which pinch
  the veins and squeeze blood toward the heart
• Valves to allow one way movement

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Distribution of Blood

• Smooth muscles in arteriole walls regulate the
  distribution of blood to the capillaries of
  organs
• The brain, heart, kidneys and liver carry a full
  load of blood
• Other organs blood supply varies depending on
  need
• Precapillary sphincters control blood flow into
  branching capillaries

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• Thoroughfare channel always stays open

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Transfer From the Blood

• Only blood vessels with thin enough walls for
  transfer
• Capillary wall consists of adjoining epithelial
  cells
• Enclose a lumen (space) just large enough for a
  blood cell to pass through

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Transfer from Blood

• The transfer of materials between the blood and
  interstitial fluid can occur by
• leakage through clefts in the capillary walls
• Larger blood proteins cant pass through
• diffusion through the wall
• (O2 and CO2)
• blood pressure
• Pressure drives fluid out of capillary
• osmotic pressure
• Drives fluid into capillary

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Transfer from Blood
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Blood

• Consists of several cellular components
• Plasma- liquid phase,
• water, dissolved ions, proteins
• Maintains the osmotic balance of the cells
  controls pH
• Red blood cells
• White blood cells
• Platelets-
• Cytoplasm pinched off of bone marrow
• Important in clotting

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Red Blood Cells

• Erythrocytes
• Carry oxygen using hemoglobin
• Formed in bone marrow
• Low number of red blood cells or iron causes
  anemia

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White Blood Cells

• Leukocytes
• Fight infections and prevent cancer cells from
  growing
• Work both inside and outside circulatory system

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Blood Clots

• Self-healing materials that plug leaks in our
  vessels
• When a blood vessel is injured they are activated
• They help trigger the formation of an insoluble
  fibrin clot that plugs the leak