Structural Organisation in Animals

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ÑËRVØÜS SÝSTËM

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It consists of segmentally arranged ganglia joined by paired longitudinal

connectives on the ventral side.

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3 ganglia lie in the thorax and 6 in the abdomen.

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The head holds a bit of a nervous system while the rest is situated along

the ventral part of its body. So, if the head of a cockroach is cut off, it will

still live for one week.

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The supra-oesophageal ganglion (brain) supplies nerves to antennae

and compound eyes.

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Sense organs: Antennae, eyes, maxillary palps, labial palps, anal cerci

etc.

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Sensory receptors of antennae monitor the environment.

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Each compound eye consists of about 2000 hexagonal ommatidia.

Using these, a cockroach can receive several images of an object. This

is called mosaic vision. It has more sensitivity but less resolution, being

common during night (hence called nocturnal vision).

RËPRØDÜÇTÏVË SÝSTËM

Cockroaches are dioecious.

MALE REPRODUCTIVE SYSTEM:

It consists of a pair of testes, seminal vesicles, accessory glands & external

genitalia.

Testes: Lie laterally in the 4^th -6^th abdominal segments.

Each testis ¾® Thin vas deferens ¾® Seminal

vesicle ¾® Ejaculatory duct ¾® Male gonopore.

Seminal vesicles: To store sperms. Sperms are

glued

together

to

form

bundles

called

spermatophores. They are discharged during

copulation. (NEET 2016)

Accessory glands: Include a mushroom shaped

gland or utricular gland (in 6^th - 7^th abdominal

segments) and phallic gland. Their secretions

nourish the sperms.

External

genitalia

(male

gonapophysis

or

phallomeres): Chitinous asymmetrical structures,

surrounding the male gonopore.

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