Overview
This lecture explains how food moves through the digestive system and highlights the roles of key accessory organs—salivary glands, liver, gallbladder, and pancreas—in digestion and absorption.
Food Movement in Digestion
- Chewed food is swallowed and moves to the stomach for further digestion.
- The small intestine absorbs nutrients from the digested food.
Accessory Organs of Digestion
- Accessory digestive organs help with ingestion, digestion, and absorption.
- Major accessory organs: salivary glands, liver, gallbladder, and pancreas.
Salivary Glands
- There are three pairs (six total) of salivary glands around the oral cavity.
- Saliva is 99% water and contains enzymes and proteins for lubrication and chemical digestion.
- Saliva is secreted into the oral cavity by two ducts on each side.
Liver
- The liver is one of the largest organs and produces bile continuously.
- Bile is a yellowish-brown fluid that emulsifies fats in the duodenum (first part of the small intestine).
- Bile travels from the liver through right and left hepatic ducts into the common hepatic duct toward the small intestine.
Gallbladder
- The gallbladder is a green, pear-shaped sac about 10 cm (4 inches) long.
- It stores and concentrates excess bile from the liver.
- Bile is released from the gallbladder into the small intestine as needed for fat digestion.
Pancreas
- The pancreas secretes pancreatic juice, a mix of digestive enzymes, water, buffers, and electrolytes.
- Pancreatic juice flows through the main pancreatic duct to the common bile duct and into the small intestine.
- It buffers stomach acids and helps break down proteins, fats, and carbohydrates.
Key Terms & Definitions
- Salivary glands — Glands around the mouth that secrete saliva to begin chemical digestion.
- Liver — Large organ that produces bile for fat digestion.
- Bile — Fluid that emulsifies fats, aiding their digestion in the small intestine.
- Gallbladder — Organ that stores and concentrates bile, releasing it as needed.
- Pancreas — Organ that produces pancreatic juice containing digestive enzymes and buffers.
Action Items / Next Steps
- Review the roles of accessory organs in the digestive process.
- Study the pathways of bile and pancreatic juice into the small intestine.