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Physiology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

Activities of digestion

A 
Motility
Secretion
Digestion
Absorption
Circulation
Excretion
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2
Q

Types of digestive systems

A

Monogastric
Modified monigastric
Ruminants/cranial fermenters
Hindgut/caudal fermentors

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3
Q

Layers of GI tissues

A 
Serosa
Longitudinal muscle
Circular muscle
Submucosa
Mucosa
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4
Q

How does GI function as a syncythium?

A

Visceral single unit smooth muscle
Autoexcitable
Gap junctions
Slow, very energy efficient

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5
Q

Electrical activity

A

Continous
Slow intrinsic electrical activity
No stable RMP

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6
Q

Types of waves

A

Slow waves- determined by rhythmicity of GI contraction, no real AP, produced by interstitial cells of Cajal (“pacemakers”), no contractions
Spike potential/waves- true AP, occurs when RMP higher than 40mV, higher slow wave potential=increased frequency of spike potential, opening of Ca++ and Na+ channels

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7
Q

Spike potentials stimulated by

A

Stretch
Ach
Parasympathetic

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8
Q

Hyper repolarization of spike waves caused by

A

Norepinephrine

Sympathetic

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9
Q

Peristalsis

A

Moves food forward towards anus
Contractile ring
Stimulated by gut distention

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10
Q

Mixing movements

A

Local intermittent constrictive contractions

Every few cm, duration 5-30s

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11
Q

Enteric nervous system

A

Internal control
Begins at esophagus to anus
Very abundant in neurons
Controls secretion and movement

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12
Q

Autonomic nervous system

A

External control

Sympathetic or pa sympathetic stimulation

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13
Q

Myenteric plexus

A

ENS
Most external plexus btw longitudinal and circular muscle layers
Controls mainly movements
Excitatory

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14
Q

Submucosal plexus

A

ENS
Most internal plexus, in submucosa
Controls secretion and local blood flow

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15
Q

Parasympathetic innervation

A

Stimulates GI activity
Vagal Nerve
Ach+VIP+GRP

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16
Q

Sympathetic innervation

A

Inhibits GI activity
Noradrenaline (alpha receptors)
Somatostatine
Neuropeptide Y

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17
Q

Gastric

A

Produced by G-cells in stomach, duodenum, pancreas
When there is distention or stimulation of Vagal N
Stimulates contraction of stomach
Stimulates release of acid

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18
Q

Motility

A

Produced in stomach, jejunum, duodenum
In presence of alkaline products
Strengthens stomach contractions
Stimulates pepsin production

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19
Q

Cholecystokinin

A

CCK
Produced in duodenum by preconceived of proteins/lipids in duodenum
Stimulates emptying of gallbladder
Stimulates secretion of pancreatic enzymes
Inhibits gastric emptying

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20
Q

Secretin

A

Produced in duodenum as response to gastric juice
Mild inhibition of motility
Stimulates pancreatic juice secretion

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21
Q

Food ingestion mechanisms

A

Prehension
Mastication
Salivation
Swallowing

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22
Q

Salivary glands

A

Parotid-serous
Mandibular-mixed
Sublingual-mucus
Zygomatic-mixed

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23
Q

Saliva contains

A 
Serous= alpha-amylase (starch)
Mucus= mucin-lubrication and surface protection
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24
Q

First secretory step of salivation

A

Acini secretes amylase, mucin and electrolytes

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25
Q

Second secretory step of salivation

A

Modification by duct cells
Active Na+resorption
Saliva becomes alkaline

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26
Q

Saliva contains

A 
97-99,5% water
Organic ions
Mucin
Bicarbonate
Organic products=antibacterial IgA, Lactoferrin, Lisosyme
Enzymes= alpha-amylas
Lingual lipase= hydrolyzes triglycerides
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27
Q

Functions of saliva

A

Lubrication, solubilization, allowing flavor, grass floating, deglutition into food bonus, oral flora control, enzymatic activity, thermoregulation, wound healing, maintenance of skin/hair

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28
Q

Three steps of swallowing

A

Voluntary- initiating process
Pharyngeal stage- involuntary, food from pharynx to esophagus
Esophageal stage- involuntary, food into stomach

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29
Q

Deglutition reflex

A

Swallowing center in medulla oblongada
Sensitive/afferent info from glossopharyngeal N (9)+trigeminal N (5)
Automatic when stimulated
Efferent info to motorimpukses via vagus N (10), trigeminal
N (5) and glossopharyngeal N (9)

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30
Q

Primary peristalsis of esophagus

A

Continuation f movement starting in pharynx to stomach every 8-10s
Controlled by ENS+extrinsic

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31
Q

Secondary peristalsis of esophagus

A

Results from distention of esophagus
Continued until food reaches stomach
ENS

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32
Q

Functions of stomach

A

Storage-accommodation
Mixing into chyme by mixing+propulsion
Slow emptying

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33
Q

Functional areas of stomach

A

Fundus, body, Antrum
Proximal region- food from esophagus, storage
Distal region- grinding+screening, into small particles

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34
Q

Receptive relaxation

A

Fundus relaxes to make room for bolts
Vagus N (10) stimulated by vagovagal reflex due to stretching of stomach
Releases NO+VIP

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35
Q

Mixing/propulsion

A

In distal region
Mixing waves towards Antrum
Interstitial cells of Cajal generates slow waves in basic rhythm
Peristaltic AP induces muscle contraction
Food pushed in both directions=propulsion

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36
Q

Stomach emptying

A

Intense anthrax peristaltic contractions=20% of mixing
Contractions become intense
Pylorus sphincter contraction allowing only water+fluids to pass
Depends on chemical and physical properties

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37
Q

Regulation of stomach emptying

A

Signals=increased gastric volume speeds up emptying by ENS/intrinsic and extrinsic/vagal control
Stretching of walls= increases gastric stimulating Antrum contractions and pyloric relaxation
Intestinal signals= chyme into duodenum starts enterogastric reflex
Inhibitory feedback if too much chyme-intrinsic/extrinsic/hormonal

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38
Q

Cholecystokinin

A

CCK

Senses high lipids= decrease motility and emptying

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39
Q

Gastric inhibitor peptide

A

GIP

Senses lipids and proteins= decreases motility and emptying

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40
Q

Secretion

A

Senses acidic substances

Inhibits anthral contractions

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41
Q

Surface mucus cells

A

Secretes mucus

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42
Q

Mucus neck cells

A

Secretes mucus

43
Q

Parietal cells

A

Produces HCl and IF (intrinsic factor)

44
Q

Chief cells

A

Produced pepsinogen and gastric lipase

45
Q

G-cells

A

Produces hormone gastric

46
Q

HCl

A

Produced by parietal cells in fundus+body

CO2+Cl- from blood- CO2+H2O=HCO3-+H+=H+ +Cl=HCl

47
Q

What increases HCl secretion?

A 
Vagus N (10)+ENS increases Ach
Gastrin+Histamine
48
Q

Histamine

A

Produced in stomach my ECL-cells

Stimulated by Ach and Gastrin

49
Q

Intrinsic factor

A

Produced by parietal cells
A glycoprotein essential for absorbation of B12 in ilium
Regulated by Vagus N (10)+ENS, Gastrin+Histamine

50
Q

Pepsinogen

A

Produced by chief cells in fundus+body

Zymogen, activated by HCl

51
Q

Pepsin

A

Active form of pepsinogen
Proteolytic enzyme
Needs pH 1,8-3,5
Regulated by Ach (vagus+ENS)

52
Q

Mucus

A

Produced by mucus neck cells+surface mucus cells in Antrum
Glycoproteins (viscid mucus) coats stomach mucosa=protection from HCl+pepsin
Alkaline due to bicarbonate
Increases by food intake and mucosa irritation
Lubrication

53
Q

Gastrin

A

Endocrine
Produced by G-cells in Antrum and duodenum
In response to peptides, amino acids, stretching
Stimulates ECL-cells to produce Histamine=increase HCl

54
Q

Histamine

A

Endocrine
Produce by ECL-cells in fundus+body
Induces HCl secretion
Stimulated by Ach+Gastrin

55
Q

Somatostatine

A

Produced in Antrum

Blocks gastrin secretion

56
Q

Cephalic phase

A

30%
CNS stimulated by taste/sight/smell/thought of food
Increase ps HCl and pepsin production
Parasympathetic by vagal N (10)= Ach and ENS

57
Q

Gastric phase

A 
50-60%
Stimulated by stretching+ chemoreceptors
Parasympathetic by vasovagal reflex and ENS
Stimulates Gastrin+Histamine secretion 
Inhibited by high acidity=stops Gastrin
58
Q

Intestinal phase

A

5-10%
Stimulated by low pH and partially digested food in duodenum
Increases Gastrin
Inhibited by distention of duodenum, presence of fatty acids and hypertonic chyme
Enterogastrix reflex (short+long, ENS+CNS)
Hormones secretion- CCK, secretin, GIP

59
Q

Small intestines

A

Duodenum, jejunum, ilium

Digestion, absorption, endocrine organ, immune barrier

60
Q

Three functions of motility in small intestines

A

Mixing chyme with enzymes mm= help digestion
Maximizing chyme contact with mucosa= help absorption
Propulsion of chyme into large intestines

61
Q

Digestive period

A 
Food intake 
Mixing contractions (segmentation contractions)
Propulsive contractions
62
Q

Interdigestive period

A

Fasting

MMC

63
Q

Segmentation/mixing contractions

A

Presence of chyme, stretching
Causes segmentation
Determined by electrical slow waves

64
Q

Propulsive contractions/peristalsis

A

Slow migration of content to large intestines

65
Q

MMC

A

Migrating myoelectric complex
Waves cleaning intestines every 45-180 min during fasting
Stimulated by motilin (ENS+CNS)

66
Q

Three phases of MMC

A

Prolonged period of resting, no contractions
Increased frequency of AP/contractility, irregular and mixing
Few minutes of peak electrical and mechanical activity, Regular contraction/propulsion

67
Q

Motility regulation

A

Stretching of duodenum wall+gastroenteritis reflex
ENS+ANS (parasympathetic=increase, sympathetic=decrease)
Hormonal control
-increased by Gastrin, CCK, insulin, motilin, serotonin
-decreased by secretin, glucagon

68
Q

Chyme arriving to duodenum leads to

A

Neutralization of acidity
Chemical digestion of macromolecules
Pancreatic+bile secretion

69
Q

Exocrine

A

Acini secretes pancreatic juice into duodenum

70
Q

Endocrine

A

Pancreatic islets produce insulin, glucose, somatostatin into bloodstream

71
Q

Acinar cells

A

Produce pancreatic enzymes (zymogen) and water

72
Q

Centriacinar/duct cells

A

Secretes bicarbonate, water, ions Na+ and K+

73
Q

Pancreatic juice

A

Water and ions
Bicarbonate-increases pH, naturalized HCl, inhibits pepsin
Pancreatic enzymes as zymogen to be activated in duodenum

74
Q

Protein digestion

A

Trysinogen, chymotrypsinogen, procarboxy peptidase

75
Q

Carbohydrates digestion

A

Pancreatic amylase

76
Q

Fats digestion

A

Pancreatic lipase, cholesterol esterase, phospholipase

77
Q

Nuclease

A

Deoxyribonucleases, ribonucleases

78
Q

Mucus

A

Produced by mucus neck cells+surface mucus cells in Antrum
Glycoproteins (viscid mucus) coats stomach mucosa=protection from HCl+pepsin
Alkaline due to bicarbonate
Increases by food intake and mucosa irritation
Lubrication

79
Q

Gastrin

A

Endocrine
Produced by G-cells in Antrum and duodenum
In response to peptides, amino acids, stretching
Stimulates ECL-cells to produce Histamine=increase HCl

80
Q

Histamine

A

Endocrine
Produce by ECL-cells in fundus+body
Induces HCl secretion
Stimulated by Ach+Gastrin

81
Q

Somatostatine

A

Produced in Antrum

Blocks gastrin secretion

82
Q

Cephalic phase

A

30%
CNS stimulated by taste/sight/smell/thought of food
Increase ps HCl and pepsin production
Parasympathetic by vagal N (10)= Ach and ENS

83
Q

Gastric phase

A 
50-60%
Stimulated by stretching+ chemoreceptors
Parasympathetic by vasovagal reflex and ENS
Stimulates Gastrin+Histamine secretion 
Inhibited by high acidity=stops Gastrin
84
Q

Intestinal phase

A

5-10%
Stimulated by low pH and partially digested food in duodenum
Increases Gastrin
Inhibited by distention of duodenum, presence of fatty acids and hypertonic chyme
Enterogastrix reflex (short+long, ENS+CNS)
Hormones secretion- CCK, secretin, GIP

85
Q

Small intestines

A

Duodenum, jejunum, ilium

Digestion, absorption, endocrine organ, immune barrier

86
Q

Three functions of motility in small intestines

A

Mixing chyme with enzymes mm= help digestion
Maximizing chyme contact with mucosa= help absorption
Propulsion of chyme into large intestines

87
Q

Digestive period

A 
Food intake 
Mixing contractions (segmentation contractions)
Propulsive contractions
88
Q

Interdigestive period

A

Fasting

MMC

89
Q

Segmentation/mixing contractions

A

Presence of chyme, stretching
Causes segmentation
Determined by electrical slow waves

90
Q

Propulsive contractions/peristalsis

A

Slow migration of content to large intestines

91
Q

MMC

A

Migrating myoelectric complex
Waves cleaning intestines every 45-180 min during fasting
Stimulated by motilin (ENS+CNS)

92
Q

Three phases of MMC

A

Prolonged period of resting, no contractions
Increased frequency of AP/contractility, irregular and mixing
Few minutes of peak electrical and mechanical activity, Regular contraction/propulsion

93
Q

Motility regulation

A

Stretching of duodenum wall+gastroenteritis reflex
ENS+ANS (parasympathetic=increase, sympathetic=decrease)
Hormonal control
-increased by Gastrin, CCK, insulin, motilin, serotonin
-decreased by secretin, glucagon

94
Q

Chyme arriving to duodenum leads to

A

Neutralization of acidity
Chemical digestion of macromolecules
Pancreatic+bile secretion

95
Q

Exocrine

A

Acini secretes pancreatic juice into duodenum

96
Q

Endocrine

A

Pancreatic islets produce insulin, glucose, somatostatin into bloodstream

97
Q

Acinar cells

A

Produce pancreatic enzymes (zymogen) and water

98
Q

Centriacinar/duct cells

A

Secretes bicarbonate, water, ions Na+ and K+

99
Q

Pancreatic juice

A

Water and ions
Bicarbonate-increases pH, naturalized HCl, inhibits pepsin
Pancreatic enzymes as zymogen to be activated in duodenum

100
Q

Protein digestion

A

Trysinogen, chymotrypsinogen, procarboxy peptidase

101
Q

Carbohydrates digestion

A

Pancreatic amylase

102
Q

Fats digestion

A

Pancreatic lipase, cholesterol esterase, phospholipase

103
Q

Nuclease

A

Deoxyribonucleases, ribonucleases

Physiology (13 decks)

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