Digestive Physiology

Question 1

What is the primary function of the digestive system?

Answer 1

To bring essential nutrients into the internal environment so they are available to every cell in the body

Question 2

What mechanisms are used to accomplish digestion?

Answer 2

-ingestion
-digestion
-motility of GI wall
-secretion

Question 3

Movement of nutrients through the GI mucosa into the internal environment

Answer 3

Absorption

Question 4

Excretion of material that is not absorbed; from rectum through the anus (defecation)

Answer 4

Elimination

Question 5

Coordination of the various functions of the digestive system (motility, secretion…)

Answer 5

Regulation

Question 6

T/F
The digestive tract is functionally an extension of the external environment; material does not truly enter the body until it is absorbed into the internal environment

Answer 6

True

Question 7

Movements of the digestive tract that:
-change ingested food from large to small particles
-churn contents of the GI lumen to mix with digestive juices and come in contact with the surface of intestinal mucosa for absorption
-propel food along the alimentary tract, eliminating digestive waste from the body

Answer 7

Mechanical digestion

Question 8

-reduced size of food particles
-mixes food with saliva in preparation for swallowing

Answer 8

Mastication
*chewing

Question 9

Process of swallowing; complex process requiring coordinated, rapid movements

Answer 9

Deglutition

Question 10

What are the 3 stages of deglutition?

Answer 10

1. Oral stage
2. Pharyngeal stage
3. Esophageal stage

Question 11

-mouth to oropharynx
-voluntarily controlled
-formation of bolus in middle of tongue
-tongue presses bolus up against soft palate and food is moved into oropharynx
*soft palate and uvula are elevated by bolus to block the opening into the nasopharynx

Answer 11

Oral stage of deglutition

Question 12

-oropharynx to esophagus
-involuntary movement
-propel bolus from pharynx to esophagus
*with swallowing, larynx moves up as bolus moves down causing epiglottis to close over trachea and bolus slips over epiglottis into laryngopharynx

Answer 12

Pharyngeal stage of deglutition
*contractions from pharynx and esophagus move bolus down through the esophagus

Question 13

-esophagus to stomach
-involuntary movement
-contractions and gravity move bolus through esophagus and into stomach

Answer 13

Esophageal stage

Question 14

T/F
Swallowing process must occur rapidly because inspiration is suspended for 1-3 seconds as food passes through pharynx

Answer 14

True
*involves respiratory system

Question 15

What are the 2 main types of motility produced by smooth muscle of the GI tract?

Answer 15

Peristalsis

Segmentation

*can occur together in alternating fashion

Question 16

Wa like ripple of muscle layer of a hollow organ; progressive motility that produces a forward movement of matter along the GI tract

Answer 16

Peristalsis
*bolus of food stretches the wall of the GI tract and triggers a reflex contraction in the smooth muscle

Question 17

Mixing motion; digestive reflexes cause forward and backward movement within a single segment of the GI tract; helps break down food particles, mixes food and digestive juices, bring digested food in contact with intestinal mucosa for absorption

Answer 17

Segmentation

Question 18

T/F
Emptying the stomach takes approx. 2-6 hours

Answer 18

True

Question 19

What happens to food while it is in the stomach?

Answer 19

Food is churned and mixed with gastric juices to form chyme
*chyme is ejected approx. every 20 seconds into the duodenum

Question 20

What is the term for chyme continually being pushed down toward the pyloric sphincter by wave of peristaltic contractions?

Answer 20

Propulsion

Question 21

What is retropulsion?

Answer 21

Occurs when chyme is forced back from the pyloric sphincter, because it stays closed most of the time

Question 22

T/F
Gastric emptying is controlled by hormonal and nervous mechanisms

Answer 22

True

Question 23

Fats and other nutrients in the duodenum stimulate the release of gastric inhibitory peptide (GIP) which travels in the bloodstream to reach the stomach and decrease peristalsis of gastric muscles therefore slowing passage of chyme into duodenum

Answer 23

Hormonal mechanism

Question 24

Enterogastric reflex; receptors in the duodenal mucosa are sensitive to presence of acid and distension; impulses over sensory and motor fibers in the vagus nerve cause a reflex inhibition of gastric peristalsis

Answer 24

Nervous mechanism

Question 25

What does segmentation in the duodenum and upper jejunum mix chyme with?

Answer 25

Digestive juices from the pancreas, liver and intestinal mucosa

Question 26

T/F The rate of peristalsis picks up as chyme approaches the end of the jejunum, moving it through rest small and into large intestine

Answer 26

True

Question 27

T/F After leaving the stomach, chyme usually takes approx. 5 hours to pass through small intestine

Answer 27

True

Question 28

What is peristalsis regulated and stimulated by?

Answer 28

Regulated by intrinsic stretch reflex: -the receptors sense distension and peristalsis decreases Stimulated by CCK - cholecystokinin: -hormone in small intestinal mucosa that detects fat in chyme and slows down digestion so fat can be absorbed/digested

Question 29

What are the components of chemical digestion: secretion?

Answer 29

Saliva Gastric juice Bile

Question 30

-secreted by salivary glands -mostly water with some mucus -amylase -sodium biocarbonate

Answer 30

Saliva

Question 31

An enzyme in saliva that begins digestion of starches

Answer 31

Amylase

Question 32

Secreted in saliva and increased the pH for optimal amylase function

Answer 32

Sodium bicarbonate

Question 33

Secreted by gastric glands which have ducts that lead the gastric lumen by way of gastric pits

Answer 33

Gastric juice

Question 34

A protease that begins the digestion of proteins *secreted as inactive pepsinogen by chief cells

Answer 34

Pepsin

Question 35

What do parietal cells of the stomach secrete to maintain an acidic environment in the stomach?

Answer 35

HCl *releases H+ into the gastric lumen at the same time the contents of the blood become more basic when the bicarbonate ion (HCO3-) moves into the blood

Question 36

-secreted by the liver; stored and concentrated in the gallbladder -specifically contains lecithin and bile salts that emulsify fats -sodium bicarbonate increase pH back to more basic level for optimal enzyme function and help neutralize chyme

Answer 36

Bile

Question 37

T/F Bile has excretions like cholesterol, products of detoxification and bile pigments called bilirubin (old RBC) *these are waste products and are excreted by the liver and eventually eliminated in feces

Answer 37

True

Question 38

The expulsion of feces from the digestive tract; acts of expelling feces is called defecation

Answer 38

Elimination

Question 39

Occurs as a result of a reflex brought about by stimulation of receptors in the rectal mucosa *when fecal matter is moved into the rectum, a reflex relaxation of the internal anal sphincter is initiated

Answer 39

Defecation *external anal sphincter is voluntary

Question 40

Contents of the lower part of the colon and rectum move at a slower than normal rate; extra water is absorbed from the feces, resulting in hardened stool

Answer 40

Constipation

Question 41

Result of increased motility of the small intestine, causing decreased absorption of water and electrolytes and a watery stool

Answer 41

Diarrhea