Physiology > GI 1 > Flashcards

GI 1 Flashcards

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1
Q

components of the GI system (2)

A
  1. Alimentary Canal (GI Tract)

2. Accessory organs

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2
Q
  1. Alimentary Canal (GI Tract) (3)
A

Mouth to anus
Lumen Contents considered outside body
30 feet in length

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3
Q
  1. Accessory organs (2)
A

Not part of GI tract

Produce substances secreted into tract

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4
Q

Produce substances secreted into tract (3)

A

Salivary glands
Exocrine pancreas
Liver and Gall Bladder

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5
Q
  1. Digestion
A

Breakdown ingested molecules into building blocks

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6
Q

Two Types of digestion

A

A. Mechanical

B. Chemical

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7
Q
  1. Secretion (3)
A

Digestive enzymes
Acid/Base
Bile

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8
Q
  1. Absorption (2)
A

Passive and Active transport processes

Moves substances from lumen of gut to blood

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9
Q
  1. Motility (3)
A

Mixing
Mechanical Digestion
Move material through tract

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10
Q
  1. Excretion (2)
A

Removal of Metabolic waste

Very little true waste in Feces (Bile pigments)

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11
Q
  1. Defense (1)
A

Gut Associated Lymphoid Tissue

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12
Q

Nutrients ingested substances (7)

A 
Carbohydrates
Fats
Proteins
DNA, RNA
Water
Electrolytes
Vitamins
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13
Q

Other ingested substances (5)

A 
Pathogens
Alcohol
Drugs (Licit, Illicit)
Toxins
Coins, Toys, Bugs
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14
Q

Four Layers

A
  1. Mucosa
  2. Submucosa
  3. Muscularis Externa
  4. Serosa
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15
Q
  1. Mucosa (3)
A

Simple Columnar Epithelium
Lamina Propria
Muscularis Mucosa
-Movement of Villi

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16
Q
  1. 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
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17
Q
  1. 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
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18
Q
  1. Serosa (2)
A

CT covering

Support GI tract in abdominal cavity

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19
Q

Epithelial layer (4)

A

Simple Columnar (microvilli)
Goblet Cells
Enteroendocrine cells (base of villi)
Stem cells

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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

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21
Q

Inside Villus (2)

A

Lacteals (lymph vessels)

Capillary network

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22
Q

Control Systems regulate conditions in

A

lumen of tract (not ECF conditions)

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23
Q

Control mechanisms are governed by

A

volume and composition of luminal contents

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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.
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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
``` Enteric Nervous System (ENS)“The Brain in the Gut” Myenteric plexus (2) ```
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
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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
skipped | Patterns of Motility (8)
``` Chewing Swallowing Esophageal transport Gastric storage, trituration, emptying Vomiting Gallbladder storage, emptying Small intestinal mixing & transport Colonic storage, defecation ```
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
``` 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
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Stimulated by: (5)
``` Autonomic (primarily parasympathetic) Thinking/seeing/smelling food Conditioned salivation Chewing Nausea ```
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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)
``` 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
skipped | 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
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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
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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
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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
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1. Voluntary Stage (3)
Initiate swallowing process Bolus of food moved into pharynx by tongue Stimulates epithelial swallowing receptor area
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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.
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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
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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
Physiology
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