HTHS Mod 17

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HTHS Mod 17
2014-03-27 19:39:30

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  1. functions of respiratory system
    • 1. provides for gas exchange
    • 2. helps regulate blood pH
    • 3. Contains smell receptors
    • 4. Filters incoming air
    • 5. Produces vocal sounds
    • 6. Secretes water and heat
  2. four respiratory processes
    • Pulmonary ventilation: moving air in/out of lungs
    • External respiration: exchange of gases at alveoli of lungs
    • Transport of respiratory gases: to tissues
    • Internal respiration: exchange of gases btwn blood & tissues
  3. Anatomically, how can respiratory system be divided? What's included in each division?
    • Upper division: nose, paranasal sinuses & pharynx
    • Lower division: larynx, trachea, bronchi, and lungs
    • The larynx (voice box) separates the two divisions
  4. structure/function of nose
    • in upper respiratory system
    • made up of hyaline cartilage making it flexible
    • Nose hair filter larger particles in air
    • Air is moisturized, warmed and filtered by turbulence inside nasal passages
    • Increased surface area and mixing of air enhances olfaction
  5. turbinates
    • another name for nasal conchae
    • they provide a turbulent area for air to pass through before reaching rest of respiratory passages
    • lined w mucous membrane which helps to trap foreign particles 
    • also warms & filters air
    • Olfactory epithelium is near superior nasal concha which increases surface area & mixes the air to help w olfaction
  6. structure/function of paranasal sinuses
    • are spaces w/in cranial and facial bones which are lined w mucous membrane
    • The air spaces make our head lighter to carry
    • Also serve as chambers to resonate sound
    • *When we went to being 2-legged, our sinuses don't drain as easy. Therefore, microorganisms & fluid can get trapped and we end up with infection
  7. Pharynx hollow
    • a hollow tube that starts at posterior part of internal nares & descends to opening of larynx
    • serves as passageway for air and food
    • has 3 divisions:
    • Nasopharynx
    • Oropharynx
    • Laryngopharynx
  8. Nasopharynx
    • lie behind the internal nares
    • purely respiratory
    • Houses eustachian tubes (auditory tubes)  and pharyngeal tonsils(adenoids)
  9. oropharynx
    • lies behind mouth w both respiratory and digestive functions
    • Houses the palatine tonsils (removed by tonsillectomy) and lingual tonsils
  10. laryngopharynx
    • lies inferior to the oropharynx and opens into the larynx and esophagus
    • Both respiratory and digestive functions
  11. larynx
    • "voice box"
    • connects laryngopharynx w trachea
    • consists of 9 pieces of cartilage
    • sits in midline of neck anterior to esophagus and superior to trachea; just inferior to hyoid bone and epiglottis
    • Opening of larynx is the glottis
  12. glottis
    • opening of the larynx, or voice box
    • includes vocal chords and opening btwn chords
    • Sound is produced by vibrations as air passes through the chords
    • Volume controlled by pressure
    • Pitch caused by tension on vocal folds
    • ~Men's vocal folds become thicker & longer during puberty under influence of male sex hormones (androgens) which produces lower pitched voice
  13. 9 pieces of cartilage which make up larynx
    • Either paired or single
    • Single: Thyroid, epiglottis, cricoid
    • Paired: arytenoid, corniculate and cuneiform
  14. Thyroid cartilage
    • also called Adam's apple
    • forms the anterior surface of the larynx
    • serves as one of the landmarks for making an emergency airway - tracheotomy (made btwn thyroid cartilage and cricoid cartilage)
  15. epiglottis
    • leaf shaped piece of hyaline cartilage that closes over the larynx when food or liquids are swallowed
    • allows gases such as oxygen through the larynx into trachea
  16. cricoid
    • a ring of hyaline cartilage that forms the inferior portion of the larynx
    • serve as one landmark for making emergency airway - tracheotomy (made btwn thyroid and cricoid cartilage)
  17. Aryteniod
    • is a paired cartilage, part of larynx
    • influence changes in position and tension of the vocal folds
  18. corniculate and cuneiform
    • is a paired cartilage, part of larynx
    • supports the vocal folds and epiglottis
  19. tracheotomy/tracheostomy
    • cut made btwn the thyroid and cricoid cartilages
    • tracheotomy is the procedure of cutting (-tomy) the trachea
    • tracheostomy means to form a mouth or opening (-stomy) in the trachea
    • semi-permanent or permanent for pts w long-term need such as w oral cancer
  20. trachea
    • "windpipe" 
    • semi-rigid tube for air
    • 16 - 20 C shaped rings of cartilage, giving support and preventing collapse of trachea, especially during inhalation
    • anterior to esophagus, posterior surface shared w esophagus
    • divides into L & R bronchi
  21. bronchi
    • trachea divides into Left and right primary bronchi (at corina)
    • further divides into secondary bronchi , tertiary bronchi, and eventually into tiny bronchioles and terminal bronchioles
    • Right primary bronchus extends more vertically, is wider, and shorter than left
    • Therefore, an aspirated object is more likely to lodge in right bronchus than left
  22. carina
    • an internal ridge where the trachea divides into the right and left bronchus
    • very sensitive area for triggering cough reflex
    • used as landmark when performing a bronchoscopy or visual exam of bronchi
  23. Lungs, and differences btwn R & L lung
    • Superior part of lung is apex, rests slightly above the clavicle
    • Inferior part is base, rests on diaphragm
    • Right lung contains 3 lobes 
    • Left lung contains 2 lobes 
    • *this is cause apex of heart rests at medial portion of L lung (cardiac notch)
    • Anterior, lateral, and posterior surfaces of lungs rest against the ribs
  24. Bronchi & lungs
    • One primary bronchus for each lung
    • One secondary bronchus for each lobe of the lung
    • Bronchi enter at hilus along w/ blood vessels
  25. hilum
    • an opening on the medial surface of each lung
    • location where the primary bronchi, blood vessels, lymphatic vessels, and nerves enter the lung
  26. In relation to base & apex, how are the lungs different
    • With the lungs, the apex is at the top of the lungs (pointy part)
    • The base is at the bottom, inferior, rests on diaphragm
  27. Divisions of bronchi
    • The primary bronchi branch to form 2nd bronchi, one for each lobe of lung
    • secondary bronchi further branch to form bronchioles 
    • bronchioles divide into several alveolar ducts
    • Alveolar ducts end in alveoli
  28. alveoli
    • grape-like clusters
    • provide large surface area for exchange of gases
    • site of gas exchange in lung
  29. What's the deal with terminal bronchiole?
    • The bronchioles end in a segment called the terminal bronchiole.  
    • Then it goes into the respiratory part of the lungs at the respiratory bronchiole & is hooked to alveoli
  30. recall definition for serous membranes
    membranes which line organs and body cavities that do not open to the external world
  31. Pleural membranes of lungs
    • double-walled serous membrane
    • consists of:
    • visceral pleura ~ adheres to lung
    • parietal pleura ~ adheres to chest wall
    • Betwn these two layers is the pleural cavity, which contains pleural fluid, which reduces friction
    • Tight contact btwn these membranes (w liquid seal and lubrication) is critical for lung function
  32. Most important muscle that powers breathing
    • the diaphragm
    • is a large, dome-shaped muscle
    • forms floor of thoracic cavity
    • contraction enlarges thoracic cavity, enabling inhalation
    • responsible for about 75% of air that enters lungs during normal breathing
  33. internal intercostal muscles
    • make up the intermediate layer of the intercostal space
    • help decrease the size of thoracic cavity during forced exhalation
    • striations point toward head
  34. Phrenic nerve
    • stimulates diaphragm muscle to contract, enabling inspiration
    • arises from the cervical plexus at levels C3, C4, and C5.
    • **"C3, C4, and C5 keep the diaphragm alive"
    • distributes over the superior surface of the diaphragm
  35. sympathetic stimulation to lungs
    • norepinephrine causes dilation of bronchial smooth muscle
    • Preganglionic cell bodies in intermediate horn of T1-T4 spinal cord
    • Synapse with postganglionic cell bodies in sympathetic chain ganglia (along side of spinal cord)
    • Nerves enter lungs at hilus forming pulmonary plexus
  36. parasympathetic stimulation to lungs
    • innervated via CN X (vagus nerve)
    • Acetylcholine is neurotransmitter released
    • Causes mucus secretion and constriction of bronchial smooth muscle
  37. Zones of respiratory tract
    • conducting zone: part of respiratory system that brings air into or out of lungs
    • respiratory zone: the part of the respiratory system where gas exchange takes place
  38. conducting zone
    • consists of all the structures that bring air to alveoli: 
    • nose, pharynx, larynx, trachea, bronchi, bronchioles and terminal bronchioles
    • Function: to filter, warm, moisten, and conduct the air to lungs
  39. respiratory zone
    • division of respiratory tract where gas exchange take place in the lungs
    • Consists of respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
  40. Upper respiratory tract
    • includes nasal cavity, oral cavity, all three divisions of pharynx, and larynx
    • full of endogenous (normal) flora
  41. Lower respiratory tract
    • includes trachea and all components of lungs (bronchi, bronchioles and alveoli)
    • is (theoretically) sterile
  42. Organization of the Right Lung
    • 1 primary bronchi = 3 lobes supplied by secondary bronchi = 10 segments supplied by tertiary bronchi
    • From there it goes into the lobules
  43. Organization of Left lung
    • supplied by 1 primary bronchi = 2 lobes (due to cardiac notch) supplied by secondary bronchi = 9 segments supplied by tertiary bronchi
    • From there it goes to lobules (functional units of lung) supplied by bronchiole
  44. lobules
    • functional part of the lung
    • Each lobule contains a lymphatic vessel, an arteriole, a venule, and a branch from a terminal bronchiole
    • The terminal bronchioles subdivide into tiny respiratory bronchioles
    • At the end of the respiratory bronchioles is where the alveoli are
  45. Describe histology of pharynx & larynx
    • parts are lined in stratified squamous epithelium for protection
    • (think of tortilla chips)
  46. Describe histology of the conducting portion of the respiratory tract?
    • respiratory epithelium (pseudostratified columnar ciliated cells)
    • contains goblet cells which produce mucus
    • mucus and cilia form mucociliary escalator
    • *Recall that pseudostratified columnar looks like there's many layers, but there's not. Only one layer & very cell touches the basement membrane.
  47. mucociliary escalator
    • in the conducting portion of respiratory tract
    • formed by mucus (made by goblet cells) and cilia
    • transports dust and other particles out of the lungs and into pharynx to be swallowed (gag!!)
  48. Describe histology of bronchi and bronchioles
    • lined with smooth muscle, which regulated the diameter of the conducting airways
    • Sympathetic = increased airway diameter
    • Parasympathetic = decreased airway diameter, increase secretions (also occurs in inflammation - ex: asthma)
  49. Describe histology of alveoli
    • *as respiratory bronchioles expand to form alveoli, histology changes
    • gas exchange will take place, so cells and structure support this function
    • lined by 2 types of epithelium:
    • Type I alveolar cells
    • Type II alveolar cells
  50. Type I alveolar cells
    • simple squamous epithelium
    • site of gas exchange
    • by far the most numerous cell lining the alveoli
    • In collaboration with capillary endothelial cells, form A-C membrane
  51. A-C membrane
    • alveolar-capillary membrane
    • formed by type I alveolar cells and capillary endothelial cells
    • a thin membrane that gases can easily diffuse across
  52. Type II alveolar cells
    • simple cuboidal epithelium
    • fewer in # than type I
    • secrete surfactant, which is a soap-like substance that decreases (or breaks up) surface tension allowing easier inflation of the alveoli and preventing the collapse of alveoli
    • *Premature infants don't have ability to make surfactant yet, so they have a hard time inflating & breathing
  53. Alveolar macrophages
    • engulf large particles and invaders, then "ride" the mucociliary escalator out of the lung
    • The "Pac-man"s
  54. respiration
    process of gas exchange in the body
  55. pulmonary ventilation
    the mass movement of air into and out of the lungs
  56. inhalation
    • movement of air into the lungs from the atmosphere
    • active process requiring muscle action
  57. Exhalation
    • movement of air out of the lungs into the atmosphere
    • passive process during quiet breathing due to the elastic recoil of the lungs
    • active (muscle help) during vigorous exercise or certain disease conditions causing difficult expiration (copd)
  58. Kinetic molecular theory
    • the idea that gas is made up of little billiard balls zipping around and colliding w each other
    • They are free to bounce around
    • The collisions of these molecules with the wall of a container is pressure
    • The speed at which the balls move is temp
  59. Where does pressure come from & how is pressure measured?
    • Pressure comes from collisions btwn the molecules and walls of container:
    • Higher temp → more collisions → higher pressure
    • More molecules → more collisions → higher pressure
    • Smaller container → more collisions → higher pressure
    • Measured in atm (atmospheres)
    • 1 atm = 760 mm Hg
  60. Boyle's law
    • says that pressure x volume (P x V) is constant @ constant temp
    • Pressure and volume are inversely related:
    • If volume goes up, pressure goes down
    • If volume goes down, pressure goes up
    • P1V= P2V2

    •  ,     
    • where  means "inverse" of
  61. Muscles used during inspiration
    • Contraction of the diaphragm and external intercostal muscles increase the volume of the thoracic cavity
    • As volume increases, pressure decreases
    • Pressure in thoracic cavity now slightly less than atmospheric pressure
    • Therefore, air will flow from high to low pressure into thoracic cavity
  62. Additional muscles used during deep, labored breathing
    • used to further enlarge the thoracic cavity
    • includes:
    • the sternocleidomastoid, which elevates the sternum
    • the scalene muscles and pectoralis minor which elevate ribs
  63. Describe muscle movements in chest
    • During inhalation:
    • the lifting of the sternum = "pump handle" = moves out anteriorly
    • action of ribs = "bucket handle" = up and out laterally
  64. Describe pressures of quiet exhalation
    • Is a passive process during quite breathing
    • Elastic recoil of chest wall & lungs causes volume in thoracic cavity to decrease
    • *As volume decreases, pressure increases. 
    • Therefore, pressure is now higher in thoracic cavity than atmospheric air & air flows out from high to low press.
  65. Describe pressure of forced exhalation
    Abdominal muscles and internal intercostals contract further, decreasing the volume of the thoracic cavity and increasing the pressure
  66. Alveolar pressure with inhalation vs exhalation
    • *Recall atmospheric pressure about 760 mm Hg
    • Inhalation: thoracic cavity increases in size & volume of lungs expands = alveolar pressure decreases to 758 mm Hg
    • This allows atmos. air flow into lungs
    • Expiration: muscles relax, thoracic cavity decreases in size & lungs recoil = alveolar pressure increases to 762 mmHg
    • Air moves from high pressure in lungs to low pressure in atmosphere
  67. atelectasis
    any abnormal structure in the alveoli of the lung, causing the lung to collapse
  68. pneumothorax
    • a collapsed lung
    • can happen when air leaks into the pleural cavity from trauma or spontaneous rupture of a bleb (weak spot on lung)
    • The pressure of the air doesn't allow lung to fully inflate
    • Thoracic cavity can't develop pressure difference
    • Surface tension takes over and causes the delicate alveolar-capillary membrane to collapse in on itself
    • *young, thin healthy males are prone for some weird reason
  69. How is a pneumothorax treated
    • a chest tube is placed btwn ribs in the wall of thoracic cavity
    • this allows air to flow out
    • tube is then removed or sealed off, hole in chest wall repaired to lungs can spontaneously re-inflate
  70. Spirometer/spirogram
    • A spirometer tests pulmonary function, which measures the volume of air exchanged during breathing and the respiratory rate
    • A spirogram is the record of this measurement
    • Four respiratory volumes and four respiratory capacities are measured
  71. What respiratory volumes are measured using a spirometer
    • Tidal Volume
    • Inspiratory reserve volume
    • expiratory reserve volume
    • residual volume
  72. Four respiratory capacities measured on a spirogram
    • Inspiratory capacity
    • Functional residual capacity
    • Vital capacity
    • Total lung capacity
  73. VT
    Tidal volume: volume of air inspired or expired during normal quiet breathing
  74. Inspiratory reserve volume
    all the air you can breathe in from the top of tidal volume (during a very deep inhalation)
  75. Expiratory reserve volume
    all the air you can breathe out from the bottom of tidal volume during a forced exhalation
  76. Residual volume
    • Air still present in lung tissue after the thoracic cavity has been opened
    • Keeps alveoli open, prevents them from collapsing
  77. Respiratory capacities
    combinations of specific lung volumes
  78. inspiratory capacity
    • the sum of tidal volume and inspiratory reserve volume
    • All the air you can suck in total
    • *expiratory capacity would be the total volume you blow out...tidal volume + expiratory reserve volume
  79. functional residual capactiy
    the sum of residual volume and expiratory reserve volume
  80. vital capacity
    • the sum of inspiratory reserve volume, tidal volume, and expiratory reserve volume
    • All the air you can breathe in, and then out
  81. total lung capacity
    sum of vital capacity and residual volume
  82. What difference is there btwn males and females regarding lung capacity
    • Males are a little bigger - total lung capacity at 6000 ml
    • Females are only 4200 ml
  83. Recall difference btwn external and internal respiration
    • External is exchange of gas in lungs (@ alveoli)
    • Internal is exchange of gas btwn blood & tissues
    • Occurs by passive diffusion, which is governed by the behavior of gases, as described by 2 gas laws
  84. 2 physical laws which explain the exchange of gases at the alveoli and tissues
    • Dalton's Law - important for understanding how gases move down their pressure differences by diffusion
    • Henry's Law - helps explain how the solubility of a gas relates to it's diffusion
  85. Dalton's Law
    • The gas molecules in a mixture basically ignore each other
    • Each contributes a little bit to pressure
    • Therefore, the total pressure is the sum of pressures coming from each gas (this is called the sum of partial pressures)
    • Ptotal = Pa + Pb + Pc + Pd .....
    • **Think of walking into Dalton's restaurant on hot date, looking Left and seeing a bouquet of flowers on a center table. There is a variety of flowers. Each group type ignores the other flowers. Each type of flower puts off it's own pressure. BUT you eat something that turns ur stomach, and you get gas REALLY bad. :-(
  86. partial pressure
    • The pressure of a specific gas in a mixture
    • The subscript is the chemical formula of the gas, Px
    • Ex: PO2  = partial pressure for oxygen; PH2O = partial pressure for water, etc.
    • Thus, the partial pressure exerted by each component in a mixture can be determined by multiplying the percentage of gas in mix by the total pressure of mixture.
  87. What does partial pressures determine?
    • the movement of O2 and CO2 btwn the atmosphere and lungs, btwn the lungs and blood, and btwn the blood and body cells
    • Each gas diffuses across a permeable membrane from the area where it's partial pressure is greater to the area where it's partial pressure is less
  88. Henry's Law
    • The amount of gas dissolved in a liquid (like blood) is proportional to the pressure of the gas above the liquid
    • *Ex: Think of a soda can. Pressure is built up within can. You unscrew the cap, you hear the hiss... that's gas escaping.  If the cap isn't put back on, to retain the pressure, all the gas with escape the drink and soda goes flat
  89. nitrogen narcosis
    • "rapture of the deep"
    • involves the heightened pressure of nitrogen in scuba diving
    • Therefore, high levels of nitrogen is forced into the solution in the blood
    • Like the person is drunk while scuba diving
  90. "the bends"
    • occurs when a diver comes up too quickly
    • The dissolved nitrogen in the blood gets released & causes damage to alveolar-capillary membrane and joints
    • "Gas bubbles"
  91. external respiration
    • occurs at alveolar-capillary membrane
    • is the diffusion of atmospheric oxygen from the alveoli of the lungs to blood in pulmonary capillaries
  92. What must an oxygen molecule pass through in it's journey from the alveolar space into the blood
    • 1 ~ the membrane and cytoplasm of the very thin type I alveolar cell
    • 2 ~ through the basement membrane of type I alveolar cell
    • 3 ~ through the basement membrane of capillary endothelial cell
    • 4 ~ across the membrane and cytoplasm of the very thin endothelial cell lining the capillary
    • The two basement membranes (2 & 3) are fused
    • Is passive diffusion, going through concentration gradient
  93. Steps in external respiration
    • 1. deoxygenated blood is carried from the heart to the lungs by pulmonary arteries and arterioles
    • 2. gas exchange takes place at the capillaries covering the alveoli
    • Carbon dioxide and oxygen are exchanged across two layers of epithelial cells. One layer makes up the wall of the capillary, and one layer makes up the wall of the alveoli.
    • 3. oxygenated blood is carried from the lungs to the heart by the pulmonary veins and venules
  94. pulmonary ventilation
    • (symbol is a V w a dot above, the dot indicates per minute)
    • the amount of air entering the lungs each minute
  95. alveolar ventilation
    • (symbol is VA w dot above)
    • amount of air entering the alveoli each minute
    • *if air enters your lungs, but doesn't enter alveoli, gases cannot be absorbed into blood
  96. perfusion
    • (symbol is Q w dot above it)
    • the amount of blood that flows through the capillaries each minute
  97. ventilation-perfusion coupling
    • the matching of pulmonary blood flow to oxygen
    • under hypoxic conditions, pulmonary blood vessels constrict
    • this forces or shunts blood to areas of higher oxygen
    • Therefore, blood flow is greatest in alveoli that have the greatest amount of oxygen flow
    • Wanting blood to go to the area's of the lungs that are the most ventilated
  98. Explain VA/Q
    • Is the ration of ventilation to perfusion
    • can be calculated and is normally about 1
    • This means that ventilation (air flow) & perfusion (blood flow) are equally matched
    • In healthy people: 
    • VA = 4.5 L/min
    • Q = 5.0 L/min
    • So ideally, ratio is about 1
  99. How is VA/Q ration changed?
    • in disease states that affect oxygen flow or blood flow
    • If ratio is disrupted, inadequate exchange occurs
    • If no air enters lungs, VA/Q = 0 (meaning blood flows but no gas exchange take place)
    • If air enters lungs but blood doesn't flow, VA/Q=∞
    • (for ex: if pt has pulmonary embolism. blood is not oxygenated & can't release waste CO2)
  100. Internal respiration
    • the exchange of O2 and CO2 btwn systemic capillaries and tissue cells
    • occurs in tissues throughout the body
    • *Recall gases diffuse from high to low pressure
    • Partial pressure of O2 lower in tissues & higher in blood = diffuses into tissues
    • CO2 is waste product of metabolism. Partial pressure higher in tissues, lower in blood = leaves tissues & enters blood
  101. Explain how oxygen is carried in bloodstream to tissues
    • Almost all the oxygen is carried by hemoglobin (98.5%) (1.5% dissolved in plasma)
    • it picks up oxygen where concentration (partial pressure) is highest and releases oxygen where it's partial pressure is lowest
    • *alveolar air has highest PO2 ; tissue has lowest PO2 
  102. Explain how carbon dioxide is carried in bloodstream to lungs
    • Most of carbon dioxide (70%) is carried in bloodstream as HCO3- (bicarbonate ion)
    • *high partial pressure of CO2 drives formation
    • 23% is bound to hemoglobin, 7% dissolved in plasma
    • Tissue has highest PCO2 , alveolar air has lowest
  103. O2-Hemoglobin saturation curve
    • shoes the proportion of Hb bound to O2
    • The higher the PO2 (X axis) the more oxygen is bound to Hb (Y axis)
    • Many things effect the curve: pH, PCO2, temperature, and pregnancy
  104. O2 sat
    • refers to the % of hemoglobin saturation (saturated w oxygen)
    • PO2 is highest in alveolar air and arterial blood, which corresponds to hemoglobin saturation of about 97%
  105. Effect of pH on O2-Hemoglobin sat. curve
    • Recall normal pH is 7.40
    • During conditions such as exercise, tissues need more oxygen. Actively working tissues generate acids as waste, lowering pH
    • If pH is lower, hemoglobin affinity curve shifts to right: less O2 bound at lung, more O2 delivered at tissues
    • If pH is higher, curve shifts to left: opposite effect- more O2 bound at lung, less O2 delivered at tissues
  106. Effect of PCO2 on O2-Hb saturation curve
    • Actively working tissues generate more CO2 waste.
    • Higher PCO2 levels shift curve right: less O2 bound at lung, more O2 delivered at tissues
    • Lower PCO2 levels shift curve to left: opposite effect - more O2 bound at lung, less O2 delivered at tissues
  107. Effect of temperature on O2-Hb Sat curve
    • If temperature is higher, Hb curve shifts right: less O2 bound at lung, more O2 delivered at tissues
    • If temp is lower, curve shifts to left: opposite effect - more O2 bound at lung, less O2 delivered at tissues
  108. Effect of Pregnancy on O2-Hb Sat curve
    • Fetal Hb has higher affinity for O2 than adult Hb
    • When Po2 is low, fetal Hb can carry 30% more O2 than maternal Hb
    • Because of this, oxygen diffuses easily from maternal to fetal blood
  109. Explain conversion of CO2 to bicarbonate ion
    • First, CO2 leaves tissues, drawn into RBC, combines w H2O to form carbonic acid (H2CO3-)
    • Carbonic acid then dissociates into HCO3- and H+
    • The bicarbonate ion leaves the RBC, making a shift w Cl- ion (called chloride shift) which goes into RBC (keeping ion charges balanced)
  110. What happens after bicarbonate ion leaves RBC
    • floats around in plasma
    • At alveoli, the reaction reverses 
    • HCO3- goes BACK into RBC, Cl- comes back out (another chloride shift takes place)
    • HCO3- combines w H+, making carbonic acid (H2CO3
    • The carbonic acid dissociates into H2O + CO2 (uses the enzyme carbonic anhydrase)
    • CO2 can then diffuse to alveoli and be exhaled
  111. buffers in the human body
    prevent rapid, drastic changes in pH of blody fluids by converting strong acids and bases into weak acids and bases
  112. carbonic acid-bicarbonate buffer system
    • most important buffer system in human biology
    • acts as H+ and/or OH- "sponge" so that pH is kept relatively constant
  113. So what's the equation of the carbonic-acid-bicarbonate buffer system
    • H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
    • *H2CO3 = carbonic acid, HCO3- = bicarbonate ion
  114. What happens when pH is low (w carbonic acid-bicarbonate buffer system)
    • H+ is increased
    • Therefore, when H+ is abundant (acidic conditions), excess H+ are "sponged up" by HCO3- to form H2CO3. = more water and Co2 are made
    •  ↤ reaction goes that way

    • H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
  115. What happens when pH is high
    • Means H+ is decreased
    • When H+ is scarce (alkaline), excess H+ is released by H2CO3 to form HCO3- and H+
    • So it pushes the reaction to the right & more bicarbonate ion is made
    •  → reaction goes this way
    • H2O + CO2 ↔ H2CO3 ↔ H+ + HCO3-
  116. How can the respiratory system help with pH levels
    Because CO2 easily converts to an acid, the respiratory system can help control blood pH by either speeding up breathing to get rid of CO2 or slowing down breathing to retain CO2.
  117. CO2 =
    • acid
    • So access CO2 in blood will make you acidic
  118. Hyperventilation
    • or excessive ventilation
    • leading to low blood CO2 , and we don't have enough acid.
    • Results in high blood pH (alkalosis)
  119. Hypoventilation
    • decreased ventilation
    • leading to high blood CO2
    • results in low blood pH (acidosis)
    • Ex: asthma or emphysema
  120. panting
    • quick, shallow breaths
    • ex: respiratory rate may increase, but may not increase ventilation
  121. eupnea
    • normal respiration
    • eu- = breathing, -pnea = breathing
  122. hyperpnea
    increased respiratory rate
  123. apnea
    temporary halt in respiration
  124. State respiratory control centers in brains stem
    medulla and pons
  125. Control of respiration in medulla
    • @ the medulla rhythmicity area
    • controls basic rhythm of respiration
    • has 2 centers: inspiratory and expiratory center
  126. inspiratory center
    • of the medulla rhythmicity area
    • stimulated the diaphragm via the phrenic nerve
    • (*C3, C4, C5 - keep the diaphragm alive)
    • stimulates external intercostal muscles via intercostal nerves
    • Inspiration normally lasts about 2 sec
  127. expiratory center
    • as most exhalation is a passive process caused by elastic recoil of lungs, expiratory center usually inactive during quiet breathing
    • During forced exhalation, stimulates internal intercostals and abdominal muscles to contract during forced exhalation
  128. control of respiration in Pons
    • Help medullary centers manage the transition btwn inhalation and exhalation
    • Has 2 centers: Pneumotaxic center & apneustic center
  129. Pneumotaxic center
    limits the duration of inspiration to prevent lungs from getting too full
  130. apneustic center
    coordinates the transition btwn inhalation and exhalation
  131. Other sources of respiratory regulation
    • Although medulla & pons control basic rhythm of respiration, R inputs from other areas:
    • cerebral cortex - voluntary control when we want it
    • Emotions (limbic system) affect breathing
    • Hypercapina(hypocarbia) - elevated PCO2, low O2, or acidosis stimulate more rapid breathing
    • Hering-Breuer reflex
    • hypothalamus - sensing fever, increases breathing
    • Moderate Pain increases breathing
    • Severe pain causes apnea
  132. Hering-Breuer reflex
    • bronchial stretch receptors, sensing overinflation, arrest breathing temporarily
    • **Think of Hering... as a her. Don't let her legs spread too far, she'll get bred. If she's bred, she gets arrested.
  133. Explain the body's built in mechanism to regulate CO2, O2, and H+ levels in the blood
    • Chemoreceptors send input to the inspiratory center to increase respirations if CO2 and/or H+ are high or Po2 is low
    • ↑ CO2, ↑ pH+, ↓O2 = Increase in rate and depth of breathing
  134. Can you die holding your breather
    • If PO2 drops from normal level of 100 mmHg to above 50 mmHg, chemoreceptors are stimulated
    • You can consciously holding ur breath (by motor cortex)
    • If PO2 drops below certain level, syncope follows, and then brainstem will take over work of breathing while unconscious
  135. Why can you hold your breath longer if you hyperventilate first
    • A low PCO2 (below 40 mmHg) doesn't signal chemoreceptors, will not stimulate inspiratory center
    • Inspiratory center responds to high CO2, not low CO2
    • Therefore, if you hyperventilate, blowing off CO2, the inspiratory center slows & you can hold your breath longer
  136. Why is it dangerous to hyperventilate & then swim underwater?
    • O2 levels may fall to dangerously low conditions before chemoreceptor reflex is activated, causing fainting (syncope)
    • Passing out under water isn't good as drowning may occur
  137. Summarize embryonic development of respiratory system
    • Lungs begin to develop as buds on the pharynx at 4th week
    • Primary and secondary bronchi visible at 5th week
    • Tertiary bronchi at 6th week
    • Lobes of lung evident at end of 8th week
    • Earliest viable premature babies are about 23 weeks gestation
  138. At 16-26 weeks of pregnancy...
    • the lungs become highly vascular & repiratory bronchioles, alveolar ducts and some primitive alveoli begin to develop
    • Infant born at 26 weeks may survive, but death frequently occurs cause resp. system so immature
    • From 26 weeks to birth, the alveoli develop
    • At birth, only about 1/6 of alveoli are present
    • they continue to develop during first eight years of life
  139. Recall water's surface tension
    • hydrogen bonding tightly holds water molecules together
    • Alveoli must overcome this surface tension to inflate
  140. Recall surfactant
    • act like soap, they reduce surface tension in water by breaking up the hydrogen bonds
    • One end of a surfactant molecule likes grease, the other end likes water
  141. Surfactants in the lungs
    • Secreted by type 2 alveolar cells
    • Acts to break up surface tension caused by water molecules in the air-liquid interface within the alveoli of the lungs
    • necessary to prevent collapse of alveoli on exhalation
  142. Surfactants & infants
    Amounts of surfactant sufficient to permit survival of a premature infant aren't produced till 26 - 28 weeks of gestation
  143. IRDS
    • Infant respiratory distress syndrome
    • results from failure to make sufficient surfactant at birth
    • Occurs in about 2/3's of infants less than 28 weeks
    • not usually seen after 38 weeks
  144. Neonates 23 - 28 weeks
    surfactant replacement may not be enough to save infant's life