Salt gland

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Salt gland

The salt gland is an organ

Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
for excreting excess salt

Salt

A salt, in chemistry, is defined as the product formed from the neutralisation reaction of acids and base . Salts are ionic compounds composed of cations and anions so that the product is electrically electric charge ....
s. It is found in elasmobranchs, seabird

Seabird

Seabirds are birds that have adaptation to life within the marine environment. While seabirds vary greatly in lifestyle, behavior and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding ecological niche have resulted in similar adaptations....
s, and some reptile

Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s. In 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, salt gland

Gland

A gland is an Organ in an animal's body that synthesizes a substance for release such as hormones or breast milk, often into the bloodstream or into cavities inside the body or its outer surface ....
s are found in the rectum

Rectum

The rectum is the final straight portion of the large intestine in some mammals, and the Gastrointestinal tract in others, terminating in the anus....
, but in birds and reptiles, they are found in the skull, in the area of the eye

Eye

Eyes are Organ that detect light, and send signals along the optic nerve to the visual system and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system....
s, nostril

Nostril

A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation....
s or mouth

Mouth

The mouth, buccal cavity, or oral cavity is the first portion of the alimentary canal that receives food and begins digestion by mechanically breaking up the solid food particles into smaller pieces and mixing them with saliva....
. In crocodile

Crocodile

A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all members of the order Crocodilia: i.e....
s, the salt is excreted through the tongue. Such glands work by active transport

Active transport

Active transport is the mediated process of moving particles across a biological membrane against a Concentration_gradient#In_biology . If the process uses chemical energy, such as from adenosine triphosphate , it is termed primary active transport....
via sodium-potassium pump that moves salt from the blood

Blood

Blood is a specialized bodily fluid that delivers necessary substances to the body's Cell s ? such as nutrients and oxygen ? and transports waste products away from those same cells....
into the gland, where it can be excreted as a concentrated solution

Solution

In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent....
.

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Encyclopedia

The salt gland is an organ

Organ (anatomy)

In biology, an organ is a biological tissue that performs a specific function or group of functions. Usually there is a main tissue and sporadic tissues....
for excreting excess salt

Salt

Seabird

Reptile

Reptiles, or members of the class Reptilia, are air-breathing, cold-blooded vertebrates that have skin covered in scale as opposed to hair or feathers....
s. In 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, salt gland

Gland

Rectum

Eye

Nostril

Mouth

Crocodile

Active transport

Blood

Solution

In chemistry, a solution is a homogeneous mixture composed of two or more substances. In such a mixture, a solute is dissolved in another substance, known as a solvent....
. Salt glands function to keep salt balance, and allow marine vertebrates to drink seawater

Seawater

Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%, or 35 parts per thousand . This means that every 1 kg of seawater has approximately 35 grams of sea salt ....
.

The need for salt excretion in reptiles (such as marine iguana

Marine iguana

The Marine Iguana is an iguana found only on the Galapagos Islands that has the ability, unique among modern lizards, to live and forage in the sea....
s and sea turtle

Sea turtle

Sea turtles are turtles found in all the world's oceans except the Arctic Ocean. There are seven living species of sea turtles: Flatback Sea Turtle, Green Sea Turtle, Hawksbill turtle, Kemp's Ridley, leatherback sea turtle, Loggerhead Sea Turtle and Olive Ridley Sea Turtle....
s) and birds (such as petrel

Petrel

This article is about the petrel seabirds. For other uses, see petrel . The flammable liquid is correctly spelt petrol.'Petrels' are tube-nosed seabirds in the bird order Procellariiformes....
s and albatross

Albatross

Albatrosses, of the biological family Diomedeidae, are large seabirds allied to the procellariidae, storm-petrels and diving-petrels in the order Procellariiformes ....
es) stems from the fact that their kidney

Kidney

The kidneys are Organ that have numerous biological roles. Their primary role is to maintain the homeostasis balance of bodily fluids by filtering and secreting Metabolomics#Metabolitess and minerals from the blood and excreting them, along with water , as urine....
s are much less efficient than those of mammals. Unlike 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....
of amphibian

Amphibian

Amphibians , such as frogs, toads, salamanders, newts and caecilians, are cold-blooded animals that metamorphose from a juvenile, water-breathing form to an adult, air-breathing form....
s, reptile and bird skin is impermeable to salt, meaning that the transition to a tougher skin meant a loss in salt-releasing ability. The evolution of a salt gland would have allowed early reptiles and birds to eat aquatic plants and animals, who have high salt concentrations. This does not, however, explain the evolution of the gland in the elasmobranchs, suggesting convergent evolution

Convergent evolution

Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action....
.

Some theories suggest that mammalian

Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
tear ducts and sweat gland

Sweat gland

The skin contains two different groups of sweat glands: apocrine sweat glands and merocrine sweat glands. Both gland types contain myoepithelial cells , specialized epithelial cells located between the gland cells and the underlying basal lamina....
s may be evolutionarily related to salt glands. Human tears are high in potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
, lending support to this theory, however most phylogenists disagree with this idea.

Salt gland

See also

Further reading

External links