How food passes from the mouth to rectum?
1. Mouth: The process begins in the mouth, where food is chewed and mixed with saliva to form a soft mass called a bolus. Saliva contains enzymes that start to break down carbohydrates.
2. Esophagus: The bolus is swallowed and travels down the esophagus, a muscular tube that connects the mouth to the stomach. Peristaltic contractions, involuntary muscle movements, push the bolus downward.
3. Stomach: The bolus enters the stomach, a J-shaped organ. The stomach secretes gastric juices, containing hydrochloric acid and enzymes such as pepsin, which further break down proteins. The bolus is churned and mixed, becoming a semi-liquid substance called chyme.
4. Small Intestine: The chyme moves into the small intestine, the longest part of the digestive system. Here, the pancreas releases pancreatic juices containing enzymes such as amylase (for carbohydrates), lipase (for fats), and protease (for proteins). The liver produces bile, which helps in the digestion and absorption of fats. The small intestine's inner lining has finger-like projections called villi and tiny hair-like structures called microvilli, increasing the surface area for nutrient absorption.
5. Large intestine (colon): Undigested material and water pass from the small intestine into the large intestine. The colon's primary function is to absorb water and electrolytes from the remaining material. Beneficial bacteria in the colon help break down certain indigestible substances, producing gases in the process.
6. Rectum: The remaining waste material, now solid, moves into the rectum, the last portion of the large intestine. It is stored here until it is eliminated through the anus during a bowel movement.