I. Other air breathing animals
a. Mesobronchi enter the lungs, and then several secondary bronchi are connected by thousands of parabronchi
b. Gas exchange occur between the air in the air capillaries of the parabronchi and the blood capillaries. Air capillaries are continuous and not blind-ended as are mammalian alveoli.
c. Tremendous surface area and continuous air flow through parabronchus in one direction during both inspiration and expiration
3. Air sacs provide continuous ventilation, with fresh air moving primarily into air sacs and then air sacs ventilating the parabronchi.
1. Use negative pressure like mammals to inspire but don’t have a diaphragm
2. Elastic recoil produces expiration like in mammals.
3. Reptiles do have alveoli like mammals.
1. Cutaneous and buccal respiration. Remember that CO2 is about 30 times more soluble than O2 . Therefore, some amphibians use cutaneous respiration to get rid of carbon dioxide but other means (gills or lungs) for obtaining oxygen.
2. Lungs for some
a. Lung may be non compartmentalized and poorly vascularized
b. Compartmentalized and well vascularized
c. Frogs ventilate by pulse pump or force pump. A frog expands its buccal cavity drawing in fresh air into the bottom of the buccal cavity with the glottis closed. Then, the glottis opens and old air expels towards the upper part of the buccal cavity due to the elastic recoil of the lungs. Now fresh air from the buccal cavity contracts and the fresh air enters the lungs. Finally the glottis closes for the next cycle.
D. Insects – Tracheal System
1. Tracheal systems are air filled tubes that travel from body surface to cells
a. Gases move fast
b. Tubes are invaginations of cuticle
c. Spiracles (tracheal entrances) can adjust to control air flow
d. Tracheoles are blind-ended tubes near cells
2. Tracheal Ventilation
- In small insects diffusion of the gases in the tracheas is rapid enough .
- Flying insects use ram ventilation or draft ventilation to ventilate tracheae.
- Larger insects and small insects during increase metabolic activity need to add convection (ventilation).
- Air sacs and tracheas are compressible and their volume changes with respiratory movements (compression and expansion of the body wall, especially the abdomen).