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

Bronchopulmonary segments and Surgical resection

Why is lung cancer so common?Why is lung cancer so common?

How are the delicate living tissues of the respiratory protected?

How are the delicate living tissues of the respiratory protected?

RespiratoryEpitheliumof Airway(Not alveolus!)

Goblet cells, ciliated cells and

the mucus escalator

Smoker’s hackSmoker’s hack

Cystic fibrosisCystic fibrosis

Figure 13-2

Anat

omic

al D

ead

Spac

e

Impaction

Sedimentation

Brownian Diffusion

Particle Filtration: deposition varies

DecreaseIn Velocity

Pulmonary arterial blood = low in O2Pulmonary arterial blood = low in O2

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 O2

Matching blood flow (Q, also called “perfusion” ) to ventilation (V) by pulmonary arterioles that constrict in response to low O2 anddilate in response to hi O2

(Note this response to O2 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 mayhave no blood flow, due to low pressure in the pulmonary circuit.

500 ml of blood inpulmonary capillarieswith surface areaequal to a tennis court(75 m2)

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 13.19

At end of normal tidal expiration

Tidal inspiration

V = VT x f

VA = (VT – VDS) x fAnatomic dead space = air remaining in conducting zone (typically 150 ml.)

What is VA if Tidal Volume is 150 ml?

O2 uptake CO2 production

O2 uptake

CO2 production= Respiratory Quotient

=0.8 for mixed diet 200mlCO2/min250 ml O2/min

= 0.8 for proteins= 0.7 for fat= 1.0 for carbohydrate

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy

Gas exchange

In what forms are O2 and CO2 found in the blood?

Figure 13.27

CO2 and O2 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!