Today In Physiology:: The Respiratory System

TODAY IN PHYSIOLOGY:

The Respiratory System CO2

O2 CO2 O2

O2

Camilo C. Roa, Jr., MD, FPCP, FPCCP Professor of Physiology and Medicine UP College Medicine - PGH

Why a respiratory system?

“Because this is where the action is going to be baby!” Dateline: Paleozoic Era, Devonian period, 408 to 360 million yrs ago. Appearance of the first amphibious creatures.

Objectives • To list the functions of the respiratory system • To point out how the anatomic, histologic, biochemical properties of the respiratory system facilitate gas exchange between man and his environment • To review physical laws governing gas exchanges • To trace the pathway of oxygen transport from the lungs to the tissues and the reverse route used in CO2 transport • To discuss the need to control breathing and the mechanisms involved

Functions of the Respiratory System • Gas Exchange • Heat Exchange • Blood Gas Homeostasis • Phonation • Defense • Bioactive substrate metabolism

The Atmosphere

Law of Partial Pressures: Patm = PN2+PO2+PH20+Petc PO2 = FiO2 x Patm N2 N2 N2 N2 O

N2

2

N2

N2

CO2 N2

N2 N2

O2 N2

O2

H2O Patm = 760mmHg

Functions of the Respiratory System

Chest Bellows

Breathing: Applying Boyles’ Law

Click on the ribs and the The Respiratory diaphram to see animations

Muscles

Uncoupling the Lungs and the Chest Wall

Pneumothorax

Statics and Dynamics of Breathing

Patmosphere = “0”

At end expiration

Statics and Dynamics of Breathing -8

Patm = 0

Palv = (-) Ppleural

At inspiration

Midinspiration

Patm = 0

Palv = (0) Ppleural

Endinspiration

The Dynamics of Breathing

Portable Spirometer

Airway Bronchodilator Response 0

Liters F E V 1

1 2 3

Obstructive pattern

Asthm a

4 1

2 6

COPD 3

4

Seconds

5

Respiratory Tract

Ventilation

Vtidal = Valveolar + Vdeadspace 

Vminute = Vtidal X resp. rate

AI R

Intrapulmonary Gas Flow

Mass Flow

CO2

O2 Diffusion

Partial Pressures of Gases in Inspired Air and Alveolar Air Insert fig. 16.20

Respiratory Zone CO2

Di

ffu s

ion

O2 1m m

Diffusio n

Conducting Zone

Dipalmitoyl phosphatidyl choline (DPPC)

Effect of Surfactant Loss

Rabbit Normal Lung: Before and After AcidSurfactant Application Lack

Neonatal Respiratory Distress Syndrome

*Pores of Khun

O2

2

CO

ion Di ffu s

Di ffu s

ion

Di ffu sio

n

Di

ffu s

ion

O2

Alveolar compartment

Alveolar compartment

Alveolo-Capillary GasbyExchange simple diffusion

Basic Gas Exchanging Unit in the Lungs

C02 02

O2 Diffusion during Normoxia

Distribution of Perfusion

Regional Distribution of Ventilation

Lung Ventilation/Perfusion Ratios • Functionally: – Alveoli at apex are underperfused (overventilated). – Alveoli at the base are underventilated (overperfused).

Picture 4

Gas Exchange and Transport At Steady State “pay-as-you-go” • Lung O2 Uptake rate = Cell O2 Utilization rate • Cell CO2 Production rate = Lung CO2 Release rate

Blood Gas Transport A IR

• Transfer of O2 from lungs to tissues. • Transfer of CO2 from tissues to lung.

O2 BLOOD

CELLS

O2

ADP * ATP

Hemoglobin in Gas Transport

(280 million Hbs/RBC)

Hemoglobin and 02 Transport

Hemoglobin in Gas Transport

Hb02 Dissociation Curve

Oxyhemoglobin Dissociation Curve

Insert fig.16.34

Carbonic anhydras e

CO2 Transport

Carbon Dioxide Transport

Insert fig. 16.38

C02 Transport • C02 transported in the blood: – HC03- (70%). – Dissolved C02 (10%). – Carbaminohemoglobin (20%).

H20 + C02

C.A.

H2C03

High PC0

2

Special Considerations • Lung defense • Lung function measurement • Control of breathing

Cough Reflex

Lung Defense: The Cough Reflex Receptors

Center

Effectors

Process of Respiratory Control Central Controller

INPUT

•Brainstem •Cerebrum

Sensors Chemoreceptors Lung receptors Peripheral receptors

OUTPUT

Effectors Respiratory muscles

Brain Stem Respiratory Centers • Neurons in the reticular formation of the medulla oblongata form the rhythmicity center: – Controls automatic breathing. – Consists of interacting neurons that fire either during inspiration (I neurons) or expiration (E neurons).

Insert fig. 16.25

Other Factors Affecting Respiration • Physical Factors – exercise – temperature

• Volition (Conscious control) • Emotional Factors – excitement – fear – anger