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 Cardiac disease Cardiac conduction abnormalities associated with Lyme disease are generally self-limited. Patients with minor cardiac involvement (first-degree atrioven

Define the Uremia and Nitrogen Disposal? In animals, faecal and renal nitrogen were enhanced and decreased uremia was seen in normal and nephrectomised animals. The mechanisms

There has been a perfect coevolution between plants and herbivorous animals. This has often developed into a mutually beneficial relationship. Whereas the plants have proved to be

What is Enzyme assay Enzyme assay may also be used to determine whether stored plant products are suitable for use as food commodities, for e.g.  α-amylase should be present

In the presence of oxygen, the process of glycolysis produces which of the following products? A) 2 glycerol B) 1 lactate C) 2 lactate D) 2 pyruvate E) 1 pyruvate

Rumen protection of nutrient (bypass nutrients) technology The amino acid and energy requirements of medium and high yielding cows and buffaloes are not fully met from the micr

Q. What is parasitism? The Parasitism is the ecological interaction in which a being lives at the expense of another. The parasite often doesn't cause immediate death of the ho

Open Heart Surgery These surgeries are done under alternative arrangements to continue oxygenated systemic blood supply, while the heart is operated on (Cardiopulmonary bypas

Q. What are cerebrovascular accidents? The Cerebrovascular accident (CVA), as well known as stroke, is the generic name given to infarction (tissue and cellular death by hypoxi