Biology 201Dr. Edwin DeMont

St. Francis Xavier University

Respiration

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Gas Exchange

Animals must supply the oxygen required for aerobic respiration and a remove the carbon dioxide. The process of

gas exchange is called respiration.

Five main types of respiratory systems exist in animals:

1. Diffusion across plasma membranes (I)

2. Tracheae (I)

3. Cutaneous (body surface) exchange (I)

4. Gills (I,V) (I: Invertebrates)

5. Lungs (I,V) (V: Vertebrates)

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Diffusion (I)

Protozoa

Cnidarian

Flatworm

Diffusion across plasma membranes

Cutaneous (body surface) exchange

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Tracheal System (I)

Tracheae are an internal system of branching tubes that brings air directly to

each cell in the body.

Video

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Book Lung (I)

Tarantula

Book lungs are sheets of internal lamellae that are exposed to air on the outside and filled with blood on the inside.

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Gills (I)

BivalveGills are very efficient

in aquatic ecosystems—gills evolved from large or small skin projections with blood inside of the

projections.

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Gills (V)

Gills may be internal or external, but gas

exchange (oxygen in and carbon dioxide out) is very efficient due to countercurrent flow.

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Lungs: Birds

Lungs of birds are a flow-through system

wherein air is conducted through

the lungs in a single direction, and avian

lungs are particularly efficient (90% of oxygen in air is

removed).

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Lungs: Humans

The alveoli (structures with a large surface

area) are the site of gas exchange in the lungs of mammals and birds.

Video

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Gas Exchanges

Gases enter or leave the

circulatory system by diffusing down

concentration gradients.

Video

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Ventilation

Mammals utilize a negative pressure

system to bring air into lungs—they inhale by

suction

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LRC: Dogs

Motion of thoracic complex and ‘visceral piston’ shown by high

speed x-ray cinematographic images of a dog galloping on a

treadmill.

Locomotor respiratory coupling in mammals.

Bramble (1989). American Zoologist. 29 (1)

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LRC: Humans

Humans utilize LRC while running.

2:1 (Footfall:Breath)