Liver (weighs 3lb)
There are 3 pairs of salivary glands: ? Sublingual – found underneath and either side of the tongue ? Submandibular – under the angle of the jaw ? Parotid – found just near the masseter muscle on each side of the face Saliva helps to lubricate food, making it easier to swallow and also stimulates the taste buds. It plays an important role in keeping the tissues of the mouth moist and clean. There is an enzyme called amylase present in saliva which is important for beginning the chemical breakdown of starches
Body fat is made from carbohydrates and proteins and fats eaten in excess of the body‘s needs and stored in the fat deposits mainly under the skin but also around organs such as the kidneys and liver. When required the stored fat can be converted into energy. In order to release these stores the energy output has to be greater than the calorie intake.
Nutrients provide the energy necessary to drive the chemical reactions required in living organisms. In addition nutrients supply the chemicals necessary for building and maintaining the body tissues. Nutrients are obtained as food and are not in a suitable state for immediate use. The digestive system is designed to perform two major functions. Food particles are broken down into molecules of small enough size to cross the plasma membrane in the process called digestion. The passage of these particles into the blood and lymphatic system is called absorption.
The digestive system organs are divided into two groups: the gastro-intestinal tract and the accessory organs. The g.i. tract (sometimes called the alimentary canal) is essentially a continuous tube from the mouth to the anus. The mouth, pharynx, oesophagus, stomach, small intestine and large intestine are all considered structures of the g.i. tract. Food is digested inside the lumen of this tract. The accessory structures aid mechanical and chemical digestion and include the teeth, tongue, salivary glands, liver, gallbladder and pancreas. The tongue and teeth function in ingestion and mechanical digestion while the other accessory structures provide secretions necessary for chemical digestion.
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