Chapter 9: Nutrition and the Human Digestive System Flashcards
Where is the bile stored?
The gallbladder.
Where does the digestive process begin?
The mouth.
What are the cells that line the surface of the stomach and what do they form?
The epithelial cells. They have undergone adaptations in structure and function to form gastric glands.
What is the content of saliva and what is its use?
Saliva contains salivary amylase which hydrolyses starch to maltose.
What is meant by digestion?
The process that breaks down large and complex pieces of food into smaller and simple pieces that can be dissolved for easy absorption.
What does the liver produce?
The bile.
What is meant by peristalsis and what is its action on bolus?
Peristalsis is the rhythmic contraction and relaxation of muscles along the alimentary canal. It acts in pushing the bolus through the oesophagus until it reaches the stomach.
Name the epithelial cells that line the stomach and the substance they secrete respectively.
Chief cells (secrete pepsinogen), parietal cells (secrete hydrochloric acid) and mucous cells (secrete mucus).
Name two other substances received by the duodenum and name their respective origins.
The bile - produced by the liver.
The pancreatic juice - secreted by the pancreas.
What are the functions of HCl in the digestion of protein in the stomach?
- Prepare a medium with a suitable pH (pH1.5 - 20) for pepsin to act.
- Stop the enzymatic action of salivary amylase.
- Kill bacteria in food.
Name the process of hydrolysis occurring with protein.
Erepsin hydrolyses peptides into amino acids.
The presence of food in the mouth stimulates the secretion of saliva from the…
…salivary glands.
Where does the bile flow into?
The bile flows into the duodenum through the bile duct.
What is the pH range of saliva and how does it affect salivary amylase?
The pH range of saliva is between 6.5-7.5 which is the optimal for the action of salivary amylase.
What is the first part of the small intestine to receive chyme?
The duodenum.
What does the pancreas secrete and how are they secreted?
The pancreas secretes pancreatic amylase, trypsin and lipase into the duodenum through the pancreatic duct.
What is meant by physical digestion and chemical digestion?
Physical digestion: Mechanical breakdown of food to form small particles.
Chemical digestion: Decomposition process of complex molecules into simple molecules.
What is pepsinogen and what is its usage?
Pepsinogen is an inactive enzyme that is activated by HCl to become pepsin. Pepsin then hydrolyses proteins into polypeptides.
How are both physical and chemical digestions achieved?
Physical digestion: Chewing and peristalsis.
Chemical digestion: Enzyme reaction.
How does the ileum affect the optimal action of enzymes?
The alkali medium in the ileum allows enzymes to act at its optimum.
The food in the stomach is mixed with gastric juice and is churned by peristaltic action of the stomach wall muscles. The contents in the stomach finally change to a semifluid called…
…chyme.
Name the process of hydrolysis occurring with lipids.
Lipase hydrolyses lipids into fatty acids and glycerols.
What is the function of mucus in the stomach lining?
To protect the stomach walls from the reaction of HCl and digestive enzymes.
What do the glands on the ileum wall secrete?
Mucus and intestinal juice which contains maltase, sucrase, lactase, lipase and erepsin.
