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
Explain Hypertensive Disorders of Pregnancy? Hypertension may have been existing before pregnancy. Alternatively, a mother may develop hypertension during pregnancy, a pregnanc

Q. How to calculate Hydrogen Ion Concentration? Ans. The hydrogen ion concentration has a significant role to play in growth of bacteria as every microorganism has a minim

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

Define effect on Oestrogens and progesterone in pregnancy? Oestrogens and progesterone are secreted by the placenta from 8-10 weeks of gestation. Progesterone increases through

Q. What is Mitral Valve and Coronary Arteries? On the PA view, mitral valve calcification is seen just to the left of the spine, below the position of the aortic valve. The lar

What are the benefits of Soil testing Soil testing is done to assess the nutrient supplying capacity of the soil. The data obtained as a result of  testing is useful for recom

How does the metachronal waves form in the ciliary row of protozoa ? Explain the cilia beating mechanism associates with it.

HEAR T OUTPUT The amount of blood pumped by heart per minute. Heart beat is 72. Pump out blood is 70 ml. This 72 × 70 = 5040 ml. ( 5 litres) blood is pumped in a minute.

Which of the following best describes why Okazaki fragments are not observed in PCR? A. DNA primase is used for the entire reaction therefore eliminating the production of Okaz

Arterial Conduits LIMA UMA: anastomosis side-t-side with diaganal8 end-lo-sode with LAD Figure: Arterial conduits Internal Mamnrary Artery (IMA)