Upper GI Flashcards by Orion O’Connor

Digestion def

The process of breaking down macromolecules to allow absorption

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Absorption def

The process of moving nutrients & water across a membrane

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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

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How many teeth are there in total and how many of each type?

32 total
8 incisors
4 canines
8 premolars
12 molars

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What layer of gut wall are the longitudinal muscles in?

Muscularis

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What layer of gut wall are the circular muscles in?

Muscularis

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What layer of gut wall is the colonic epithelium?

Mucosa

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What layer of gut wall are the submucosal glands in?

Submucosa

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What layer of gut wall are the ganglion nerves and cells in?

Submucosa + Muscularis

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What layer of gut wall is the stomach epithelium in?

Mucosa

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What layer of gut wall is the small intestine epithelium in?

Mucosa

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What is the major muscle involved in biting force?

Masseter
-Several other muscles control jaw position

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What are the salivary glands and what do they secrete?

-Parotid
-Sublingual
-Submaxillary

Secrete:
Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion)

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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

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At what vertebral level does the trachea start?

C5-C6

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At what vertebral level does the trachea finish?

T4/T5

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At what vertebral level does the diaphragm start?

T10

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At what vertebral levels does the oesophagus start and end?

Starts at C5
Ends at T10

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At what vertebral level does the aorta start?

T2ish

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Function of the oesophagus

Conduit for food, drink & swallowed secretions from pharynx to stomach

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Is the oesophageal epithelium keratinising?

It is non-keratinising

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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?

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