1. Motility
2. Secretion
3. Digestion
4. Absorption

Tone is a constant level of contraction. 

It maintains steady intragastric pressire on the contents AND prevents permanent stretched after distension.

1. Propulsive movements: Propels the contents forward, depends on which region of the tract.

2. Mixing movements: A) Mixes food with digestive juices  B) Faciliates absorption by exposing 

Alpha 1,4

&

Alpha 1,6

(A water molecule is used up)

1. Mucosa (inner most)

2. Submucosa

3. Muscalaris Externa 

4. Serosa (outter most)

1.  Mucosa membrane
1. Epithelial cells for protection & absorption
2. Mucus cells
3. Endo & Exo glands
2. Lamina Propia
1. Connective tissue & GALT
2. Small blood vessels and Lymphs
3. Muscalaris Mucosa
1. Thin smooth muscle

What's in the submucosa?

1. Thick layer of connective tissue 
1. Elasticity & distensibility
2. Submucosa Plexes
3. Support for larger blood vessels & Lymphs

1. Autonomous Smooth Muscle

2. Intrinsic Nervous System (INS)/ ENS

3. Extrinsic Nerves/ ANS

4. GI Hormones

What do we mean by smooht muscle being tonic?

Explain the process for a slow wave initiation?

1. Myenteric plexes (Motility)
1. Smoth muscle 
2. Submucosa Plexes( Secretion) 
1. Secretory glands

T/F: 

Does the Extrinsic nerve (ES)/ANS affect the motility and secretion?

It influences motility by regulating the INS/ENS.

& secretion by changing the leves of GI hormone secretion.

NOT DIRECT STIMULATION

SNS: relaxes smooth muscle

PNS: Excites smooth muscle to contract

T/F

Are post-ganglionic PSN fiber part of the ENS?

What are the three types of receptors found in the DT?

& if they're stimulated, what kind of response do they elicit?

1. Chemoreceptors
2. Mechanoreceptors
3. Osmoreceptors

• They elicit neural reflexes (short/long) or secrete hormones.

Receptive Relaxation, vegally mediated,

allows the food to accomodate food withouth disrupting tonicity and therefore keeping a constant intragastric pressure.

1. Filling
2. Storage
3. Mixing
4. Epmtying

T/F

Intragastric pressure only changes when you eat more than 1 liter of food 

Food must be kept in stomach for proper mixing purposes. 

Also, the small intestines can only absorp small pieces of chyme, so the stomach works as a reservoir so the small intestines can work efficiently. 

T/F

Are contractions in the fundus stronger than the ones in the body and antrum?

Production of chyme 

Propulsion of contents

Retropulsion

Strong peristaltic waves

What's the role of strong antral peristaltic waves?

T/F

The pyloric sphicter experiences tonic contraction, which keeps it close at all times.

When does the pyloric sphicter reaches max. contraction?

& how does it relate to retropulsion?

When strong peristaltic waves reached the pyloric sphicter it completely closes, which causes chyme to propel backwards, thus mixing. 

Redundancy of this cylcle is called retropulsion.

T/F

The amount of chyme that escapes into the duodenum depends on the streght of the antral peristaltic contractions.

True. 

A direct relationship.

The intensity & rate of peristalsis, gastric emptying, depends upon the influence of factors from the _____, ______ & _______.

& how do they exert their influence. 

Stomach, Duodenum & Pain

By alteration of delopolarization or hyperpolarization of the smooth muscle.

1. Amount of chyme in the stomach 
1. Stomach distension: stretch of of the smooth muscle which triggers an increased in motility and thus faster emptying.
2. The greater the fluidity of chyme the faster the contents would move into the small intestines. 

T/F

Stomach factors increased gastric emptying, meanwhile the duodenum factors decreased gastric emptying

1. Acidity

2. Fat (most effective)

3. Distension

4. Hypertonicity.

The presence of the broken down monomers increased the osmolarity in the lumen. Which means water would want to move out into the lumen.

Osmoreceptors get activated to reflexly inhibit this process. 

T/F 

Osmolarity of the contents depends on the # of molecules present not on their size.

Blood carries this hormones up to the stomach

1. Secreted by the I cells in the small intestines
2. Induces pyloric sphicter contractions
1. Binds to CCK A subtyp recpetors

Mucus cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. exocrine
2. Alkaline mucus
3. Mechanical, distension
4. Protects mucosa against mechanical, pepsin, & acid injury.

Chief cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. Exocrine
2. Pepsinogen
3. ACh & Gastrin
4. Protein Digestion

Parietal cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. Exocrine cells
2. HCl & Intrinsic factor
3. ACh, gastrin & Histamine
4. HCl- Activates pepsinogen, breaksdown connective tissue, denatures proteins, kills microorganisms. IF- facilitates Vit. B12 in the terminal illeum.

Enterochromaffin (ECL) cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. Endo-paracrine cells
2. Histamine
3. Ach, Gastrin
4. Stimulates Parietal cells.

 G cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. Endo
2. Gastrin
3. Protein & Ach
4. Stimulates Parietal, chief, & ECl cells.

D cells

1. (exo or endo)
2. Released?
3. Simuli?
4. Effect?

1. Endo
2. Somatoastin
3. Low pH 
4. Inhibits parietal, G, & ECL cells.