Unit 4 Ch. 21 Flashcards
What are accessory digestive organs?
salivary glands, exocrine pancreas, liver and gallbladder
What is the GI tract composed of?
- oral cavity (mouth/pharynx)
- esophagus
- stomach
- small intestine (duodenum, jejunum, ileum)
- large intestine (cecum, appendix, colon, rectum)
We are donuts
-Yes we are
What are the 4 layers of the digestive tract (innermost to outermost)
Inner to outer:
- Mucosa
- Submucosa
- muscularis externa
- serosa
What is the Mucosa composed of?
- 3 layers, highly folded to increase SA for absorption
- mucous membrane- protective surface, exocrine:digestive juice secretion, endocrine: secretion of Blood borne hormones
- lamina propria- thin connective lymphoid
- muscularis mucosa- thin smooth muscle, modifies folding pattern.
What is are the submucosa, muscularis externs, and serosa?
- Submucosa: elasticic connective tissue. Contains blood and lymph
- Muscularis externa: 2 layers and nerve network called myentric plexus
- Serosa: CT covering secrets friction prevention fluid. Mesentery for proper position
What are the four basic digestive processes?
- Motility: mixing
- Secretion: addition of organic digestives
- Digestion: biochemical breakdown
- Absorption: transfer from GI to blood (or lymph)
How does the digestive system establish motility?
2 types of movement:
- propulsive: pushes content forward
- mixing: exposing surface area for breakdown. No net movement.
What’s true of secretions?
- energy requirement due to active transport and synthesis of secretory products.
- Material taken from blood to form secretions, then returned later.
How is digestion accomplished?
- Accomplished by hydrolysis (add H2O at binding sites)
- Proteins -> amino acids
- Fats (triglycerides)-> monoglycerides
- carbs-> monosaccharides
Where does absorption occur?
- small intestine
- uptake of small absorbable units
What is saliva?
- Mostly water (95%) then protein and electrolytes
- amylase (maltose), mucus (lube), lysozyme (antibacterial)
- AIDS SPEECH
- cleans mouth
- neutralizes acids. (mouth slightly acidic)
Salivary reflex?
- simple: chemoreceptors and -pressurereceptors with food
- conditioned: no food necessary
What are the two stages of swallowing?
- oropharyngeal stage: mouth to pharynx to esophagus
- esophageal stage: esophagus to stomach (cant stop)
- all or none, medulla center stimulated
What is the oropharyngeal stage of swallowing?
- tongue prevents re-entering of bolus
- uvula is elevated to seal nasal passage
- glottis closes and epiglottis folds over glottis
- Swallowing center inhibits breathing
What is the esophageal stage of swallowing?
- peristaltic wave pushes bolus forward
- lodged bolus triggers secondary peristaltic wave
What is the basic anatomy of the stomach?
- Gastroesophageal sphincter: prevents stomach contants to esophagus
- Fundus: thin smooth muscle, top part
- Body: main part, thin smooth muscle
- Antrum: lowest portion, thick smooth muscle
- pyloric sphincter: barrier between stomach and duodenum
What is the functional role of the stomach?
- Food storage
- HCl secretion and enzymes to begin protein digestion
- Pulverize and mix to produce chyme
What are the 4 aspects of gastric motility?
- Filling: 20x expansive.
- Storage
- Mixing: Peristaltic contractions produce chyme. Strongers ones push food through pyloric sphincter.
- Emptying
What factors affect gastric emptying?
- Stomach: amt./ fluidity of chyme
- Dudodenum: Fat (Slow process), Acid (inactivates pancreatic enzymes), Hypertonicity, Distension (too much chyme)
The following are located in the oxyntic mucosa (body and fundus). What do they do/secrete?
- Mucuous cells
- Chief cells
- Parietal cells
- Stem Cells
- Surface epithelial cells
- Mucuous cells: mucus and HCO3-
- Chief cells: pepsinogen, gastric lipase
- Parietal cells: HCl(activates pepsin) and intrinsic factor (B12)
- Stem cells: parent cells for all mucosa cells
- epithelial cells: thick, viscous alkaline mucus
- D Cells: somatostatin, inhibits acid secretion
- G cells: gastrin, acid secretion
What is located in the pyloric gland area (antrum)?
- Glands that secrete mucus/pepsinogen
- NO HCl
What is the role of HCl in the stomach?
- secreted by parietal, carbonic anhydrase
- doesn’t digest
- activates pepsinogen
- denatures proteins/kills microorgs
What is the role of pepsin?
- pepsin digests proteins
- pepsinogen stored in chief cells
- HCl cleaves to activate
- pepsin is autocatalytic