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Digestive System
Digestive Tract, Pancreas, & Liver
65
Physiology
Undergraduate 3
12/08/2012

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Cards

Term
What are the four digestive processes?
Definition
  1. Motility
  2. Secretion
  3. Digestion
  4. Absorption
Term
What is Tone? & how is beneficial to gastric smooth muscle?
Definition

Tone is a constant level of contraction. 

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

Term
What is motility?
Definition
Motility refers to the muscular contractions that mix and propels forward the contents in the stomach.
Term
What are the two motility phasic movements? & what do each one do?
Definition

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 

Term
Hydrolysis of carbohydrates. At what locations does glycosic linkages take place?
Definition

Alpha 1,4

&

Alpha 1,6

(A water molecule is used up)

Term
What are the four layers of the digestive tract?
Definition

1. Mucosa (inner most)

2. Submucosa

3. Muscalaris Externa 

4. Serosa (outter most)

 

Term
What are the 3 layers of the mucosa layer and what is them?
Definition
  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
Term

What's in the submucosa?

 

Definition
  1. Thick layer of connective tissue 
    1. Elasticity & distensibility
  2. Submucosa Plexes
  3. Support for larger blood vessels & Lymphs
Term
What is the serosa layer for?
Definition
It secretes a fluid that lubricates and prevents friction b/w the digestive organs and the surrounding viscera.
Term
What are four different ways to regulate the digestive function?
Definition

1. Autonomous Smooth Muscle

2. Intrinsic Nervous System (INS)/ ENS

3. Extrinsic Nerves/ ANS

4. GI Hormones

 

Term

What do we mean by smooht muscle being tonic?

 

Definition
That experiences spontaneous rhytmic depolarization and repolarizations.
Term

Explain the process for a slow wave initiation?

 

Definition
(Fundus) ->Muscalaris externa -> Muscalaris Externa-> Intestitial cells of cajal (Pacemaker cells) -> Inititates BER waves
Term
What happens if BER waves reach threshold?
Definition
A volley of AP is triggeredd at each peak, which results in rhythmic cycles of contraction. Also peristaltic waves get initiated
Term
What factors would cause BER waves to reached threshold?
Definition
Mechanical, Neuronal & Hormonal
Term
The rate/ frequency of digestive contractility is depend on?
Definition
Depends on the rate established by the pacemaker cells.
Term
The intensisty/strength of the digestive contractility activities depends on?
Definition
Depends on the # of AP that occur when BER waves reach threshold.
Term
How do we get different degrees of contractility?
Definition
By varying the cytosolic [Ca+2]
Term
T/F: The ENS is a complete nervous system w/in the digestive tract
Definition
True
Term
ENS/INS: Where do the efferent neurons innervate?
Definition
  1. Myenteric plexes (Motility)
    1. Smoth muscle 
  2. Submucosa Plexes( Secretion) 
    1. Secretory glands
Term

T/F: 

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

Definition
True
Term
How doe the EN/ ANS affect motility & secretion?
Definition

It influences motility by regulating the INS/ENS.

& secretion by changing the leves of GI hormone secretion.

NOT DIRECT STIMULATION

Term
What effect does the SNS & PNS have on gastric smooth muscle?
Definition

SNS: relaxes smooth muscle

PNS: Excites smooth muscle to contract

Term
Which component of the ANS arrives via the vagus nerve?
Definition
PNS
Term

T/F

Are post-ganglionic PSN fiber part of the ENS?

Definition
True
Term

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

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

Definition
  1. Chemoreceptors
  2. Mechanoreceptors
  3. Osmoreceptors
  • They elicit neural reflexes (short/long) or secrete hormones.
Term
What is define as motility in terms of filling?
Definition

Receptive Relaxation, vegally mediated,

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

Term
Motility in terms of ...(4)
Definition
  1. Filling
  2. Storage
  3. Mixing
  4. Epmtying
Term

T/F

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

Definition
True
Term
What do we mean by motility in terms of storage?
Definition

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. 

Term

T/F

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

 

Definition
False
The body & Antrum have thicker smooth muscle layers.  
Term
Where in the stomach does mixing takes place?
Definition
The antrum
Term
What incorporates motility in terms of mixing?
Definition

Production of chyme 

Propulsion of contents

Retropulsion

Strong peristaltic waves

Term

What's the role of strong antral peristaltic waves?

 

Definition
Mixes food witht the digestive juices to produce chyme and propels chyme forward toward the pyloric sphicter.
Term

T/F

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

Definition
True
Term

When does the pyloric sphicter reaches max. contraction?

& how does it relate to retropulsion?

Definition

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.

Term

T/F

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

Definition

True. 

A direct relationship.

Term

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

& how do they exert their influence. 

Definition

Stomach, Duodenum & Pain

By alteration of delopolarization or hyperpolarization of the smooth muscle.

Term
How does the stomach influence gastric emptying?
Definition
  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. 
Term

T/F

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

Definition
True
Term
What four major factors from the duodenum influence gastric emptying?
Definition

1. Acidity

2. Fat (most effective)

3. Distension

4. Hypertonicity.

Term
How does FAT in the duodenum affect gastric empyting?
Definition
Its presence stimulates the release of CCK
Term
How does ACID in the duodenum affect gastric empyting?
Definition
The presence of acidic chyme causes the release of secretin
Term
How is acid in the duodenum neutralize?
Definition
Sodium Bicarbonate that was released by the pancreas.
Term
What would happen if we do not neutralize the acidic chyme in the duodenum?
Definition
It might damage the duodenum mucosa layer & innactivate the pancreatic digestive enzymes.
Term
How does Hypertonicity in the duodenum affect gastric empyting?
Definition

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. 

Term

T/F 

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

Definition
True
Term
How does distension in the duodenum affect gastric empyting?
Definition
Too much chyme in the duodenum inhibits the emptying of more chyme.
Term
What typeof responses do dudodenum factors elicit in order to regulate gastric emptying?
Definition
They either elicit hormonal or neural responses, which would slow down antral peristaltic activity.
Term
Duodenum factors Neuranol response
Definition
Mediated by the entertogastric reflex.
Term
What is the enterogastric reflex composed of ?
Definition
The ENS & ANS
Term
Duodenum Factors Hormonal Response
Definition
Involves the release of several hormones from the small intestine mucosa, known as the esterogastrones.
Term
How is CCK & Secretin transported up to the stomach?
Definition

Blood carries this hormones up to the stomach

 

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

 

Term
How does pain affect gastric emptying?
Definition
Increases SNS, thus decreasing motility, and therefore gastric emptying.
Term
From what cells is Secretin release?
Definition
Secreted by endocrine cells known as S cells in the small intestines
Term
Where are the gastric juices secreted from?
Definition
Gastric Mucosa
Term
Where in the stomach do we find most of the exocrine cells?
Definition
fundus & body
Term
Where in the stomach do we find most of the endocrine cells?
Definition
Antrum
Term

Mucus cells

  1. (exo or endo)
  2. Released?
  3. Simuli?
  4. Effect?
Definition
  1. exocrine
  2. Alkaline mucus
  3. Mechanical, distension
  4. Protects mucosa against mechanical, pepsin, & acid injury.
Term

Chief cells

  1. (exo or endo)
  2. Released?
  3. Simuli?
  4. Effect?
Definition
  1. Exocrine
  2. Pepsinogen
  3. ACh & Gastrin
  4. Protein Digestion
Term

Parietal cells

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

Enterochromaffin (ECL) cells

  1. (exo or endo)
  2. Released?
  3. Simuli?
  4. Effect?
Definition
  1. Endo-paracrine cells
  2. Histamine
  3. Ach, Gastrin
  4. Stimulates Parietal cells.
Term

 G cells

  1. (exo or endo)
  2. Released?
  3. Simuli?
  4. Effect?
Definition
  1. Endo
  2. Gastrin
  3. Protein & Ach
  4. Stimulates Parietal, chief, & ECl cells.
Term

D cells

  1. (exo or endo)
  2. Released?
  3. Simuli?
  4. Effect?
Definition
  1. Endo
  2. Somatoastin
  3. Low pH 
  4. Inhibits parietal, G, & ECL cells.
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