Respiratory System

1
Respiratory System

• Chapter 19

2
Structural divisions

• Upper respiratory (nose, pharynx, associated
  structures)
• Note-some books say nose-larynx for upper
• Lower respiratory (larynx, trachea, bronchi,
  lungs)
• Note-some books say trachea-lungs for lower

3
Functional divisions

• Conducting portions-series of tubes and cavities
  both inside and outside the lungs (nose, pharynx,
  larynx, trachea, bronchi, bronchioles, and
  terminal bronchioles that filter, warm, and
  moisten air and conduct it to lungs
• Respiratory portion-tissues inside the lungs
  where gas exchange occurs, including respiratory
  bronchioles, alveolar ducts, alveolar sacs, and
  alveoli

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Organs of the Respiratory system

• Nose-has external and internal portions
• Functions
• Provides passageway for air
• Moistens and warms air
• Filters and cleans air
• Resonating chambers for speech
• Detect odors

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Structures in nose

• Vibrissae (nose hairs)-filter large particles
  from air (bugs, dust)
• Nasal cilia-trap and move small particles away
  from lungs
• Nasal conchae-increase air turbulence and ensure
  that most air contacts mucous membrane
• Olfactory mucosa-contain smell receptors
• Respiratory mucosa-pseudostratified ciliated
  epithelium containing goblet cells
• Nasal septum-separates 2 nares
• Paranasal sinuses are continuous with nasal
  cavity and serve as resonating chambers as well

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Organs of Respiratory system continued

• 2. Pharynx-throat
• Divided into 3 parts
• A. nasopharynx (air passage), contains uvula and
  pharyngeal tonsils
• B. oropharynx-food and air, contains fauces
  (opening from throat), and the other two sets of
  tonsils
• C. laryngopharynx-food and air
• Nasopharynx has 5 openings including auditory
  tubes, internal nares, and opening into
  oropharynx

7
Continued

• 3. Larynx-voice box (located at 4-6th cervical
  vertebrae
• Functions
• Keeps food and drink out of airway
• Sound production
• Contains 9 C rings of hyaline cartilage
• Muscular walls help in voice production and
  swallowing
• Glottis-opening of larynx (superiorly)
• Epiglottis-leaf shaped piece of cartilage that
  covers glottis during swallowing
• False vocal cords-help close glottis
• True vocal cords-produce sound (fasterhigher
  pitch)
• Have thyroid cartilage or Adams apple, arytenoid
  cartilage, and cricoid cartilage

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http//www.as.uky.edu/Biology/faculty/bonner/HISTO
LOGY/Respiratory20system/Respiratory20system.htm

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Voice production

• Superior pair of folds in larynx is ventricular
  fold or false vocal cords
• Inferior pair of folds is vocal folds or true
  vocal cords
• Pitch is controlled by tension on vocal folds
• Increase in tension causes them to vibrate
  faster, increasing pitch
• Whispering-vocal folds dont vibrate so no pitch

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Continued

• 4. Trachea-windpipe
• Functions air passageway, clean warm and
  moisten air
• Contains rings of hyaline cartilage and ciliated
  pseudostratified epithelium
• Divides into left and right primary bronchi which
  enter lungs (carina or internal ridge is formed
  at last tracheal cartilage)
• Next divide into secondary bronchi (one for each
  lobe 3 on right, 2 on left)
• Next into tertiary or segmental bronchi
• Next into terminal bronchioles, respiratory
  bronchioles, then alveolar ducts, alveolar sacs
  containing alveoli

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Alveoli (300 million)

• Sites of gas exchange
• Contain Type I and Type II alveolar cells
• Type I allow for diffusion of gases (simple
  squamous epithelium)
• Type II produce surfactant (simple cuboidal
  cells) which reduces surface tension to keep
  alveoli from collapsing

12
Lungs

• Right and left lungs
• Left divide into 2 lobes, are smaller than right
  and have a cardiac notch to accommodate the
  heart, also has oblique fissure and hilum (notch
  accepting vessels and bronchi)
• Right has 3 lobes, larger than left, and has
  oblique and horizontal fissures, and hilum
• Covered by 2 layers of serous membrane called
  visceral and parietal pleura
• Pneumothorax is air in pleural space

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Respiration

• Pulmonary ventilation-breathing
• Movement of air into lungs (inspiration or
  inhalation)
• Movement of air out of lungs (expiration or
  exhalation)
• External respiration- movement of oxygen from
  lungs to blood, and movement of carbon dioxide
  from blood to lungs
• Internal respiration-movement of blood to tissue
  cells, and movement of carbon dioxide from tissue
  cells to blood

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Mechanics of pulmonary ventilation

• Atmospheric pressure is weight of air
• This is the force that moves air into the lungs
• 1 atmosphere is equal to 760 mm Hg (at sea level)
• Boyles law-at constant temperature, the pressure
  of a given quantity of gas is inversely
  proportional to its volume

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Phase one of pulmonary ventilation

• Inspiration (inhalation)-requires energy
• Air flows into the lungs when the thoracic
  pressure falls below atmospheric pressure
  Heres how
• Diaphragm contracts and moves downward when
  stimulated by phrenic nerve and expand chest
  cavity (75 of air flow)
• External intercostal muscles contract and expand
  chest cavity too (25), creating a drop in
  alveolar pressure and intrapleural pressure)
• According to Charles Law the volume of a given
  quantity of gas is directly proportional to its
  absolute temperature (as inhaled air is warmed,
  it expands and helps inflate the lungs)
• Deep inhale requires sternocleidomastoid,
  pectoralis minor, and scalene muscles to
  participate.

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Phase two

• Expiration or exhalation-passive process caused
  by recoil of lungs
• Air is forced out of lungs when thoracic pressure
  rises above atmospheric pressure
• Caused by diaphragm and external intercostals
  relaxing and elasticity of lung
• For forceful exhale, can use internal
  intercostals and abdominals

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Physical influences on pulmonary ventilation

• 1. Resistance to airflow-any condition which
  narrows or obstructs the airway increases
  resistance so that more pressure is required to
  maintain same airflow (asthma, emphysema, chronic
  bronchitis all increase airway resistance). Also
  diameter of bronchioles is a factor (smooth
  muscle control)
• Bronchoconstriction-reduce air flow
• Bronchodilation-increase air flow
• 2. Pulmonary compliance-the ease at which lungs
  expand
• Reduced by degenerative lung diseases like TB
  (low compliance means the lungs resist expansion)

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Continued

• 3. Alveolar surface tension-surfactant reduces
  the surface tension in the alveoli and prevents
  collapsing during exhale (respiratory distress
  syndrome is due to lack of surfactant)

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Neural control of pulmonary ventilation

• Control centers in brain (pons and medulla)
  control breathing and adjust rate and depth of
  breathing depending on oxygen and carbon dioxide
  levels
• Afferent connections to brain (hypothalamus and
  limbic system signals respiratory control
  centers)
• Chemoreceptors moniter pH, Oxygen and Carbon
  dioxide,
• Vagus nerve irritation (smoke, etc) transmits to
  respiratory centers
• Inflation reflex-prevents over inflating
• Limited voluntary control (cant hold breath
  indefinitely)

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Patterns

• Apnea-temporary cessation of breathing
• Epnea-normal breathing
• Dyspnea-labored breathing (gasping)
• Hyperpnea-increased rate and depth of breathing
  (exercise induced, etc)
• Hypoventilation-reduced pulmonary ventilation
• Hyperventilation-increase pulmonary ventilation
  in excess of metabolic demand (breath into paper
  sac to calm)
• Respiratory arrest-permanent cessation of
  breathing

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Nonrespiratory movement

• Laughing Crying
• Yawn cough
• Sneeze talking
• Singing hiccup
• -Valsalva maneuver-forced exhalation against a
  closed glottis as occurs when defecating (will
  help slow down a racing heart)

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Measurements

• Four measurements (respiratory volumes)
  determined by a spirometer (normal respiration
  rate is 12 breaths per minute in adult)
• 1. tidal volume-amount of air inhaled and
  exhaled with each breath (500 mL)
• 2. inspiratory reserve volume-amount of air
  inhaled during forced inhale including tidal
  volume (3000 mL)
• 3. expiratory reserve volume-amount of air
  exhaled during forced exhale including tidal
  volume (1100mL)
• 4. Residual volume-amount of air remaining in
  lungs after forced exhale (never completely empty
  lungs) (1200 mL)

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Additional Measurements-respiratory capacity

• 1. vital capacity-maximum amount of air that can
  be exhaled after taking in deepest breath
  possible (VCTVIRVERV) (4600 mL)
• 2. inspiratory capacity-maximum volume of air
  than can be inhaled following exhalation of
  resting tidal volume (ICTV IRV) (3500 mL)
• 3. Functional residual capacity-volume of air
  remaining in lungs after exhalation of resting
  volume (FRCERV RV) (2300mL)
• 4. Total lung capacity-total volume of air that
  lungs can hold (TLCVC RV)(460012005800mL)

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Dead Space

• Anatomical dead space-areas of conducting zone
  that contain air that never contributes to gas
  exchange in alveoli (about 150mL of tidal volume)
• Alveolar dead space-alveoli that collapse or are
  obstructed and are not able to function in gas
  exchange

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Pulmonary function tests

• Enable obstructive pulmonary disorders to be
  distinguished from restrictive disorders
• Obstructive disorders-do not reduce respiratory
  volumes but narrow the airway and interfere with
  airflow
• Restrictive disorders- stiffen lungs and reduce
  compliance and vital capacity

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Laws

• Daltons Law-each gas in a mixture of gases
  exerts its own pressure as though no other gases
  were present
• Henrys Law-the quantity of gas that will
  dissolve in a liquid is proportional to the
  partial pressure of the gas and its solubility

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Daltons Law

• The pressure of a specific gas in a mixture is
  its partial pressure and is usually written Px
  where x is the chemical formula of the gas
• Total pressure is the sum of all partial
  pressures
• Atmospheric air is a mix of nitrogen, oxygen,
  water vapor, carbon dioxide and a few other gases
  in tiny quanities
• The partial pressure determines the movement of
  oxygen and carbon dioxide between atmosphere and
  lungs, lungs and blood, and blood and body cells
  (diffusion)

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Henrys Law

• In body fluids, the ability of a gas to stay in
  solution is greater when partial pressure is
  higher and when it has a high solubility in water
• The higher the partial pressure of a gas over a
  liquid, and the higher the solubility, the more
  the gas will stay in solution
• In comparison to oxygen, more carbon dioxide is
  dissolved in plasma because the solubility of
  carbon dioxide is 24 times greater than oxygen

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Rate of pulmonary and systemic gas exchange

• In blood and lungs, alveolar air diffuses from
  alveoli to blood capillaries because partial
  pressure of alveolar air is 105 mmHg and blood
  capillaries is 40 mmHg.
• Diffusion continues until Po of capillary blood
  reaches 105 mmHg (equilibrium)
• Rates of exchange depends on partial pressure
  differences of the gases, surface area for gas
  exchange, molecular weight and solubility, and
  diffusion distance

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Oxygen transport

• Oxygen doesnt dissolve easily in water, so only
  1.5 of the oxygen in blood is dissolved in
  plasma
• 98.5 is bound to hemoglobin (oxyhemoglobin),
  each heme can bind to one oxygen
• Each 100 mL of oxygenated blood contains the
  equivalent of 20 mL gaseous oxygen (0.3 mL in
  plasma and 19.7 mL in hemoglobin)

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Relationship between hemoglobin and oxygen
partial pressure

• The higher the partial pressure of oxygen, the
  more oxygen combines with hemoglobin
• If deoxyhemoglobin is completely converted to
  oxyhemoglobin, it is said to be fully saturated
• Carbon monoxide has a higher affinity for
  hemoglobin, so it binds easier

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Carbon dioxide transport

• Under normal circumstances, 100 mL of
  deoxygenated blood contains 53 mL of gaseous
  carbon dioxide, which is transported in one of
  three ways
• 1. dissolved CO2 (7)
• 2. bound to hemoglobin as carbaminohemoglobin
  (23)
• 3. bicarbonate ion (70)-transported in blood
  plasma

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Controls

• If PCO2 or Hydrogen ion content rises in the
  blood, breathing rate increases (this is the MOST
  important thing in the control of
  respiration.i.e. elevated carbon dioxide)
• Low blood oxygen has little effect, if very low
  it stimulates aortic bodies and carotid bodies
  and breathing rate and tidal volume increase
• Hyperventilation lowers carbon dioxide levels and
  a person may lose consciousness (breathe into bag)

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Modifications

• 200 mL of oxygen are used each minute by cells,
  but during strenuous exercise you use more
• Several things help with increased demand1.
  cortical influences on respiration
• 2. chemoreceptors and proprioceptors
• 3. inflation reflex
• Other influences include limbic system, temp,
  pain, stretching anal sphincter muscle,
  irritation of airways, blood pressure

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READ

• Dont forget clinical applications, green boxes,
  and terms.
• Especially read the box on COPD