Exam 4: Digestive System

Question 1

functions of the digestive system

5 primary, 2 associated

Answer 1

primary:
-ingestion, movement of food, digestion (mechanical and chemical), absorption, and excretion
associated:
-immune defense, endocrine secretions

Question 2

composition of the digestive system

Answer 2

alimentary canal (digestive tract) - tube within a tube
accessory organs:
tongue, teeth, salivary glands, liver, gallbladder, pancreas

lumen of alimentary canal considered functionally external to the body

Question 3

histology layers (4)

Answer 3

mucosal
submucosa
muscularis externa
serosa/adventitia

Question 4

mucosal layer

Answer 4

-mainly epithelium - changes
depending on where you are
-basement membrane supporting it: lamina propria
-muscularis mucosa: muscle layer around, shape and secretions in layer

Question 5

epithelium in stomach, esophagus, intestine, rectum

Answer 5

stomach: columnar cells
esophagus: non keratinized stratified squamous
intestine: villi in columnar
rectum: nonkeratinized stratified squamous

Question 6

submucosa layer

Answer 6

dense, irregular connective tissue that supports the glands and blood vessels

Question 7

muscularis externa layer

Answer 7

circular muscle and longitudinal muscle
work together to give peristalsis waves
-circular would constrict and longiudinal would push it along

Question 8

serosa/adventitia layers

Answer 8

serosa: stomach and intestines, serous membranes that lubricate and protect, secretes fluid to avoid rubbing

adventitia: pharynx, esophagus, rectum
protective CT layer - no serous secretions, in places where no rubbing should occur

Question 9

enteric plexus - autonomic nervous system

Answer 9

parasympathetic: inc muscle activity, tone, gland secretions
sympathetic: dec all activity - directs blood flow to skeletal muscle
stress can cause GI distress

Question 10

enteric plexus is formed by 2 separate plexuses

Answer 10

submucosa and myenteric

Question 11

submucosa plexus

Answer 11

contains stretch and chemical receptors
controls shape of mucosa ad degree of secretion

-closer to the lumen, sensitive to what moves through lumen

Question 12

myenteric plexus

Answer 12

located between circular and longitudinal muscle layers

controls paristalsis
-faster if higher motility, slower if you want to process food slowly

Question 13

oral cavity components and functions

Answer 13

components: tongue, teeth, gingiva, tonsils
receives secretions from salivary glands

site of mastication (chewing)
beginning of chemical digestion

Question 14

dentition - adult

Answer 14

adult: 2,1,2,3/2,1,2,3 x2
2 incisors, 1 canine, 2 premolars, 3 molars
long roots

Question 15

dentition-deciduous/baby teeth

Answer 15

2,1,2/2,1,2 x 2
short roots
only 3 types of teeth - no premolars

Question 16

tooth anatomy - regions

Answer 16

root: embedded in bone
- well into alveolar process of mandible or maxilla
neck: protected by gum tissue
- sensitive to decay since not well protected by crown
crown: external surface
- strong and protective, enamel

Question 17

root canal

Answer 17

contains pulp (blood vessels and nerve)

• of decay in this you can get abscess bacteria in bloodstream
• if infected may have to get a root canal - they remove the pulp

Question 18

dentin

Answer 18

• secretory cells in channels
• cells secrete cementin to attach to socket
• produce periodontal ligaments
• matrix similar to bone by higher % of hydroxyapatite
• if lose a tooth you lose the stimulation to alveolar process area and can lose bone mass

Question 19

enamel

Answer 19

hardest substance in body (97% hydroxyapatite)
cells degenerate after production
-important to keep enamel healthy, if it wears away you get access to dentin and can get cavities

Question 20

why is saliva produced? (3)

Answer 20

chemical digestion
lubrication of food
defense of oral cavity

Question 21

saliva composition

Answer 21

water
electrolytes and buffer
mucins- lubrication of food 
antibodies (IgA)
enzymes

Question 22

types of salivary enzymes (2)

Answer 22

salivary amylases: begins carbohydrate digestion

lingual lipase: begins lipid digestion

both inactived in stomach acid environment

Question 23

functions of tongue and ulva

Answer 23

tongue: positions food, aids in forming bolus, contains taste buds
ulva: prevents food from entering nasopharynx

Question 24

3 phases of deglutition

Answer 24

both voluntary and involuntary reflex

buccal phase, pharyngeal phase, esophageal phase

Question 25

buccal phase of deglutition

Answer 25

1st phase

tongue compresses bolus against hard palate and begins to move bolus back (voluntary!!)

Question 26

pharyngeal phase of deglutition

Answer 26

2nd phase
tongue depresses and moves bolus into oropharynx contacting pharyngeal arches (now INVOLUNTARY action begins!!)
larynx lifts as epiglottis closes glottis
upper esophageal sphincter opens

Question 27

esophageal phase of deglutition

Answer 27

3rd phase
bolus enters esophagus and peristalsis takes over
upper esophageal sphincter closes
larynx returns to position with glottis open
breathing can resume

Question 28

esophagus

Answer 28

moves bolus though peristalsis

nonkeratinized startified squamous of mucosa does not have goblet cells

Question 29

2 extra layers of lubrication and protection for esophagus

Answer 29

submucosal glands: secrete mucus in upper part of esophagus, lubricates esophageal lining

cardiac glands: in lamina propria of esophogastric junction

• protects lower esophagus from reguritated acidic gastric secretions
• pyrosis (heart burn, acid reflux) occurs when secretions overwhelmed

Question 30

regions of the stomach

Answer 30

4 or 5
-cardac
-fundus (collects gas)
-body: most digestion in stomach here, rugae
-pyloric region: where chyme getting ready to leave stomach
can be divided in 2: antrum: till mixing wih gastric secretion and pyloric canal: getting ready to go into SI

Question 31

the environment of the adult stomach is maintained at a pH between

Answer 31

1.5 and 2

Question 32

digestive action of the stomach

Answer 32

• bolus enters, subjected to peristaltic waves that mix the food with mucous secretions in fundus forming chyme. salivary digestion continues
• stretch receptors stimulate G-cells to release gastrin
• gastrin activates chief and parietal cell secretions
• chief cells release pepsinogen
• HCl from parietal cells activates pepsinogen to form pepsin pH 2
• Parietal cells release intrinsic factor to bind V B12
• inc gastrin results in inc stomach motility
• chyme mixes with gastric secretions

Question 33

what do stretch receptors stimulate

Answer 33

G cells to release gastrin

Question 34

what does gastrin activate

Answer 34

chief and parietal cells

Question 35

chief cells release

Answer 35

pepsinogen

Question 36

what does HCl from parietal cells activate

Answer 36

pepsinogen to pepsin pH2

Question 37

what to parietal cells release

Answer 37

intrinsic factor to vitamin B12

Question 38

what enters the bloodstream during a large meal due to inc stimulation of parietal cells

Answer 38

alkaline tide

chloride shift, bicarb going out , makes you tired

Question 39

stomach action in an infant

Answer 39

can only get a pH of 5

modified chief cell secretions:
- renin released- in presence of Ca, acts on casein protein in milk to form curds
alpha and beta stay soluble due to kappa
renin breaks kappa - not soluble, curds

• gastric lipase: digests milk fat
• both secretions optimal at pH 5

Question 40

3 phases in stomach response

Answer 40

cephalic, gastric, intestinal

Question 41

cephalic phase - stomach response

Answer 41

gastric secretions begin in response to thinking, smelling or seeing food - have not ingested yet

Question 42

gastric phase- stomach response

Answer 42

• stretch receptors directly trigger G cells and indirectly trigger parietal and chief cells
• chemoreceptors monitor pH level (can be stimulated by anxiety, caffeine)

Question 43

intestinal phase - stomach response

Answer 43

• regulation of stomach emptying

- stretch receptors result in CCK and GIP release

Question 44

CCK

Answer 44

stimulates pancreatic and gallbladder secretions

Question 45

GIP

Answer 45

stimulates pancreas and slows motility of stomach in response to high fat meals