GI 1 Flashcards
1
Q
components of the GI system (2)
A
- Alimentary Canal (GI Tract)
2. Accessory organs
2
Q
- Alimentary Canal (GI Tract) (3)
A
Mouth to anus
Lumen Contents considered outside body
30 feet in length
3
Q
- Accessory organs (2)
A
Not part of GI tract
Produce substances secreted into tract
4
Q
Produce substances secreted into tract (3)
A
Salivary glands
Exocrine pancreas
Liver and Gall Bladder
5
Q
- Digestion
A
Breakdown ingested molecules into building blocks
6
Q
Two Types of digestion
A
A. Mechanical
B. Chemical
7
Q
- Secretion (3)
A
Digestive enzymes
Acid/Base
Bile
8
Q
- Absorption (2)
A
Passive and Active transport processes
Moves substances from lumen of gut to blood
9
Q
- Motility (3)
A
Mixing
Mechanical Digestion
Move material through tract
10
Q
- Excretion (2)
A
Removal of Metabolic waste
Very little true waste in Feces (Bile pigments)
11
Q
- Defense (1)
A
Gut Associated Lymphoid Tissue
12
Q
Nutrients ingested substances (7)
A
Carbohydrates Fats Proteins DNA, RNA Water Electrolytes Vitamins
13
Q
Other ingested substances (5)
A
Pathogens Alcohol Drugs (Licit, Illicit) Toxins Coins, Toys, Bugs
14
Q
Four Layers
A
- Mucosa
- Submucosa
- Muscularis Externa
- Serosa
15
Q
- Mucosa (3)
A
Simple Columnar Epithelium
Lamina Propria
Muscularis Mucosa
-Movement of Villi
16
Q
- Submucosa (3)
A
CT Layer Blood and lymph vessels Submucosal Plexus Network of neurons -Projections to luminal surface cells, muscularis mucosa, and to -Myenteric plexus
17
Q
- Muscularis Externa (3)
A
Circular Muscle -Contraction narrows lumen Longitudinal muscle -Contraction shortens tube Myenteric Plexus -Network of neurons -Input from Autonomic NS -Projections to Submucosal Plexus, Circular, and Longitudinal muscle
18
Q
- Serosa (2)
A
CT covering
Support GI tract in abdominal cavity
19
Q
Epithelial layer (4)
A
Simple Columnar (microvilli)
Goblet Cells
Enteroendocrine cells (base of villi)
Stem cells
20
Q
Tremendous surface area available for absorption of materials from lumen (3)
A
Circular Folds
Villi
Microvilli (Brush Border)
-Increases SA 600x over flat surface
21
Q
Inside Villus (2)
A
Lacteals (lymph vessels)
Capillary network
22
Q
Control Systems regulate conditions in
A
lumen of tract (not ECF conditions)
23
Q
Control mechanisms are governed by
A
volume and composition of luminal contents
24
Q
Afferent (Sensory)
(3)
A
- Responds to stretch, inflammation, nutrients, endocrine factors.
- Synapses in enteric nervous system, prevertebral ganglia, spinal cord, brainstem.
- Vagal nerves mainly afferent to brainstem.
25
Efferent (Secretomotor) (3)
somatic
sympathetic
parasympthetic
26
Somatic –
CN XII (tongue), V (chewing), IX, X (swallowing); Pudendal n. – ext. anal sphincter
27
Sympathetic –
post-ganglionic fibers (NEpi) to enteric nervous system, vasculature, ducts, parenchyma; usually inhibitory.
28
Parasympathetic (vagus, pelvic) –
ENS functions as post-ganglionic fibers, actions are stimulatory or inhibitory, depending on final neurotransmitter receptor.
29
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Enteric Nervous System (ENS)“The Brain in the Gut”
Myenteric plexus (2)
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Linear chain of neurons that extend the entire length of GI Tract
Control muscle of muscularis externa
30
When ENS is stimulated (5)
Increase tone of gut wall
Increase intensity of rhythmic contractions
Slight increase in rate of rhythmic contractions
Increase conduction velocity of electrical waves along gut wall
Inhibition of sphincter contraction
31
submucosal plexus controls function of each minute segment of tract
Local control of (3)
Intestinal secretions
Absorption
Contraction of mucosal muscle
32
Endocrine Regulation of Digestive Function (4)
Endocrine cells scattered in gut mucosa.
Specialized cells: one cell – one hormone (mostly).
Specific cell types localized to regions of gut.
Cells “taste” luminal contents.
33
Paracrine Factors (3)
Cells similar to endocrine.
Released into interstitial fluid, diffuses to target (may “overflow” into the circulation).
Two established gut paracrine factors: histamine (ECL cell), somatostatin (D cell).
34
Histamine is mainly released by
gastrin
35
Somatostatin is mainly released by
luminal H+
36
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| Patterns of Motility (8)
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Chewing
Swallowing
Esophageal transport
Gastric storage, trituration, emptying
Vomiting
Gallbladder storage, emptying
Small intestinal mixing & transport
Colonic storage, defecation
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37
Skeletal (voluntary, striated) –
mouth, oropharynx, upper esophageal sphincter, upper 1/3 of esophagus, external anal sphincter.
38
Smooth (involuntary) –
lower 2/3 of esophagus, stomach, small intestine, large intestine, gallbladder, biliary and pancreatic ducts.
39
Importance of Portal Vein (2)
Collects all venous outflow from most GI organs.
| All portal outflow goes to liver before entering vena cava.
40
All portal outflow goes to liver before entering vena cava.
Nutrients, hormones, drugs, toxins “scanned” by liver.
41
Types of Saliva (2)
serous
| mucus
42
1. Serous (3)
Watery secretion containing ptyalin (α amylase)
Moisten and dissolve food
Small amount of chemical digestion
43
2. Mucus (2)
Thick secretions containing mucin
| Lubrication and protection of surfaces
44
Types of Salivary Glands (4)
Parotid - Serous Gland
Submandibular - Mixed
Sublingual - Mixed
Many tiny buccal glands - Mucus
45
Constituent: water
Function:
Facilitates taste and dissolution of nutients, aids in swallowing
46
Constituent: bicarbonate
Function:
Neutralizes refluxed gastric acid
47
Constituent: mucins
Function:
Lubrication
48
Constituent: amylase
Function:
Starch Digestion
49
Constituent: lysozyme, lactoferrin, igA
Function:
Innate and acquired immunity
50
Constituent: epidermal and nerve growth factors
Function:
? Mucosal growth and protection
51
Saliva
| Produce up to -- L/day..
1.5
52
Secretion strictly under --- reflex control.
neural
53
Parasympathetic NS (Ach/Muscarinic Receptors) (4)
Predominate regulator of saliva production
Critical for initiation of saliva secretion
Critical for sustaining high levels of saliva secretion
Vasodilation of blood vessels supplying salivary glands
54
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Parasympathetic NS (Ach/Muscarinic Receptors)
Causes:
```
Up to 20x increase in saliva production by acinar cells
55
Reflex Activation of Parasympathetic Stimulated Saliva Production (4)
Taste (especially sour) and tactile stimuli (presence of smooth objects) on tongue surface
Smell of food (especially if it is a food that is not liked)
Ingestion of irritating foods
Nausea
56
Sympathetic NS (NE/Adrenergic receptors) (2)
Minor role
| Potentiates Parasympathetic effects
57
As flow rate increases, the saliva: (2)
more closely resembles the plasma (less hypotonic)
| Becomes more basic
58
Unstimulated Salivation (3)
69% submandibular glands
26% parotid glands
5% sublingual glands
59
Saliva Inhibited by: (4)
Fear
Sleep
Fatigue
Dehydration
60
Stimulated Salivation (3)
69% Parotid
26% submandibular
5% sublingual
61
Stimulated by: (5)
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Autonomic (primarily parasympathetic)
Thinking/seeing/smelling food
Conditioned salivation
Chewing
Nausea
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62
Rates of saliva production are not dependent on ---, flow rates remain constant in spite of
age
| acinar degeneration
63
SALIVARY GLAND DYSFUNCTION- XEROSTOMIA
Subjective feeling of a dry mouth.
64
SALIVARY GLAND DYSFUNCTION- XEROSTOMIA
| most common causes (5)
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Polypharmacy (>4 drugs/day)
Anxiety and depression (and medications used for treatment)
Insufficient hydration
Radiation to the head and neck
Sjogren syndrome
```
65
Sjogren syndrome (3)
Autoimmune destruction of mucous membranes and moisture-secreting glands
Decreased production of tears and saliva
Dry eyes and mouth
66
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| CONSEQUENCES AND MANAGEMENT OF XEROSTOMIA (7)
Increased caries due to reduced oral clearance of sugars, dietary acids, oral bacteria
Halitosis
Disrupted sleep due to dry mouth; wake up to sip water and moisten mouth
Difficulty lubricating and swallowing food
Dry mouth (feel thirsty, dry, cracked lips)
Impaired sense of tastes
Heartburn
67
Dry mouth (feel thirsty, dry, cracked lips) (2)
Burning mouth sensation
| Dry/sore oral mucosa
68
Heartburn (3)
Low saliva; decreased buffering
Loss of protective growth factors in saliva
Lengthened healing time for ulcers
69
Management (4)
Avoid acidic, spicy, crunchy and coarse foods.
Alcohol-free toothpastes and rinses.
Oral moisturizers, sips of water, sugarless chewing gum.
Sialogogues such as pilocarpine and cevimeline before meals (cholinergic agonists)
70
MASTICATION
Rhythmic opening and closing of mandible that is coordinated with tongue movements
71
MASTICATION
| Functions (2)
1. Prepare food bolus for swallowing
| 2. Initiate digestive and metabolic activities
72
Mechanical digestion – Reduce particle size (3)
Break up cells
Break up indigestible cellulose
Increase surface area/decrease particle size for mixing with digestive enzymes
73
Mix food with saliva (serous and mucous) (4)
Chemical digestion (mainly carbohydrates)
Sufficient plasticity
Surface lubrication
Cohesive structure
74
2. Initiate digestive and metabolic activities (2)
Digestion of carbohydrates in mouth
| Initiate reflexes to prepare digestive tract for incoming food
75
Deglutition (Swallowing)
| three stages
1. Voluntary Stage
2. Pharyngeal Stage
3. Esophageal Stage
76
1. Voluntary Stage (3)
Initiate swallowing process
Bolus of food moved into pharynx by tongue
Stimulates epithelial swallowing receptor area
77
2. Pharyngeal Stage (5)
Involuntary
Mediated by swallowing center in brainstem
Soft palate pulled upward and closes off nasopharynx
Epiglottis closes off trachea (Respiration inhibited for < 2 sec.)
Upper Esophageal Sphincter (UES; Pharyngoesophageal Sphincter) relaxes
78
3. Esophageal Stage (2)
Coordinated muscle contractions to move bolus through esophagus into stomach (aborally).
≈ 10 sec.
79
Esophageal Function:Sphincters and Peristalsis (3)
1. Transport of solids and liquids from Pharynx to stomach
2. Prevents air intake - UES
3. Prevents reflux (stomach to esophagus) -LES
80
Peristalsis =
wave of contraction that moves bolus through esophagus
81
Primary Peristalsis-
continuation of peristaltic wave initiated during pharyngeal phase of swallowing (8-10 sec)
82
Secondary Peristalsis- activated by
esophageal distension from retained food in esophagus
83
secondary peristalsis
| Function (2)
Clearing a bolus that was not wholly expelled by primary wave
Removing any gastric contents that reflux back into the lower esophagus
84
Upper and lower esophageal sphincters
remain closed between swallows.
| Both have tonic contractile properties.
85
Upper esophageal sphincter relaxes during ---.
swallow
86
Lower esophageal sphincter relaxes as
peristaltic wave approaches.
87
Gastro-Esophageal Reflux Disease (3)
Reflux of gastric contents into esophagus
Common and potentially disabling
Treated by inhibiting gastric acid secretion
