Formation of primary urine in malpighian tubules, Biology

Formation of Primary Urine in Malpighian Tubules

The formation of primary urine in malpighian tubules is due to secretion and not due to ultrafiltration. The cells of the malpighian tubules actively transport potassium from the haemolymph and concentrate it in the lumen. This results in the passive osmotic entry of water followed by the diffusion of other low molecular weight substances like salts, sugar, and uric acid. Figure will help you in understanding this phenomena. The rate of urine formation in insects is proportional to the concentration of K+ in the haemolymph. Thus, active transport of K+ is primarily responsible for generating urine flow in the excretory organs of insects.

2189_Malpighian Tubules of Insects.png

Figure: Functions of Malpighian Tubules of Insects

As the potassium-rich isosmotic tubular fluid moves towards the gut, there is secretion of molecules like uric acid and reabsorption of sugars and ions. However, major modification in the composition of the fluid occurs in the hind gut, particularly the rectum, where there is extensive reabsorption of water and physiologically important solutes like K+. Uric acid, which enters the hind gut as water soluble potassium urate, gets precipitated facilitating further withdrawal of water. Insects that live on liquid or wet food excrete large amounts of hypoosmotic liquid urine. On the other hand, insects that live on dry food produce extremely dry excreta. To facilitate water reabsorption, the rectum in terrestrial insects show modifications referred to as rectal glands or rectal pads.

Posted Date: 1/16/2013 1:44:40 AM | Location : United States







Related Discussions:- Formation of primary urine in malpighian tubules, Assignment Help, Ask Question on Formation of primary urine in malpighian tubules, Get Answer, Expert's Help, Formation of primary urine in malpighian tubules Discussions

Write discussion on Formation of primary urine in malpighian tubules
Your posts are moderated
Related Questions
Which of the below is NOT hormone associated with male reproductive physiology: a) Prolactin b) Testosterone c) Interstitial hormone d) Follicle-stimulating hormone

In about 80 per cent of ARF patients, ASO titre is significantly raised. ASO titres vary with age, geographical area and other fevers, which influence frequency of streptococcal in

Assume that you have a stock solution of epinephrine at a concentration of 1mg/ml. Further assume that there are 20 drops/ml. a. Calculate the number of drops of the stock solution

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Acquired Aortic Stenosis :  a) Rheumatic: In developing countries rheumatic aortic valve disease is more common than degenerative one. Mitral valve involvement is a common as

Q. Can you explain Cholera? Cholera is one of the diseases which had caused epidemics all over the world. The organism which causes the disease is Vibrio cholerae. It is an

What are the special anatomic considerations in posterior maxilla?  Posterior maxilla has very poor  quality of bone demanding special consideration in implant placement. These

Q. What do you mean by Current Impediments? Given the impressive list of past achievements, we expect that quantitative process to biological problems will continue to repay us


Which are the groups of living beings that form the protist kingdom? The protist kingdom contains protozoans and algae. (Two groups of fungi with same characteristics to protoz