CIRCULATORY SYSTEM

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CIRCULATORY SYSTEM
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• Circulatory System
• heart, blood, and blood vessels
• transport oxygen and nutrients to organs and
  tissues throughout the body
• carry away waste products

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I. Functions

• Increases blood flow
• meet increased energy demands during exercise
• regulates body temperature
• conveys disease-fighting elements of immune
  system to regions under attack
• white blood cells and antibodies
• sends clotting cells and proteins to the affected
  site
• stop bleeding and promote healing

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II.Circulatory System Components

• Heart - divided into four chambers
• right atrium, right ventricle, left atrium, left
  ventricle

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• Chamber walls composed of myocardium
• contracts continuously and rhythmically to pump
  blood.

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• Pumping action of the heart -two stages for
  each heart beat
• Diastole-when the heart is at rest
• Systole-when the heart contracts to pump
  deoxygenated blood toward the lungs and
  oxygenated blood to the body.

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• During each heartbeat, typically about 60 to 90
  ml (about 2 to 3 oz) of blood are pumped out of
  the heart.
• If the heart stops pumping, death usually occurs
  within four to five minutes.

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• Three types of blood cells
• oxygen-bearing red blood cells
• disease-fighting white blood cells
• blood-clotting platelets, all of which are
  carried through blood vessels in plasma
• plasma is yellowish, consists of water, salts,
  proteins, vitamins, minerals, hormones, dissolved
  gases, and fats.

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• Three types of blood vessels
• arteries carry blood away
• thicker walls to withstand the pressure of blood
  being pumped from heart
• veins - toward heart
• lower pressure
• one-way valves to prevent blood from flowing
  backwards away from heart
• capillaries
• tiny links b/w arteries and veins where oxygen
  and nutrients diffuse to body tissues
• smallest of blood vessels, are only visible by
  microscope ten capillaries lying side by side are
  barely as thick as a human hair.

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• Inner layer of blood vessels
• lined with endothelial cells - create a smooth
  passage for blood transit
• surrounded by connective tissue and smooth muscle
  for
• Expansion - during exercise to meet demand for
  blood and to cool body
• Contraction - after injury to reduce bleeding
  and/or conserve body heat

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• If all the arteries, veins, and capillaries in
  the human body were placed end to end, the total
  length would equal more than 100,000 km (more
  than 60,000 mi)they could stretch around the
  earth nearly two and a half times.

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• Arteries, veins, and capillaries - divided into
  two systems
• Systemic - carries oxygenated blood from heart to
  all tissues in body except lungs and returns
  deoxygenated blood carrying waste products, such
  as carbon dioxide, back to heart.
• oxygen-rich blood ejected under high pressure out
  of
• heart's main pumping chamber (L. ventricle)
  through
• largest artery (aorta)
• smaller arteries branch off from aorta to various
  parts of the body
• smaller arteries in turn branch out into even
  smaller arteries (arterioles)
• arterioles become progressively smaller
  eventually forming capillaries - blood pressure
  is greatly reduced

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• interstitial fluid fills the gaps between the
  cells of tissues or organs
• dissolved oxygen and nutrients then enter the
  cells from interstitial fluid by diffusion
• carbon dioxide and other wastes leave the cell
  via interstitial fluid, cross capillary walls,
  and enter blood.
• after delivering oxygen to tissues and absorbing
  wastes, deoxygenated blood in capillaries then
  starts the return trip to heart

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• capillaries merge to form tiny veins, called
  venules
• venules join together to form progressively
  larger veins
• veins converge into two large veins
• inferior vena cava-brings blood from the lower
  half of body
• superior vena cava-brings blood from upper half
• Both join at the right atrium of heart

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• FYI
• Varicose Veins
• pressure is dissipated in arterioles and
  capillaries
• blood in veins flows back to heart at very low
  pressure, often running uphill when a person is
  standing
• Flow against gravity allowed by one-way valves
• several centimeters apart in veins
• Veins with defective valves (allow the blood to
  flow backward) become enlarged or dilated to form
  varicose veins

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Varicose veins
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• Pulmonary Circulation
• deoxygenated blood returning from organs and
  tissues travel from R. atrium to R. ventricle.
• pushed through pulmonary artery to lung
• pulmonary artery divides forming pulmonary
  capillary region
• microscopic vessels pass adjacent to alveoli (air
  sacs) - gases are exchanged across thin membrane
• oxygen crosses membrane into blood while carbon
  dioxide leaves blood through same membrane
• newly oxygenated blood then flows into pulmonary
  veins and is collected by L. atrium of the heart
  (collecting pool for L.ventricle)
• contraction of L. ventricle sends blood into
  aorta
• completing circulatory loop

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SUP. VENA CAVA
AORTIC ARCH
PUL. VEINS
L. LUNG
R. LUNG
PUL. ARTERY
HEART
AORTA
INF. VENA CAVA
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• On average, a single blood cell takes roughly 30
  seconds to complete a full circuit through both
  the pulmonary and systemic circulation.

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III. Additional Functions Features

• Transports nutrients and removes toxins
• Absorbed through intestine wall via network of
  capillaries and veins that drain the intestine -
  hepatic portal
  circulation (HPC)
• HPC carries nutrients/toxins to the liver for
  further metabolic processing.
• Liver stores sugars, fats, and vitamins
  releases to the blood as needed
• Liver also cleans blood by removing waste product
  and toxins. After hepatic portal blood has
  crossed the liver cells veins converge to form
  the large hepatic vein that joins the vena cava
  near the right atrium.

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• Body Temperature Regulation
• exercise muscles generate heat
• blood supplying muscles with oxygen and nutrients
  absorbs much heat and carries to other parts of
  body
• If body gets too warm, vessels near skin enlarge
  disperse excess heat outward through skin
• If cold, blood vessels constrict to retain heat.

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• Hormone Transportation
• Endocrine system collection of
  hormone-producing glands
• Regulates rate of metabolism, growth, sexual
  development, and other functions.
• chemical messengers (hormones) released directly
  into bloodstream
• transported to specific organs and tissues

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• WBC Antibody Transport and Clotting
• WBC and antibodies circulate in blood
• transported to infection sites
• coagulation system - composed of
• Platelets and clotting factors circulate in blood
• Damaged blood vessels are repaired by forming
  clots

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• Supporting Organs
• Brain/nervous system
• monitor blood circulation
• send signals to heart or blood vessels to
  maintain constant blood pressure.
• Bone Marrow
• Site of new blood cell manufacture
• Spleen
• Old blood cells are broken down
• valuable constituents, such as iron, are recycled
• Kidneys
• metabolic waste products removed from blood
• also screens for excess salt
• maintains blood pressure
• balance of minerals and fluids

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