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THE DIGESTIVE SYSTEM
The digestive system breaks down ingested material into fuel for the cells while allowing for the efficient disposal of waste. The major structures of the digestive system are divided into hollow and solid organs.
- The hollow organs are considered non-sterile on the inside of your otherwise sterile body beause of their connection with the outside environment via the nose, mouth, and anus. They carry products of digestion.
- ESOPHAGUS: carries food from the oropharynx to the stomach via peristalsis.
- STOMACH: physically grinds and chemically digests food.
- GALLBLADDER: stores bile produced by the liver, which helps digest fats when passed to the duodenum via a duct (bile duct).
- small intestines (duodenum, jejunum, and ileum) absorb the chemically broken down carbohydrates, proteins, and fats from food while peristalsis moves the intestinal contents toward the
- large intestines (ascending, transverse, descending colon; rectum) are primarily responsible for continuing peristalsis to move fecal contents toward the anus for defecation and for managing water absorption based on hydration needs of the body.
- The solid organs are highly vascular, carrying large amounts of blood.
- LIVER: detoxifies the blood, produces proteins and produces bile to aid fat digestion.
- PANCREAS: secretes hormones vital for energy balance (insulin and glucagon) and enzymes for carbohydrate and protein digestion.
When food is ingested, it is physically macerated by the teeth and exposed to salivary enzymes. After reaching the stomach, further breakdown by acids, enzymes, and muscular contractions occurs. The food, now known as "chyme" is moved through the intestines by peristalsis. Peristalsis is the smooth muscle contractions that squeeze, push, and move food through the GI tract. The nutrients from the food are absorbed by the intestines on their way to the colon. The remainder is excreted during bowel movements.
The pancreas secretes more specialized enzymes during this process; they are designed to help cut apart proteins and carbohydrates for easy absorption by the small intestine. The liver creates bile, which helps with the uptake of fatty acids from food. The liver later plays a role in removing toxic byproducts of digestion and preventing them from doing damage to the body.