Gastrointestinal tract Flashcards
Describe the main components of the GI tract
mouth, oesophagus, stomach, (pancreas, liver, gallbladder), small and large intestine, anus
Discuss the control mechanisms of the GI tract
- autonomic nervous system
- parasympathetic nerves stimulate digestion
- sympathetic nerves inhibit digestion - Enteric nervous system - 2 nerve plexus in the gut walls can sense the luminal contents and control muscles and glands (2nd brain)
- myenteric plexus and submucosal plexus
- has sensory, motor, interneurone, muscle and gland components - Gut peptides - paracrine and hormonal
(neural, paracrine and hormonal)
Describe gastric functions (stomach)
Motility - gastric accommodation, trituration, gastric emptying
Digestion - digestive juice
Protection - acid/proteases, mucus
Absorption
Discuss the morphology of the gastric glands
Gastric pits - indentations in the stomach epithelial lining which are the entrances to 3-5 tubular shaped gastric glands
then other types of cells in the gland - mucous neck, parietal, chief, enteroendrocine
How is the function of the GI tract achieved overall? (4 ways)
Digestion
chemical - enzymes
mechanical - motility (mixing, grinding)
absorption
Approx how much saliva in ml is secreted?
1500ml
Approx how much bile, pancreatic and intestinal secretions in ml?
bile - 500ml
pancreatic - 1500ml
intestinal - 1500ml
Approx how much is absorbed in ml from the small intestine?
8500ml
What are the transit times in the mouth, oesophagus, small intestine and large intestine?
Mouth - 1 min
Oesophagus - 10 seconds
small intestine - 3-6 hours
large intestine - 1-2 days
What are the 4 levels of structural organisation of the GI tract?
Mucosa
Submucosa
Muscularis
Serosa
What are the 4 levels of structural organisation of the GI tract?
Mucosa (mucous epithelium, lamina propria, muscularis mucosse)
Submucosa
Muscularis (circular and longitudinal muscle layers)
Serosa (connective tissue and peritoneum)
What is swallowing/deglutition?
process by which food passes from mouth to stomach
What are the 3 phases of swallowing?
Oral phase
Pharyngeal phase
Oesophageal phase
Which phases of swallowing are voluntary and involuntary?
Oral - voluntary
Pharyngeal - involuntary
Oesophageal - involuntary
What happens in the oral phase?
Tongue moves upwards- compress bolus against hard palate. Respiration inhibited
Retraction of tongue forces bolus into pharynx, closes of oral cavity
What happens in the pharyngeal phase?
Involuntary movement pushes bolus from pharynx into oesophagus
Soft palate reflected backward closing nasal pharynx
What happens in the pharyngeal phase?
Involuntary movement pushes bolus from pharynx into oesophagus
Soft palate reflected backward closing nasal pharynx
how long and wide is the oesophagus?
25cm length and 2cm in diameter from pharynx to the stomach
What happens in the oesophageal phase?
Upper oesophageal sphincter relaxes and bolus moves into oesophagus
Start primary peristaltic wave (Vagal – vagus nerve)
Secondary peristaltic wave (Enteric)
Lower oesophageal sphincter relaxes
What does the lower oesophageal sphincter prevent?
Prevents reflux of material back into the oesophagus
What are the 4 main regions of the stomach?
Cardia, Fundus, Body, Pylorus
What are the two openings of the stomach?
Oesophagus and duodenum
What are the 4 main regions of the stomach?
Cardia, Fundus, Body (Corpus), Antrum/Pylorus
What is the role of mucus in the stomach?
Mechanical abrasion
Prevents autodigestion