Digestion pt.2

What are the 3 phases?

What are the 3 phases?

Cephalic

Gastric

Intestinal

How is the cephalic phase activated?

Activated by the taste of food, smell, and when you see and think of the food.

How long does the cephalic phase lasts

few seconds to minutes

How much of Gastric juices is released during the cephalic phase?

1/3

Where does the sight and thought of food goes to?

Cerebral cortex then hypothalamus

Where does the smell and taste of food goes to?

Goes directly to hypothalamus

What kind of fibers does the vagus nerve have and where does it go?

• Parasympathetic fibers

• goes to the submucosal plexus

Where does submucosal plexus send signals to?

• Sends signals to the mucus glands which then secretes mucus.

• The parietal cell will produce the HCI and Intrinsic factor which helps absorb vitamin B12

How do you make pepsin?

Pepsinogen mixes with HCI

What is pepsin responsible for?

Responsible for breaking down proteins

What else does the submucosa plexus also activates?

Activates the endocrine cells called g cells.

What do g cells secrete?

Secretes a hormone called gastrin

How does the Gastric phase start?

• Starts when a bolus enters the stomach

How long does it the gastric phase last?

Can last for hours

How much of gastric juices are released?

2/3

What is Distension?

When the bolus enters the stomach and causes the stomach to stretch out

What happens when the bolus enters the stomach?

It becomes more base

What happens when there is change in the pH of your stomach?

Change in pH is sensed by chemoreceptors

What receptors sense when there is distension and where does it send signals to?

Stretch and chemoreceptors, it sends signals to the myentric plexus

Where is the myenteric plexus located ad what does it contain ?

Located in the muscularis externa and contains the lonitudunal and circular muscles

What muscle is in the stomach?

Oblique muscle

What will happen if the myenteric plexus stimulates the muscle to contract?

It will cause mixing waves so the bolus mixes w/ ACID and cause peristalsis. Which moves the bolus toward the end of stomach

What are partially digested proteins called?

peptones

…

Peptones-→sensed by g cells-→release of gastrin →pariatal, chief cells, and myentric plexus →

Where will the Gastrin go once it is released?

It will go to the bloodstreams and then to the parietal calls causing more HCI, pepsinogen, and chief cells to be released.

Where does cephalic phase take place?

Takes place before the stomach

Where does the Gastric phase take place?

takes place in the stomach

Where does the intestinal takes place?

takes place in the intestines

How does the intestinal phase start?

Starts when chyme enters the intestine

What happens to chyme when it is in the stomach?

It is pushed toward the pyloric sphincter

How much can the pylorus region of the stomach can hold?

30 ml of chyme

What is the pylorus made up of?

It is made up of the antrum and pyloric canal

Why does 3 ml of chyme pass through the duodenum?

So the body can test to see what’s in it

What happens when pep tones are present?

G- cells in the duodenum secrete Gastrin ( G34 Gastrin)

…..

Gastrin will go to chief cells and cause the release of pepsinogen. It will mix with HCI and make pepsin which will break pep tones in the duodenum.