Histo Lecture 5
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What are the 3 main functions of the lungs?
- Gas exchange
- Host defense
Process of moving air between the atmosphere and alveoli
Process of transporting oxygen from the atmosphere to cells
What are the 4 main functions of the nose/nasal cavities?
- Air conditioning function
- Warm air to body temperature
- Humidifies are before reaching trachea
- Filter all particles larger than 6 micrometers in diameter
What is the Trachea?
- Airway route from nose/mouth/pharynx to bronchi
- -Cartilage rings within trachea maintain patency of tracheal lumen
What are Bronchi?
- Branches from Trachea, one per lung; branch into several smaller bronchi
- -Less extensive cartilage (compared to trachea) in walls maintain patency
What are Bronchioles?
Branches of Bronchi?
What are Alveoli?
Functional unit of gas exchange
What are Type 2 cells?
Cells within the alveoli that produce Surfactin
What are Type 1 cells?
Exchange oxygen with capillary bed
What does Surfactin do?
- Exists within pulmonary system
- Acts like a detergent
- Reduces surface tension
What are Pleura?
Thin epithelial membranes covering the lungs and inner chest wall (visceral & parietal pleura)
What is the Pleural Space?
Contains small amount of pleural fluid that lubricates the pleura as they move over each other during breathing.
Pleural fluid is filtered by what?
What is Pleural pressure?
- Pressure of the fluid in the lung pleura
- -At reast, maintained at a negative value (-5cmH2O) in relation to atmospheric pressure
What is Alveolar pressure?
- Pressure of air inside the alveoli
- -At rest (with glottis open), is equal to atmospheric air pressure (denoted as = 0 cmH2O)
What is Transpulmonary pressure?
- Difference between pleural (outside lung) and alveolar pressures (inside)
- -Is a measure of the elastic recoil pressure of the lungs
What is Inspiration?
- Increased trans-pulmonary pressure promotes air flow into lungs
- -Pleural pressure is decreased
What is Expiration?
- Decreased transpulmonary pressure promotes air flow out of lungs
- -Pleural pressure is increased
Describe the mucus created by the lungs
Glycoprotein rich, viscous fluid that traps particles for removal
What is Periciliary fluid?
- Watery (serous) fluid that rests on epithelium of the respiratory tract
- Allows cilia to move mucus easily
What is Pleural effusion?
- Interstitial fluid build-up in pleural space
- Promotes atelectasis
What is pulmonary edema?
Fluid build-up in the interstitium and alveoli; creates decreased gas exchange within the alveoli
What is Empyema?
Pleural effusion created by bacterial infection (often brought on by pneumonia)
What is Pneumothorax?
- Introduction of air into pleural space
- Allows air pressure in pleural cavity to rise causing alveolar collapse (atelctasis)
What muscles are engaged in Inspiration?
- External intercostals
- Anterior serratus
What muscles are involved in Expiration?
- -Primarily passive process
- Internal intercostals
- Abdominal muscles assist with forceful expiration
What is Spirometry?
Measure of pulmonary ventilation volumes
What is Tidal volume?
volume of air with each normal breath
What is Inspiratory reserve volume?
Extra volume of inspired air over normal tidal volume with a full-force inspiration
What is Expiratory reserve volume?
Maximum extra volume of air expired with forceful expiration
What is Residual volume?
Volume of air remaining in lung after most forceful expiration
What is Inspiratory Capacity?
Tidal volume + inspiratory reserve volume
What is Functional residual capacity?
Expiratory reserve volume + residual volume
What is Vital Capacity?
Inspiratory reserve vol + tidal vol + expiratory reserve vol
What is total lung capacity?
vital capacity + residual volume
What is Dead space?
- Area of respiratory passageway not involved with gas exchange
- Air in nose, pharynx, trachea, bronchi and larger bronchioles
Where is airway resistance the greatest?
Bronchi and larger bronchioles due to the small number of these passages and their arrangement in series
Smaller bronchiols have lower airway resistance due to:
Large numbers and parallel arrangement
Smaller bronchiols determine lung dysfunction with disease states due to:
Ease of blockage
Edema, mucus, hypertrophy of bronchiole wall, and smooth muscle contraction create:
How does the Sympathetic ANS affect pulmonary function?
Causes release of epinephrine (from adrenal gland) which promotes bronchiole dilation
How does the parasympathetic ANS play a role in pulmonary function?
Promotes bronchiole constriction and icnreased mucus production
Albuterol mimics what?
Catecholamines to induce dilation
How does the cough reflex work?
- Irritant is sensed by bronchi and trachea
- Afferents travel along CN X to the medulla
How does the sneeze reflex work?
Irritation in nasal passages stimulates afferents traveling with CN V to the medulla
What physically is the processes of coughing?
- Rapid inspiration
- Epiglottis closes, vocal cords shut to trap air in lungs
- Abdominal muscles contract forecfully to expel air out when epiglottis and vocal cord open
How does sneezing work physically?
Similar to coughing except uvula depresses to force expired air out through the nose
what are responsible for diffusion of O2 and CO2?
Diffusion results from random movement of molecules in relation to what?
The concentration gradient
What is partial pressure?
Fluid-air interface for dissolved gases
What are are partial pressures of gas in solution dependent on?
Gas concentration and solubility coefficient
Increased solubility INCREASES/REDUCES overall partial pressure?
Constant exchange of O2 and CO2 must be coordinated with what and why?
Pulmonary ventilation to maintain appropriate gas concentrations
Slow replacement of alveolar air prevents what?
Prevents sudden changes in gas concentrations in the blood
PCO2 is maintained at what?
Venous blood partial pressures are what?
- PCO2 = 45mmHg
- PO2 = 40mmHg
Alveolar air partial pressure are what?
- PCO2 = 40mmHg
- PO2 = 104mmHg
What is a Respiratory Unit?
Respiratory bronchiole, alveolar ducts, atria and alveoli
What all is included in the Respiratory Membrane?
- Surfactant layer
- Alveolar epithelium
- Alveolar basement membrane
- Interstitial space
- Capillary basement membrane
- Capillary endothelium
How does membrane thickness affect diffusion?
Diffusion is inversely proportional to thickness (membrane thickens w/ lung pathology)
How does membrane surface area affect diffusion?
Diffusion is proportional to surface area available (s.a. decreases w/ lung pathology)
How does gas diffusion coefficient affect diffusion?
Diffusion is proportional to solubility of gas (CO2 diffuses 20X faster than O2)
How does partial pressure of gases affect diffusion?
Gas diffusion is directly proportional to differences in partial pressures
What is used to assess lung function and possible disease?
Spirometry - Maximal inspiration followed by full, forceful expiration
What is Forced vital capacity (FVC)?
Total volume expelled
What is Forced expiratory volume (FEV1)?
Volume expelled in the first second of expiration
What is FEV1/FVC?
Ratio that identifies lung dysfunction as either restritive (interstitial fibrosis) or obstructive disease (emphysema, asthma, bronchitis)
Obstructive disease has a ratio that is what?
What is interstitial fibrosis?
- Dysfunction in pulmonary compliance
- Difficuty in getting air into lungs
- Restricted gas exchange due to thickened respiratory membrane
What is Va/Q?
Ratio of ventilation to perfusion
What is normal value of Va/Q?
- At this level, gas exchange is optimal
Low Va/Q ratios indicate inadequate ventilated, termed what?
What happens in a physiologic shunt?
- Some perfused blood fails to be oxygenated and is "shunted" back to the heart
- Indicates damage to alveoli or blockage of bronchioles resulting in lack of ventilation for oxygenating the blood
High Va/Q ratios indicate inadequate perfusion, termed what?
Physiologic dead space
What happens in physiologic dead space?
- All of the ventilated air does not reach blood to allow gas diffusion
- Indicated disruption of pulmonary circulation due to blockage (pulmonary embolism) or increased vascular resistance (pulmonary hypertension)
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