Chapter 37 Respiratory System

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Chapter 37 Respiratory System
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Respiratory System (Breathing)
(Cellular) Respiration Breathing
Chemical Process Food is oxidized by enzymes converted to ATP (most ATP from mitochondria) Mechanical or Physical Exchange of O2 CO2 (inhalation and exhalation)
Cellular Process Occurs in every cell of the body 2. Usually occurs in Specialized Organs/ body surface (In simpler organisms thru skin/ cell membrane)
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Respiration vs Breathing
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Variations in Breathing Structures (represents
evolutionary trends)

• Cell membrane? in unicellular organisms
• Ex Cnidaria, Porifera
• 2. Moist skin? mucus secreting cells maintain
  moisture
• Ex Worm phyla
• Tracheae? air enters spiracles (opening along
  abdomen) which leads into tracheal tubes to small
  air sacs surrounded by body fluid w/in sinus
• Ex Insects (grasshopper)

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• 4. Gills? thin filamentous structures composed of
  capillaries and flat squamous epithelial cells
• Ex Fishes, immature amphibians, crayfish, skin
  gills on starfish, mollusks (clam)

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Cont. Variations in Breathing Structures

• Oops!!! Forgot this slide!
• 5. Lungs? mature amphibian, reptiles, birds,
  mammals (possess diaphragm)
• () skin
• 6. Stoma? Opening on underside of leaf- gas
  exchange
• 7. Lenticels? openings in stem when leaf drops
• (Roots possess root hairs- gases diffuse across
  into root)

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Breathing Organs Overview

1. Earthworm? moist skin
2. Starfish? skin gills
3. Clams? gills (squid)
4. Grasshopper? tracheae
5. Crayfish? gills
6. Perch? gills
7. Human? lungs

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Human Respiratory System

• Nasal Cavity? ciliated columnar epithelium-
  secrete mucus
• Pharynx? back of throat
• Epiglottis? flap of tissue over glottis
• Glottis? opening to trachea
• Larynx? voice box
• Trachea? windpipe
• Left and right bronchus(i)? bronchial tubes that
  leads to bronchioles
• Bronchiole? smaller branches w/in lungs
• Alveolus (i)? microscopic air sac
• Capillary bed around alveoli? site of gas
  exchange (oxyhemoglobin H6 4O2 H6O)
• 11. Venules? small veins
• 12. Pulmonary veins to left atrium- part of the
  pulmonary circuit of the circ system
• 13. Pulmonary artery to lungs (fr right ventricle)

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Breathing Muscles

• Diaphragm? sheet of voluntary muscle found
  between the thoracic and abdominal cavities in
  mammals
• Intercostal (rib muscles)? muscles b/t rib bones
  (internal external layers)

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Breathing Mechanism

• Inhalation- intake of air due to contraction of
• 1. Diaphragm- when diaphragm contracts it
  straightens
• 2. External intercostal- when contracted these
  muscles lift rib cage up and out
• 3. Thoracic cavity enlarges air rushes into
  inflate lungs (Intrathoracic pressure low- low
  pressure on lungs)
• - Result Inhalation occurs
• Exhalation
• 1. Muscles relax, volume decreases, pressure
  increases and exhalation occurs

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Negative Pressure Breathing
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Nerves Controlling Breathing (Medulla)

• Phrenic Nerve
• Motor nerve from medulla which causes contraction
  of diaphragm and intercostal muscles
• Motor nerves? transmit impulses AWAY from CNS
  to effectors
• RESULT Inhalation
• 2. Vagus Nerve
• Mixed nerve (both sensory motor) sensory fibers
  transmit impulses to brain indicating that
  diaphragm intercostals muscles are contracted
• - Signals inhibits further stimulation by
  phrenic nerve
• RESULT Exhalation

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• 3. BLOOD pH 7.4
• - CO2 conc of blood is the factor which
  regulates breathing rate (blood pH)
• CO2 H2O ? ? ? H2CO3 ? H
  HCO3-
• RBC (lungs) carbonic anhydrase
  carbonic acid (plasma 90)
• Carbonic Anhydrase? enzyme in RBC which converts
  CO2 H2O to H2CO3 H (also reverses this rxn
  at the lungs)
• - Lowers blood pH (below 7.4)? stimulates
  medulla to increase breathing rate via phrenic
  nerves

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• 4. Hyperventilation
• Rapid breathing (over breathing- inhaling too
  much O2) reduces the CO2 levels in the blood
• Less CO2 causes dilation of arteries blood
  pressure lowers (carotid arteries to the brain)
  brain receives less blood? dizzy, light-headed,
  weak (vasoconstriction)

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• CO2 Transfer from Body Tissues to Blood and
  Lungs
• CO2 leaves cells and enters tissue spaces
• CO2 enter capillaries
• CO2 reacts with H2O (RBC) ? H2CO3
• H2CO3 ? dissociates into H and HCO3-
  (bicarbonate ion)
• HCO3- leave RBC and enter plasma
• Blood travels to lungs and enters lung
  capillaries
• HCO3- reenters RBC
• HCO3- H ? H2CO3
• H2CO3 carbonic anhydrase (enzyme)? H2O CO2
• W/in RBC, CO2 enters plasma
• CO2 leaves lung capillary and enters alveolar
  space (resultCO2 exits out of mouth)

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• O2 Transfer from Blood to Body Tissues
• RBC enters lung capillary
• O2 from alveolar space enters lung capillary
  plasma
• O2 enters RBC from plasma combines with
  hemoglobin (Hb) oxyhemoglobin
• RBC carry oxyhemoglobin out of lung to body
  tissues
• O2 laden RBC enter tissue capillary
• Oxyhemoglobin breaks down, releasing O2 into
  plasma
• O2 leaves plasma and enters tissue space
• O2 enters tissue cells from tissue space
• RBC returns to lungs via circulatory system

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• CO2 conc in metabolically active cells is much
  greater than in capillaries, so CO2 diffuses from
  the cells into the capillaries
• 7 of the CO2 directly dissolves in the
  plasma
• 23 binds to the amino groups in hemoglobin
• 70 is transported in the blood as bicarbonate
  ion
• - H2O in the blood combines with CO2 to form
  bicarbonate ions (via carbonic anhydrase)
• - This removes the CO2 from the blood so
  diffusion of even more CO2 from the cells into
  the capillaries continues yet still manages to
  "package" the CO2 for eventual passage out of the
  body

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- In the alveoli capillaries, bicarbonate
combines with a hydrogen ion (proton) to form
carbonic acid, which breaks down into carbon
dioxide and water (via carbonic anhydrase) - CO2
then diffuses into the alveoli and out of the
body with the next exhalation