Motility of the lower GIT Flashcards
In the GIT which organs are accessory organs?
- those involved in secretion purposes
- liver
- pancrease
- gallbladder
- oral salivary glands and the tongue
What is the classification of the lower GIT?
- inferior to the suspensory muscle of the duodenum
- ligament of Treitz
What are the 4 main components of the lower GIT?
1 - small intestines
2 - large intestines
3 - rectum
4 - anus
What are the 3 parts of the small intestines, from top to bottom?
1 - duodenum = shortest
2 - jejunum = medium
3 - ileum = longest
Generally how long does digestion in the small intestines take?
- 3-5 hours
The small intestines (SI) has adapted and evolved to maximise digestion and absorption. How has the surface of the SI adapted to increase its surface area and this absorption?
- brush border micro villi
There are 2 types of motility in the small intestines, what are they?
1 - segmentation which is mixing and circulation providing maximum exposure to villi
2 - peristaltic contractions to propel chyme
During segmentation contractions of the GIT, what happens?
- mixing of chyme
- stretch receptors trigger myenteric muscle contraction
During segmentation contractions of the GIT, is there any net movement or is segmentation just to mix digesta?
- no net movement
- mixing only
During propulsive peristalsis of the GIT, is there any net movement or is segmentation just to mix digesta?
- movement of chyme through the digestive tract
During propulsive peristalsis how does the GIT know to contract and move chyme?
- stretch receptors trigger myenteric plexus stimulation of muscle contraction
- net movement forwards
In addition to stretch receptors activiting propulsive peristalsis, what else can contribute to GIT motility?
- hormones
- excitation via gastrin, CCK, insulin, motilin
- inhibition via secretin and glucagon
There are a number of propulsive peristalsis reflexes that are triggered once chyme enters the lower GIT, stretches the GIT and stimulates the mysenteric plexus. Gastroenteric reflex is one of those reflexes, what is this?
- gastric distention activates myenteric plexus
- this promotes peristalsis with small intestine
There are a number of propulsive peristalsis reflexes that are triggered once chyme enters the lower GIT, stretches the GIT and stimulates the mysenteric plexus. Gastroileal reflex is one of those reflexes, what is this?
- food in the stomach is recognised
- causes peristalsis in the ileum
- ileocecal valve opens and contents enter the large intestine
There are a number of propulsive peristalsis reflexes that are triggered once chyme enters the lower GIT, stretches the GIT and stimulates the mysenteric plexus. The migrating motor complex s one of those reflexes, what is this?
- a pattern of electrical activity in the lower GIT
- purpose is to move SI contents
- occur between meals (around every 90 minutes)