7.4 UPPER GI PERISTALSIS (swallowing, esophageal peristalsis, and gastric motility) Flashcards
What are the focal areas of the peristalsis of the upper GI tract?
- Chewing and Swallowing (5th cranial nerve or called the trigeminal)- innervates the muscle involved in chewing and is controlled by nuclei in the brainstem. Example of a reflex mechanism.
- Esophageal Motility
- Gastric Motility
- Small Intestinal Motility
- Large Intestinal Motility
What are the 3 stages of Deglutition (swallowing)?
- Voluntary - initiates swallowing process (as swallowing begins the soft palate is pulled upward toward the nares to ensure that food doesn’t enter the nasal cavities.
- Pharyngeal - passage of food through pharynx into esophagus
- Esophageal - passage of food from pharnyx to stomach
Primary Peristalsis
(employs CNS involvement)
- Continuation of pharyngeal peristalsis
- Coordinated by swallowing center
- Cannot occur after vagotomy (striated muscle)
Secondary Peristalsis
(reflex signal occurs locally through the enteric nervous system as well as swallowing centers in medulla.
- Induced by distention
- Stretch related afferent sensory input to ENS and swallowing center are both involved
- Can and does occur after vagotomy (SM)
Esophageal Manometry
measures the strength and muscle coordination of the esophagus after swallowing
List the main themes of GI tract Motility?
*Ingestion
* Propulsion
* Digestion: mech. & chem.
* Absorption: nutrients & water
* Defecation
CVA (stroke)/cranial nerves damage
Swallowing Disorder
Aspiration – UES and pharyngeal contractions are not coordinated
- Secondary peristalsis is still functional
Muscular diseases
Swallowing Disorder
- Myasthenia Gravis: a chronic autoimmune disease that causes muscle weakness
- Polio: is an infectious disease caused by the poliovirus. It can spread through contaminated food or water.
- Botulism: a rare but potentially fatal disease that occurs when the body is exposed to a toxin produced by the bacterium Clostridium botulinum.
Anesthesia
Swallowing Disorder
aspiration of stomach contents.
GASTROESOPHAGEAL REFULX DISEASE (GERD)
- Heartburn/acid indigestion (1/10 people)
- Backwash of acid, pepsin, and bile into esophagus
- Can lead to –
- stricture of esophagus (scar tissue)
- asthma (aspiration)
- chronic sinus infection (reflux into throat
** Barret’s Esophagus**
Barrett’s Esophagus
- chronic exposure to stomach contents results in normal esophageal tissue being replaced by tissue that is similar to the intestinal lining.
- The stratifies squamous epithelium that normally lines the esophagus is replaced by a simple columnar epithelium with goblet cells as the esophagus tries to heal its damaged epithelium. This is associated with an increased risk of developing esophageal cancer.
Gastric smooth muscle
Relaxes to accommodate food - orad area (receptive relaxation which is referred to as vagovagal reflex)
- Mixes food with gastric juice
- caudad area (retropulsion)
- Propels chyme into duodenum - caudad area
(antral pump)
What factors increase Emptying?
(a) Increased tone of orad stomach
(b) Forceful peristaltic contractions
(c) Decreased tone of pylorus
(d) Absence of segmental contractions in intestine
What are factors that decrease Emptying?
Activation of receptors in intestinal mucosa initiates enterogastric reflexes. This decreases gastric emptying by:
(a) Relaxation of orad stomach
(b) Decreased force of peristaltic contractions
(c) Increased tone of pyloric sphincter
(d) Segmentation contractions in intestine
Order the sites that food would pass through/by after chewing until the bolus reaches the duodenum.
- Uvula
- Pharynx
- Upper esophageal Sphincter
- Diaphragm
- Lower esophageal Sphincter
- Cardia
- Fundus
- Antrum
- Pyloric Sphincter
