Chapter 35: Pulmonary Structures Flashcards
primary function of pulm system
Exchange of gases between the environmental air and blood
gas exchange processes
Ventilation: Movement of air into and out of the lungs
Diffusion: Movement of gases between air spaces in the lungs and the bloodstream
Perfusion: Movement of blood into and out of the capillary beds of the lungs to body organs and tissues
Pulmonary system: Carries out the first two processes
Cardiovascular system: Carries out the third process
gas exchange airways: acinus
Respiratory bronchioles
Alveolar ducts
Alveoli: Primary gas exchange units
structures of pulm system
Upper airways
Two lungs
-> Lobes: Right lung (three lobes); left lung (two lobes)
-> Segments, then lobules
Lower airways
Blood vessels serve the pulmonary system
Chest wall or thoracic cage
Diaphragm: Involved in ventilation, dome-shaped muscle separates the thoracic and abdominal cavities
Mediastinum: Space between the lungs in the chest cavity, containing the heart, great vessels, and esophagus
Conducting airways
upper airways
Upper airways: Warms and humidifies air
Nasopharynx
Oropharynx
Larynx: Connects the upper and lower airways
lower airways
Trachea
Bronchi
Terminal bronchioles
trachea
Carina: Ridge where the trachea divides into the right and left bronchi.
Hila: Where the right and left bronchi enter the lungs, along with blood and lymph vessels.
Goblet cells: Produce mucus.
Cilia: Are hairlike structures inside trachea and bronchial.
Goblet and cilia help propel foreign material upward to enable it to be coughed up.
common place of aspiration
Aspiration tends to be on the right side. Bacteria tends to migrate to right side. Right side is shorter, fatter, and straighter –path of less resistance. Left side is at more of an angle.
gas exchange airways
Alveoli: Primary gas exchange units
Oxygen enters the blood, and carbon dioxide (CO2) is removed.
Type I alveolar cells: Alveolar structure
Type II alveolar cells: surfactant production -> prevents lung collapse increase surface tension
Contain alveolar macrophages: Ingest foreign material, and remove it through the lymphatic system.
One cell thick alveoli membrane. Capillaries membrane is one cell thick. O2 can diffuse through membrane fast. O2 -> blood -> Hg. CO2 -> lungs > breath out.
Smokers lose surfactant -> prone to alveoli collapse
chest walls
Includes the skin, ribs, and intercostal muscles.
Functions: Protects the lungs from injury; its muscles, in conjunction with the diaphragm, perform the muscular work of breathing.
Thoracic cavity: Is contained by the chest wall and encases the lungs.
pleura
Serous membrane
Adheres firmly to the lungs
Folds over itself, and firmly attaches to the chest wall
Visceral pleura: Membrane covering the lungs
Parietal pleura: Lining the thoracic cavity
pleural space or pleural cavity
Fluid lubricates the pleural surfaces, allowing the two layers to slide over each other without separating.
Pressure in the pleural space: Negative or sub atmospheric (−4 to −10 mm Hg)
Between lungs and chest wall
ventilation
Is the mechanical movement of gas or air into and out of the lungs.
Is not the same as respirations.
Minute volume: ventilatory rate is multiplied by the volume of air per breath. normal is 6 L/min. tidal vol (mL) x breathing rate per minute. amount of air moved in or out of the lungs per minute. increases with exercise as both tidal volume and breathing rate increase.
Alveolar ventilation: Must be measured by arterial blood gases. Measures partial pressure of carbon dioxide (Paco2) =bets indicator of ventilation.
neurochemical control of ventilation
PaCO2 -> central chemoreceptors (brain) -> brainstem resp center -> mm of breath -> alveolar vent. *pCO2 is drive to breath
PaO2 and blood pH -> peripheral chemoreceptors -> brainstem resp centers -> mm of breathing -> alveolar vent
resp. center
Is located in the brainstem.
Receives impulses from chemoreceptors in the carotid and aortic bodies: Detects the Paco2 and the amount of oxygen in the arterial blood.
Becomes active when increased ventilatory effort is required.
phrenic nerve innervates diaphragm -> contracts -> ventilation
Pneumotaxic and apneustic centers: Are located in the pons.
Modifiers of the inspiratory depth and rate are established by the medullary centers.
lung receptors
irritant, stretch, juxta pulmonary cap repcetors
irritant receptors
Are sensitive to noxious substances.
When stimulated cause cough, bronchoconstriction, and increase respiratory rate.
sense: chemicals, dust, cold air
effects: coughing, bronchoconstriction
stretch receptors
Are sensitive to noxious substances.
When stimulated cause cough, bronchoconstriction, and increase respiratory rate.
sense: lung inflation
effect: inflation terminates
juxta pulmonary cap receptors
Are sensitive to increased pulmonary capillary pressure.
sense: chemicals, stretch, pulm edema
effect: shallow breathing, bronchoconstriction, mucus secretion
muscle, joint receptors
sense: chest wall position, muscle tension
effect: normal breathing
ANS
ANS -> PSNS (ACH) -> cause smooth mm to contract (bronchoconstriction) are the main controllers of airway caliber
ANS -> SNS (E) -> cause smooth mm relaxation (bronchodilation)
mechanics
- lungs always want to come in and chest wall always wants to come out
end of expiration: lung and chest wall recoil, diaphragm relax.
inspiration: diaphragm contracts, lung and chest wall expand, muscular contraction dominates.
end of inspiration: diaphragm still contracted, muscular contraction maintains inflation
expiration: diaphragm relaxing, lung recoil dominates
lung compliance
Elastic properties of the lungs and chest wall
Compliance: Measures lung and chest wall distensibility. Represents the relative ease with which these structures can be stretched. Reciprocal of elasticity
Low: Increased work of inspiration. Stiff lungs. Pulmonary fibrous, ARDS, anything that cases restriction
High: Increased work of expiration. Easy to inflate; has lost some elastic recoil. Ex. Emphysema
gas transport
Delivery of oxygen to the cells of the body and the removal of CO2
Four steps
1. Ventilation of the lungs
2. Diffusion of oxygen from the alveoli into the capillary blood
3. Perfusion of systemic capillaries with oxygenated blood
4. Diffusion of oxygen from systemic capillaries into the cells
Diffusion of CO2 occurs in the reverse order.
02 transport in the blood
O2 from the alveoli diffuse into the blood, then O2 enters the RBC and binds to Hb. 3% of O2 is dissolved in plasma while 97% is bound to Hb -> oxyHb. the binding is reversible.
pulmonary gas exchange
Respiration- Movement of gasses across alveoli- capillary membrane AND systemic capillary-cell.
Diffusion-Movement of gases down a pressure gradient from an area of high pressure to an area of low pressure
ex. pO2 in alveoli ~104 and pO2 in venous end of cap 40 -> O2 diffuses to cap.
Partial pressure of gasses:
The pressure exerted on a surface by the molecules of individual gasses.
PP of O2 can be calculated for a given atmospheric pressure by multiplying concentration of a gas by the atmospheric (barometric pressure).
example: 760 mm Hg x 21% = 150 mm Hg
factors affecting diffusion through alveolar-cap membrane
Partial Pressure of Gasses: higher altitude decrease partial pressure of atmospheric O2
Pressure Gradient
Lung Surface Area: Emphysema decreased lung SA
Membrane Thickness: Interstitial lung dz, Lung fibrous increased thickness.
Length of Gas Exposure: Increased activity decreases gas exposure
gas exchange in the alveolus
inhaled O2 diffuses across membrane to oxygenate blood. CO2 diffuses into alveolus to be expelled thru exhalation
determinants of O2 status
3 Major determinants
PaO2: Must Get from ABG results, PP of Oxygen dissolved in arterial blood, 3% of total O2, Normal range 80-100mm Hg
SaO2 and SpO2: Percentage of oxygen bound to Hgb in the blood, Normal value > 95%, COPD Pat: 88-93%***, Qualify for home O2 < 88%
Hemoglobin: Major carrier of O2 therefore important in tissue oxygenation
classifications of hypoxemia
normal: 80-mmHg
mod: 60-80 mmHg * not uncommon for COPD
severe: 40-60 mmHg
very severe: <40 mmHg
oxyhb dissociation curve
plays an important part in determining the affinity of O2 to Hb, which directly affects diffusion. relationship of pp of PaO2 and SaO2
Once we get to a certain spot, curve bottoms out. Sao2 90 an PaO2 60 -.> o2 starts unloading quickly
right shift of oxyhb curve
causes: acidosis, hyperthermia, hypercapnia, increased 2,3 DPG
O2 doesn’t leave Hg or bind to Hg the normal way. Sa02 90 PaO2 80. O2 available for tissues. Ex. Exercise and septic. Doesn’t last forever. O2 readily leaves Hg in these conditions
left shift of oxyHb curve
causes: alkalosis, hypothermia, hypocapnia, decreased 2,3-DPG
Hg holds onto O2. SaO2 90 PaO2 40. Early resp. Failure.
pulm gas exchange: perfusion
Perfusion: pumping or flow of blood into tissues and organs. Altered by (3) factors:
Cardiac output: mCO =SV X HR, MAP is used clinically to reflect adequate perfusion
- Gravity
- ventilation/perfusion. Zones of west -> zone 1: apex, perfusion is absent. zone 2. perfusion is sporadic. zone 3. perfusion is constant
CO2 transport
CO2 is carried in the blood 3 ways:
Dissolved in plasma
Transported as Bicarb
Combined with blood proteins
*indirect measurement of bicarb
