The Pulmonary System

Structure and Function

Lungs

Lung tissue weighs 1 kg and covers half a tennis court (50-100 square feet)

Lung tissue is 20-50 times larger than the body’s external surface

Hold 4-6 liters of air. Unattached to ribs;

suspended inside the pleural sacs.

Function

Ventilation. Breathing (air in and air out) Conduction.

Movement of air through the pulmonary system

Respiration. Gas exchange (O2 and CO2)

Conduction Zone (humidify, filter)

Nasal cavity and Pharynx Nose moistens, warms, and filters air;

mouth does not.

Larynx - voice box Epiglottis Valsalva maneuver

Conduction Zone (humidify, filter)

Trachea conducting tube (transports

air) Bronchi

Branches contains muscle, serves to

dilate and constrict Anatomic dead space

Respiration

Bronchioles further branching

Alveolar sacs (300 million) Each alveoli is surrounded by a

network or covering of capillaries.

Almost forms a “sheet” of blood.

At rest, a single blood cell passes by 2 or 3 alveoli in about 0.5 to 1.0 seconds

http://www.innerbody.com/image/card06.html

Respiration (gas exchange)

Occurs through thin walls (0.3 micrometers)

Diffusion of gases from high to low concentration.

Types of Respiration

Pulmonary (external) Transfer of O2 and CO2 at the lungs. 250 mL of oxygen is exchanged per minute at rest 200 mL of CO2 is exchanged per minute at rest These numbers can increase up to 25 times during

heavy exercise Cellular (internal) respiration - transfer of O2

and CO2 in the tissues.

Mechanics of Breathing

Pleura

Pair of membranes (inner and outer) surrounding the lungs

Fluid in between two sacs provides the only attachment of the lungs to the thorasic cavity (ribs).

Pleura

Pleura

Pneumothroax

Pressure

Inspiration Air moves into the lungs

due to a lower pressure inside the lungs

Expansion of the rib cage and the lowering of the diaphragm increase the volume

As the volume gets larger, the pressure becomes lower.

                                                             

Pressure

Expiration Air moves out of the lungs

due to a higher pressure inside the lungs

Constriction of the rib cage and the raising of the diaphragm decrease the volume

As the volume gets smaller, the pressure becomes higher.

Muscles of Ventilation

Inspiration Rest

diaphragm and E.IC muscles

Exercise pectorals, scalenes, SCM

Expiration Rest

no muscles Exercise

abs, I.IC. muscles)

Lungs and Exercise

At rest, the blood is 97-98% saturated with oxygen

Exercise, the blood remains 97-98% saturated

Healthy lungs do not limit a person’s ability to exercise

However, respiratory muscles need to be trained like any other skeletal muscle