Question

Which part of the cockroach has both exoskeleton and endoskeleton?
A. Head
B. Thorax
C. Abdomen
D. All of the above

Answer 1

Hint: The exoskeleton is the outer rigid covering for the body which provides protection from predators and provides flexibility due to innumerable muscle attachment. On the other hand, the endoskeleton is the skeleton of the inside of the body, it is developed within skin or can be deeper in tissues.

Complete answer:
- Head of the cockroach has both an endoskeleton as well as an exoskeleton. The exoskeleton of the cockroach extends internally and forms endoskeleton elements inside the head. These elements are called apodemes and are responsible for muscle attachment so , the option (A) is correct
- Thorax has only exoskeleton and no endoskeleton. Thorax is divided into three parts – prothorax , mesothorax and metathorax .Its exoskeleton is made out of four chitinous sclerites, a dorsal tergite or tergum, ventral sclerite is sternum and two lateral sclerites, called pleura or pleuritis.
- Abdomen is of ten segments. It also has an exoskeleton and no endoskeleton , which is formed of hardened sclerites. Abdominal segment has a dorsal tergum, ventral sternum and between them there is membranous pleuron on each side. Each pleuron has three sclerites and has two latero-tergites arising from tergites.

The correct answer is (A) i.e. Head.

Note: The body wall of cockroach is made up of two layers:
outer cuticle. Cuticle is invaginated forming endoskeletal elements like tentorium in the head and apodemes in the thorax which provide sites for attachment of muscles.
- The cuticle has three different layers: outer primary cuticle or epicuticle, middle thick exocuticle and inner thick endocuticle. Exo- and endocuticle together constitute the so-called 'pro-cuticle'.
- Inner hypodermis- Hypodermis is a single layered epithelium. Some of its cells are modified into large oval trichogen cells which provide secretion of movable bristles on the body. Large irregular cells called 'oenocytes' secrete wax which covers over the cuticle.