Upper GI tract (36) Flashcards
(30 cards)
What is digestion?
the process of breaking down macromolecules to allow absorption
Which structures make up the foregut?
- oesophagus
- stomach
- liver
- pancreas
- biliary system
What are the layers of the gut wall?
- mucosa: epithelium, lamina propria, muscularis mucosae
- submucosa: connective tissue containing nerve plexus
- muscularis: smooth muscle containing nerve plexus
- serosa/adventitia: connective tissue
What is the function of the oesophagus?
- conduit for food, drink and swallowed secretions from pharynx to stomach
- traverses 3 different body cavities: neck, thorax and abdomen
What is the structure of the epithelium in the oesophagus?
- squamous, non-keratinising
- mucus secreting glands–> lubrication of food
- ‘wear and tear’ lining for extremes of temp.
What is the is the structure of the muscle in the oesophagus?
- inner circular muscle
- longitudinal muscle
What is the gastro-oesophageal junction?
- passes through diaphragmatic hiatus- diaphragm prevents reflux
- where pale pink mucosa (squamous) of oesophagus meets red mucosa of stomach (columnar)- EPITHELIAL TRANSITION
- gastric folds- rugae
Why are gastric folds present?
inc. absorptive SA
What are the 4 phases of swallowing?
- stage 0: oral phase- food broken down by teeth, saliva, tongue
- stage 1: pharyngeal phase- food goes from oral cavity to pharynx
- stage 2: upper oesophageal phase- upper sphincter opens + closes, sequential contractions of longitudinal muscle
- stage 3: lower oesophageal phase- lower sphincter opens and closes
What is absorption?
the process of moving nutrients and water across a membrane
What are the functions of the stomach?
- secrete acid and pepsin to break food into smaller particles
- hold food, releasing it in a controlled rate into duodenum
- kill parasites and certain bacteria
What is the structure of the stomach?
- cardia- just below oesophagus
- fundus- bulbous bit
- body- most of stomach
- antrum
- pylorus- outlet
- pyloric sphincter
What is the function of the circular muscle in the stomach?
- segmentation
- keeps food in stomach so can get broken down
- weaker contraction than peristalsis
- fluid chyme towards pyloric sphincter, solid chyme pushed back to body
What is a gastric chief cell?
- protein- secreting epithelial cell, so rich in RER and Golgi
- secretion granules at apex- release protein into lumen
- secretes PEPSINOGEN (proenzyme)
What is a parietal cell?
- helps to create HCl (which is important to pepsinogen–>pepsin)
- contain tubulovesicles, which house the H+/K+ ATPase pumps
- many mitochondria bc requires lots of ATP
- internal canaliculi- deep infoldings that inc. SA
How does the parietal cell work?
- CO2 comes from capillaries, mixes with water, using enzyme CARBONIC ANHYDRASE–> HCO3- and H+ produced
- K+ comes into cell from capillaries and gets secreted into gastric lumen
- K+ gets exchanged w/ H+ using the pump, and comes into the cell
- H+ goes into lumen and combines w/ Cl- to give HCl
What is the role of HCl?
converts pepsinogen to pepsin
What is gastrin?
- hormone secreted by G cells in antrum of stomach
- stimulates parietal cell to produce HCl
What are the phases of gastric secretion?
- cephalic phase
- gastric phase
- intestinal phase
What structures make up the mid gut?
- small intestine
- part of large intestine
What structures make up the hind gut?
- colon
- rectum
How many teeth do we have and what types?
32 in total
- 8 incisors
- 4 canines
- 8 premolars
- 12 molars
What muscle is responsible for biting/largest jaw muscle?
masseter muscle
What digestive enzymes are produced by the salivary glands?
- lingual lipase–> breaks down lipids
- salivary amylase–> breaks down carbohydrates
