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Digestive System Flashcards

(103 cards)

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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
Second secretory step of salivation
Modification by duct cells Active Na+resorption Saliva becomes alkaline
26
Saliva contains
``` 97-99,5% water Organic ions Mucin Bicarbonate Organic products=antibacterial IgA, Lactoferrin, Lisosyme Enzymes= alpha-amylas Lingual lipase= hydrolyzes triglycerides ```
27
Functions of saliva
Lubrication, solubilization, allowing flavor, grass floating, deglutition into food bonus, oral flora control, enzymatic activity, thermoregulation, wound healing, maintenance of skin/hair
28
Three steps of swallowing
Voluntary- initiating process Pharyngeal stage- involuntary, food from pharynx to esophagus Esophageal stage- involuntary, food into stomach
29
Deglutition reflex
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)
30
Primary peristalsis of esophagus
Continuation f movement starting in pharynx to stomach every 8-10s Controlled by ENS+extrinsic
31
Secondary peristalsis of esophagus
Results from distention of esophagus Continued until food reaches stomach ENS
32
Functions of stomach
Storage-accommodation Mixing into chyme by mixing+propulsion Slow emptying
33
Functional areas of stomach
Fundus, body, Antrum Proximal region- food from esophagus, storage Distal region- grinding+screening, into small particles
34
Receptive relaxation
Fundus relaxes to make room for bolts Vagus N (10) stimulated by vagovagal reflex due to stretching of stomach Releases NO+VIP
35
Mixing/propulsion
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
36
Stomach emptying
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
37
Regulation of stomach emptying
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
38
Cholecystokinin
CCK | Senses high lipids= decrease motility and emptying
39
Gastric inhibitor peptide
GIP | Senses lipids and proteins= decreases motility and emptying
40
Secretion
Senses acidic substances | Inhibits anthral contractions
41
Surface mucus cells
Secretes mucus
42
Mucus neck cells
Secretes mucus
43
Parietal cells
Produces HCl and IF (intrinsic factor)
44
Chief cells
Produced pepsinogen and gastric lipase
45
G-cells
Produces hormone gastric
46
HCl
Produced by parietal cells in fundus+body | CO2+Cl- from blood- CO2+H2O=HCO3-+H+=H+ +Cl=HCl
47
What increases HCl secretion?
``` Vagus N (10)+ENS increases Ach Gastrin+Histamine ```
48
Histamine
Produced in stomach my ECL-cells | Stimulated by Ach and Gastrin
49
Intrinsic factor
Produced by parietal cells A glycoprotein essential for absorbation of B12 in ilium Regulated by Vagus N (10)+ENS, Gastrin+Histamine
50
Pepsinogen
Produced by chief cells in fundus+body | Zymogen, activated by HCl
51
Pepsin
Active form of pepsinogen Proteolytic enzyme Needs pH 1,8-3,5 Regulated by Ach (vagus+ENS)
52
Mucus
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
Gastrin
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
Histamine
Endocrine Produce by ECL-cells in fundus+body Induces HCl secretion Stimulated by Ach+Gastrin
55
Somatostatine
Produced in Antrum | Blocks gastrin secretion
56
Cephalic phase
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
Gastric phase
``` 50-60% Stimulated by stretching+ chemoreceptors Parasympathetic by vasovagal reflex and ENS Stimulates Gastrin+Histamine secretion Inhibited by high acidity=stops Gastrin ```
58
Intestinal phase
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
Small intestines
Duodenum, jejunum, ilium | Digestion, absorption, endocrine organ, immune barrier
60
Three functions of motility in small intestines
Mixing chyme with enzymes mm= help digestion Maximizing chyme contact with mucosa= help absorption Propulsion of chyme into large intestines
61
Digestive period
``` Food intake Mixing contractions (segmentation contractions) Propulsive contractions ```
62
Interdigestive period
Fasting | MMC
63
Segmentation/mixing contractions
Presence of chyme, stretching Causes segmentation Determined by electrical slow waves
64
Propulsive contractions/peristalsis
Slow migration of content to large intestines
65
MMC
Migrating myoelectric complex Waves cleaning intestines every 45-180 min during fasting Stimulated by motilin (ENS+CNS)
66
Three phases of MMC
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
Motility regulation
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
Chyme arriving to duodenum leads to
Neutralization of acidity Chemical digestion of macromolecules Pancreatic+bile secretion
69
Exocrine
Acini secretes pancreatic juice into duodenum
70
Endocrine
Pancreatic islets produce insulin, glucose, somatostatin into bloodstream
71
Acinar cells
Produce pancreatic enzymes (zymogen) and water
72
Centriacinar/duct cells
Secretes bicarbonate, water, ions Na+ and K+
73
Pancreatic juice
Water and ions Bicarbonate-increases pH, naturalized HCl, inhibits pepsin Pancreatic enzymes as zymogen to be activated in duodenum
74
Protein digestion
Trysinogen, chymotrypsinogen, procarboxy peptidase
75
Carbohydrates digestion
Pancreatic amylase
76
Fats digestion
Pancreatic lipase, cholesterol esterase, phospholipase
77
Nuclease
Deoxyribonucleases, ribonucleases
78
Mucus
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
Gastrin
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
Histamine
Endocrine Produce by ECL-cells in fundus+body Induces HCl secretion Stimulated by Ach+Gastrin
81
Somatostatine
Produced in Antrum | Blocks gastrin secretion
82
Cephalic phase
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
Gastric phase
``` 50-60% Stimulated by stretching+ chemoreceptors Parasympathetic by vasovagal reflex and ENS Stimulates Gastrin+Histamine secretion Inhibited by high acidity=stops Gastrin ```
84
Intestinal phase
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
Small intestines
Duodenum, jejunum, ilium | Digestion, absorption, endocrine organ, immune barrier
86
Three functions of motility in small intestines
Mixing chyme with enzymes mm= help digestion Maximizing chyme contact with mucosa= help absorption Propulsion of chyme into large intestines
87
Digestive period
``` Food intake Mixing contractions (segmentation contractions) Propulsive contractions ```
88
Interdigestive period
Fasting | MMC
89
Segmentation/mixing contractions
Presence of chyme, stretching Causes segmentation Determined by electrical slow waves
90
Propulsive contractions/peristalsis
Slow migration of content to large intestines
91
MMC
Migrating myoelectric complex Waves cleaning intestines every 45-180 min during fasting Stimulated by motilin (ENS+CNS)
92
Three phases of MMC
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
Motility regulation
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
Chyme arriving to duodenum leads to
Neutralization of acidity Chemical digestion of macromolecules Pancreatic+bile secretion
95
Exocrine
Acini secretes pancreatic juice into duodenum
96
Endocrine
Pancreatic islets produce insulin, glucose, somatostatin into bloodstream
97
Acinar cells
Produce pancreatic enzymes (zymogen) and water
98
Centriacinar/duct cells
Secretes bicarbonate, water, ions Na+ and K+
99
Pancreatic juice
Water and ions Bicarbonate-increases pH, naturalized HCl, inhibits pepsin Pancreatic enzymes as zymogen to be activated in duodenum
100
Protein digestion
Trysinogen, chymotrypsinogen, procarboxy peptidase
101
Carbohydrates digestion
Pancreatic amylase
102
Fats digestion
Pancreatic lipase, cholesterol esterase, phospholipase
103
Nuclease
Deoxyribonucleases, ribonucleases

Physiology (13 decks)

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