Respiration in Non-Homeotherms - Anatomy & Physiology

()Map CARDIORESPIRATORY SYSTEM (Map)

Fish

Fish live in a relatively dense and viscous fluid, which has little oxygen carrying capacity. In order to gain sufficient gaseous exchange for survival, fish have developed a highly efficient system which has a large surface area, and utilises energy - the gills.

Gills

Gills are in the walls of both sides of the pharynx and are composed of filaments which increase the surface area. When a fish breaths, it takes in water into the mouth, which is then forced out through the gills.

A Countercurrent Exchange system is in place within the gills to make gaseous exchange more efficient.

Amphibia

In amphibian species, the skin forms the major, and sometimes only respiratory organ.

The skin of amphibia is:

• Thin
• Poorly keratinised
• Highly vascularised
• Moist to promote diffusion of gases

Aquatic amphibians may also have internal gills and Pharyngeal Slits.

Most Amphibia also have lungs for breathing. This contains interconnecting septa which divide the lumen into Faveoli, compartments which open into a central chamber within each lung.

Reptiles

Reptiles have a fundamentally different respiratory system to that of mammals, in that they lack a bronchial tree.

Route of Air in the Reptiliant Respiratory System:

1. Air enters via nares
2. Nasal Cavity
3. Choana
4. Glottis (base of tongue)
5. Trachea
6. Bronchi
7. Lungs

The lungs are paired, with respiration only occuring in the cranial region.

The Respiratory surface is composed of Faveoli, honeycomb shaped structures which line the walls.

Lizards

• No diaphragm
• Simple, saclike, paired lungs.
• Cranial part of lung is site of respiratory function
• Caudal part of lung forms air reservoir
• Ventilation occurs via expansion and contraction of the ribs

Snakes

• Larynx projects medially from the floor of the mouth and is fused with the first few cartilage rings of the trachea. This forms a rigid Glottis.
• Tongue is fixed at the rostral point of the oral cavity.
• Generally only the right lung is present. The lung of snakes is very fragile.
• Inspiration is an active process, made possible by expansion of the ribs. It occurs approx once every 30 seconds in large, healthy snakes. Expiration is a passive prcoess.

Chelonians

• Have paired lungs in the Dorsal Cavity. Intestines etc lie in the Ventral Cavity. These are separated by a diaphragmatic septum which has no muscular part.
• Lungs are ventilated by leg movement in terrestrial animals.