Tag: digestion

The oral cavity leads into a short pharynx, which serves as a common passage for food and air. The oesophagus and the trachea (wind pipe) open into the pharynx. A cartilaginous flap, called as epiglottis, prevents the entry of food into the glottis opening of the wind pipe during swallowing.

The epiglottis is a flexible flap at the superior end of the larynx in the throat. It acts as a switch between the larynx and the esophagus to permit air to enter the airway to the lungs and food to pass into the gastrointestinal tract. The epiglottis also protects the body from choking on food that would normally obstruct the airway.

Amylase is a digestive enzyme that acts on starch in food, breaking it down into smaller carbohydrate molecules. It is produced at two sites. First, salivary glands in the mouth make salivary amylase, which begin the digestive process by breaking down starch when the food is chewed. The starch is converted to maltose, a smaller carbohydrate. When starchy foods like rice or potatoes begin to break down in the mouth, a slightly sweet taste is detected, as maltose is released. So, if we chew a piece of bread (made of polysaccharides) long enough, it will begin to taste sweet because amylase is breaking down starches to dissaccharides such as maltose. Thus, option C is correct.

Carbohydrate digestion begins in the mouth or buccal cavity. The salivary glands in the mouth secrete saliva, which helps to moisten the food. The food is then chewed while the salivary glands also release the enzyme salivary amylase, which begins the process of breaking down the polysaccharides in the carbohydrate food.

A bolus is a mass of food that (with animals that can chew) has been chewed at the point of swallowing. Under normal circumstances, the bolus then travels down the oesophagus to the stomach for digestion. Bolus has the same colour as the food that has been chewed by the person and is different from chyme. The bolus is a rolled up ball-like structure formed when the animal is about to swallow. Its pH is alkaline because of the presence of saliva. Thus, option A is correct.

Digestion of food starts in the mouth in humans. In the mouth masticated food gets mixed with saliva secreted by salivary gland. Saliva is a mixture of water, electrolytes, ptyalin enzyme (salivary amylase). The digestion of starch is initiated in the mouth due to the action of salivary amylase. Enzymatic hydrolysis helps in the partial breakdown of starch into maltose, isomaltose.

The pharynx is an organ found in vertebrates and invertebrates. In humans, the pharynx is a part of the digestive system and also of the conducting zone of the respiratory system. The conducting zone includes nose, larynx, trachea, bronchi and bronchioles and their function is to filter, warm and moisten air and conduct it into the lungs.
Therefore, the correct answer is option A.

The food is ingested through the mouth. The mouth contains tongue, teeth and salivary glands. Teeth break the food into smaller particles. This process is called as mastication. The chewed food is mixed with saliva. Saliva is a watery fluid secreted by the salivary glands. Saliva contains a type of enzyme called the salivary amylase, which converts starch into sugar. The tongue is a muscular organ. Tongue helps to mix saliva in the food. It also helps to push the food down the food-pipe or oesophagus. Taste receptors are present in tongue and give us the sense of taste. 

The fist stage of digestion in human being takes place in the buccal cavity where the chewing and churning of food and mixing of saliva occurs. Saliva consists salivary amylase which acts on the starch molecule of food and converts it into the simple form. The semisolid food with saliva in buccal cavity is called as a bolus. Bolus is then transferred to the stomach with the help of peristaltic movement of the oesophagus. Thus, the correct answer is option C.