Small Intestine: Intestinal Juice and Motility – Digestive System Organs (Nursing)

00:01 So if we take a closer look at the intestinal juices, we find that one to two liters are secreted daily in response to distention or irritation of the mucosa and the intestines.

00:16 The major stimulus for the production of intestinal juice includes hypertonic or salty or acidic chyme.

00:26 It is slightly alkaline and isotonic with our blood plasma at about a pH of 7.4 it consists largely of water, but also contains some mucus and this mucus is from the duodenal glands as well as the goblet cells of the mucosa.

00:48 Chyme from the stomach is going to come into the small intestines with partially digested carbohydrates and proteins as well as undigested fats.

00:59 It takes about three to six hours in the small intestines to then absorb all of the nutrients and most of the water from this chyme.

01:10 So, how are we actually going to digest this? The enzymes are going to come from substances such as vile, bicarbonate, digestive enzymes which are imported from the liver and the pancreas.

01:25 Also the Villi are going to release brush border enzymes which are bound to the plasma membranes in those microvilli that are going to perform the final digestion of chyme.

01:39 Chyme entering the duodenum is usually salty or hypertonic.

01:44 Therefore chyme delivery has to be slow so that we don't have too much water loss from our blood into the small intestines.

01:55 Also the low pH of chyme needs to be adjusted upward because right now it's very acidic and the environment inside of the intestines is more closely aligned with our blood plasma so slightly alkaline.

02:12 The chyme needs to be mixed with bile and pancreatic juices in order to continue their digestion as the bile is going to help with the emulsification of fats and the pancreatic juice also contains enzymes that are able to break down all of the different biomolecules.

02:31 And then recall that we have the enterogastric reflex, and enterogastrone which are going to control that movement of food into the duodenum and prevent it from being overwhelmed by causing a decrease in gastric motility as the size of the duodenum begins to get larger or distend when chyme is entering.

02:56 So how does this work? After a meal segmentation is going to be the most common motion found in the small intestines.

03:05 It's going to be initiated by intrinsic pacemaker cells and it's going to mix and move the contents of the small intestine toward the ileocecal valve away from the duodenum.

03:20 The intensity of segmentation is altered by long and short reflex as well as hormones.

03:28 So for example parasympathetic innervation is going to increase motility while sympathetic innervation will decrease motility.

03:39 Between meals so after when you're not a lot of activity occurring in the small intestines, peristalsis is increased.

03:48 This is initiated by a rise in the hormone motilin and the late intestinal phase.

03:55 Each wave starts distal to the previous wave and is referred to as the migrating motor complex.

04:05 This allows for meal remnants as well as bacteria and debris to move toward the large intestine and between meals.

04:14 And a complete trip from the duodenum to the ileum between meals will take about two hours.

04:24 So now let's look at how we go from the small intestine to the large intestine.

04:31 A sphincter known as the ileocecal sphincter relaxes and admits chyme that is going to come from the small intestines into the large intestine.

04:43 This happens, when the gastro ileal reflex enhances the force of segmentation in the ileum of the small intestine.

04:53 Also gastrin, the hormone is going to increase the motility of the ileum.

05:00 The ileocecal valve flap will then close when chyme exerts backward pressure.

05:07 And this will prevent regurgitation of the chyme that's now in the large intestine back into the ileum.