2. Respiration
 OXYGEN- one of the most important requirements
of animals.
 CONSTANT & ABUNDANT SUPPLY
 Necessary for metabolic processes
 CO2 – released as waste product
Gaseous exchange that occurs between an organism and its environment.

3. Respiratory System
 All respiratory processes involve diffusion of gases
through moist and semi-permeable membranes to
hasten respiration
 Simple organisms
 Direct diffusion of gases in and out of their
integument
 Larger more complex animals
 Presence of a system which functions mainly to
transport gases reciprocally between the cells and the
external environment

4. Respiratory
Systems of different
organisms
AQUATIC Animals
• Gills that extract oxygen that is dissolved in water
ARTHROPODS
• Tracheal system
ARACHNIDS
• Book lungs
VERTEBRATES
• Lungs

5. Amphibians
AMPHIBIANS
• Pulmonary respiration – through the lungs
• Cutaneous respiration – through the skin
• Buccopharyngeal respiration – through the
mouth. An extensive network of blood vessels
runs throughout the frog skin. O2 can pass
through the membranous skin, thereby directly
entering into the blood vessels.

6. Respiratory System of Amphibians: Anatomy
a. Esophagus opening
b. Vomerine teeth
1. Grove of the maxilla
2. Maxillary teeth
3. Internal nares
4. Bulge of Eye ball
5. Eustachian tube
opening
6. Jaw ridge
7. Underside of the tongue
8. Glottis
9. Cut muscle and bone

7. Respiratory System of Amphibians: Anatomy
 Glottis
 Slit-like opening at the floor of the pharynx
 Cricoid cartilage and Arytenoid cartilage
 Larynx
 Directly below the glottis
 Hollow cartilaginous structure
 Bronchi
 Very short tubes that connects that larynx to the lungs
 Lungs
 Large, sac-like, thin-walled, elastic structures

8. Guide Questions
 Frogs have Vocal Cords and Vocal Sacs. Differentiate the two
 Vocal cords: produces the sound
 Vocal sacs: amplifies the sound
 How do frogs respire underwater?
 Through CUTANEOUS RESPIRATION: the oxygen present in the
water diffuses through the frog’s skin directly into the blood vessels
 How are the skin and the lining of the mouth able to serve as
organs of respiration in the frog?
 Skin: O2 from the air dissolves in the moist skin (see CUTANEOUS
RESPIRATION)
 Lining of the mouth: much like the skin but the movement of the
mouth-floor can facilitate the gas exchange

9. Guide Questions
 Breathing in frogs is called positive pressure breathing. Describe
this type of breathing.
 Valves in the nostrils close and the throat pouch pushes upwards
forcing the air into the lungs. As the frog raises the floor of it’s
mouth, air is forced down the trachea
 Differentiate positive pressure breathing from negative pressure
breathing
 Positive: air is PUSHED down via PRESSURE pump
 Negative: air is PULLED down via SUCTION pump
 What is the significance of a moist semi-permeable membrane in
the respiratory process?
 The moist surface allows the O2 to dissolve from the air
 The semi-permeable membrane allows the O2 to diffuse form the
external to the internal environment

10. Guide Questions
 Why are respiratory organs closely associated with the circulatory
system?
 The circulatory system transports the gases that are acquired and
expelled through the respiratory system
 Differentiate between external and internal respiration, and
between inhalation and exhalation.
 External respiration: exchange of gases between the lungs of the
organism and the external environment
 Internal respiration: exchange of gases between the blood vessels
and the tissue cells (the gases then diffuse into or out of the cells)
 Inhalation: diaphragm relaxes, lungs inflate, O2 is taken into the body
 Exhalation: diaphragm contracts, lungs deflate, CO2 is expelled from
the body

11. References
Biology 22 General Zoology Laboratory Manual
Hallare, A.V. Student Handbook in General Zoology Part 2
www. Biology-resources.com/frogs.html
www.science.jrank.org/pages/5827/Respiration.html