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143 Cards in this Set

  • Front
  • Back
Main functions of the digestive system?
transfer nutrients, water, and electrolytes from ingested food into the body's internal environment
4 basic processes of the digestive system?
1. Motility

2. Secretion

3. Digestion

4. Absorption
Describe the motility of the digestive system?
muscular contractions that mix and move contents forward in the digestive tract
-mostly smooth muscle with autonomic control
-propulsive movements
-various speeds
Describe the secretion process of the digestive system?
transfer of digestive juices by exocrine glands into the digestive tract
-aids in digestion
-there are specific types with different jobs
-many secretions are reabsorbed and used again
-cells require H2O and energy to do their jobs
Describe the basic process of digestion by the digestive system?
A chemical change (hydrolysis) of large molecules (Carbs, Proteins, Fats) into smaller, absorbable subunits (Glucose, Amino Acids, Lipids)
Describe the basic process of Absorption by the digestive system?
Passage of products of digestion (ex. glucose), plus water, vitamins, and electrolytes, into blood and lymph to be utilized throughout the body.
10 organs of the digestive system?
1. mouth

2. pharynx

3. esophagus

4. small intestine

5. large intestine

6. salivary glands

7. exocrine pancreas

8. liver

9. gallbladder

10. stomach
What kind of muscle is in the digestive tract?
smooth muscle
The smooth muscle of the walls of the digestive tract maintain a low level of what?
contraction, tone
Two types of digestive motility?
1. Propulsive movements
(moves forward, various speeds)

2. Mixing movements (mixed with digestive juices, facilitating digestion and absorption)
2 general components of the digestive system?
1. Tract

2. Accessory organs
Describe the digestive tract?
A continous tube that consist of mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
15 ft. long.
Lumen continous with outside environment.
Name 3 accessory organs of the digestive system?
1. salivary glands

2. exocrine glands

3. biliary system (liver and gallbladder)
How does the mouth and salivary glands demonstrate motility?
How does the mouth and salivary glands demonstrate secretion?
How does the mouth and salivary glands display digestion?
Carbohydrate digestion begins
How does the mouth and salivary glands demonstrate absorption?
-does not absorb food
-absorbs a few meds
How does the pharynx and esophagus demonstrate motility?
How does the pharynx and esophagus demonstrate secretion?
How does the pharynx and esophagus demonstrate digestion?
How does the pharynx and esophagus demonstrate absorption?
How does the stomach demonstrate motility?
receptive relaxation, peristalsis
How does the stomach demonstrate secretion?
Gastric juice
-Intrinsic factor
How does the stomach demonstrate digestion?
Carbohydrate continues, protein begins
How does the stomach demonstrate absorption?
-no food
-few lipid soluble substances (alcohol and aspirin)
How does the exocrine pancreas demonstrate motility?
it doesn't
How does the exocrine pancreas demonstrate secretion?
Digestive enzymes
-Trypsin, chymotrypsin
How does the exocrine pancreas demonstrate digestion?
Digestion of carbohydrates, fats, proteins, nucleic acids in duodenal lumen
How does the exocrine pancreas demonstrate absorption?
it doesn't
How does the liver demonstrate motility?
it doesn't
How does the liver demonstrate secretion?
-bile salts
-alkaline secretion
How does the liver demonstrate digestion?
Bile salt facilitates fat digestion and absorption
How does the liver demonstrate absorption?
it doesn't
How does the small intestine demonstrate motility?
migrating motility complex
How does the small intestine demonstrate secretion?
Succus entericus
-enzymes in brush border
How does the small intestine demonstrate digestion?
In lumen by pancreatic enzymes and bile: Carbos and protein continue; fat completed
How does the small intestine demonstrate absorption?
All nutrients
-most electrolytes and H2O
How does the large intestine demonstrate motility?
Haustral contractions, mass movements
How does the large intestine demonstrate secretion?
How does the large intestine demonstrate digestion?
it doesn't
How does the large intestine demonstrate absorption?
Salt and H2O, converting contents to feces
The entire GI tract wall generally has the same what?
4 layers of the GI tract?
1. mucosa

2. submucosa

3. muscularis externa

4. serosa
What does the mucosa line?
the luminal surface
3 components of the mucosa?
1. mucous membrane

2. lamina propria

3. mucularis mucosa
Describe the mucous membrane of the mucosa?
inner epithelial layer with exocrine and endocrine cells
Describe the lamina propria of the mucosa?
middle layer of connective tissue, small bl. vessels, nerve fibers, lymph ducts
Describe muscularis mucosa of the mucosa?
outer, sparse layer of smooth muscle, both circular and longitudinal muscles in tract.
Describe the submucosa of the GI tract?
lies under the mucosa, connective tissue with blood and lymph vessels and submucous nerve plexus
Describe the muscularis externa of the GI tract?
MAJOR smooth muscle layer, lies between submucosa and outer serosa
-really does the work of pushing the food (propulsive and mixing)
3 things that the muscularis externa contains?
1. Inner circular layer of muscle

2. Outer longitudinal layer of muscle

3. Myenteric nerve plexus
Describe the actions of the inner circular layer and outer longitudinal layer of muscle in the muscularis externa of the GI tract?
produces contractions that produce propulsive and mixing movements
Describe the location of the myenteric nerve plexus of the muscularis externa of the GI tract wall?
Between the two smooth muscle layers
Describe the Serosa of the GI tract?
Outer connective tissue layer:
-Continous with mesentery (which suspends the digestive tract) along much of tract.
Describe the microvilli of the small intestine?
project off of each epithelial cell in the mucosa of the lumen
-increase surface area so absorption will be at peak
-increase absorption 600X
What is the source of new cells in the small intestine?
Crypt of Lieberkuhn
What is a central lacteal?
lymph duct that runs through the center of the epithelial cells in the small intestine.
4 factors that regulate digestive motility and secretion?
1. Autonomous smooth muscle function

2. Intrinsic nerve plexuses

3. Extrinsic nerves

4. Gastrointestinal hormones
Describe how Autonomous smooth function aids in digestive motility and secretion?
Cells display rhythmic, spontaneous variations in membrane potentials (inherent in smooth muscles). The inherent rate of several digestive processes (ex. peristalsis and segmentation) depend on pacesetter cells in tract with this characteristic.
Describe how the intrinsic nerve plexuses aid in digestive motility and secretion?
Myenteric and submucous plexuses: the enteric nervous system, signaling the GI tract from within the wall. Has inhibitory and stimulatory neurons. Inherent to the tract itself. So has it's own nervous system within the wall. Has as many neurons as you would find in the spine. RELAXATION.
Intrinsic nerve plexuses influences all what?
facets of the digestive system
Variety of nerves present in the intrinsic nerve plexuses?
Includes sensory (respond to stimuli in tract) and neurons that innervate smooth muscle cell and endocrine and exocrine cells.
Describe extrinsic nerves of GI tract?
From the ANS innervate digestive structures from outside the system. They modify digestive tract motility and secretion. The parasympathetic nerves signal maximum digestive activity. RELAXED.
If you were under sympathetic conditions what would happen with digestion?
your body wouldn't care about digestion because you would be in fight or flight mode.
Describe how gastrointestinal hormones influence digestive motility and secretion?
Endocrine glands within the mucosa; hormones signal digestive responses.
What do the receptors in the GI tract respond to?
local chemical or mechanical changes
3 types of receptors in the GI tract?
1. Chemoreceptors

2. Mechanoreceptors

3. Osmoreceptors
What do the chemoreceptors in the GI tract respond to?
Chemicals in lumen
What do the mechanoreceptors in the GI tract respond to?
stretch or tension within the wall
What do the osmoreceptors in the GI tract respond to?
osmolarity of luminal contents
Activation of the receptors in the digestive system produces what?
neural reflexes or secretion of hormones
Receptors in the digestive system alter the activity of what?
effector cells, smooth muscle cells, and endocrine and exocrine glands.
The two types of neural reflexes.
1. short reflexes (all the things you need intrinsic)

2. long reflexes (calling in the ANS)
How does fight or flight effect outcomes of digestive tract?
decreases them by utilizing external ANS.
Local changes in the digestive tract stimulate what?
Receptors in the digestive tract
External influences stimulate what?
extrinsic automatic nerves
The receptors in the digestive tract stimulate what?
1. intrinsic nerve plexuses

2. extrinsic automatic nerves

3. Gastrointestinal hormones
The extrinsic automatic nerves stimulate what?
1. intrinsic nerve plexuses

2. Gastrointestinal hormones

3. smooth muscle

4. exocrine gland cells

5. endocrine gland cells
The intrinsic nerve plexuses stimulate what?
1. Gastrointestinal hormones

2. Smooth muscle contraction (for motility)

3. Exocrine gland cells (secretion of digestive juices)

4. Endocrine gland cells (secretion of gastrointestinal and pancreatic hormones)
What do the gastrointestinal hormones stimulate?
1. Smooth muscle

2. Excocrine gland cells

3. Endocrine gland cells
Exocrine gland cells affect what?
secretion of digestive juices
Endocrine gland cells affect what?
secretion of GI and pancreatic hormones
What kind of reflex are the intrinsic nerve plexuses?
What kind of reflex are the extrinsic automatic nerves?
Overall function of the mouth, pharynx, and esophagus?
Food moistened and lubricated by saliva, chewed to breakdown into smaller pieces, swallowed, and peristalsis moves it thru the esophagus to stomach
Physically describe the mouth? (4)
1. entrance to digestive tract

2. opening formed by muscular lips

3. palate separates mouth from nasal passage

4. tongue consists of voluntarily controlled skeletal muscles
Physically describe the pharynx?
cavity at the rear of throat
Physically describe the esophagus? (2)
1. muscular tube extending from the pharynx to the stomach

2. guarded at both ends by sphincters: pharyngoesophageal sphincter and gastroesophageal sphincter
Describe the pharyngeosophageal sphincter?
part of pharynx that prevents burping
Describe the gastroesophageal sphincter?
part of pharynx that prevents contents of stomach from moving back up into the esophagus
What glands secrete saliva?
salivary glands
What kind of enzyme does salive contain? What does it break down?
Contains salivary amylase. Breaks down polysaccharides.
The secretion of saliva is increased by what branch of the ANS?
Both branches; The sympathetic and parasympathetic.
Salivary secretion is continous and can be reflexively increased by what 2 things?
1. simple, unconditioned salivary REFLEX coordinated by the salivary center in the medulla

2. Acquired, or conditioned, reflex occurs without oral stimulation
What does saliva keep clean?
The mouth and teeth
What is the first step in digestion?
Mastication by the teeth (chewing)
What are the two functions of mastication?
1. grinds and breaks food into smaller pieces

2. mixes food with saliva and stimulates taste buds
What is swallowing motility associated with?
the pharynx and esophagus
Swallowing is initiated when what happens?
When food bolus exerts pressure on receptors in the pharynx
Once swallowing has been initiated what do the receptors in the pharynx do?
send afferent impulses to the swallowing center in the medulla, this triggers various swallowing responses.
How is food prevented from entering wrong passageways? (2)
1. Closing of glottis by tilting of epiglottis: preventing food from entering respiratory tract

2. Elevation of uvula: preventing food from entering nasal passages
What is peristalsis?
movement of food thru the esophagus to the stomach
Where is the swallowing center and what does it initiate?
in the medulla. initiates primary peristaltic wave.
What do peristaltic waves do?
push food thru the esophagus
Unless your swallowing what does the gastroesophageal sphincter do?
stays closed (contracted) to prevent reflux, heartburn
What is the esophageal secretion? What is its purpose?
Secretion is mucus. It lubricates to prevent damage by sharp objects and it protects the esophageal wall from acid contents of the stomach.
The esophagus is only responsible for what?
only motility not digestion.
The digestive system is what kind of muscle?
Smooth, except for the top and bottom
3 main functions of the stomach
1. stores food (body)

2. Begins protein digestion, using HCl and enzymes

3. Forms chyme, solution of partially digested food via mixing (antrum)
Main function of the body of the stomach?
stores food
Main function of the antrum of the stomach?
forms chyme (solution of partially digested food) via mixing
The stomach is a (?) shaped chamber?
a J shaped chamber
3 sections of the stomach.
1. fundus

2. body

3. antrum
The wall of muscle in the fundus and body of the stomach could be described as what?
What does the fundus and the body of the stomach secrete? (4)
1. mucus

2. HCl

3. Pepsinogen

4. Intrinsic factor
The wall of the muscle in the antrum of the stomach could be described as what?
thicker than the muscle of the fundus and body
What does the antrum secrete?
1. mucus

2. gastrin

3. small amount of pepsinogen
What does the epithelial layer of the stomach do?
(in the entire stomach) it invaginates into the mucosa, increasing surface area and creating glands
What kind of cells are at the opening of the glands created by the epithelilal layer?
mucus cells (create mucus)
What kind of cells line the glands created by the epithelial layer?
chief cells, parietal cells, and more
Where is the fundus of the stomach located?
above the body and the gastroesophageal sphincter
What gland area is within the antrum?
the pyloric gland area
What does the pyloric sphincter and gland area do?
Prevents food from moving into intestine before it's time
4 general aspects of gastric motility?
1. filling

2. storage

3. mixing

4. emptying
Describe the filling aspect of gastric motility?
1. Can hold up to 1L

2. can accomodate 20-fold increase in volume by receptive relaxation
Receptive relaxation?
reflexive relaxation of stomach as it receives food (how it expands)
Describe storage aspect of gastric motility?
1. occurs in fundus and body

2. Pacesetter cells in FUNDUS generate slow-wave potentials that sweep down the stomach (3/min)

3. Weak contractions in the fundus and body because of thin muscle (ideal for storage)
Where are the pacesetter cells?
In the fundus
Describe the mixing aspect of gastric motility?
1. occurs in antrum

2. occurs here b/c more muscular so real mixing can occur

3. peristaltic movements are much stronger because walls are thick and muscular
Describe emptying aspect of gastric motility?
1. strong peristaltic contractions force food thru pyloric sphincter into duodenum

2. amount varies but is approx. 3ml to 30ml

3. held in antrum till pushed thru pyloric sphincter
During gastric emptying what action in the stomach drive the chyme from the stomach into the small intestine?
peristaltic action
What 2 things cause an increase in gastric motility during gastric emptying?
1. Distension of the stomach (fluidity of stomach contents)

2. Increased by: signaling by vagus nerve and hormone gastrin P
Gastric empting is largely controlled by what 4 factors in the duodenum?
1. fat

2. acid

3. hypertonicity

4. distension
What really has the most control over gastric emptying (not the stomach)?
small intestine
What prevents gastric emptying? (2)
1. Undigested fat, unneutralized acid, increase in osmolarity, distension

2. Inhibited by: Neural (intrinsic/extrinsic reflexes) or hormonal response (secretin and CCK: inhibitory enterogastrones)
Vomiting is AKA?
Emesis is what?
vomiting, forced expuslion of gastric contents thru the mouth
What, surprisingly, does not actively participate in vomiting?
stomach, esophagus, and associated sphincters all relaxed
What causes vomiting?
force by: contraction of RESPIRATORY MUSCLES (push against stomach)
What coordinates vomiting?
vomiting center in medulla
5 possible causes of vomiting?
1. tactile stimulation

2. irritation / distension of stomach and duodenum

3. elevated intracranial pressure

4. chemical agents

5. psychogenic factors
What can severe vomiting lead to?
dehydration and circulatory problems (blood pressure problems)
How can vomiting be helpful?
digestion of noxious material