Tag: digestive system - organs

Digestion starts in mouth and starch is the biomolecule whose digestion is first carried out by Ptyalin enzyme present in saliva.
No digestion occurs in oesophagus. It functions to transport semi solid bolus of food from mouth to stomach.
Intestine comes after stomach. Stomach is important for digestion of proteins.

Digestion of food starts in mouth. It is carried out in following two ways

• Mechanical digestion which is breaking of food into smaller chunks with the help of teeth and aided by muscular tongue.
• Chemical digestion due to ptyalin (salivary amylase) in saliva
• So, the correct answer is 'Mouth'

The alimentary canal begins with an anterior opening the mouth, and it opens out posteriorly through the anus. The mouth leads to the buccal cavity or oral cavity. The oral cavity has 32 teeth and a muscular tongue. The buccal cavity is lined with mucous membrane, whose secretions keep mouth moist.

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.