Tag: digestion

The pharynx serves as a common pathway for both the respiratory system (air) and the digestive system (food).

The alimentary canal is a long tube through which food is taken into the body and digested. In human beings, this passage is about 30 ft (9 m) long." The alimentary canal, or the digestive tract as it is most commonly known, is 9 meters from the oesophagus to the anus.

During swallowing, the epiglottis acts as a flap that closes over the glottis (the opening to the trachea) to prevent food from entering the windpipe.

In humans, the alimentary canal begins with an anterior opening, called mouth and it opens out posteriorly through another opening, anus. Such an alimentary canal is called complete. In some animals like coelenterates only single opening is present, such an alimentary canal is called incomplete. 

The digestive functions of saliva include moistening food, and helping to create a food bolus, so it can be swallowed easily. Saliva contains the enzyme amylase that breaks some starches down into maltose and dextrin. The pancreas produces a juice containing several enzymes that break down carbohydrates, fats, and proteins in food. Hence, partial digestion occurs in the mouth.

Sodium-potassium pumps in the axonal membrane ionic gradients across the membrane by active transport of Na${+}$ outwards and K${+}$ inwards.

Amylase is an enzyme that catalyses the hydrolysis of starch into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion in mouth. Protein digestion begins in the stomach with the action of an enzyme called pepsin. Lipids are digested mainly in the small intestine by bile salts through the process of emulsification, which allows lipases to divide lipids into fatty acids and glycerol. The large intestine is the final section of the gastrointestinal tract that performs the vital task of absorbing water and vitamins while converting digested food into faeces. 

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 carbohydrate food.

There are two kinds of digestion: mechanical and chemical. In mechanical digestion, food particles are physically broken down into smaller pieces. It begins in the mouth where the food is chewed. 

An organ that helps with digestion but is not part of the digestive tract. The accessory digestive organs are the tongue, salivary glands, pancreas, liver, and gallbladder. Chemical digestion in the small intestine relies on the activities of three accessory digestive organs the liver, pancreas, and gallbladder. The digestive role of the liver is to produce bile and export it to the duodenum. The gallbladder primarily stores, concentrates, and releases bile. The pancreas produces pancreatic juice, which contains digestive enzymes and bicarbonate ions, and delivers it to the duodenum.