Human Anatomy and Physiology

Physiology of air breathing The lungs

Respiration

Oxygen utilization varies with activity Rest: 200 ml/min. Exercise: 6,000 ml/min.

Importance Breathing increases due to metabolic

demands Regulated by pH of ECF

Organization

Conducting zone Trachea, 1° - 3° bronchi

Respiratory zone Bronchioles, alveolar ducts

alveoli

Trachea1°

2°

3°

brochioles

Alveolor ducts

alveoli

Functions of pathway

Conducting zone Warm, cleanse and humidify air Phonation (vocal cords) Regulation of air flow (dilation/constriction)

Functions of pathway Respiratory zone

Gas exchange

Functions of pathway Respiratory zone

Cell type I (gas exchange) Cell type II (surfactant)

Gas Exchange Gases must penetrate 3 membranes

1.

2.

3.

Diffusion distances Shorter is better

Animal Diffusion distance (µm)

Toad

Birds

pigeon

swallow

shrike

Mammals

rat

human

shrew

1.3 - 3.0

0.1 - 1.4

0.09

0.17

0.13 - 0.26

0.36 - 2.5

0.27

Lung ventilation Closed compartment

Head, diaphragm, sternum, ribs and intercostal muscles

Pleura Parietal (chest) Visceral (lungs) Pleural fluid

Ventilation steps

Exchange of air between atm. and alveoli Ventilation, bulk flow

Exchange of O2 and CO2 between alveoli and lung capillaries Diffusion

Transport of gases by blood Bulk flow

Exchange of gases between blood and tissues Diffusion

Ventilation

Inspiration Expiration

Atmospheric Pressure760 mm Hg

Alveolar Pressure<760

Alveolar Pressure>760

Ventilation

What pressure changes? Ans: alveolar pressure Bulk flow: F = K (∆P) How does pressure change?

Ventilation Cavities

Pleural, pulmonary Intrapleural pressure. Why have it?

Tendency of lung recoil Surface tension of alveolar fluid Opposed by chest wall elasticity

Intrapulmonary pressure Balloon within a balloon

Ventilation

ExpirationInspiration

Ventilation

Air flow

Flow (F) = ∆P/R ∆P: change in pressure between

atmosphere and alveoli R: resistance of airways

Air flow

∆P: altered by contraction of inspiratory and expiratory muscles

Resistance Inversely proportional to 4th power of radius

€

R =1

r4 A B

€

R =1

1

€

R =1

81

Air flow Lung compliance

V = change in volume P = change in pressure

V

P

Athletes have a high lung compliance

Lung volumes Respirometer

Lung volumes

Dead space Anatomical dead space Alveolar dead space (inspired dead space)

Total dead space