Fish gills are branching organs on the side of fish heads. They have a large number of small blood vessels called capillaries. Afterwards, the oxygen is delivered by the blood that runs through the fish's body, similar to how humans consume oxygen. Mollusks and crustaceans also use gills to pull the oxygen in the water as it runs over the gill.

How do Fish Gills Work?

To survive, fish must also take in oxygen and expel carbon dioxide. Instead of lungs, fish use capillaries. Capillaries are tiny, branching organs on the side of their heads that contain a significant number of smaller blood vessels. All bony fish have a bony plate called an operculum, shaped like a comb but shaped like an operculum. Water runs over the gills, and oxygen passes through the capillaries to the blood by opening its mouth.

You can learn more about the structure of fish gills in the following paragraph.

Structure of Fish Gills

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The Structure of fish gills consists of plate-like filaments covered by a lamellar web that encloses a capillary blood network.

How does Fish Breathe?

Fish gills breathe differently than humans. However, because fish live in lakes, seas, and oceans, they have a different breathing pattern. They have filament in gills whose function is to supply the blood with oxygen.

Moreover, The below para will explain how the gill filament, gill arches, and gill rakers work.

Gill Filaments

The gill filaments of fish provide oxygen to their blood by taking oxygen from the water. Each filament contains thousands of fine, flexible branches (lamellae) that are exposed to the water. Oxygen is absorbed and ultimately re-emitted into the fish's blood.

Gill Arches

A fish's body is filled with three or more gill arches, usually shaped like a boomerang and composed of cartilaginous or bony segments connected at the back. Each gill arch comprises an upper and a lower limb. In addition to supporting the gills, the gill arches also help the blood vessels.

Gill Rakers

There are bony projections on the fish's gill arches called "gill rakers" that help them to feed. These projections are positioned forward and inward and vary in shape and number according to the fish's diet.

Learn the Fish Gills Histology

The gill tissue is anatomically and histologically different from other animal tissues, making terrestrial and aquatic tissues so distinct. Recent studies have shown that the anatomy and histology of fish gills differ from other tissues.

Each phone fish gill has a pair of paired filaments, or primary lamellae, divided into two rows. Moreover, Hemi Branches are the primary lamellae of a gill arch, and together they form a holobranch.

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FAQs on Fish Gills: How Fish Breathe and Survive Underwater

1. What are fish gills and what is their primary function?

Gills are the respiratory organs of most aquatic animals, including fish, allowing them to breathe underwater. Their primary function is gas exchange. They are expertly designed to extract dissolved oxygen from the water and release carbon dioxide, a waste product, from the bloodstream.

2. What are the main parts that make up a fish's gill?

A fish's gill is a complex structure with several key parts working together:

Gill Arch: This is a bony or cartilaginous arch that provides structural support for the entire gill.
Gill Filaments: These are the soft, thread-like tissues that extend from the gill arch in two rows.
Lamellae: Found on the gill filaments, these are tiny, plate-like structures. They are rich in blood capillaries and vastly increase the surface area available for absorbing oxygen.

3. Why are healthy fish gills bright red?

Healthy fish gills appear bright red because they contain a very dense network of tiny blood vessels called capillaries, located just under a very thin layer of tissue. This high concentration of blood is essential for efficiently picking up oxygen from the water and transporting it throughout the fish's body. The red colour comes from the haemoglobin in the blood.

4. How does the 'countercurrent exchange' system in gills help fish breathe so efficiently?

Countercurrent exchange is a clever biological mechanism that makes fish respiration highly efficient. It means that water flows over the gills in the opposite direction to the blood flowing within the gills. This arrangement ensures that as the blood moves along the gill, it always encounters water with a higher oxygen concentration, allowing it to absorb the maximum possible amount of oxygen.

5. How are the gills of a shark different from those of a bony fish like a tuna or carp?

The main difference is in their external protection and structure. Bony fish have a single gill opening on each side of their head, which is covered by a hard, protective flap called an operculum. The operculum actively pumps water over the gills. In contrast, sharks and rays (cartilaginous fish) lack an operculum and instead have five to seven separate gill slits that open directly to the outside water.

6. What is the difference between a holobranch and a hemibranch?

These terms describe the structure of the gill filaments on a single gill arch. A holobranch is a complete gill where filaments are present on both the front (anterior) and back (posterior) sides of the arch. A hemibranch, or half-gill, has filaments attached to only one side of the gill arch.

7. Is it possible for a fish to drown in water?

Yes, in a sense, a fish can suffocate or drown if the water does not contain enough dissolved oxygen. Gills are designed to extract existing oxygen from the water, not to create it. If the water is polluted, too warm, or stagnant, oxygen levels can drop too low for the fish to breathe, leading to suffocation.