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8 DIGESTION AND ABSORPTION SCAN CODE Digestion and Absorption DIGESTION AND ABSORPTION 16
DIGESTION AND ABSORPTION 9 SCAN CODE Digestion and Absorption Chapter 16 Digestion and Absorption 1. Food and Nutrition ● Food is any substance consumed to provide nutritional support for an organism. It is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. ● Nutrition is the biochemical and physiological process by which an organism uses food to support its life. ● The process of nutrition involves the following five steps: ● Ingestion- It includes the processes that take place while the food is in the mouth also known as a buccal cavity (such as chewing and grinding) and swallowing of the food - which sends it onward down the digestive tract. ● Digestion- It is the process of breaking down food into simpler substances that can then be absorbed and assimilated into the tissues of the body. ● Absorption- The digested food is absorbed into the bodily fluids from the alimentary canal. The major process of absorption takes place in the small intestine with the help of villi, minute finger-like processes lined against the walls of the small intestine. ● Assimilation- the process by which chemicals from food are taken into the cells of the body after digestion and absorption. The food is absorbed by blood and is transported to various parts of the body by the blood vessels. ● Egestion- the process of removing the undigested food material from the body through the anus. Fig.16.1: Processes involved in Nutrition ● Nutrients are substances used by an organism to survive, grow, and reproduce. The seven major classes of relevant nutrients for animals (including humans) are carbohydrates, dietary fiber, fats, proteins, minerals, vitamins, and water. ● Nutrients can be grouped as either macronutrients (carbohydrates, dietary fiber, fats, proteins, and water needed in gram quantities) or micronutrients (vitamins and minerals needed in milligram or microgram quantities). ● Macronutrients are the nutrients your body needs in larger amounts, namely carbohydrates, protein, and fat. These provide your body with energy, or calories.
DIGESTION AND ABSORPTION 10 SCAN CODE Digestion and Absorption Fig.16.2: Macronutrients ● Micronutrients are the nutrients your body needs in smaller amounts, which are commonly referred to as vitamins and minerals. Fig.16.3: Micronutrients ● Biomacromolecules in food cannot be utilized by the human body in their original form. They have to be broken down and converted into simple substances in the digestive system. This process of conversion of complex food substances to simple absorbable forms is called digestion. ● Food provides energy and organic materials for growth and repair of tissues. ● The water plays an important role in metabolic processes and also prevents dehydration of the body. Fig.16.4: Food: The Source of Nutrients
DIGESTION AND ABSORPTION 11 SCAN CODE Digestion and Absorption 2. Digestive System ● The human digestive system consists of the alimentary canal and the associated glands (Digestive glands). Fig.16.5: Human Digestive System A table representing the parts of digestive system Parts of Alimentary canal Digestive Gland Mouth (Oral Cavity- Tongue and Teeth) Salivary glands Pharynx and Oesophagus Liver Stomach Pancreas Small Intestine and Large Intestine Gastric glands Anus Intestinal glands 2.1 Alimentary Canal ● The alimentary canal begins with an anterior opening – the mouth, and it opens out posteriorly through the anus. 2.1.1 Mouth ● In human anatomy, the mouth is the first portion of the alimentary canal that receives food and produces saliva. ● It leads to the buccal cavity or oral cavity. 2.1.2 Oral Cavity ● The oral cavity includes the lips, the inside lining of the lips and cheeks (buccal mucosa), the teeth, the gums, the front two- thirds of the tongue, the floor of the mouth below the tongue, the bony roof of the mouth. ● The roof of the oral cavity is called the palate. Anterior part is hard palate and the posterior smooth part is soft palate. Freely hanging from the soft palate, a small flap-like structure is uvula. Fig.16.6: Human Oral Cavity