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ANP 1107 > Digestive system > Flashcards

Digestive system Flashcards

1
Q

How does the enteric nervous system regulate smooth muscle activity?

A

excites smooth muscle through nerves secreting acetylcholine or substance P and inhibits smooth muscle with vasoactive intestinal peptide (VIP) or nitric oxide (NO).

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2
Q

What role do hormones play in GI regulation?

A

respond to local chemical factors, nerve signals, or stretch and can act locally or travel via the blood to influence secretory or contractile activity in adjacent organs

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3
Q

What is the digestive function of the mouth?

A

The mouth is the only part of the GI tract for ingestion - - Its digestive functions involve mechanical (chewing) and chemical processes (enzyme secretion from salivary glands)
- also starts the propulsive act of swallowing

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3
Q

What are the mechanical and chemical digestive processes in the mouth?

A
  • Mechanical digestion: Chewing (mastication), which is partly voluntary and partly reflexive.
  • Chemical digestion: Enzymes from the salivary glands begin the breakdown of food, especially starches.
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4
Q

Does the mouth absorb nutrients?

A

does not absorb nutrients, with some exceptions such as nitroglycerine.

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4
Q

What are the functions of saliva?

A
  • Cleanses the mouth.
  • Dissolves food chemicals for tasting.
  • Moistens and compacts the food bolus.
  • Contains salivary amylase, which begins starch digestion.
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5
Q

What are the different types of salivary glands and their contributions to saliva?

A
  • Parotid glands: Predominantly serous cells, produce ~25% of saliva.
  • Submandibular glands: Serous & mucous cells, produce ~70% of saliva.
  • Sublingual glands: Predominantly mucous cells, produce ~5% of saliva.
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6
Q

What are intrinsic salivary glands and their secretions?

A

Intrinsic (buccal) salivary glands secrete lingual lipase

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6
Q

What is the composition of saliva?

A
  • 97-99.5% water (hypo-osmotic), pH 6.75-7.
  • Contains electrolytes, amylase (for starch digestion), mucin (for lubrication), urea & uric acid (metabolic waste products).
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7
Q

What other secretions are found in saliva, and what is their purpose?

A

contains IgA antibodies, lysozyme, and defensins
- make sure that bad bacteria is denatured

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8
Q

What is the average output of saliva per day?

A

1000-1500 ml/day

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9
Q

What is the role of intrinsic salivary glands in salivation?

A

provide continuous secretion of 0.1 ml/min to keep the mouth moist

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10
Q

How do extrinsic salivary glands differ in their secretion?

A
  • activated by food intake or other stimuli
  • can produce up to 4 ml/min of saliva.
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11
Q

How is salivation regulated?

A

ANS
- chemoreceptors and mechanoreceptors in the mouth signal the salivatory nuclei in the brainstem
- increased parasympathetic activity promotes serous secretion

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12
Q

What stimulates chemoreceptors and mechanoreceptors in the mouth?

A
  • chemoreceptors are activated most strongly by acids
  • mechanoreceptors are activated by any mechanical stimulus in the mouth
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13
Q

How does sympathetic stimulation affect salivation?

A
  • increases mucous secretion and can constrict blood vessels serving the salivary glands, leading to dry mouth (xerostomia)
  • stress
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14
Q

What external factors can trigger salivation?

A

sight, smell, or even the thought of food, and also by irritation in the lower GI tract, such as from bacteria, spicy food, or hyperacidity.

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15
Q

What is deglutition (swallowing), and how is it coordinated?

A
  • the process of swallowing, involving over 22 muscle groups in the tongue, soft palate, pharynx, and esophagus
  • It occurs in two phases: buccal and pharyngeal-esophageal
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16
Q

What happens during the buccal phase of swallowing and what does stimulation of the tactile cells do?

A
  • the tongue forces the food bolus against the hard palate, then contracts to push the bolus into the oropharynx
  • tactile receptors in the pharynx stimulate reflex activity.
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17
Q

What happens during the pharyngeal-esophageal phase of swallowing?

A
  • is involuntary and controlled by the swallowing center in the medulla and lower pons
  • Cranial nerves, including the vagus nerve, coordinate peristalsis to move food into the esophagus.
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18
Q

What is heartburn, and what causes it?

A

burning, radiating pain due to gastric juice regurgitation into the esophagus
- causes: gastric reflux, overeating, obesity, pregnancy, GERD

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19
Q

What is the function of the stomach?

A

serves as a temporary storage tank and begins the chemical breakdown of proteins, converting food into chyme

20
Q

What is the mechanical digestion process in the stomach?

A

occurs via the churning action of the stomach, which involves the muscular layers of the stomach (specifically the smooth muscle layers) and propulsion of food

21
Q

What is the primary type of enzymatic digestion in the stomach?

A

pepsin - protein digester

22
Q

What role does rennin play in the stomach, and in which population is it secreted?

A

Renin - enzyme that helps digest milk
- children’s primary food source

23
Q

What types of drugs can be absorbed by the stomach?

A

alcohol and NSAIDS are easily absorbed through the stomach mucosa
- regular absorption can irritate the stomach lining

24
Q

What is the essential function of the stomach for life?

A

the production of intrinsic factor, which is required for VB12 absorption in the small intestine

25
Q

How does the secretion of hydrochloric acid (HCl) aid in digestion?

A
  • break down food particles into chyme
  • denature proteins and nucleic acids
  • activate pepsinogen into pepsin for protein digestion
  • destroy bacteria to prevent infection
26
Q

What are the 3 phases of gastric secretion that are the same as the head, stomach and small intestine?

A

Head - cephalic
Gastric - stomach
Intestinal - intestine

27
Q

What triggers the Cephalic Phase of digestion?

A

triggered by sensory inputs such as smell, taste, sight, or even the thought of food
- activates the vagal nuclei in the brainstem stimulating gastric juice secretion

28
Q

How long does the Cephalic Phase last?

A

short-lived, lasting only a few minutes before food enters the stomach

29
Q

What is the main stimulus for the Gastric Phase?

A
  • stomach distension, peptides and low acidity
  • lasts 3-4 hours and contributing to the majority of gastric secretion
30
Q

What happens when the stomach is distended during the Gastric Phase?

A
  • activates mechanoreceptors, leading to vagal reflexes that release Ach, stimulating the secretion of gastric juices
31
Q

What does gastrin do in the Gastric Phase?

A
  • stimulates the release of gastric juices, including HCL from parietal cells
  • is triggered by peptides and low pH in the stomach
32
Q

How does caffeine affect the gastric phase?

A

increases gastrin secretion, promoting more gastric juice production

33
Q

What triggers the Intestinal Phase of digestion?

A

triggered by intestinal gastrin from the duodenum, stimulated by the entry of chyme into the small intestine

34
Q

What is the role of enterogastrones in the Intestinal Phase?

A

secretin and cholecystokinin slow down gastric secretion and emptying to protect the small intestine for excess acidity and ensure efficient digestion

35
Q

How is HCl secretion regulated in the stomach?

A
  • HCl is pumped into the stomach lumen in response to gastrin, ACh and histamine
  • H+ derived from carbonic acid, with Cl- following to maintain balance
36
Q

What is the alkaline tide?

A

the increase in blood pH caused by the release of bicarbonate into the bloodstream (from parietal cells) as Cl is secreted into the stomach where it joins with H+ to form HCl

37
Q

What is the cause of ulcers in the GI tract and where is it most likely to happen?

A

acid secretion damages the lining of the stomach or duodenum, often due to a lack of protective mucus,
- duodenum and esophagus

38
Q

What are the major risk factors for ulcers?

A

smoking, NSAID, alcohol, chronic disease and infection with helicobacter pylori

39
Q

How does cimetidine (Tagamet) help with ulcers?

A

inhibits the histamine-H2 receptor interaction, reducing acid production in the stomach and promoting healing of ulcers

40
Q

What is receptive relaxation in the stomach?

A

the process that allows the stomach to stretch without increasing internal pressure, enabling it to accommodate food
- mediated by interstitial cells set by basic electrical rhythm (BER)

41
Q

How does the basic electrical rhythm (BER) function in gastric motility?

A

generates subthreshold depolarization every 20 seconds in the stomach
- contributes to the rhythmic movement of food
- regulated by neural and hormonal factors to produce depolarization

42
Q

How long does it typically take for the stomach to empty?

A

within 4 hours after meal
- depends on the meal’s volume and contents

43
Q

How do the contents of a meal affect gastric emptying?

A

Carbs empty quickly, while fatty meals slow down gastric emptying because fats coat the chyme (emptying time up to 6 hours)

44
Q

What regulates the rate of gastric emptying?

A

feedback from the duodenum through neural and hormonal signals, which adjust the rate based on food contents and digestion needs

45
Q

What triggers vomiting (emesis)?

A

excessive stretching of stomach or intestines
- also irritants: toxins, alcohol, or spicy food
- stimulate the emetic center in medulla (abdominal and diaphragm contractions)

46
Q

What are the components of bile?

A
  • bile salts
  • bile pigment (bilirubin)
  • cholesterol
  • neutral fats
  • phospholipids
  • electrolytes
47
Q

What is the role of bilirubin in bile?

A

derived from hemoglobin breakdown - pigment
- converted by intestinal bacteria into stercobilin, giving feces their brown color

48
Q

What is the only digestive function of the liver?

A

produce bile
- important for emulsifying fats for digestion and absorption

49
Q

What is the role of the gallbladder in digestion?

A

stores bile and releases it into the duodenum upon stimulation, aiding in the digestion of fats

50
Q

Why is bile important for digestion?

A

acts as a fat emulsifier, breaking down large fat molecules into smaller droplets for the digestive enzymes

51
Q

What stimulates bile production and release into the duodenum?

A

present of fat in the small intestine is the most potent stimulus for bile production and release via the hormone cholecystokinin (CCK)

ANP 1107 (7 decks)

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