Class 4 Ch 1

Explanation
We have two sets of teeth in our lifetime. The first set, known as primary or baby teeth, start to appear around 6 months of age and are eventually replaced by the second set, known as permanent or adult teeth. Baby teeth begin to fall out around the age of 6 or 7, and by the age of 13, most people have all their permanent teeth. These permanent teeth are meant to last for the rest of our lives, although some individuals may require dental treatments or replacements due to various reasons.

Explanation
Digestion is the process of breaking down food into simpler forms that can be absorbed and used by the body. It involves mechanical and chemical processes that occur in the digestive system. Respiration refers to the exchange of gases, breathing is the process of inhaling and exhaling air, and "None" is not a valid option as it does not describe the breaking down of food. Therefore, the correct answer is Digestion.

Explanation
Saliva is indeed secreted by salivary glands. Salivary glands are located in the mouth and produce saliva, which helps in the digestion process by moistening food, breaking it down, and initiating the chemical breakdown of carbohydrates. Saliva also helps in maintaining oral hygiene by washing away bacteria and food particles, and it contains enzymes that aid in the digestion of starches. Therefore, the statement is true.

Explanation
The process of digestion begins in the mouth because this is where food enters the body and is broken down by chewing and mixing with saliva. The saliva contains enzymes that start the process of breaking down carbohydrates. Once the food is chewed and mixed with saliva, it forms a bolus that can be easily swallowed and continue its journey through the digestive system. Therefore, it is true that the process of digestion begins in the mouth.

Explanation
Canines are commonly known as "pointed teeth" due to their sharp and pointed shape. They are located at the corners of the dental arches and are designed for tearing and cutting food. Canines are typically longer and more prominent than other teeth, making them easily distinguishable. They play a crucial role in the process of biting and chewing, helping to grip and tear food before it is further broken down by the molars and premolars.