Histo Lecture 5

• Gas exchange
• Host defense
• Metabolism

Process of moving air between the atmosphere and alveoli

Process of transporting oxygen from the atmosphere to cells

• Air conditioning function
• Warm air to body temperature
• Humidifies are before reaching trachea
• Filter all particles larger than 6 micrometers in diameter

• Airway route from nose/mouth/pharynx to bronchi
• -Cartilage rings within trachea maintain patency of tracheal lumen

• Branches from Trachea, one per lung; branch into several smaller bronchi
• -Less extensive cartilage (compared to trachea) in walls maintain patency

Branches of Bronchi?

Functional unit of gas exchange

Cells within the alveoli that produce Surfactin

Exchange oxygen with capillary bed

• Exists within pulmonary system
• Acts like a detergent
• Reduces surface tension

Thin epithelial membranes covering the lungs and inner chest wall (visceral & parietal pleura)

Contains small amount of pleural fluid that lubricates the pleura as they move over each other during breathing.

Lymphatics

• Pressure of the fluid in the lung pleura
• -At reast, maintained at a negative value (-5cmH2O) in relation to atmospheric pressure

• Pressure of air inside the alveoli
• -At rest (with glottis open), is equal to atmospheric air pressure (denoted as = 0 cmH2O)

• Difference between pleural (outside lung) and alveolar pressures (inside)
• -Is a measure of the elastic recoil pressure of the lungs

• Increased trans-pulmonary pressure promotes air flow into lungs
• -Pleural pressure is decreased

• Decreased transpulmonary pressure promotes air flow out of lungs
• -Pleural pressure is increased

Glycoprotein rich, viscous fluid that traps particles for removal

• Watery (serous) fluid that rests on epithelium of the respiratory tract
• Allows cilia to move mucus easily

• Interstitial fluid build-up in pleural space
• Promotes atelectasis

Fluid build-up in the interstitium and alveoli; creates decreased gas exchange within the alveoli

Pleural effusion created by bacterial infection (often brought on by pneumonia)

• Introduction of air into pleural space
• Allows air pressure in pleural cavity to rise causing alveolar collapse (atelctasis)

• Diaphragm
• External intercostals
• SCM
• Anterior serratus
• Scalenes

• -Primarily passive process
• Internal intercostals
• Abdominal muscles assist with forceful expiration

Measure of pulmonary ventilation volumes

volume of air with each normal breath

Extra volume of inspired air over normal tidal volume with a full-force inspiration

Maximum extra volume of air expired with forceful expiration

Volume of air remaining in lung after most forceful expiration

Tidal volume + inspiratory reserve volume

Expiratory reserve volume + residual volume

Inspiratory reserve vol + tidal vol + expiratory reserve vol

vital capacity + residual volume

• Area of respiratory passageway not involved with gas exchange
• Air in nose, pharynx, trachea, bronchi and larger bronchioles

Bronchi and larger bronchioles due to the small number of these passages and their arrangement in series

Large numbers and parallel arrangement

Ease of blockage

Bronchiolar dysfunction

Causes release of epinephrine (from adrenal gland) which promotes bronchiole dilation

Promotes bronchiole constriction and icnreased mucus production

Catecholamines to induce dilation

• Irritant is sensed by bronchi and trachea
• Afferents travel along CN X to the medulla

Irritation in nasal passages stimulates afferents traveling with CN V to the medulla

• 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

Similar to coughing except uvula depresses to force expired air out through the nose

Alveoli

The concentration gradient

Fluid-air interface for dissolved gases

Gas concentration and solubility coefficient

Reduces

Pulmonary ventilation to maintain appropriate gas concentrations

Prevents sudden changes in gas concentrations in the blood

40 mmHg

• PCO2 = 45mmHg
• PO2 = 40mmHg

• PCO2 = 40mmHg
• PO2 = 104mmHg

Respiratory bronchiole, alveolar ducts, atria and alveoli

• Surfactant layer
• Alveolar epithelium
• Alveolar basement membrane
• Interstitial space
• Capillary basement membrane
• Capillary endothelium

Diffusion is inversely proportional to thickness (membrane thickens w/ lung pathology)

Diffusion is proportional to surface area available (s.a. decreases w/ lung pathology)

Diffusion is proportional to solubility of gas (CO2 diffuses 20X faster than O2)

Gas diffusion is directly proportional to differences in partial pressures

Spirometry - Maximal inspiration followed by full, forceful expiration

Total volume expelled

Volume expelled in the first second of expiration

Ratio that identifies lung dysfunction as either restritive (interstitial fibrosis) or obstructive disease (emphysema, asthma, bronchitis)

<0.8

• Dysfunction in pulmonary compliance
• Difficuty in getting air into lungs
• Restricted gas exchange due to thickened respiratory membrane

Ratio of ventilation to perfusion

• 0.8
• At this level, gas exchange is optimal

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

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)