All Topics  
Rete mirabile

 

 
   Email Print
   Bookmark   Link
 

 

Rete mirabile
 
 
  Topics Rete mirabile Topic Home

A rete mirabile (Latin
Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
 for 'wonderful net'; plural retia mirabilia) is a complex of arteries
Artery

Arteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood....
 and vein
Vein

In the circulatory system, veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein and umbilical veins, both of which carry oxygenated blood....
s lying very close to each other, found in some vertebrate
Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s. The rete mirabile utilizes countercurrent blood flow within the net (blood flowing in opposite directions.) It exchanges heat
Heat

In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
, ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s, or gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
es between vessel walls so that the two bloodstreams within the rete maintain a gradient with respect to temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
, or concentration of gases or solutes.
effectiveness of retia is primarily determined by how readily the heat, ions, or gases can be exchanged.






Discussion
Ask a question about 'Rete mirabile'
Start a new discussion about 'Rete mirabile'
Answer questions from other users
Full Discussion Forum



Encyclopedia


A rete mirabile (Latin
Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
 for 'wonderful net'; plural retia mirabilia) is a complex of arteries
Artery

Arteries are blood vessels that carry blood away from the heart. All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood....
 and vein
Vein

In the circulatory system, veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein and umbilical veins, both of which carry oxygenated blood....
s lying very close to each other, found in some vertebrate
Vertebrate

Vertebrates are members of the subphylum Vertebrata, chordates with Vertebras or Vertebral columns. The grouping sometimes includes the hagfish, which have no vertebrae, but are genetically quite closely related to lampreys, which do have vertebrae....
s. The rete mirabile utilizes countercurrent blood flow within the net (blood flowing in opposite directions.) It exchanges heat
Heat

In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
, ion
Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s, or gas
Gas

In physics, a gas is a state of matter, consisting of a collection of particles without a definite shape or volume that are in more or less random motion....
es between vessel walls so that the two bloodstreams within the rete maintain a gradient with respect to temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
, or concentration of gases or solutes.

Effectiveness

The effectiveness of retia is primarily determined by how readily the heat, ions, or gases can be exchanged. And, for a given length they are most effective with respect to gases or heat, then small ions, and decreasingly so with respect to other substances.

Birds

In bird
Bird

Birds are wing, Bipedalismal, endothermic , vertebrate animals that lay egg . There are around 10,000 living species, making them the most numerous tetrapod vertebrates....
s with webbed feet, a rete mirabile in the legs and feet transfers heat from the outgoing (hot) blood in the arteries to the incoming (cold) blood in the veins, with the net effect that the internal temperature of the feet is much closer to the ambient temperature, thus reducing heat loss. In this example the rete mirabile functions as a biological heat exchanger
Heat exchanger

A heat exchanger is a device built for efficient heat transfer from one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact....
. A similar structure is seen in other vertebrate extremities, including the neck of the dog
Dog

The dog is a domesticated subspecies of the Gray Wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties....
, in order to protect the brain when the body overheats; mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
ian testes, which are more productive at lower temperatures; fishes such as tuna
Tuna

Tuna are several species of ocean-dwelling fish in the family Scombridae, mostly in the genus Thunnus. Tunas are fast swimmers?they have been clocked at 70 km/h ?and include several species that are warm-blooded....
, whose core temperature is higher than that of the cold deep waters they inhabit; and penguin
Penguin

Penguins are a group of Aquatic animal, flightless bird birds living almost exclusively in the Southern Hemisphere. Highly adapted for life in the water, penguins have countershading dark and white plumage, and their wings have become Flipper ....
s who have them in the feet, flippers and nasal passages, to limit body heat lost to the cold environments in which they live.

Fish

In some fish
Fish

A fish is any marine biology vertebrate animal that is typically ectothermic , covered with scale , and equipped with two sets of paired fins and several unpaired fins....
, a rete mirabile fills the swim bladder with 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]]...
, decreasing the fish's buoyancy
Buoyancy

In physics, buoyancy is the upward force that keeps things afloat. The net upward buoyancy force is equal to the magnitude of the weight of fluid displaced by the body....
. A countercurrent exchange system is utilized between the venous and arterial capillaries. By lowering the pH
PH

pH is a measure of the Acid or Base of a solution. It is defined as the cologarithm of the Activity of dissolved hydrogen ions . Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations....
 levels in the venous capillaries, oxygen unbinds from blood hemoglobin
Hemoglobin

Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells of vertebrates, and the tissues of some invertebrates....
. This causes an increase in venous blood oxygen concentration, allowing the oxygen to diffuse through the capillary membrane and into the arterial capillaries, where oxygen is still sequestered to hemoglobin. The cycle of diffusion continues until the concentration of oxygen in the arterial capillaries is supersaturated (larger than the concentration of oxygen in the swim bladder). At this point, the free oxygen in the arterial capillaries diffuses out into the swim bladder via the gas gland.

Mammals

In mammal
Mammal

Mammals are a class of vertebrate animals whose name is derived from their distinctive feature, mammary glands, with which they feed their young....
s, an elegant rete mirabile in the efferent arteriole
Efferent arteriole

The efferent arterioles are Blood vessel that are part of the Urinary tract of organisms. The efferent arterioles form from a convergence of the Capillary of the Glomerulus ....
s of juxtamedullary glomeruli is important in maintaining the hypertonicity
Tonicity

Tonicity measures the ability of a solution to exert an osmotic pressure upon the membrane. Osmolality and osmolarity measure concentration of the solutes independently on their ability to cross the membrane....
 of the inner zone of the renal medulla
Renal medulla

The renal medulla is the innermost part of the kidney. The renal medulla is split up into a number of sections, known as the renal pyramids. Blood enters into the kidney via the renal artery, which then splits up to form the arcuate arterioles....
. It is the hypertonicity of this zone, resorbing water osmotically
Osmosis

Osmosis is the diffusion of a solvent through a Semipermeable membrane, from a solution of low solute concentration to a solution with high solute concentration , up a solute concentration gradient....
 from the renal collecting ducts as they exit the 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....
, that makes possible the excretion of a hypertonic urine
Urine

Urine is a liquid waste product of the body secreted by the kidneys by a process of filtration from blood called urination and excreted through the urethra....
 and maximum conservation of body water.

Vascular retia mirabilia are also found in the limbs of a range of mammals. These reduce the temperature in the extremities. Some of these probably function to prevent heat loss in cold conditions by reducing the temperature gradient between the limb and the environment. Retia mirabilia also occur frequently in mammals that burrow, dive or have arboreal lifestyles that involve clinging with the limbs for lengthy periods. In these cases, the rete mirabile may lower limb temperature and therefore the metabolic requirement for oxygen and nutrients in the tissues of the limb. This would be desirable when the blood supply to the limb is limited as a result of a "diving reflex" diverting blood away from the limbs during diving or burrowing or because of postural restrictions on blood supply in the case of clinging, arboreal animals. In the last case, slow-moving arboreal mammals such as sloths, lorises and arboreal anteaters possess retia of the highly developed type known as vascular bundles. The structure and function of these mammalian retia mirabilia are reviewed by O'Dea (1990).

In giraffe
Giraffe

The giraffe is an African even-toed ungulate mammal, the tallest of all land-living animal species, and the largest ruminant. It is covered in large, irregular patches of yellow to black fur separated by white, off-white, or dark yellowish brown background....
s, a rete mirabile in the neck equalizes blood pressure when the animal bends down to drink.

The ancient physician Galen
Galen

Aelius Galenus or Claudius Galenus , better known as Galen of Pergamum , was a prominent Ancient Rome physician and philosopher of Greek origin, and probably the most accomplished medical researcher of the Roman period....
 mistakenly thought that human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
s also have a rete mirabile in the neck, apparently based on dissection of sheep
Sheep

#REDIRECT Domestic sheep...
 and misidentifying the results with the human carotid sinus
Carotid sinus

In human anatomy, the carotid sinus is a localized dilation of the internal carotid artery at its origin, the common carotid artery bifurcation....
, and ascribed important properties to it; it fell to Vesalius
Vesalius

Andreas Vesalius was an Anatomy, physician, and author of one of the most influential books on human anatomy, De humani corporis fabrica . Vesalius is often referred to as the founder of modern human anatomy....
 to demonstrate the error.

External links