6.1 Structure of the digestive system Flashcards
Describe the structure of the human digestive system.
The human digestive system includes the mouth, esophagus, stomach, small intestine (duodenum, jejunum, ileum), large intestine, rectum, and anus, along with accessory organs like the liver, pancreas, and gallbladder. Digestion begins in the mouth with saliva and continues with the breakdown of food in the stomach and small intestine, where nutrients are absorbed. The large intestine reabsorbs water and forms feces
What are the tissue layers in transverse sections of the small intestine?
From the outside to the inside: serosa (connective tissue), longitudinal muscles, circular muscles (both responsible for peristalsis), submucosa (connective tissue with blood vessels), mucosa (inner lining with villi), and epithelium (covers the villi)
How does the contraction of circular and longitudinal muscles in the small intestine assist digestion?
The contraction of circular and longitudinal muscles mixes the food with digestive enzymes and moves it along the gut through peristalsis. This action ensures efficient digestion and nutrient absorption by continually exposing food to digestive enzymes and intestinal wall
What is the role of the pancreas in digestion?
The pancreas secretes digestive enzymes into the lumen of the small intestine, including amylase for starch, lipases for lipids, and proteases for proteins, aiding in the breakdown of food molecules into absorbable units
How are macromolecules digested and absorbed in the small intestine?
Enzymes from the pancreas and the intestine break down macromolecules into monomers. Amylase, lipases, and proteases from the pancreas, along with intestinal enzymes like maltase and lactase, digest starch, lipids, and proteins. The monomers are then absorbed into the bloodstream or lymph
Why are villi important in the small intestine?
Villi increase the surface area of the epithelium over which absorption occurs. They contain capillaries and lymphatic vessels (lacteals) for the absorption of nutrients, minerals, ions, and vitamins. The large surface area ensures efficient nutrient uptake
What methods of membrane transport are used to absorb different nutrients in the small intestine?
Four main methods:
1) Simple diffusion for hydrophobic molecules,
2) Facilitated diffusion for hydrophilic monomers via protein channels,
3) Active transport for nutrients against concentration gradients, requiring ATP,
4) Pinocytosis for absorbing fat droplets
Explain starch digestion and nutrient transport from the small intestine to the liver.
Starch is broken down into maltose and maltotriose by amylase, then into glucose by intestinal enzymes. Glucose is absorbed by villi and transported via the hepatic portal vein to the liver, where it’s processed or stored as glycogen
How does dialysis tubing model the absorption of digested food in the intestine?
Dialysis tubing represents the intestinal epithelium; it’s semi-permeable, allowing small molecules like glucose to pass while blocking larger ones like starch. This models how nutrients are absorbed from the intestine into the bloodstream
