Understanding the Human Digestive and Respiratory Systems

Nutrition: The digestive system (introduces food and transforms it), respiratory system (obtains O₂ and eliminates CO₂), circulatory system (transports nutrients and oxygen), and excretory system (releases waste substances outside the organism). Digestive System The gastrointestinal tract (about 8 meters long, starts in our mouth and ends at our anus) consists of the following parts: oral cavity, pharynx, esophagus, stomach, small intestine, and large intestine. The mucus, produced by an inner cell called the mucous membrane, creates a lubricant substance called mucus. Accessory glands include salivary glands, the liver, and the pancreas. Digestion: This is the process by which foods are transformed into nutrients. Mechanical processes (like chewing) and chemical processes (through digestive enzymes, the substances in food become simple components). Digestive Mouth: The process of digestion begins here. Salivation: Saliva is a watery liquid that initiates the digestion of starch molecules through an enzyme called amylase. It also destroys some bacteria using lysozyme and facilitates the formation of the bolus, as saliva contains mucin. Chewing: This is a mechanical process where teeth are the structures responsible for grinding and crushing (baby teeth). Swallowing: The tongue pushes the bolus towards the pharynx, from there it goes to the esophagus, and ends in the stomach. Digestive Process in the Stomach: Peristaltic movement (the cardia separates the stomach from the esophagus) and the pylorus separates the stomach from the small intestine (pepsin and hydrochloric acid are involved). Small Intestine: The ileocecal valve separates it from the large intestine. The duodenum is 25 cm long and shaped like a horseshoe, the jejunum is the longest part, and the ileum follows. Pancreas: Produces hormones (insulin and glucagon) and pancreatic juice (in the duodenum). The Liver: Located on the right side of the abdomen, it produces bile, which does not contain digestive enzymes but has bile salts that break down fats and destroys toxic molecules. Food Absorption: This is the passage of nutrients into the blood (the small intestine is covered by villi). Respiratory System: Cells need O₂ for cellular respiration, and the waste product is CO₂. Respiratory Tract: Made up of tubes (nasal openings, red pituitary, nasal cavities, pharynx, larynx/vocal cords, trachea, bronchi, bronchioles/alveoli). Gas Exchange: A network of capillaries forms the lungs, which are elastic bodies.