How well do you know your digestive system?

Overview of Digestive System and Its Functions

• The digestive system functions to digest food, absorb nutrients, and eliminate waste.
• The oral cavity consists of the mouth, lips, salivary glands, gums, and tongue. The lingual frenulum limits the movement of the tongue, while the papillae of the tongue are able to detect different tastes.
• Mechanical digestion of food occurs through the teeth, which include incisors, cuspids/canines, premolars, and molars.
• Enzymes are catalysts that change the rate of reaction without undergoing any apparent change themselves, while substrates are the substances undergoing changes due to the enzyme.
• Saliva moistens and lubricates food, and contains constituents such as water, salivary amylase (ptyalin), and mucin. Its pH ranges from 6.4 to 6.9.
• Gastric juice is a fluid secreted by the gastric wall in the stomach, with a pH of 1.6-1.8 without food and 4 with digested food. It contains hydrochloric acid (HCI).
• The chemistry of digestion involves colored pigments such as bilverdin (green pigment in bile), bilirubin (reddish-yellow pigment from breakdown of heme), and urochrome (yellow pigment in urine).
• The process of digestion involves mastication (chewing food in the oral cavity), followed by swallowing which is regulated by the medulla oblongata. The epiglottis moves to cover the tracheal opening and prevent aspiration of food into the lungs.
• The upper esophageal sphincter consists of skeletal muscles that regulate movement of food from the pharynx to the esophagus, while the lower esophageal sphincter closes tightly to prevent reflux of stomach contents into the esophagus.
• The stomach is J-shaped, below the diaphragm, and has four parts: cardia (entrance), fundus, body, and pylorus (outlet). Its capacity is 1500 ml.
• The stomach functions to store food, secrete digestive fluids, and propel the partially digested food.
• The digestive system plays a crucial role in maintaining overall health and well-being.