The document summarizes the human digestion process in three phases: 1) The cephalic phase prepares the body for eating through saliva production and stomach distention. 2) The gastric phase lasts 3-4 hours where the stomach breaks down food using gastric acid and enzymes. 3) The intestinal phase has two parts where partially digested food triggers hormone release and most digestion occurs in the small intestine before entering the large intestine.

1. Human digestion process

2. Introduction Cephalic phase - This phase occurs before food enters the stomach and involves preparation of the body for eating and digestion Gastric phase - This phase takes 3 to 4 hours. It is stimulated by distention of the stomach and alkaline pH . Intestinal phase - This phase has 2 parts, the excitatory and the inhibitory. Partially-digested food fills the duodenum . This triggers intestinal gastrin to be released .

3. ORAL CAVITY In humans, digestion begins in the oral cavity where food is chewed . Saliva is secreted in large amounts (1-1.5 litre/day) by three pairs of exocrine salivary glands (parotid, submandibular, and sublingual) in the oral cavity. Swallowing transports the chewed food into the esophagus .

4. ESOPHAGUS The esophagus , a narrow, muscular tube about 20 centimeters, long and ends at the cardiac orifice of the stomach . The chewed food is pushed down the esophagus to the stomach through peristaltic contraction of these muscles

5. STOMACH In the stomach, food is further broken apart thoroughly mixed with a gastric acid and digestive enzymes that denature proteins . The acid itself does not break down food molecules

6. PANCREAS The pancreas is an organ that releases hormones and enzymes to help digestion . It releases substances through special cells called the Islets of Langerhans . Amazingly, the pancreas is the only organ in the human body to belong to two systems of function (the digestive system due to its role in breaking down nutrients and the endocrine system for its role in hormone production).

7. LIVER The liver is an organ present in vertebrates and some other animals. It plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, and detoxification. This organ also is the largest gland in the human body .

8. Small intestine After being processed in the stomach, food is passed to the small intestine via the pyloric sphincter . The majority of digestion and absorption occur here as chyme enters the duodenum .

9. Large intestine After the food has been passed through the small intestine, the food enters the large intestine . The large intestine is roughly 1.5 meters long, with three parts: the cecum at the junction with the small intestine , the colon , and the rectum .

10. By… Araceli Carmona Ayora Cristina Alcaide Cabello Mª Aurora Carmona Muñoz Ana Belén Fernández Marín 3º A