Upper gastrointestinal Tract Flashcards
What is digestion?
Digestion is the process of breaking down macromolecules to allow absorption
What is absorption?
Absorption is the process of moving nutrients & water across a membrane
What is the basic plan of the gut wall?
- Mucosa
- epithelium
- Lamina propri (loose connective tissue)
- Musculsris mucosae - submucosa (connective tissue contain nerve plexus)
- Muscularis: smooth muscle containing nerve plexus
- Seroda/Adventitia: connective tissue +/- epithelium
Describe the teeth
TEETH - 32 in total •8 incisors •4 canines •8 premolars •12 molars
What are the muscles in the oral cavity?
•Masseter muscle – largest jaw muscle
- responsible for biting
•Several muscles control position of mandible
What are the salivary glands?
•Food mixed with saliva (aqueous secretion & digestive enzymes)
•Lingual lipase (fat digestion)
Salivary amylase (carbohydrate digestion
What does the tongue do?
- Intrinsic muscles
- fine motor control & moving food
- Extrinsic muscles
- gross movement of tongue (in, out, up & down)
- Assists mechanical digestion
What is the epithelium of the oesophagus like?
- Non-keratinising
- ‘Wear & Tear’ lining (extremes of temp. & texture)
- Lubrication – Mucus secreting glands (& saliva)
What is the muscle like in oesophagus?
- Tonically active
- Swallowing centre
- Peristalsis
- Circular muscle
What is the Gastro-oesphgeal junction?
- Reflux – prevented by diaphragm
- Epithelial transition
- Gastric folds - rugae
What is stage 0 in swallowing?
- Stage 0: Oral phase
- Chewing & saliva prepare bolus
- Both oesophageal sphincters constricted
What is stage 1 in swallowing?
- Stage 1: Pharyngeal phase
- Pharyngeal musculature guides food bolus towards oesophagus
- Both oesophageal sphincters open
What is stage 2 in swallowing?
- Stage 2: Upper oesophageal phase
- Upper sphincter closes
- Superior circular muscle rings contract & inferior rings dilate
- Sequential contractions of longitudinal muscle
What is stage 3 in swallowing?
- Stage 3: Lower oesophageal phase
* Lower sphincter closes as food passes through
What are functions of stomach?
- Breaks food into smaller particles (acid & pepsin)
- Holds food, releasing it in controlled steady rate into duodenum
- Kills parasites & certain bacteria
how does acid stop going up?
- Neg pressure in thorax
- Pos in abdomen
- Os in Abdominal in collapsed state
- Liagemtns
When does epithelium change?
- Squamous excretory in stomach
- Protective in oesophagus
- Pink and red mucous meet
- When acid in, inflammation of oesophagus and red streaks and if persistent for years epithelium changes columnar epithelium protect.
- Metaplasai, displasai and then cancer
When does epithelium change?
- Squamous excretory in stomach
- Protective in oesophagus
- Pink and red mucous meet
- When acid in, inflammation of oesophagus and red streaks and if persistent for years epithelium changes columnar epithelium protect.
- Metaplasia, displasai and then cancer
What are the different sections of the stomach?
- Cardia & Pyloric Region: Mucus only
- Body & Fundus: Mucus, HCl, pepsinogen
- Antrum: Gastrin
- Invaginates into mucosa – Tubular glands
What is special about stomach?
-Acid •2L/day •150mM H+ (3 mill x that in blood) -Mucins = gel coating •HCO3- trapped in mucus gel -pH at: •Epithelial surface = 6-7 •Lumen = 1-2
What happens in peristalsis?
20% stomach contractions
•Propels chyme towards colon
•more powerful as moves from LOS to pyloric sphincter
•ANS essential
What happens in segmentation?
80% stomach contractions •Weaker. • Fluid chyme towards Pyloric sphincter •Solid chyme pushed back to body •Stretching activates enteric NS
What is the chief cell?
- Protein-secreting epithelial cell
- Abundant RER
- Golgi packaging and modifying for export
- Masses of apical secretion granules
What does the chief cell secrete?
pepsinogen
HCL coverts to pepsin
What is the parietal cell?
Resting:
•Many mitochondria (requires lots of ATP)
•Cytoplasmic tubulovesicles (contain H+/K+ ATPase)
•Internal canaliculi (extend to apical surface)
-Helps in formation of HCL
How is HCL produced?
- CO2 from capillaries goes into parietal cell
2, CO2 mixes with water with enzyme carbonic anhydroase - Potassium comes into cells from capillaries and gets secreted into gastric lumen
- Na+ into capillaries
- K+ gets ex changed with H+ via hydrogen potassium ATPase pump
6, Bicarbonate acid goes back into circulation - Hydrogen ion combines with chloride ion atP provides energy
- H+ and K+ gets exchnaged
- K+ ion goes into cells and H+ goes out of cell
What is gastrin?
-Hormone secreted by G cells
-Stimulates to partial cell to release HCL
•Pyloric antrum
•Local peptide hormones – Gastrin
•Stimulate histamine release from chromaffin cells (lamina propia)
What is the cephalic phase?
- Parietal cell needs stimulus
1. Neuro: through sight and smell: vagus nerve
2. Homronal local pancreatic: gastrin secreted by pancreas into bloodstream stimulating parietal cells, hormone
3. Local - Local reflexes, local neural response from nerves in stomach wall: different neural plexuses
- Makes stomach secrete more HCL and more enzymes
What is intestinal phase?
- enterhormones: Signal from intestinal to brain come back via vagus nerve
- Or small bowel secrete hormones: gastric inhibitory peptide, cholecystokinin and secretin (what are entergastrones)
What are enterogastrones?
Enterogastric reflex either stimulates or surpasses secretion of HCL or eosin)
What are excitatory intestinal phase?
Protein concentration in duodenum stimulates gastrin secretion
How can you produce drugs to decrease acid secretion?
- G poteins
- Histamine
- Acetylcholine
- Block gastrin secretion
- Omeprazole: inhibit H+ and K+ Atpase
- Ranitidine for histamine-2 blocker (reversible inhibitor if action of histamine at H2 histamine receptor in gastric pariatal cell)
Which stimuli would be most likely to decrease acid secretion in stomach?
Chyme fatty acid content
