A missing fingernail takes 4 to 5 months to grow back.

Lungs are the essential respiratory organ and its principal is to transport oxygen from atmosphere into the bloodstream.

Unbiblical cord is an essential organ, which passes the blood between the fetus and the placenta.

The liver is the largest gland in the human body. It is located in the right upper quadrant of the abdominal cavity.

Liver helps in fighting infections by synthesizing antibodies, regulates the blood clotting  and produces bile which helps in digestion of fats.

A humerus is a long bone in the arm or forelimb which extends from the shoulder to the elbow.

Blood group O does not have any antigen on its surface and can be donated to individual containing any blood group.

 Canines are sharp pointed teeth. These are called dog teeth as dog's dentition consist mostly of canines.

Eye pupil is the only part of human body that can increase to eight times its smallest size.

There are essentially 3 types of muscles in the humans body, those are skeletal, cardiac and smooth.

The receptor is the right answer as it reserves the chemical signals externally from the calls.

Metamorphism is the process when a young organism that looks nothing like an adult, becomes an adult. It is not a necessary life process because not all species go through it.