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04. Human Digestive System

Key Terms

Prepared by: learnloophq@gmail.com

Last edited 25 days ago by Learn LoopHQ.

Chapter: 04. Human Digestive System

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Nutrition: The process of obtaining and using food substances.

Nutrients: All chemical compounds which nourish our body.

Food: Any substance which contains nutrients.

Carbohydrates: Energy-giving nutrients formed in green plants during photosynthesis.

Fats: Energy-rich food substances that produce more energy than carbohydrates.

Proteins: Body-building organic molecules essential for growth and repair, with nitrogen as an essential element.

Amino acids: Building blocks of proteins, formed as a result of protein digestion.

Vitamins: Protective food needed in very small quantities for body growth, maintenance, and proper use of other nutrients.

Minerals: Balancing food needed in small quantities for proper body growth and to maintain good health.

Macronutrients: Carbohydrates, fats, and proteins, needed by our body in large quantities.

Micronutrients: Vitamins and minerals, needed by our body in minute quantities.

Dietary fibres (Roughage): Cellulose fibres obtained from vegetables, salads, fresh fruits, and whole grains, essential for proper bowel movement.

Ingestion: The process of intake of food.

Digestion: The breaking down of complex insoluble organic compounds into simple soluble molecules by the action of digestive enzymes.

Absorption: The process by which molecules of digested food are taken into the blood through the intestinal wall.

Assimilation: Utilisation of absorbed nutrients by the body cells for energy and synthesis of new protoplasm for growth.

Egestion (or Defecation): The removal of undigested solid part of the food as faeces.

Alimentary Canal: A 9 metres long, coiled food tube, open at both ends, beginning with the mouth and ending with the anus.

Digestive Glands: Glands that make and store the digestive juices or enzymes which help in digestion.

Dentition: The arrangement of different types and number of teeth in the buccal cavity.

Milk teeth: The first set of 20 teeth appearing from the age of 6 months onwards, which are replaced by permanent teeth.

Permanent teeth: The second set of 32 teeth that replace milk teeth, appearing between 6 to 8 years of age.

Wisdom teeth: Four molars added to the permanent teeth after the age of 18 years.

Taste buds: Structures on the tongue which identify sweet, salt, bitter and sour tastes.

Gullet: The opening of the food channel (oesophagus) in the pharynx.

Glottis: The opening of the air channel or windpipe (trachea) in the pharynx.

Uvula (Epiglottis): A muscular flap that guards the opening of the trachea in the pharynx, closing the glottis during swallowing.

Peristalsis: The progressive wave of muscle contractions that proceeds along the wall of oesophagus, pushing the food content forward.

Chyme: The fine pulp formed when the stomach churns the food.

Sphincter: A ring of circular muscle fibres around an opening, which closes when contracted.

Cardiac sphincter: The sphincter that guards the opening of the oesophagus into the stomach.

Pyloric sphincter: The sphincter that guards the opening of the stomach into the duodenum.

Villi: Numerous finger-like projections on the wall of the ileum (small intestine) that absorb digested food.

Lacteal: Lymph vessels present in each villus for the absorption of glycerol and fatty acids.

Caecum: A small pouch, poorly developed and nonfunctional in humans, that serves as the site of cellulose digestion in grass-eating mammals.

Vermiform appendix: A blind tube arising from the caecum, considered a vestigial organ in humans.

Rectum: The approximately 20 cm long tube that opens to the exterior by the anus, storing faeces before egestion.

Anal sphincter muscles: Muscles that guard the anus, controlling the expulsion of faeces.

Saliva: Watery secretion of salivary glands that moistens and lubricates food and contains salivary amylase.

Bile juice: Produced by the liver and stored in the gall bladder, it neutralises acidity of chyme and emulsifies fats.

Pancreatic juice: Produced by the pancreas, it contains enzymes for the digestion of sugars, fats and proteins.

Vestigial organs: Organs which have no function in the body (e.g., human caecum, appendix).

Enzymes: Proteins that speed up chemical reactions occurring within the body, also called biocatalysts.

Biocatalysts: A term for enzymes, referring to their ability to speed up chemical reactions in living organisms.

Hydrolytic enzymes: Digestive enzymes that catalyse or speed up the digestion of food by breaking it into its basic units.

Carbohydrases: Carbohydrate digesting enzymes (e.g., salivary amylase and pancreatic amylase).

Lipases: Fat digesting enzymes (e.g., gastric lipase, intestinal lipase and pancreatic lipase).

Proteases: Protein digesting enzymes (e.g., pepsin and trypsin).

Indigestion (Dyspepsia): A feeling of pain or discomfort in the stomach and upper part of the abdomen.

Obesity: A condition of the body gaining extra weight due to overeating, storing fat in the body.

Undernutrition: A state when the body gets less than the required nutrients, becoming weak and sick.

Malnutrition: A state where there is a shortage of one or more nutrients, caused due to the intake of an unbalanced diet.

Balanced diet: The diet which contains all the essential nutrients in just the right proportion.

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