Question

Thin Malpighian tubules in cockroaches are present at the junction of ………….
A) Foregut and midgut
B) Midgut and hindgut
C) Foregut and hindgut
D) Midgut and gizzard

Answer 1

Malpighian tubules are fine, unbranched, yellow tubules that lie more or less free in the haemocoel. Each tubule is lined by glandular, ciliated cells having brush borders. These extract metabolic wastes like potassium and sodium urate, water and carbon dioxide from the blood.

Complete answer:
Malpighian tubules are an excretory part of cockroaches. They open into the alimentary canal, at the junction of the midgut and the hindgut. The alimentary canal of the cockroach is present in the body cavity and divided into three regions – foregut, midgut and hindgut.

I) The foregut consists of the mouth and the mouth opens into a short tubular pharynx, which passes and bends into a narrow tubular passage called the oesophagus. The oesophagus opens into a sac-like structure called a crop. The crop is followed by a gizzard which has an outer layer of circular muscles and has six teeth that help in grinding the hard food particles.
II) Midgut is a narrow tube of uniform diameter without the inner lining of the cuticle. A ring of blind caeca called enteric, which secretes digestive juice, at the junction of the foregut and midgut.
III) Hindgut- It is slightly broader than the midgut and is lined internally by cuticles. It opens by an anus, lying posteriorly below the 10th tergum. At the junction of the midgut and hindgut, there is a ring of about 150 thin yellowish Malpighian tubules, which helps in excretion.

So, the correct answer is option (B) Midgut and Hindgut.

Note: A large amount of water and bicarbonates of potassium and sodium are reabsorbed with the help of these tubules and then transferred to the blood. Uric acid is carried to the alimentary canal of the insect and is finally passes out through the anus. Due to this, the insect is called uricotelic. A few accessory excretory organs are – cuticle, fat bodies, etc.