Fish gills are highly folded organs located on the sides of the head that allow for efficient gas exchange. They have a network of capillaries and lamellae that divide the gill filaments, providing a large surface area for oxygen diffusion. The gills have a good blood flow and thin membranes that allow for countercurrent exchange, maximizing oxygen transfer from the water to the bloodstream.

1. Fish Gills
Primary organs of respiration
Highly folded structure
Located at side of Head
High Blood Flow
https://www.tes.com/lessons/zKJjkBvGKEGCfQ/creatures-of-the-world http://reptools.rutgers.edu/Fu
1

2. Structure of Gills
Gill Filaments: short threads
-Network of capillaries
-Divided into Lamella(gas exchange site)
Gill Arches: support gills
Gill Rakers: help in fish feeding
Operculum: protect gills
http://biologyaqaalevelnotes.blogspot.com/2017/05/exchange-and-transport-systems-gas_48.html https://www.earthlife.net/fish/gills.html
2

3. Adaptation of Gills for
Efficient Gas Exchange
Large surface area
- allow more diffusion of gases
Permeable membranes
-allow gases to diffuse
Thin(Flattened cell)
-short diffusion distance
Good Vascular supply
-Maintain concentration gradient
https://www.pathwayz.org/Tree/Plain/FISH+-GAS+EXCHANGE
3

4. Respiratory System of Fish
Use their mouth to breathe
Exchange oxygen &
carbon dioxide
Lamella increase surface area
4

5. Countercurrent Exchange &
Concurrent Exchange
Countercurrent Exchange
- Gases flows in opposite direction
- Maximize oxygen transfer
Concurrent Exchange
-Gases flow in same direction
-No longer diffusion
5

6. Gill Ventilation
1. Fill mouth cavity
2. Fill gill cavity
3. Expel water from gill cavity
4. Reset for new cycle
https://branagan12.weebly.com/blog/the-respiratory-system-of-a-bluefin-tuna https://kuensting.org/school/bb/systems/gas_exchange.htm 6

7. Shark Breathing
RAM VENTILATION
Swimming with Mouth open
ttps://giphy.com/gifs/ocean-sharks-Xe60pAwmEygNO
BUCCAL PUMPING
Contraction of Buccal muscle
7

8. 8