Structural Organisation in Animals Test - 42

• The muscle cells which are present in the heart are called cardiac muscles. These are the modified involuntary muscles. 
• Cardiac muscles have the property of both the striated muscles and smooth muscles. 
• They are striated muscles with single nuclei. The muscle fibres are fused and intercalated discs are present.
• Cardiac muscle is highly resistant to fatigue due to the rich supply of special blood vessels. 
• Thus, cardiac muscles continuously contract and relax and regulate the functions of the heart.
• So, the correct answer is option C. 

The walls of the alveoli are lined with simple squamous epithelial cells known as alveolar cells. This single layer of squamous cells is ideal for the diffusion of gases in the lungs. The cells are characterized by the presence of a compactly arranged cells with single nucleus placed on the basement membrane.

The moist skin of earthworm helps in the respiration by diffusion of oxygen. But if its skin become dry, they will not able to respire and due to lack of oxygen i.e., asphyxia they will die.

• The gizzard is a short muscular organ that has chitin in form of proventricular teeth and the plate. These teeth serve to facilitate food grinding. 
• Mandibles and maxillae are the mouthparts of a cockroach. 
• The rectum is the posterior part of the hindgut. 
  The correct answer is C.

In the insects, there are small glands which are located behind the brain. These glands are known as corpora allata. These are type of endocrine glands. This gland is known to secrete the juvenile hormones. The juvenile hormones are important in different phenomenons. The hormones are also important for development of the larvae and preventing metamorphosis by the hormone called as neotenin. They are important for the production of eggs in the female insects. The hormones also regulate the events like the diapause, and polyphenisms.

• A tendon is a band of connective tissue that connects muscle to bone. The tendons and muscles work together to control joint movement. It is strong and can resist stress. 
• A ligament connects a bone to another bone, usually at the joints. 
• Collagen is the fibrous protein present in our body. It is the building material of certain tissues such as tendons. 
• Cartilage is soft, gel-like padding between bones that protects joints and facilitates movement.

Correct Option: C

Explanation:

• Myogenic- is a type of heart that functions in a rhythmic fashion. The muscle of the heart doesn’t require a neural stimulus to beat.

• In the neurogenic heart, present in most arthropods like cockroaches, the heartbeats are initiated by a nerve signal.

Hence, the cockroach has a neurogenic heart.

Clitellum is the ring like structure which is present in the worms. It helps in the storage of sperms. It secretes a viscous fluid which forms a cocoon for storage of eggs. The embryo of the earthworm develops into the cocoon. It is present in the 14$^{th}$, 15$^{th}$ and 16$^{th}$segments.