nutrition in humans

• Food processing in the digestive tract involves crushing food with teeth to generate small, uniform particles
• Food is wetted in the mouth by saliva secreted by salivary glands to aid in smooth passage
• Saliva contains an enzyme called salivary amylase that breaks down starch into simple sugars
• Food is mixed with saliva and moved around the mouth by the muscular tongue while chewing
• Peristaltic movements along the digestive tract help push food forward for proper processing
• Food moves from the mouth to the stomach through the oesophagus or food-pipe
• Stomach expands when food enters and mixes it with digestive juices released by gastric glands
• Gastric glands in the stomach release hydrochloric acid, pepsin (a protein digesting enzyme), and mucus
• Hydrochloric acid creates an acidic environment to facilitate pepsin's action, while mucus protects the stomach lining
• Sphincter muscle regulates the exit of food from the stomach into the small intestine
• Small intestine is the longest part of the alimentary canal and is the site of complete digestion of carbohydrates, proteins, and fats
• Liver and pancreas secrete enzymes into the small intestine to aid in digestion
• Bile juice from the liver emulsifies fats, making them easier for enzymes to act on
• Pancreatic juice contains enzymes like trypsin for proteins and lipase for emulsified fats digestion
• Intestinal juice from the small intestine glands converts proteins to amino acids, carbohydrates to glucose, and fats to fatty acids and glycerol
• Villi in the small intestine increase the surface area for absorption of digested food
• Absorbed food is transported by blood vessels to cells for energy, tissue building, and repair
• Unabsorbed food moves to the large intestine where water absorption occurs, and waste is eliminated through the anus
• Anal sphincter regulates the exit of waste material from the body