BIOL 133 GI APPLE

• What is the digestive system composed of?

  The digestive system includes the organs of the alimentary canal and accessory structures.
• What is the alimentary canal?


  The alimentary canal is a long, hollow tube that extends from the mouth to the anus and is involved in the digestion and absorption of food.
• What forms the alimentary canal?

  The alimentary canal forms a continuous tube that is open to the outside environment at both ends.
• List the organs of the alimentary canal.

  The organs of the alimentary canal are the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• What are the accessory digestive structures?

  The accessory digestive structures include the teeth, tongue, salivary glands, liver, pancreas, and gallbladder.
• What are the four tissue layers of the alimentary canal wall?

  The four tissue layers of the alimentary canal wall are mucosa, submucosa, muscularis, and serosa.
• What is the role of the enteric nervous system?


  It controls the gut's functions.
• How does the autonomic nervous system contribute to the digestive system?


  It provides additional control over digestion from outside the gut.
• What do blood vessels do in the digestive system?

  Blood vessels transport nutrients absorbed by mucosal cells and supply oxygen to the digestive organs.
• How are lipids absorbed?

  Lipids are absorbed via lacteals.
• What is the second function of blood vessels in digestion?

  They supply nutrients and oxygen to the digestive organs.
• How are the more anterior parts of the alimentary canal supplied?

  They are supplied by arteries branching off the aortic arch and thoracic aorta.
• How is the inferior alimentary canal supplied?

  It is supplied by arteries branching from the abdominal aorta.
• What organs does the celiac trunk supply blood to?

  The celiac trunk supplies blood to the liver, stomach, and duodenum.
• Which arteries supply blood to the small and large intestines?

  The superior and inferior mesenteric arteries supply blood to the remaining small and large intestines.
• What are the main functions of the digestive system?

  The digestive system ingests and digests food, absorbs nutrients, and excretes indigestible components.
• What are the six activities involved in digestion?

  The six activities are ingestion, motility (including propulsion and peristalsis), mechanical digestion, chemical digestion, absorption, and defecation.
• How are the processes of digestion regulated?

  The processes of digestion are regulated by neural and hormonal mechanisms.
• What are some examples of neuronal mechanisms involved in digestion regulation?

  Neuronal mechanisms include mechanoreceptors, chemoreceptors, and osmoreceptors.
• Where are GI hormones secreted from?

  GI hormones are secreted by endocrinocytes located in the mucosal epithelium of the stomach and small intestine.
• What does gastrin do?

  Gastrin stimulates the secretion of gastric acid by the parietal cells of the stomach mucosa in response to the presence of food.
• What hormones are made by the duodenum?

  The duodenum makes secretin, which tells the pancreas to make bicarbonate, and cholecystokinin (CCK), which tells the pancreas to make enzymes and the gallbladder to release bile. It also makes gastric inhibitory peptide, which slows down stomach activity.
• What starts mechanical digestion in the mouth?

  Mechanical digestion in the mouth begins with the tongue and teeth.
• What begins chemical digestion in the mouth?


  Saliva begins chemical digestion in the mouth.
• What is saliva primarily composed of?

  Saliva is primarily water (98 to 99.5%) along with ions, glycoproteins, enzymes (such as amylase), growth factors, and waste products.
• What is the function of the pharynx?

  The pharynx serves as a passage for food from the mouth to the esophagus for digestion and for air from the nasal cavity to the larynx for respiration.
• What happens during swallowing (deglutition)?

  During swallowing, the soft palate rises to close off the nasopharynx, the larynx elevates, and the epiglottis folds over the glottis to prevent food from entering the trachea.
• What are the components of the esophagus?

  The esophagus includes an upper esophageal sphincter made of skeletal muscle, a lower esophageal sphincter made of smooth muscle, and cells that secrete mucus to ease the passage of food bolus.
• What is the function of the upper esophageal sphincter?

  The upper esophageal sphincter controls the movement of food from the mouth into the esophagus.
• What is the function of the lower esophageal sphincter?

  The lower esophageal sphincter regulates the passage of food from the esophagus into the stomach and prevents the backflow of stomach contents into the esophagus.
• What activities does the stomach participate in during digestion?

  The stomach participates in all digestive activities except ingestion and defecation. It vigorously churns food.
• What does the stomach secrete to aid in digestion?

  The stomach secretes gastric juices that break down food and absorb certain drugs, including aspirin and some alcohol.
• What role does the stomach play in digestion?

  The stomach begins the digestion of protein and continues the digestion of carbohydrates and fats.
• What is chyme and how is it released from the stomach?

  Chyme is the acidic liquid formed by the stomach's digestion process. It is gradually released into the small intestine through the pyloric sphincter.
• What do parietal cells produce?

  Parietal cells produce hydrochloric acid (HCl) and intrinsic factor.
• What is the role of hydrochloric acid produced by parietal cells?

  Hydrochloric acid (HCl) produced by parietal cells is responsible for the high acidity (pH 1.5 to 3.5) of the stomach contents. It activates the protein-digesting enzyme pepsin and helps to denature proteins.
• What do chief cells secrete?

  Chief cells secrete pepsinogen, the inactive proenzyme form of pepsin.
• What is the role of pepsinogen secreted by chief cells?

  Pepsinogen, secreted by chief cells, is converted to pepsin, an active enzyme for protein digestion, in the presence of hydrochloric acid (HCl).
• What do enteroendocrine cells secrete?

  Enteroendocrine cells secrete various hormones into the interstitial fluid of the lamina propria, including gastrin.
• What are the three main regions of the small intestine?

  The three main regions of the small intestine are the duodenum, the jejunum, and the ileum.