Digestive System Flashcards
(37 cards)
Name all the organs of the gastrointestinal (GI) system; Name and discuss the functions of three accessory digestive organs associated with the oral cavity
rgans of the GI system: Oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus. Accessory organs with oral cavity: teeth (mastication), tongue (manipulation of food/bolus formation), salivary glands (secrete saliva with enzymes like amylase and lingual lipase).
Digestion – name and discuss the three types of physical digestion. Describe: (a) peristalsis (b) segmentation
Three types of physical digestion: Mastication (chewing), Segmentation (back-and-forth mixing in stomach/intestine), Emulsification (fat droplet breakdown by bile). Peristalsis: rhythmic contractions that move content distally. Segmentation: mixing movements that enhance contact with digestive juices.
What is the function of saliva in digestion?
Saliva lubricates food, dissolves chemicals for taste, and contains salivary amylase (digests starch) and lingual lipase (digests triglycerides, esp. in infants). It also protects the oral cavity.
Name and discuss the voluntary and involuntary phases of deglutition (swallowing)
Voluntary phase: Tongue pushes bolus into oropharynx. Involuntary (pharyngeal-esophageal) phase: Uvula blocks nasopharynx, epiglottis blocks airway, peristalsis propels bolus into esophagus.
Name the 2 parts of the pharynx involved in deglutition; “swallowed substances have the right of way over airflow” – discuss how this is accomplished.
Oropharynx and laryngopharynx are involved in deglutition. Swallowed substances have the right of way due to coordinated closure of the nasopharynx (by uvula) and laryngeal inlet (by epiglottis).
Name and describe the 4 layers of GI wall; name, give the location and the functions of the two enteric plexuses.
4 layers of GI wall: (1) Mucosa - includes epithelium and lamina propria, sometimes with microvilli; (2) Submucosa - contains Meissner’s plexus; (3) Muscularis externa - circular & longitudinal muscles, Auerbach’s (myenteric) plexus; (4) Serosa - outermost peritoneal layer.
Why is the lower esophageal sphincter, also known as a cardiac sphincter referred to as a physiological sphincter?
The lower esophageal (cardiac) sphincter is called a physiological sphincter because it lacks a distinct thickened muscular ring but functions via diaphragm reinforcement. .
Explain how this contributes to GERD (gastroesophageal reflux disease)
If weakened, acidic reflux occurs -> GERD
Discuss the two types of modifications of the gastric wall. What is chyme?
Gastric wall modifications: (1) Gastric pits with glands (chief, parietal, G cells, etc.), (2) Rugae - folds that flatten to expand volume. Chyme is the semifluid mix of food and gastric juice.
Which organ in the GI tract is the most distensible and why?
The stomach is the most distensible GI organ, expanding from 50 mL to up to 4 liters, due to flattening of rugae.
What are the locations and functions of the greater omentum and the lesser omentum ?
Greater omentum: hangs from the greater curvature of the stomach; stores fat, contains immune cells. Lesser omentum: connects lesser curvature to liver; pathway for blood vessels.
Name and indicate the secretion/s of each type of cell in the gastric glands
Gastric gland cells: Chief cells - pepsinogen (zymogen), gastric lipase; Parietal cells - HCl, intrinsic factor; G cells - gastrin; Enterochromaffin-like cells - histamine; D cells - somatostatin; Mucous cells - alkaline mucus. Pepsinogen is secreted as inactive to avoid autodigestion.
What do the parietal cells produce?
Parietal cells - HCl, intrinsic factor;
What cell type secretes a zymogen and why?
Chief cells - pepsinogen (zymogen),
The gastric juice is highly acidic (pH 1.3 – 2) – what are functions of the HCl?
D.12 (Digestive System):
Functions of HCl: activates pepsinogen to pepsin, denatures proteins, kills pathogens. Maintains pH ~2 for digestion.
Explain 3 ways the gastric wall protects itself against corrosion by the high acidic gastric content.
Protection against acid: (1) thick alkaline mucus layer; (2) tight epithelial junctions; (3) rapid cell turnover. Ulcers form when these are breached.
How do s gastric ulcers form?
Ulcers form when these are breached.
Name and discuss the mechanism of action of 4 different types of antiulcer drugs
Four drugs: antacids (neutralize acid), H2 blockers (block histamine), PPIs (block H+ pumps), antibiotics (e.g., for H. pylori).
What is peptic ulcer disease (PUD)? What is the function of Brunner’s glands?
Peptic ulcer disease = gastric + duodenal ulcers. Brunner’s glands in the duodenum secrete bicarbonate-rich fluid to neutralize acid and prevent ulcers.
What organ in the GI tract is the longest?
Small intestine is the longest GI organ.
What organ is between the pyloric sphincter and the ileocecal valve?
The small intestine
Name the three parts of the small intestine.
duodenum, jejunum, ileum
Name and discuss the structural modifications of the small intestinal wall that increase the surface area available for absorption. What is the brush border?
Surface area enhancers: (1) Plicae circulares - slow chyme movement; (2) Villi - folds with blood/lacteals; (3) Microvilli - form the brush border with enzymes (e.g., lactase). Brush border enzymes complete digestion.
Explain why alcoholics and individuals who have undergone bariatric surgery may develop pernicious anemia
Parietal cells secrete intrinsic factor for B12 absorption in ileum. Alcoholics/bariatric surgery patients may lack intrinsic factor, causing pernicious anemia.
