Aquatic respiration

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Aquatic respiration

Aquatic respiration is the process

Biological process

A biological process is a process of a living organism. Biological processes are made up of any number of chemical reactions or other events that results in a Chemical transformation....
whereby an aquatic animal

Aquatic animal

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life.Natural environments and the animals that live in them can be categorized as aquatic or terrestrial ecoregion ....
obtains oxygen

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
from water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
.

Earth's natural bodies of water have a low oxygen concentration--much lower than the level of oxygen in air at the earth's surface. Smaller organisms can obtain sufficient oxygen through the skin

Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
(e.g. flatworm

Flatworm

The flatworms, known in scientific literature as Platyhelminthes are a Phylum of relatively simple bilaterian, Segmentation , soft-bodied invertebrate animals....
s), but larger organisms require special structures to collect enough oxygen to sustain life. This oxygen comes from molecules of oxygen gas (O₂) dissolved in the water.

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Encyclopedia

Aquatic respiration is the process

Biological process

Aquatic animal

Oxygen

Water

Skin

Flatworm

Gill

A gill is an anatomical structure found in many aquatic ecosystem organisms. It is a respiration organ whose function is the extraction of oxygen from water and the excretion of carbon dioxide....
s for respiration

Respiration (physiology)

In animal physiology, respiration is the transport of Oxygen from the outside air to the cells within Tissue s and the transport of carbon dioxide in the opposite direction....
which have:

large surface area
Surface area

Surface area is how much exposed area an object has. It is expressed in square units. If an object has flat Face , its surface area can be calculated by adding together the areas of its faces....
which is needed for more oxygen to get in.
high blood flow
small/short diffusion distances
contain 4 gill arches (Bony fish
Osteichthyes

Osteichthyes , also called bony fish, are a taxonomy group of fish that includes the ray-finned fish and lobe finned fish . The split between these two classes occurred around 440 mya ....
es), two gill arches (Cartilaginous fish
Chondrichthyes

Chondrichthyes or cartilaginous fishes are jawed fish with paired Fins, paired nares, scales, two-chambered hearts, and skeletons made of cartilage rather than bone....
) or 7 gill baskets (Lampreys) on each side of the fish's head
each gill arch has 2 rows (hemibranchs) of gill filaments
each gill filament has many lamella
Lamella

Lamella is a term for a platelike structure, appearing in multiples, that occurs in various situations, such as biology or materials sciences. It implies a thin layer , the same derivation as for `laminate'....
e

The interesting thing in fish is a long bony cover for the gill that can be used for pushing water. Some fishes pump water using the operculum. Without an operculum, other methods are required, such as ventilation

Ventilation (physiology)

In respiratory physiology, ventilation is the rate at which gas enters or leaves the lung. It is categorised under the following definitions:...
. Some species of shark

Shark

Sharks are a type of fish with a full Cartilage skeleton and a highly Streamlines, streaklines and pathlinesd body. They respire with the use of five to seven gill slits....
s use this system. When they swim, water flows into the mouth and across the gills. Because these sharks rely on this technique, they must keep swimming in order to respire.

Bony fish use a type of countercurrent flow

Countercurrent exchange

Countercurrent exchange along with Concurrent exchange comprise the mechanisms used to transfer some property of a fluid from one flowing current of fluid to another across a semipermeable membrane or thermally-conductive material between them....
to maximize the intake of oxygen that diffuse

Diffusion

Molecular diffusion, often called simply diffusion, is a net transport of molecules from a region of higher concentration to one of lower concentration by random molecular motion....
through the gill. Countercurrent flow occurs when deoxygenated blood moves through the gill in one direction while oxygenated water moves through the gill in the opposite direction. This mechanism maintains the concentration gradient thus increasing the efficiency of the respiration process as well. Cartilaginous fish do not have a countercurrent flow system as they lack bones which are needed to have the opened out gill that bony fishes have.

The genesis of the aquatic respiratory rhythm

One of the main characteristics of aquatic respiration is that, just like terrestrial respiration, it is rhythmic. Aquatic respiration requires continuous cycling between an inspiratory phase and an expiratory phase. During expiration, gill muscles are contracted, which expels water from the gill baskets. Carbon Dioxide is released from the fish into the water. During inspiration, muscles are relaxed, and the elasticity of the gill baskets that have been contracted during the expiratory phase, stretches them, causing fresh water to enter. The duration of one respiratory cycle can vary both by species and the time of day, from 0.5 seconds to 4 seconds.

Scientists have investigated what part of the body is responsible for maintaining the respiratory rhythm. They found that neuron

Neuron

Neurons are responsive cell in the nervous system that process and transmit information by electrochemical Signal . They are the core components of the brain, the vertebrate spinal cord, the invertebrate ventral nerve cord, and the peripheral nerves....
s located in the brainstem of fishes are responsible for the genesis of the respiratory rhythm (). The position of these neurons is slightly different from the centers of respiratory genesis in mammals but they are located in the same brain compartment, which has caused debates about the homology

Homology

Homology may refer to:* Homology , analogy between human beliefs, practices or artifacts due to genetic or historical connections.* Homology : similar structures due to shared ancestry....
of respiratory centers between aquatic and terrestrial species. In both aquatic and terrestrial respiration, the exact mechanisms by which neurons can generate this involuntary rhythm are still not completely understood (see Involuntary control of respiration).