Question

Number of alary muscles in cockroach
(a) 12
(b) 13
(c) 9
(d) 7

Answer 1

Hint: Alary muscle in cockroaches occurs in the heart wall and it helps in blood circulation. Alary muscles are associated with the blood vascular system of cockroaches. The blood vascular system in the cockroach is open and Lacunar type. Haemocoel is the blood-filled body cavity in cockroaches. The heart of a cockroach is an elongated muscular tube on the mid-dorsal side beneath the terga( thorax and abdomen).

Complete answer:
The alary muscles are 12 pairs in number. It helps in alternate contraction and relaxation of the heart. The pumping force that propels the hemolymph is provided by the pulsations of the heart. The respiratory movements of the abdomen and contraction of alary muscles increase this force.

The heart of the cockroach consists of 13 chambers. The last two chambers are very small. The chambers are separated from each other by deep construction. The opening of each chamber into another is guarded with valves that allow blood from behind forward. The large body cavity or hemocoel is divided into 3 wide and flattened sinuses. The dorsal pericardial sinus containing the heart. A pair of fan- like, triangular alary muscles in the floor of the pericardial sinus in each segment reinforces the dorsal diaphragm by their broad bases and also connect it, by their pointed tips with the tergite of the segment.
So, the correct answer is ‘12’.

Additional information:
- Blood or the hemolymph of the cockroach has a clear plasma and numerous corpuscles called hemocytes.
- Being devoid of respiratory pigment, it does not serve for gaseous exchange.
- Its plasma contains about 70% of water, the rest of it is composed of amino acids, uric did, protein, sugars, and fats.
- The wall of the heart is composed of outer connective tissue and median muscle cells.
- The heart consists of 13 funnel- shaped and sequentially arranged chambers.

Note:
- Alary muscles in cockroach are innervated by axons continuing electron- dense granules of her 100 mm in diameter.
- These are thought to be typical neurosecretory axons based on their ultrastructural appearance. Mitochondria were located near the Z- line area and were sent from the middle portion of the sarcomere.
- A transverse membrane system was present which formed dyad structures with a relatively coarse sarcoplasmic reticulum.