Digestion and Intestinal Absorption (part 1) Flashcards
state the 4 primary functions of the digestive system
- digestion
- absorption
- secretion
- mobility
state the main hierarchical structure of the gastrointestinal tract (6 main structures)
mouth –> pharynx –> oesophagus –> stomach –> small intestine –> large intestine
state the 4 accessory organs in the gastrointestinal tract
- salivary glands
- liver
- gallbladder
- exocrine pancreas
state the 4 main structures (inside –> out) of the gastrointestinal wall
- mucosa
- sub-mucosa
- muscularis externa
- serosa
state the 2 enteric nervous system structures within the gastrointestinal wall
- sub-mucosal plexus
2. myenteric plexus
state, and define, the 3 structures in the ‘mucosa’ (inner layer of the gastrointestinal wall)
- epithelium - contains both endocrine + exocrine cells
- lamina propria - loose connective tissue
- muscularis mucosa - layer of smooth muscle
state, and define, the 2 structures in the ‘sub-mucosa’ (lateral to the mucosa in the gastrointestinal wall)
- blood + lymphatic vessels - penetrate layers above and below as well
- sub-mucosal plexus - a network of neurones for control of muscular activity
state, and define, the 3 structures in the ‘muscularis externa’ (lateral to the sub-mucosa in the gastrointestinal wall)
- circular muscle - contraction produces narrowing of lumen
- myenteric plexus - innervated via autonomic NS, also connected to the sub-mucosal plexus
- longitudinal muscle - contraction shortens the lumen
state, and define, the function of the ‘serosa’ (outer layer of the gastrointestinal wall) - 2 points
- connective tissue surrounding the outer surface of the tract
- sheets of connective tissue connect serosa to the abdominal wall to hold the GI tract in place
state, and explain, what it is meant by the key term - ‘cephalic phase’ (3 facts)
- brains anticipation of food (sight, smell, or thought)
- saliva production increased - parasympathetic NS activity
- stimulation of gastric juice + insulin secretion
state the 4 functions of the mouth in the digestion process
- mechanical breakdown of food
- mixing of food with saliva
- initiate chemical digestion of carbs (salivary amylase)
- antibacterial action
state the 4 functions of saliva in the digestion process
- bicarbonate (neutralises acid)
- mucus - lubricates and protects from abrasion
- salivary amylase - breakdown of carbs
- lysozymes - destroy certain bacteria (prevents tooth decay)
state the 2 functions of salivary amylase in the digestion process
- begins carb digestion
2. begins starch hydrolysis (limited - <5% starch digestion, unless chewing is prolonged)
state the function of the following: 1)Pharynx, and 2) Oesophagus in the digestion process
- Pharynx - conduction of food into oesophagus
2. Oesophagus - conduction of food into the stomach
what does the Epiglottis do during swallowing?
the Epiglottis closes to prevent aspiration of food into the trachea
explain the role of sphincters in the process of digestion
sphincters at the bottom of the Pharynx and in the opening into the stomach prevent movement of air and stomach contents re-entering the oesophagus
state, and explain, what it is meant by the key term - Peristalsis (2 points)
- the movement of contents in a tube due to progressive contraction
- this ‘wave’ compresses the lumen and forces food through
state what it is meant by the key term - ‘secondary peristalis’
if a particularly large bolus does not reach the stomach, then reflexes initiate repeated waves of activity in the muscle surrounding the oesophagus
state the 5 functions of the stomach in the digestion and absorption process
- mechanical breakdown of food (and churning - chyme)
- secretion of acid (HCl) - kills bacteria
- pepsin secreted as ‘pepsinogen’ - begins protein digestion
- gastric lipase
- storage
state the 4 functions of the small intestine in the digestion and absorption process
- chemical digestion of all nutrients (pancreatic and brush border enzymes)
- absorption of digestive end products, water, ions and vitamins
- hormone secretion
- secretion of bicarbonate rich fluid
state the 3 functions of the ‘colon’ (large intestine) in the digestion and absorption process
- absorption of ions and water
- transformation of ‘chyme’ into faeces
- storage of faeces
state what it is meant by the key term - chyme
the pulpy acidic fluid which passes from the stomach to the small intestine, consisting of gastric juices and partly digested food
state the role of the rectum in the digestion and absorption process
storage of faeces
what is needed for Vitamin B12 absorption?
gastric intrinsic factor (GIF)
what activates pepsinogen
pepsinogen is activated into pepsin by the stomaches acid environment
state the two other cell types in the stomach, as well as their functions
- entero-chromaffin-like cells (ECL) - release histamine
2. D cells - secrete somatostatin
explain the negative feedback loop of HCl secretion into the acid (3 points)
- ACh (enteric nerve), histamine and Gastrin have a positive effect on production
- HCl secretion has a positive effect on somatostatin secretion
- somatostatin inhibits action of HCl secretion, histamine secretion, and gastrin secretion
where is gastrin secreted by
G cells release gastrin
explain what it is meant by potentiation (in consideration of HCl secretion in the stomach)
activation of 3 substances combined is greater than the sum of the individual effects
state the 4 stimuli which initiate the ‘Gastric Phase’ (in the stomach)
- stomach distension
- acidity
- amino acids
- peptides
state the location in the gastrointestinal wall, and the function, of the - epithelium
mucosa, contains both exocrine and endocrine cells
state the location in the gastrointestinal wall, and the function, of the - lamina propria
mucosa, loose connective tissue (between the epithelium and the muscularis mucosa)
state the location in the gastrointestinal wall, and the function, of the - muscularis mucosa
mucosa, layer of smooth muscle
state the location in the gastrointestinal wall, and the function, of the - blood and lymphatic vessels
sub-mucosa, penetrate layers above and below as well
state the location in the gastrointestinal wall, and the function, of the - sub-mucosal plexus
sub-mucosa, a network of neurones for control of muscular activity
state the location in the gastrointestinal wall, and the function, of the - circular muscle
muscularis externa, contraction produces narrowing of the lumen
state the location in the gastrointestinal wall, and the function, of the - myenteric plexus
muscularis externa, innervated by the autonomic NS, also connected to the sub-mucosal plexus
state the location in the gastrointestinal wall, and the function, of the - longitudinal muscle
muscularis externa, contraction produces shortening of the lumen
state what it is meant by the key term - churning
The stomach lining contains muscles which physically squeeze and mix the food with strong digestive juices
