Hemolymph
The hemolymph occurs in some groups of animals as a circulating body fluid. A highly developed respiratory system enables an almost complete reduction in the blood vessel system . This phenomenon can be observed in some arthropods , such as crustaceans (gill breathing system) or insects ( tracheal system ). In these, the secondary body cavity ( Coelom ) and the primary body cavity merge to form the so-called Mixocoel . The organs lie in the Mixocoel, and a mostly colorless liquid ishes around them. Since there is an open blood circulation system, the Mixocoel fluid is mixed with the original blood . This is why the hemolymph is often referred to as the “blood of insects” or “blood of crustaceans”.
function
The hemolymph does not contain red blood cells and is similar to a mixture of blood plasma and lymph fluid . The mostly colorless liquid is among other things a carrier of nutrients , hormones and metabolic products . The hemolymph mediates temperature equalization and has a similar function to human blood in defending against pathogens or closing wounds .
Hemolymph transport
General
The heart is a greatly shortened tube that lies in a dorsal part of the body cavity, the pericardial sinus . The hemolymph enters the heart through segmental, lateral ostia (openings with valve flaps), which it presses into a system of open and closed arteries by contraction of the striated heart muscles .
Sooner or later the hemolymph flows into the Mixocoel. There are no veins, the hemolymph penetrates the heart again through the ostia due to the negative pressure that is created in the heart. In the case of very small representatives of the arthropods, there is even a complete regression of the circulatory system and an altered function of the hemolymph.
At Crustacea
In crustaceans, the hemolymph is also pressed from the heart through arteries into the Mixocoel. There, the low-oxygen hemolymph collects in blood spaces that are delimited by connective tissue septa. From there it penetrates the gills and is enriched with oxygen and conveyed through vessels to the pericardial sinus.
With insects
The heart of the insects is in the abdomen and is tubular. An aorta adjoining the head extends from the heart (comparable to the dorsal vessel of the annelids ). The contraction of the striated, ring-shaped heart muscles leads to a narrowing of the heart's lumen that progresses from back to front. The ostia close. Flap-like valves in the heart muscle prevent the blood substitute from flowing back. The hemolymph exits the heart through the systole and flows through the mixocoel, sometimes in discrete paths, and collects again in the pericardial sinus . The hemolymph returns to the heart through the ostia. As an alternative to a tubular heart, the pumping movement can also take place by pushing abdominal segments into one another; leg or wing hearts can also be implemented in addition to the heart.
The hemolymph of numerous insects contains the disaccharide trehalose.
See also
- blue blood pigment hemocyanin (analogue of hemoglobin , the red blood pigment)
literature
- Volker Storch, Ulrich Welsch: Kükenthal zoological internship. 26th edition. Spectrum Akademischer Verlag, Heidelberg 2009, ISBN 978-3-8274-1998-9 , chapter Arthropoda
Individual evidence
- ↑ Do flies have hearts? on: RP Online. May 4, 2005.
- ↑ Eckehard Buddecke: Outline of Biochemistry. 6th edition. Walter de Gruyter Verlag, 1980, ISBN 3-11-008388-4 , p. 165.