Respiratory system of insects
Encyclopedia
The respiratory system
of insects is the means by which insects obtain oxygen
from the air.
. The scientific tracheal system within an individual is composed of interconnecting transverse and longitudinal tracheae which maintain equivalent pressure throughout the system. These tracheae branch repeatedly, eventually forming tracheoles, which are blind-ended, water-filled compartments only one micrometer in diameter. It is at this level of the tracheoles that oxygen is delivered to the cells for respiration.
The trachea are water-filled due to the permeable membrane
of the surrounding tissue
s. During locomotion, the water level retracts due the increase in concentration of lactic acid
in the muscle cells. This lowers the water potential
and the water is drawn back into the cells via osmosis
and air is brought closer to the muscle cells. The diffusion pathway is then reduced and gases can be transferred more easily.
Insect
s have spiracles on their exoskeleton
s to allow air to enter the trachea
. In insects, the tracheal tubes primarily deliver oxygen
directly into the animals' tissue
s. The spiracles can be opened and closed in an efficient manner to reduce water loss. This is done by contracting closer muscles surrounding the spiracle. In order to open, the muscle relaxes. The closer muscle is controlled by the central nervous system
but can also react to localized chemical stimuli. Several aquatic insects have similar or alternative closing methods to prevent water from entering the trachea. Spiracles may also be surrounded by hairs to minimize bulk air movement around the opening, and thus minimize water loss.
of the abdomen
along with coordinated spiracle contraction and relaxation to generate cyclical gas exchange patterns and to reduce water loss into the atmosphere. The most extreme form of these patterns is termed discontinuous gas exchange
cycles (DGC).
Respiratory system
The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange. In humans and other mammals, the anatomical features of the respiratory system include airways, lungs, and the respiratory muscles...
of insects is the means by which insects obtain oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
from the air.
The Respiratory System
Air enters the respiratory systems of most insects through a series of external openings called spiracles. These external openings, which act as muscular valves in some insects, lead to the internal respiratory system, a densely networked array of tubes called tracheaInvertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
. The scientific tracheal system within an individual is composed of interconnecting transverse and longitudinal tracheae which maintain equivalent pressure throughout the system. These tracheae branch repeatedly, eventually forming tracheoles, which are blind-ended, water-filled compartments only one micrometer in diameter. It is at this level of the tracheoles that oxygen is delivered to the cells for respiration.
The trachea are water-filled due to the permeable membrane
Cell membrane
The cell membrane or plasma membrane is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. It basically protects the cell...
of the surrounding tissue
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s. During locomotion, the water level retracts due the increase in concentration of lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...
in the muscle cells. This lowers the water potential
Water potential
Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure, or matrix effects such as surface tension...
and the water is drawn back into the cells via osmosis
Osmosis
Osmosis is the movement of solvent molecules through a selectively permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides...
and air is brought closer to the muscle cells. The diffusion pathway is then reduced and gases can be transferred more easily.
The Structure of the Spiracle
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
s have spiracles on their exoskeleton
Exoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
s to allow air to enter the trachea
Invertebrate trachea
The invertebrate trachea refers to the open respiratory system composed of spiracles, tracheae, and tracheoles that terrestrial arthropods have to transport metabolic gases to and from tissues....
. In insects, the tracheal tubes primarily deliver oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
directly into the animals' tissue
Biological tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
s. The spiracles can be opened and closed in an efficient manner to reduce water loss. This is done by contracting closer muscles surrounding the spiracle. In order to open, the muscle relaxes. The closer muscle is controlled by the central nervous system
Central nervous system
The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...
but can also react to localized chemical stimuli. Several aquatic insects have similar or alternative closing methods to prevent water from entering the trachea. Spiracles may also be surrounded by hairs to minimize bulk air movement around the opening, and thus minimize water loss.
Development of knowledge
Insects were once believed to exchange gases with the environment continuously by the simple diffusion of gases into the tracheal system. More recently, however, large variation in insect ventilatory patterns have been documented and insect respiration appears to be highly variable. Some small insects do demonstrate continuous respiration and may lack muscular control of the spiracles. Others, however, utilize muscular contractionMuscle contraction
Muscle fiber generates tension through the action of actin and myosin cross-bridge cycling. While under tension, the muscle may lengthen, shorten, or remain the same...
of the abdomen
Abdomen
In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity...
along with coordinated spiracle contraction and relaxation to generate cyclical gas exchange patterns and to reduce water loss into the atmosphere. The most extreme form of these patterns is termed discontinuous gas exchange
Discontinuous gas exchange
Discontinuous gas-exchange cycles , also called discontinuous ventilation or discontinuous ventilatory cycles, follow one of several patterns of arthropod gas exchange that have been documented primarily in insects; they occur when the insect is at rest...
cycles (DGC).