Physiology This Week Hemorrhage Diagram due on Friday: 15 minutes to complete from memory. Check the website for Schedule of times Assistants are available. Lab this week: Respiratory Physiology. A case study and lung function tests. Bring your textbook and a calculator. Announcement about Exam Schedule.

Bronchopulmonary segments and Surgical resection Why is lung cancer so common? How are the delicate living tissues of the respiratory protected?

Respiratory Epithelium of Airway (Not alveolus!) Goblet cells, ciliated cells and the mucus escalator Smoker’s hack Cystic fibrosis

What does a river delta and your lungs have in common? Mixing of Freshwater (inspired air) and Salt water (alveolar air) Slower velocity of flow in delta (respiratory zone)

Figure 13-2 Anatomical Dead Space Impaction Sedimentation Brownian Diffusion Particle Filtration: deposition varies Decrease In Velocity

Pulmonary arterial blood = low in O 2 Cartilage prevents collapse of airways during expiration. V/Q inequality = imperfect match between air flow and blood flow Response of pulmonary arterioles to low P O 2

Matching blood flow (Q, also called “perfusion” ) to ventilation (V) by pulmonary arterioles that constrict in response to low O 2 and dilate in response to hi O 2 (Note this response to O 2 is opposite that of systemic arterioles!) Thus, poorly ventilated regions of the lung will receive less blood flow. So…. Q is “matched” to V, but not perfectly. And low perfusion in a region leads to bronchoconstriction.

V/Q inequality V/Q inequality is the result of an imperfect match between blood flow and air flow At rest, capillaries at the upper extend of the lungs may have no blood flow, due to low pressure in the pulmonary circuit.

500 ml of blood in pulmonary capillaries with surface area equal to a tennis court (75 m 2 )

Type I pneumocytes are simple squamous epithelia that comprise the majority of the surface area. Type II pneumocytes secrete surfactant. Gas exchange by diffusion based on gradients. Elastin fibers in interstitium stretch with inhalation, recoil assists exhalation. Chronic inhalation of irritants stimulates alveolar macrophages……… Degradation of elastin & Isolation by fibroblasts (fibrosis)

Surfactant reduces surface tension which reduces the mechanical effort of ventilation and prevents the collapse of smaller alveoli. Who cares? Respiratory Distress Syndrome of the Newborn

Elastin fibers in interstitium stretch with inhalation, recoil assists exhalation. Chronic inhalation of irritants stimulates alveolar macrophages……… Degradation of elastin & Isolation by fibroblasts (fibrosis) Compliance and elastance of balloon and plastic bag. Syringe with internal spring

Figure Who cares? Respiratory Distress Syndrome of the Newborn Law of LaPlace Surfactant reduces surface tension which reduces the mechanical effort of ventilation and prevents the collapse of smaller alveoli.

Figure At end of normal tidal expiration Tidal inspiration

V = V T x f V A = (V T – V DS ) x f Anatomic dead space = air remaining in conducting zone (typically 150 ml.) What is V A if Tidal Volume is 150 ml?

O 2 uptakeCO 2 production

O 2 uptake CO 2 production = Respiratory Quotient =0.8 for mixed diet 200mlCO 2 /min 250 ml O 2 /min = 0.8 for proteins = 0.7 for fat = 1.0 for carbohydrate C 6 H 12 O O2 → 6 CO H 2 O + energy

Gas exchange In what forms are O 2 and CO 2 found in the blood?

Figure CO 2 and O 2 bound to Hb do not contribute to partial pressure (no longer a dissolved gas!) Bound & Free Peripherial chemoreceptors can detect ONLY dissolved gasses! Partial Pressures are the same, but total oxygen content differs!