Flashcards in Physiology of mastication, swallowing & GI tract motility Deck (70):
What is the Digestion tract?
Series of Organs running from Mouth to Anus (Oral to Aboral)
How is the digestive tract separated?
By the use of Sphincters
What is the function of the Mouth and Oropharynx?
Chop food, lubricate it, start carbohydrate and fat digestion, propel food to oesophagus
What is the function of the Oesophagus?
Transportation of food to the stomach
What is the function of the stomach?
-Stores food temporarily.
- Continues with digestion
-Initiates protein digestion
- Delivery of Chyme to the small intestine
What is the function of the small intestine?
Principal site of absorption of nutrients
What is the function of the Large intestine?
- Reabsorb fluids and electrolytes
- Stores faecal matter before regulated expulsion
What are the accessory structures of the Digestive tract?
- Salivary glands
- Liver and Gall bladder (Hepatobiliary system)
What are the parts of the small intestine?
What part of the pancreas is used in the digestive system?
What sphincter prevents reflux?
The lower Oesophageal sphincter
What are the basic digestive processes?
What is motility?
This is the mechanical activity that involves smooth muscle. This includes:
What parts of digestive system bring about motility throughout the digestive tract?
External anal sphincter
What causes secretion form the accessory structures for digestion?
Hormonal or Neural signals
What do digestive secretions contain?
Organic compounds (enzymes, bile, mucus)
What is digestion?
The breakdown of biochemical foodstuffs from large indigestible units into smaller soluble units
How are Carbohydrates broken down?
Carbohydrates are broken down into Monosaccharides by Amylases and Disaccharidases
How are proteins broken down?
Proteins are broken down into amino acids, dipeptides and tripeptides by Proteases and Dipeptidases
How are fats broken down?
Fats are converted into Monoglycerides and three fatty acids by Lipases
What is Absorption?
The Transfers of absorbable products of digestion from the digestive tract to the blood or lymph
What are the layers of the digestive tract wall?
What is contained in the mucosa layer of the digestive tract wall?
What is contained in the submucsoa layer?
• connective tissue
• larger blood and lymph vessels
• nerve network – submucous plexus
What is the serosa?
The series is the outermost layer of the digestive tract wall. It is fibrous in nature and secrets secretes serous fluid which allows organs to move against each other.
How is Gastrointestinal motility achieved?
Activity of smooth muscle
What does the circular muscle contraction do to the lumen of the digestive tract?
Lumen becomes narrower and longer
What does contraction of the longitudinal muscle cause to the lumen of the digestive tract?
Lumen becomes shorter and fatter
What allows the spread of electrical activity in the GI tract?
What do the Gap junctions allow do for the signal?
Allows spread of electrical current to all cells and allows them to work as a syncytium
Describe the electrical activity in the stomach, small intestine and large intestines?
Spontaneous electrical activity that occurs as slow slaves
What shape are gap junctions?
They are spindle and allows cells to be attached to all of their neighbours
What produces the slow waves in the digestive tract?
Interstitial cells of Cajal - These are pacemarker cells
Describe contraction in terms of electrical current the digestive tract?
Contraction can only occur if the slow wave amplitude is sufficient to trigger the action potential
What is the upstroke of the action potential mediated by in the digestive tract?
Mediated by voltage-activated Ca 2+ channels
What is the downstroke of the action potential mediated by
Mediated by K+ voltage activated channels
How is the force of contraction determined in terms of action potentials for the digestive tract?
Force is related to the number of action potential/ the length of burst of the discharged that are above the threshold.
Where are the Interstitial cells of Cajal located?
Located in the Longitudinal and circular muscle of the submucosa
How many contractions/ slowness does the stomach have per minute?
3 slow waves per minute
How many contractions/ slowness does the small intestine have per minute?
1-12 per minute
8 in the terminal ileum
Describe the difference in slow waves in the part of the small intestine?
The slow waves are less in the distal small intestine than the proximal intestine. This means there is a net movement forwards in the small intestine
Describe the difference in slow waves in the parts of the large intestine?
The slow waves are less in the distal large intestine than the proximal intestine. This means there is a net movement backwards in the large intestine
What is the number of slow waves of the large intestine per minute?
8 waves per minute
Where are the cell bodies of the enteric nervous system located?
The cell bodies are located within the Myenteric Plexus and the Submucous Plexus
How are the ganglia in the enteric nervous system in the intestine connected?
Connected by the interganglionic fibre tracts
Describe the overall regulation of the go tracts nervous system?
It is auto regulated through the enteric nervous system. However there is extrinsic modifying factors from the central nervous system and hormones
What is the parasympathetic innervation for the digestive tract?
Vagal nerves and sacral nerves. This is a vagalsacral outflow
What are the effects of the parasympathetic system on the GI tract?
Increased secretions, Increased blood flow and smooth muscle contraction
Causes relaxation of some sphincters
What is the sympathetic innervation of the GI tract
Where does the sympathetic system synapse to the ganglia?
In the pervertebral ganglia:
What is the effect of the sympathetic system on the GI tract?
Decreased motility, secretion and blood flow.
Describe the pathway for a nerve reflex
Sensory neruone to Interneurone to Effector neurone
What is an example of a local reflex?
What is an example of a short reflex?
Intestino-Intestinal Inhibitory Reflex
What is an example of a long reflex?
What is Peristalsis?
A wave of contraction that normally proceeds along the gut in an aboral direction
Describe the mechanism of Peristalsis?
Muscle contractions behind the bolus of food. Longitudinal muscle relaxes and release of VIP and NO from the inhibitory motor-neurone. The circular muscle contracts and releases ACh and substance from excitatory motor-neurone.
Muscle relaxes infant of the bolus of food. Longitudinal muscle contracts due to release of ACh and substance P. The circular muscle relaxes due to release of VIP and NO
What is segmentation?
This is mixing or churning movements, rhythmic contractions of circular muscle layer that mix and divide luminal contents.
Where are tonic contractions found and what are they?
Tonic contractions are found in the sphincters of the GI - they are sustained contractions.
What is the function of the Upper oesophageal sphincter?
Relaxes to allow swallowing. It closes during inspiration
What is the function of the Lower oesophageal sphincter?
Relaxes to permit entry of food to the stomach and closes to prevent reflux of the gastric contents
What is the function of the pyloric sphincter?
Regulated gastric emptying and usually prevents duodenal gastric reflux
What is the function f the Ileocecal sphincter?
Regulates the flow from the ileum to the colon
What are the 6 sphincters of the GI tract?
Upper Oesophageal sphincter
Lower Oesophageal sphincter
What are the parts of the mouth?
What is the medical term for swallowing?
What are the two phases of deglutition?
Describe the stages of the oropharyngeal stage of deglutition?
Bolus formed in the mouth
Tongue forces bolus into pharynx
Pressure stimulates pharyngeal pressure receptors
Afferent impulse to the swallowing centre in the medulla
Efferent initiate an all or nothing response - signal may fire or not fire
Upper oesophageal sphincter opens
Good passes through pharynx into the oesophagus
What happens to the larynx and the vocal cords during swallowing?
The larynx is elevated and the vocal cords close across the larynx