The Respiratory System

Pulmonary Anatomy and Physiology

Chapter 15: 393-423

What is Respiration? Closely Matched to Activity Includes:

Breathing: Moving air into lungsGas Exchange: Between lungs and bloodGas Transport: By the bloodGas Exchange: Between blood and

tissues Cellular Respiration: O2 use

Pulmonary Overview:Structure and FunctionMechanics of Breathing

Lung Volumes and CapacitiesGas Exchange

Gas Laws: Partial PressuresO2, CO2, and pH Homeostasis

Control of VentilationSpecial Issues: Exercise/Disease

The Lungs and Homeostasis!The primary effector in Maintaining

constant blood gases:O2

CO2

pH (H+ and HCO3-)

You Guessed it! Exercise causes a blood gas homeostatic emergency!

Pulmonary AnatomyUpper Respiratory Tract:

Nose, Nasal Cavity,Pharynx etc.Lower Respiratory Tract:

Larynx, Trachea, BronchiLungs

Pleural MembraneCirculation and Lymphatics

Structure and Function:Ventilation: Breathing –

airways/respiratory musclesGas Exchange: Interface between

air/blood AlveoliPulmonary capillariesVERY thin diffusion distanceVERY great surface area

Assignment:

Read pages 393-406Note: How do pressure

gradients affect breathing (page 402-403)

What is surfactant?What is a “pneumothorax”?

Horace Pippin: “Cabin in the Cottonfields” 1930’s

Gases and Gases in Solution

Oxygen is a gas!Atmospheric Gases:

Concentrations:Oxygen: 21%Nitrogen: 78+%Carbon Dioxide: 0.03%

Concentration vs. Partial PressureConcentration (content) reflects

the relative amount of gas in a gas mixture

Pressure: The force of “bouncing” gas molecules against the walls of any container (lungs, atmosphere, balloons)

Speaking of Balloons!Let’s fill this

balloon with expired air from our lungs:

What are the gases?

Put in the fridge

Pressure and Partial PressurePressure: The force of ALL the gas

molecules as they “bounce of the walls”

Partial Pressure: The force of one particular TYPE of gas molecule as they bounce…In this room: Partial Pressure of guys

vs. girls…

Gas Laws: The effect of T and V on P…What happens to molecular

movement when they heat up? T = P

What happens to the force exerted against the walls, when the walls close in? V = P

General Gas Law:

•PV = TOr: P = T/VP = 1/VP = T

Let’s check out the balloon…

Temperature and VolumeWhat happened

to the cooled balloon?

Why “Hot Air Balloons?

Hot air molecules “expand”…

Calculating Partial PressuresThe atmospheric pressure at

sea level is 760 mm Hg:21% of that pressure force is

from oxygen molecules:760 mmHg X .21 = 160 mmHg

Pressure and Diffusion:Gas Molecules move from levels of

high pressure to lower pressurePRESSURE GRADIENTThe pressure gradient of O2

between the alveoli and pulmonary capillary DRIVE O2 into the blood

Oxygen “Gradients” in the Lung:Pulmonary

Capillary = 40 mmHg

Alveolus= 105 mmHg

When the blood leaves the lung= 105 mmHg

40

105

105

105

105

Gas Pressures: mmHg

160 105 40 105 40

0.3 40 45 40 45

Atm AlvDeoxyBlood

OxyBlood

TissueCells

PO2

PCO2

Oxygen and TissuesThe relative

pressures of CO2 and O2 drive oxygen into the tissues and CO2into the blood

Ventilation:

Inspiration: Breathing inDiaphragm contractsThorax ExpandsIncreased Volume = Decreased

Pressure compared to the airAir Moves from high to low

pressures

Ventilation:Expiration: Breathing out

Diaphragm relaxesThorax recoilsDecreased Volume = Increased

Pressure compared to outside air

Air moves out of the lungs

Surfactant:Lungs Expand: Pleural membranes

pull lungs out during inspirationAlveoli Expand: Surfactant coats

the inner surface of the alveoli, and reduces surface tension –which keeps the alveoli from collapsing during exhalation

The Purpose of Ventilation:To Get Oxygen from the

atmosphere to the needy tissuesGas enters the blood only

from the alveoli. The remainder of the respiratory

tract is “Dead Space”

Gas Exchange:Efficiency Depends on:

Pressure Gradients between alveoli and capillary PO2

Solubility constant:(O2 is OK)Diffusion Distance: 2 cells thickSurface Area: All those alveoli increase

the surface area of the lungs to 70 m2

The Hemoglobin Assist!Hemoglobin in Red Blood Cells

increases the O2 carrying capacity of the blood

Hemoglobin has a “heavy attraction” (affinity) to oxygen

Hemoglobin carries ~98.5% of the O2 in the blood

Hemoglobin-Oxygen Dissociation Curve:

Carbon Dioxide:Highest in the tissuesHigh solubility and diffusion7% dissolved in plasma23% combine with hemoglobin

70% combine with H2O

CO2 + H2O H2CO3

Bicarbonate and pHAt physiologic conditions (tissues):

H2CO3 H+ + HCO3-

So CO2 causes a decrease in pH

CARBONIC ANHYDRASE is the enzyme catalyst

Breathing and pHIn the lung, the reaction reverses:

H2CO3 H2O + CO2

So Exhaling blows off CO2 …

AND reduces H+

RESPIRATORY COMPENSATION (of acidosis)

Assignment:

Read Pages: 406-410Read Lab for MondayHave a good weekend!