Trace the path of food from ingestion to defecation and describe what happen at each stop? Also name enzymes.
http://www.besthealth.com/besthealth/bodyguide/reftext/html/dige_sys_fin.html
http://www.google.com/search?source=ig&hl=en&rlz=1G1GGLQ_ENUS355&q=digestive+system
To trace the path of food from ingestion to defecation, let me break it down into the steps involved at each stage:
1. Ingestion: Food enters the body through the mouth during the process of eating. Chewing helps break down the food into smaller pieces, increasing its surface area for further digestion. Saliva is produced by the salivary glands and released into the mouth, containing an enzyme called amylase. Amylase begins the digestion of carbohydrates, breaking them down into smaller molecules.
2. Swallowing: After chewing, the food is formed into a soft mass called a bolus. The tongue pushes the bolus to the back of the mouth, triggering the swallowing reflex. The bolus then moves down the esophagus (food pipe) through muscular contractions called peristalsis, which helps propel it towards the stomach.
3. Stomach: When the bolus enters the stomach, it is mixed with gastric juices containing a combination of hydrochloric acid and digestive enzymes. The main enzymes in the stomach are pepsin, which breaks down proteins into smaller peptides, and gastric lipase, which starts the digestion of fats. The stomach also churns and contracts, further breaking down the bolus and mixing it with digestive juices, forming a semi-fluid mixture called chyme.
4. Small Intestine: The chyme passes through the pyloric sphincter, entering the small intestine. The small intestine is where the majority of digestion and absorption of nutrients take place. The chyme mixes with digestive enzymes from the pancreas and bile from the liver. The pancreas secretes enzymes such as pancreatic amylase, pancreatic lipase, and trypsin, which assist in the breakdown of carbohydrates, fats, and proteins respectively. The bile, stored in the gallbladder, helps emulsify fats, making it easier for enzymes to break them down. The inner lining of the small intestine also produces various enzymes including enterokinase, which activates trypsinogen to trypsin for protein digestion.
5. Absorption: As the chyme moves through the small intestine, nutrients are absorbed into the bloodstream. Villi and microvilli, finger-like projections lining the inner walls of the small intestine, increase the surface area for absorption. Nutrients such as glucose, amino acids, and fatty acids are transported into the bloodstream, where they are then distributed to various cells and tissues throughout the body.
6. Large Intestine: The remaining undigested and unabsorbed substances, mainly fiber and water, move into the large intestine (colon). Here, water is absorbed from the chyme, making it more solid. Beneficial gut bacteria present in the large intestine help break down certain types of fiber, producing gases like methane and hydrogen. The bacteria also produce some vitamins, like vitamin K and biotin, which are absorbed into the bloodstream.
7. Defecation: The waste product, known as feces, is formed as the undigested material, bacteria, and other waste products are moved through the colon. The rectum stores the feces until it is eliminated from the body through the canal during the process of defecation.
Please note that various enzymes are involved at different stages of digestion to break down different types of nutrients. The enzymes mentioned above, such as amylase, pepsin, pancreatic amylase, pancreatic lipase, trypsin, and others, play crucial roles in breaking down carbohydrates, proteins, and fats into their respective building blocks for absorption and utilization by the body.