Question

The spiracles found in cockroach are
(a) Two pair in the thorax and a hundred pairs in the abdomen
(b) Two pair in the thorax and six pair in the abdomen
(c) Two pair in thorax and eight pair in the abdomen
(d) Two pair in the thorax and four pair in the abdomen

Answer 1

Hint: The respiratory system of cockroaches is made up of an air tube trachea which opens out in the form of an aperture called spiracles. These spiracles are present in the thoracic and abdominal region and a total of ten in number.

Complete Answer:
The respiratory system of a cockroach is a network of air tubes called the trachea which opens out laterally in the form of paired spiracles. The spiracles are 10 in pairs, in which two pairs lie at the mesothoracic or metathoracic region, whereas the remaining eight pairs lie at the abdomen region. The function of spiracles gets regulated by the sphincter. The spiracles consist of the atrium which has a valve and plates. The atrium rises to the main trachea which further gets divided into tracheoles. During respiration, the air gets to enter into the spiracles which further reach the tracheoles where the oxygen gets dissolved into the tissue fluid of tracheoles which later get diffused into the cell. After the diffusion of oxygen into the cell, the carbon dioxide gets diffused out from the cell to the tissue fluid which further ejects out during expiration. During locomotion, the body of cockroaches shows contraction and relaxation of the abdomen and this contraction and relaxation perform respiration.

So, the correct answer is ‘Two pairs in the thorax and eight pairs in the abdomen’.

Note:
Some carbon dioxide that gets produced during oxidation gets diffused out to the blood, this carbon dioxide also shows diffusion in the cuticle which leads to ejection of carbon dioxide from the body. The cuticle of the cockroach is permeable to carbon dioxide therefore it leads to its diffusion.