Upper GI Flashcards
Digestion def
The process of breaking down macromolecules to allow absorption
Absorption def
The process of moving nutrients & water across a membrane
Give the 4 layers of the gut wall and what they’re made of
Mucosa:
-Epithelium
-Lamina propria
-Muscularis mucosae
Submucosa:
-Connective tissue
Muscularis:
-Smooth muscle(With nerve plexus)
Serosa/Adventitia:
-Connective tissue+/-epithelium
How many teeth are there in total and how many of each type?
32 total
8 incisors
4 canines
8 premolars
12 molars
What layer of gut wall are the longitudinal muscles in?
Muscularis
What layer of gut wall are the circular muscles in?
Muscularis
What layer of gut wall is the colonic epithelium?
Mucosa
What layer of gut wall are the submucosal glands in?
Submucosa
What layer of gut wall are the ganglion nerves and cells in?
Submucosa + Muscularis
What layer of gut wall is the stomach epithelium in?
Mucosa
What layer of gut wall is the small intestine epithelium in?
Mucosa
What is the major muscle involved in biting force?
Masseter
-Several other muscles control jaw position
What are the salivary glands and what do they secrete?
-Parotid
-Sublingual
-Submaxillary
Secrete:
Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion)
What is the purpose of the tongue and what are the 2 divisions of muscles that control it and what different functions do they control?
Assists mechanical digestion
Extrinsic muscles
-Gross movement of tongue
Intrinsic muscles
-Fine motor control and food movement
At what vertebral level does the trachea start?
C5-C6
At what vertebral level does the trachea finish?
T8
At what vertebral level does the diaphragm start?
T10
At what vertebral levels does the oesophagus start and end?
Starts at C5
Ends at T10
At what vertebral level does the aorta start?
T2ish
Function of the oesophagus
Conduit for food, drink & swallowed secretions from pharynx to stomach
Is the oesophageal epithelium keratinising?
It is non-keratinising
What is the oesophagus lubricated by?
Mucus and saliva
What does the wear and tear lining nature of the oesophagus mean?
It is in the extremes of temperature and texture
What kind of sphincters are present in the oesophagus and how are they controlled?
Upper oesophageal sphincter: Skeletal muscle
Lower oesophageal sphincter: Smooth and skeletal muscle
What type of muscle is responsible for oesophageal peristalsis?
Circular muscle
What is interesting about the association between gravity and the lower oesophageal sphincter?
The smooth muscle is tonically active- So is able to keep food from travelling back up the oesophagus when upside down
What occurs in stage 0 in swallowing?
Oral phase:
Chewing & saliva prepare bolus
Both oesophageal sphincters constricted
What occurs in stage 1 in swallowing?
Pharyngeal phase:
Pharyngeal musculature guides food bolus towards oesophagus
Both oesophageal sphincters open
What occurs in stage 2 in swallowing?
Upper oesophageal phase:
Upper sphincter closes
Superior circular muscle rings contract & inferior rings dilate
Sequential contractions of longitudinal muscle
What occurs in stage 3 in swallowing?
Lower oesophageal phase:
Lower sphincter closes as food passes through
How does the epithelial structure change when passing the gastro-oesophageal junction?
Goes from stratified squamous to simple columnar
What muscle is gastric reflux prevented by?
The diaphragm
What is the purpose of the gastro-oesophageal epithelial transition
Transition from a largely musculature structure to a secretory structure
3 major stomach functions
Breaks food into smaller particles (acid & pepsin)
Holds food, releasing it in controlled steady rate into duodenum
Kills parasites & certain bacteria
What forms the stomach gel coating?
HCO3- trapped in the mucus gel
What is secreted by the antrum?
Gastrin
Where is stomach mucus secreted?
Cardia and pyloric regions
What is secreted by the body and fundus?
Mucus, HCl, Pepsinogen
What is the pH at the epithelial surface and in the lumen?
Epithelial surface: 6-7
Lumen: 1-2
How much stomach acid is produced per day?
2L
What are the 2 types of muscle contractions in the stomach, what do they each do and which nervous systems are needed for them to function?
Peristalsis - 20% of contractions
Propels chyme towards colon-more powerful as moves from LOS to pyloric sphincter
ANS essential
Segmentation - 80% of contractions
Weaker.
Fluid chyme towards Pyloric sphincter
Solid chyme pushed back to body
Stretching activates enteric NS
What are gastric chief cells and what do they secrete?
Protein-secreting epithelial cell
Abundant RER
Golgi packaging and modifying for export
Masses of apical secretion granules
Secretes pepsinogen
What are 3 cytoplasmic components of gastric parietal cells?
Many mitochondria (requires lots of ATP)
Internal canaliculi (secretory surface)
Cytoplasmic tubulovesicles (contain H+/K+ ATPase)
What occurs to gastric parietal cells when in secreting state?
Microvilli project into canaliculi
Tubulovesicles fuse with membrane
How do gastric parietal cells produce/secrete stomach acid?
K+ is drawn into the parietal cell through the basal membrane, releasing Na+ through an antiporter
K+ moves through another channel directly into the cannaliculi
Carbonic Anhydrase catalyses the reaction between CO2 and H2O to produce HCO3-, which is antiported with Cl-, Cl- travels into the cannaliculi through another direct channel
H+ moves into the cannaliculi through an ATPase H+/K+ antiporter
H+ and Cl- combine in the gastric lumen to form HCl - stomach acid
What occurs to pepsinogen when reacted with HCl?
Converts to pepsin to break down proteins
What is the function of gastrin and what prompts its secretion?
Produced from G-cells in the pyloric antrum
G cells stimulated by distension, produces gastrin which then stimulates parietal cells to produce HCl
What are the 3 phases of gastric secretion?
Cephalic
Gastric
Intestinal
What occurs in the cephalic phase of gastric secretion?
Vagus innervation of the stomach to produce HCl
What occurs in the gastric phase of gastric secretion?
Food enters the stomach, still innervated by the vagus nerve leading to production of HCl and pepsin
What occurs in the intestinal phase of gastric secretion?
Chyme is produced in duodenum
When ph<2 or lipids are present in duodenum gastric inhibitory peptides like cholecystokinin and secretin inhibit gastric secretion(HCl/pepsin).
What occurs in the excitatory intestinal phase of gastric secretion?
Protein concentration in duodenum stimulates gastric secretion
SUMMARY OF GASTRIC SECRETORY PHASES
