Motility of the GI tract Flashcards
What is the landmark between the upper and lower GI tract?
The ligament of Treitz
Which site in the GI tract is the primary site of absorption?
The small intestine
Which nerve plexus is involved in peristalsis?
Myenteric nerve plexus
Describe the nervous system control of peristalsis within the oesophagus (secondary wave)
facilitated by stretch. under control of vagus nerve and the myenteric plexus
Why does the GI tract require sphincters?
To prevent the backwards movement of the GI tract
The myenteric plexus is located in the ________ layer and controls ________ and contraction.
muscular, motility
The submucosal plexus is located in the ___________ layer and controls glandular _________ and blood flow.
submucosal, secretions
What is the term for the folds of the stomach that stretch to hold the contents of the stomach?
Ruggae
Which phase of deglutition is the only voluntary one?
The oral phase (initiation of swallowing in the oral cavity)
Signals from motor efferents from which cranial nerves promote muscular contractions within the pharyngeal phase of swallowing?
Trigeminal (V)
Glossopharyngeal (IV)
Vagal (X)
What are the four layers of the GI tract?
- Mucosa (innermost layer)
- Submucosa
- Muscularis externa
- Serosa (outermost layer)
This layer is the interface between the contents of the abdominal cavity and the GI tract
the epithelium (part of the mucosal layer)
Which layer of the GI tract contains the GALT?
The lamina propria (part of the mucosal layer)
This layer contains a thin layer of CT which is home to a multitude of bv’s and lymphatic vessels.
This is where we encounter the nerve plexus that is responsible for the secretion of substances
submucosal layer
In which layer of the GI tract will the myenteric nerve plexus be found?
In the muscularis externa layer. The myenteric plexus is in between a layer of circular muscle and a layer of longitudinal muscle.
this layer encompasses the GI tract. Responsible for protection, and also secretes substances to reduce friction between the GI tract and neighbouring structures.
The serosa
What two features of the small intestine aid absorption of nutrients?
Microvilli in the brush border, and large surface area
What reflex activates the myenteric plexus to promote peristalsis of the small intestine?
gastroenteric reflex (stimulated by either duodenal distention or changes to pH)
What feature separates the ileum from the ascending colon?
the ileo-cecal valve
What is the function of the ileo-cecal valve?
Prevents back flow of contents from ascending colon (the cecum) into the small intestine
In the large intestine, mixing occurs mainly due to _______ __________.
haustral churning
What are the two reflexes that initiate “mass movements” of bowel contents from the sigmoid colon to the rectum?
the gastro-colic and duodeno-colic relfexes (occur after meals, on stretching from the ANS)
Movement of which muscle generates the pressure gradient needed to permit emesis?
the diaphragm
Which hormones STIMULATE motility of the small intestine?
Gastrin, CCK, insulin, and motilin
Which hormones have an INHIBITORY action on the motility of the small intestine?
Secretin, glucagon
What anatomical structure controls the emptying of chyme from the ileum into the colon?
The ileocecal valve
Absence of the migrating motor complex in the small intestine can lead to what?
Bacterial overgrowth of the small intestine
what are the three phases of emesis?
Nausea, retching, and expulsive phase (emesis)
what anatomical structure prevents the aspiration of vomit into the respiratory tract during emesis?
the epiglottis
Where is the “vomiting” centre of the CNS?
In the brainstem- the medulla oblongata
What detects blood bourne chemicals and innervates the central “vomiting centre?”
the chemoreceptor trigger zone
Name the three main things that can trigger the emetic reflex
Vomiting centre in the medulla
Chemreceptor trigger zone (detects blood born chemicals)
Laryrinth/inner ear vestibular system
