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FHB Exam 3: GI & Metabolism > GI III & IV: Cephalic, Oral, and Esophageal Phases > Flashcards

GI III & IV: Cephalic, Oral, and Esophageal Phases Flashcards

1
Q

Does absorption happen in the mouth?

A

In general, no; the exception is alcohol and certain drugs

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2
Q

What is xerostomia?

A

Also known as dry mouth, caused by impaired salivary secretion; can be congenital or autoimmune; decrease in secretion reduces pH in oral cavity (due to less bicarb), leading to tooth decay, esophageal erosions, and difficulty swallowing

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3
Q

What are the most important muscles involved in chewing?

A
  • Temporalis (most impt.)
  • Masseters
  • Lateral pterygoids
  • Medial pterygoids
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4
Q

What are secretions elicited by?

A

secretagogues, which are substances that act on secretory cells and stimulate secretion

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5
Q

Secretions in the GI tract come from which 3 sources?

A
  • Glands associated with the GI tract (salivary glands, pancreas, liver)
  • Glands formed by the gut wall itself (Brunner’s glands in duodenum)
  • Intestinal mucosa

(secretions include water, electrolytes, protein, and humoral agents)

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6
Q

When does most stimulation of salivary secretion occur?

A

during cephalic and oral phases of a meal

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7
Q

Where does digestion of carbs and starches begin?

A

oral cavity

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8
Q

Which enzymes are present during the oral phase?

A
  • salivary amylase (breakdown of carbohydrates)

- lingual lipase (breakdown of fats)

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9
Q

What are the 3 pairs of major salivary glands?

A
  • parotid: serous secretions
  • submandibular: mixed secretions
  • sublingual: mucous secretions
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10
Q

What are the two types of secretions in the mouth?

A

-serous (water, electrolytes, enzymes)
-mucous (mucin glycoprotein)
(and then there are also mixed secretions that are 50/50 mucous and serous)

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11
Q

Saliva is produced by the salivary glands at what rate?

A

1L per day (secretes its own weight)

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12
Q

How is saliva formed?

A

2-step process:

1) Formation of isotonic plasma-like solution by acinar cells (primary secretion / initial saliva)
2) Modification of plasma-like solution by ductal cells (via complex transport mechanisms) to produce hypotonic final saliva

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13
Q

How is salivary secretion regulated?

A

It is exclusively neural (except in the GI system itself…certain GI secretions are neural AND hormonal). Salivary secretion is stimulated by BOTH sympathetic and parasympathetic divisions, although parasympathetic is the most dominant.

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14
Q

Stimulation of salivary cells results in which physiological effects?

A
  • increased saliva production
  • increased bicarbonate and enzyme secretions
  • contraction of myoepithelial cells
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15
Q

What accounts for final saliva being hypotonic?

A

1) Ductal cells are relatively water-impermeable, so water is not absorbed along with solute
2) There is net absorption of solute (because more NaCl is absorbed than KHCO3 is secreted)

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16
Q

How does composition of saliva vary with flow rate?

A
  • highest flow rates: final saliva almost similar to plasma (or initial secretion)
  • lowest flow rates: final saliva most dissimilar to plasma (because ductal cells have more time to extract electrolytes=hypotonic)
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17
Q

What is the exception to the general trend of ionic composition varying with flow rate?

A

HCO3-, for its secretion is selectively stimulated when saliva production is stimulated

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18
Q

Where is the swallowing center located?

A

in the medulla and lower pons

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19
Q

The swallowing reflex specifically inhibits which two processes?

A

respiration and food entrance into trachea while swallowing

20
Q

Digestion is under involuntary control after which point?

A

After bolus passes upper esophageal sphincter

21
Q

Motor impulses from the swallowing center travel to the pharynx and upper esophagus via ________ and to the remaining esophagus via _______.

A

cranial nerves; vagal motor neurons

22
Q

What is relaxation of the esophageal sphincters mediated by during the esophageal phase?

A

peptidergic fibers in the vagus nerve that release VIP

23
Q

What is receptive relaxation?

A

When the orad region of the stomach relaxes at the same time as the LES relaxes, which reduces pressure in the orad and helps movement of the bolus into the stomach

24
Q

What are the 2 main functions of the esophagus and esophageal sphincters?

A

1 ) Propel food from pharynx to stomach

2) Sphincters protect airway from swallowed material and esophagus from acidic gastric reflux

25
Q

What are the main functions of the UES and LES?

A
  • UES keeps air out of upper end of esophagus (prevents us from taking in unwanted materials from the envt.)
  • LES keeps gastric acid contents out of lower end of esophagus (protects us from gastric reflux)
26
Q

Where is the vomiting center located?

A

reticular formation in the pons

27
Q

What are some of the stimuli that elicit the cephalic phase of the integrated response to a meal?

A

cognitive stimuli, including the idea of food, olfaction, visual stimuli, and auditory stimuli

28
Q

Olfactory stimuli increase salivary secretion via which nerve?

A

CN IX (glossopharyngeal)

29
Q

What is the secretory unit of the GI tract?

A

acinar cells (a type of specialized epithelial cell)

30
Q

Salivary glands are formed by 2 main anatomical structures:

A

1) Acinus (secretory unit)

2) Network of collecting ducts (empty secretory juice into gut)

31
Q

What would happen if a patient had an adenoma in his or her parotid gland?

A

difficulty swallowing, chewing and speaking; poor salivation leading to dry mouth and bad breath

32
Q

What are the main functions of saliva?

A
  • lubrication of ingested food w/ mucus to aid movement through esophagus
  • protection of oral cavity by diluting/buffering ingested foods and maintaining healthy tissue (contains lysozyme, which can lyse bacterial cell walls)
  • initial digestion of starches and lipids by salivary enzymes
33
Q

Describe the composition of saliva.

A
  • inorganic constituents: water, bicarb, ions, fluoride (inorg. constit. entirely dependent upon stimulus and rate of salivary flow)
  • organic constituents: salivary amylase, lingual lipase, glycoprotein, lysozyme, kallikrein
34
Q

Salivary secretion is hypotonic, meaning it has…

A

-higher K+ and HCO3- concentrations
-lower Na+ and Cl- concentrations
(has lower osmolarity)

35
Q

The esophageal phase of swallowing is controlled by what?

A

swallowing reflex AND enteric nervous system

36
Q

During swallowing, how is the secondary peristaltic wave initiated?

A

by a primary peristaltic contraction, which propels food downs the esophagus and distends it

37
Q

What is the purpose of secondary peristalsis in swallowing?

A

Repetitive secondary peristalsis clears the esophagus of the bolus.

38
Q

Which pressure is lower - intraesophageal or abdominal?

A

intraesophageal

39
Q

What is the problem created by intraesophageal pressure being lower than abdominal pressure?

A
  • must have a way to keep air out of upper end of esophagus (done by UES)
  • must have a way to keep gastric acid contents out of the lower end of the esophagus (done by LES)
40
Q

Does the muscularis mucosa get thicker or thinner in the small and large intestine?

A

thinner… this part of the GI tract does not have to handle food pieces that are quite as large as the ones being propelled through the esophagus

41
Q

True or false: patients with GERD have squamous epithelia absent close to the stomach.

A

True- the transition from squamous to columnar epithelium occurs higher up in patients with GERD.

42
Q

How is GERD treated?

A
  • H2 receptor antagonists (ex: ranitidine)

- proton pump inhibitors (ex: omeprazole)

43
Q

What is achalasia?

A

A motility disorder of the esophagus in which the smooth muscle layer of the esophagus does not have normal peristalsis, and the LES does not relax normally in response to swallowing. Common symptoms include dysphagia, regurgitation, and chest pain.

44
Q

What are some characteristics of the vomiting act?

A
  • reverse peristalsis of small intestine
  • relaxation of pyloric sphincter and stomach to receive intestinal contents
  • forced inspiration against closed glottis decreases intrathoracic pressure and increases intraabdnominal peressure
45
Q

What happens during retching (aka, dry heaving)?

A

The UES remains closed, so gastric contents are forced into the esophagus but do not enter the pharynx. It often precedes vomiting.

FHB Exam 3: GI & Metabolism (17 decks)

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