Mechanism of gaseous exchange in aquatic respiratory structures

1. Topic:-
“Mechanism of respiratory gaseous
exchange in the aquatic respiratory
structure:”

2. Name:
Farwah Zameer
Roll nO:
Bs Zool/FA19/501
Assignment:
Animal Physiology(MECHANISM OF RESPIRATORY GASEOUS
EXCHANGE IN AQUATIC RESPIRATORY STRUCTURE)
Submitted tO:-
Dr. Shakeela Parveen

3. MECHANISMS OF GASS EXCHANGE :-
Gass exchange is the interchange of O2 and
CO2 between an organism and its environment – It is also
called respiration…..

4. Aquatic Respiration:-
Aquatic respiration is the process whereby an aquatic
organism exchanges respiratory gases with water, obtaining oxygen
from oxygen dissolved in water and excreting carbon dioxide and some
other metabolic waste products into the water(e.g: Ammonia)…..

5. Mechanism of respiratory gaseous exchange
in Fishes:-
The gases exchange in Fishes are gills…..One gills made up of
many gill filament…..In Fishes gills are present in pharynx called the
pharangeal region ……The color of gills is dark red or brown due to
presence of large number of blood capillaries….
The structure of the gills are following;

6. Gill StructureS:-
Gill Filaments:- The site of gas exchange (each gill filament consists of an upper
and lower surface covered with minute ridges as lamellae)…[Minute ridges that
cover the upper and lower surface is called Lamellae]
Gill Rakers:-Appendages along the front edge of the gill arch
Gill Arches:-Support the gills
Swim Bladder:-Gas filled chamber that allow the bony fish to remain floating in
the water gilstructure….Swim bladders are similar to lungs, but are found in fishes
that live in more oxygen-rich environments .
Operculum:- Gill cover that protects the gills in bony fish. It opens to the outside
at its back edge and helps to pump water across the gills. Flap,cover and protects
the gills of bony fishes…(e.g: lionfish)

8. Gill Slits:-
In pharangeal region ,the walls on either side show slits which
open to the exterior.These slits are called gill slits…..Gill slits present on
the cartilaginous fishes(e.g:Shark).
In Fishes gills are present on the pharynx region….
Pharynx:-
( The region between the buccal cavity(mouth) and oesophagus is
called pharynx…)

9. Acha

10. Inhalation: Exhalation:

11. Types of Gills:-
Three primary types of gill morphology are found in fishes:
Holobranch :– Gill bar with anterior and posterior rows of gill filaments
(jawed fishes)
Hemibranch :– Gill bar with gill filaments found on either the posterior
or anterior side (sharks)
Pseudobranch :– Gill bar with posterior filaments modified to serve a
nonrespiratory function such as sensory or salt balance

13. Mechanism of respiratory gaseous exchange in
Fishes:-
• The gas exchange organs in fish are the gills. Like other animals, fish require a gas
exchange surface that: - is thin, but well protected from damage. – is moist, so
gases can dissolve before they diffuse…..
• Gills Water contains a very low percentage of dissolved oxygen (1%) compared
with air (20%), so fish require a gas exchange system with a very large surface
area which is very efficient at extracting O 2 from the water. Most fish have 4 pair
of gills, located at the back of the mouth on both sides of the head.
• The gills are attached to bony gill arches.
• The gill arches have comb-like structures called gill rakers which trap dirt and
debris in the water and prevent them from clogging up the gills.
• The gills are external to the body cavity and protected in most fish by a bony plate
called an operculum.
e.g:-Sharks and other cartilaginous fish have gill slits instead of an operculum
covering their gills.

15. Gas exchange in the gill lamellae:-
The gas exchange system is linked to the blood transport system in
fish. As water passes across the gills, O 2 from the water diffuses
through the lamellae folds and into the blood capillaries inside. The
blood then carries O 2 from the gills to all of the body cells and CO 2
from the body cells back to the gills. CO 2 then diffuses from the blood
capillaries in the lamellae out into the water.
Lamellae:-
Each gill filament is made up of plate like structure called Lamellae
which have a rich supply of blood capillaries…..The lamellae serve to
increase the surface area greatly of gill filaments.

17. Cocurrent exchange of gases:-
The flow of gases over the gills is in the same direction.
Enhancing the effeciency of the fish gills fresh water flow in one
direction (Same direction)….
Counter-Current exchange of gases:-
The flow of gases over the gills is in opposite direction is the
counter-current exchange of gases….
Water and blood flow in gills flow in the opposite direction maintain a
favorable concentration gradient for diffusion of both gases (Oxygen
and Carbon dioxide)….

19. Counter-Current gaseous exchange in Fishes:-
Counter-Current exchange Gas exchange in fish gills is very efficient
Because the flow of water over the gills is in the opposite direction to
the flow of blood through the capillaries in the lamellae(minute ridges
over the gill surface cover upper and lower surface). This is called
counter-current flow.
Because of counter-current flow, blood flowing in the capillaries always
meets water with a higher oxygen concentration, which allows
diffusion to occur all the way along the lamellae.
This results in over 80% of the available oxygen being extracted from
the water as it flows over the gills.l