Question

Which of the following is not a human salivary gland?
A. Parotid
B. Submaxillary
C. Sublingual
D. Infra orbital

Answer 1

Salivary glands are a group of organs present in the mouth that secrete saliva to help in the digestion of food. They are exocrine glands that secretes substances outside the body. They are found only in mammals. Saliva is made up of $98\%$ water but also contains electrolytes, enzymes and mucus. In humans three major pairs of salivary glands are found.

Complete answer:
Option D Infra orbital: Infra orbital salivary glands are additional salivary glands present in animals like cats and rabbits. They are located on the floor of the orbit below the eye and responsible for secreting tears into the ducts. Infra orbital glands are not found in humans.
Option D is correct.
Option A Parotid: Parotid is the largest salivary gland present in humans. Each gland is approximately $60$ mm long and $30 - 40$mm wide. They are located within the cheeks. They secrete about $20\%$ of the total saliva. The saliva from parotid helps in the first phase of digestion of the food.
Option A is not correct.
Option B Submaxillary: The submaxillary glands are also known as submandibular glands. They are a pair of major salivary glands located below the lower jaws of humans. They are responsible for producing nearly $65$ - $70\%$ of saliva in the oral cavity.
Option B is not correct.
Option C Sublingual: The sublingual glands are located inferior to the tongue and anterior to the submandibular glands. Their secretion is mucous in nature. They produce approximately $5\%$ of total saliva entering the oral cavity.
Option C is not correct.

Therefore the correct answer is option D. Infra orbital.

Note:
Saliva has many uses. The salivary enzyme alpha amylase helps to break down the starch present in the food into simpler sugars like glucose and maltose. When food is chewed, the salivary glands are activated to secrete enzymes to break down the food. Saliva has lubricating properties that protects the cavity of the mouth, teeth and throat. It also dissolves the food particles and cleanses the mouth after every meal.