Gas exchange

pulmonary gas exchangegaseous exchangealveolar gas exchangeexchangeexchangedexchange of gasesgasgas exchanginggas exchanging unitsInteraction with circulatory systems
Gas exchange is the physical process by which gases move passively by diffusion across a surface.wikipedia
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Lung

lungspulmonaryright lung
This is the case with the alveoli, which form the inner surface of the mammalian lung, the spongy mesophyll, which is found inside the leaves of some kinds of plant, or the gills of those molluscs that have them, which are found in the mantle cavity.
Their function in the respiratory system is to extract oxygen from the atmosphere and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange.

Respiration (physiology)

respirationrespiratoryrespiratory physiology
In aerobic organisms, gas exchange is particularly important for respiration, which involves the uptake of oxygen and release of carbon dioxide.
Breathing in brings air into the lungs where the process of gas exchange takes place between the air in the alveoli and the blood in the pulmonary capillaries

Pulmonary alveolus

alveolialveolarpulmonary alveoli
However, in most larger organisms, which have a small surface-area to volume ratios, specialised structures with convoluted surfaces such as gills, pulmonary alveoli and spongy mesophyll provide the large area needed for effective gas exchange. Gas exchange occurs in microscopic dead-end air-filled sacs called alveoli, where a very thin membrane (called the blood-air barrier) separates the blood in the alveolar capillaries (in the walls of the alveoli) from the alveolar air in the sacs.
A pulmonary alveolus (plural: alveoli, from Latin alveolus, "little cavity") is a hollow cup-shaped cavity found in the lung parenchyma where gas exchange takes place.

Blood–air barrier

blood-air barrieralveolar capillariesalveolar capillary beds
Gas exchange occurs in microscopic dead-end air-filled sacs called alveoli, where a very thin membrane (called the blood-air barrier) separates the blood in the alveolar capillaries (in the walls of the alveoli) from the alveolar air in the sacs.
The blood–air barrier (alveolar–capillary barrier or membrane) exists in the gas exchanging region of the lungs.

Mammal

mammalsMammaliamammalian
This is the case with the alveoli, which form the inner surface of the mammalian lung, the spongy mesophyll, which is found inside the leaves of some kinds of plant, or the gills of those molluscs that have them, which are found in the mantle cavity.
After gas exchange in the pulmonary capillaries (blood vessels in the lungs), oxygen-rich blood returns to the left atrium via one of the four pulmonary veins.

Circulatory system

cardiovascularcirculationcardiovascular system
The gas exchangers are therefore frequently coupled to gas-distributing circulatory systems, which transport the gases evenly to all the body tissues regardless of their distance from the gas exchanger.
Gas exchange occurs in the lungs, whereby is released from the blood, and oxygen is absorbed.

Bronchiole

bronchiolesbronchialrespiratory bronchiole
The marked difference between the composition of the alveolar air and that of the ambient air can be maintained because the functional residual capacity is contained in dead-end sacs connected to the outside air by long, narrow, tubes (the airways: nose, pharynx, larynx, trachea, bronchi and their branches and sub-branches down to the bronchioles).
They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start of the respiratory zone delivering air to the gas exchanging units of the alveoli.

Bronchus

bronchibronchialbronchial tubes
The marked difference between the composition of the alveolar air and that of the ambient air can be maintained because the functional residual capacity is contained in dead-end sacs connected to the outside air by long, narrow, tubes (the airways: nose, pharynx, larynx, trachea, bronchi and their branches and sub-branches down to the bronchioles).
No gas exchange takes place in the bronchi.

Fish gill

gillsGillGill openings
2). This is the situation seen in the gills of fish and many other aquatic creatures.
The high surface area is crucial to the gas exchange of aquatic organisms as water contains only a small fraction of the dissolved oxygen that air does.

Respiratory tract

airwayupper respiratory tractlower respiratory tract
Air is brought to the alveoli in small doses (called the tidal volume), by breathing in (inhalation) and out (exhalation) through the respiratory airways, a set of relatively narrow and moderately long tubes which start at the nose or mouth and end in the alveoli of the lungs in the chest.
Each of these bronchi branches into a secondary (lobar) bronchus that branches into tertiary (segmental) bronchi, that branch into smaller airways called bronchioles that eventually connect with tiny specialized structures called alveoli that function in gas exchange.

Heart

cardiachuman heartapex of the heart
All the blood returning from the body tissues to the right side of the heart flows through the alveolar capillaries before being pumped around the body again.
As these pass by alveoli carbon dioxide is exchanged for oxygen.

Breathing

breathventilationrespiration
Air is brought to the alveoli in small doses (called the tidal volume), by breathing in (inhalation) and out (exhalation) through the respiratory airways, a set of relatively narrow and moderately long tubes which start at the nose or mouth and end in the alveoli of the lungs in the chest.
Breathing (or ventilation) is the process of moving air into and out of the lungs to facilitate gas exchange with the internal environment, mostly by bringing in oxygen and flushing out carbon dioxide.

Stoma

stomatastomatalpores
Gases diffuse into and out of the intercellular spaces within the leaf through pores called stomata, which are typically found on the lower surface of the leaf.
In botany, a stoma (plural "stomata"), also called a stomate (plural "stomates") (from Greek στόμα, "mouth"), is a pore, found in the epidermis of leaves, stems, and other organs, that facilitates gas exchange.

Gill

gillsplastrongill filament
However, in most larger organisms, which have a small surface-area to volume ratios, specialised structures with convoluted surfaces such as gills, pulmonary alveoli and spongy mesophyll provide the large area needed for effective gas exchange. 2). This is the situation seen in the gills of fish and many other aquatic creatures.
A high surface area is crucial to the gas exchange of aquatic organisms, as water contains only a small fraction of the dissolved oxygen that air does.

Respiratory acidosis

acidosis, respiratoryacidityP CO 2
If these homeostats are compromised, then a respiratory acidosis, or a respiratory alkalosis will occur.
Lung diseases that primarily cause abnormality in alveolar gas exchange usually do not cause hypoventilation but tend to cause stimulation of ventilation and hypocapnia secondary to hypoxia.

Respiratory system

respiratoryrespirationrespiratory organs
They do not have any dedicated respiratory organs; instead, every cell in their body can absorb oxygen from the surrounding water, and release waste gases to it.
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants.

Fick's laws of diffusion

Fick's law of diffusionFick's lawdiffusion constant
Diffusion is a passive process, meaning that no energy is required to power the transport, and it follows Fick's Law:

Reptile

reptilesReptiliaSauropsida
All reptiles breathe using lungs.
Aquatic turtles have developed more permeable skin, and some species have modified their cloaca to increase the area for gas exchange.

Bird anatomy

parabronchitarsusair sacs
Alternative arrangements are cross current systems found in birds.
The walls of the air sacs do not have a good blood supply and so do not play a direct role in gas exchange.

Insect

Insectainsectsbugs
Unlike the invertebrates groups mentioned so far, insects are usually terrestrial, and exchange gases across a moist surface in direct contact with the atmosphere, rather than in contact with surrounding water.
There are many different patterns of gas exchange demonstrated by different groups of insects.

Arachnid

Arachnidaarachnidsarachnoid
The other main group of terrestrial arthropod, the arachnids (spiders, scorpion, mites, and their relatives) typically perform gas exchange with a book lung.
There are characteristics that are particularly important for the terrestrial lifestyle of arachnids, such as internal respiratory surfaces in the form of tracheae, or modification of the book gill into a book lung, an internal series of vascular lamellae used for gas exchange with the air.

Diffusion

diffusediffusesdiffusive
Gas exchange is the physical process by which gases move passively by diffusion across a surface.

Membrane

membranousmembranesBiomembrane
For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.

Biological membrane

membranemembranesbiological membranes
For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.

Metabolism

metabolicmetabolizedmetabolic pathways
Gases are constantly consumed and produced by cellular and metabolic reactions in most living things, so an efficient system for gas exchange between, ultimately, the interior of the cell(s) and the external environment is required.