GI tract Flashcards
1
Q
What organs make up the digestive system?
A
Digestive tract, salivary glands, exocrine pancreas, liver, gallbladder.
2
Q
What type of muscles are found in the mouth and pharynx?
A
Striated muscle.
3
Q
What is the main function of the mucous membrane in the digestive tract?
A
Protection, secretion, and absorption.
4
Q
What does the submucosa provide in the digestive tract?
A
Elasticity and contains larger vessels and nerves.
5
Q
What are the two layers of the muscularis externa?
A
Circular and longitudinal layers.
6
Q
What is the function of serosa?
A
Prevents friction and suspends organs via the mesentery.
7
Q
What do sphincters prevent in the GI tract?
A
Reflux between specialized compartments.
8
Q
What are the two types of motility in the GI tract?
A
Propulsive and mixing.
9
Q
What is the role of exocrine glands in digestion?
A
They secrete digestive juices into the lumen.
10
Q
What are the three types of macronutrients digested in the GI tract?
A
Carbohydrates, proteins, and fats.
11
Q
Where does most absorption occur in the digestive system?
A
Small intestine.
12
Q
What are the four factors regulating digestive system function?
A
Autonomous smooth muscle function, intrinsic nerve plexuses, extrinsic nerves, GI hormones.
13
Q
What are the cells of Cajal responsible for?
A
Generating slow-wave potentials in the GI tract.
14
Q
What does the enteric nervous system regulate?
A
GI motility, secretion, and absorption.
15
Q
How does sympathetic stimulation affect the GI tract?
A
It inhibits contraction and secretion.
16
Q
What are GI hormones produced by?
A
Endocrine cells throughout the GI tract.
17
Q
What are the three types of GI sensory receptors?
A
Chemoreceptors, mechanoreceptors, osmoreceptors.
18
Q
What is the function of saliva?
A
Lubricates food, starts digestion of starch, and provides oral hygiene.
19
Q
Which enzyme in saliva begins starch digestion?
A
Amylase.
20
Q
What triggers the conditioned salivary reflex?
A
Anticipation of food without oral stimulation.
21
Q
What prevents air from entering the esophagus?
A
Pharyngoesophageal sphincter.
22
Q
What prevents gastric contents from regurgitating into the esophagus?
A
Gastroesophageal sphincter.
23
Q
What are the three main regions of the stomach?
A
Fundus, body, and antrum.
24
Q
What is the barrier between the stomach and duodenum?
A
Pyloric sphincter.
25
What is chyme?
Thick liquid mixture of food and gastric secretions.
26
What is gastric emptying influenced by?
Volume of chyme, fat, acid, hypertonicity, and duodenal distension.
27
Which hormone inhibits antral contractions during high-fat digestion?
Cholecystokinin (CCK).
28
What are the consequences of vomiting?
Loss of acid, dehydration, and metabolic alkalosis.
29
Which cells in the stomach secrete HCl?
Parietal cells.
30
Why is intrinsic factor important?
It is necessary for B12 absorption.
31
What activates pepsinogen into pepsin?
HCl.
32
What is the main role of gastrin?
Stimulates HCl and histamine secretion.
33
What protects the gastric lining?
Mucus and bicarbonate.
34
What non-nutrients are absorbed by the stomach?
Ethyl alcohol and aspirin.
35
What are the two main secretions of the pancreas?
Digestive enzymes and bicarbonate.
36
Which enzyme is essential for fat digestion?
Pancreatic lipase.
37
What are bile salts essential for?
Emulsifying and absorbing fats.
38
What organ secretes bile?
Liver.
39
What happens if bile ducts are blocked?
Feces become grayish white.
40
What is the primary motility of the small intestine during digestion?
Segmentation.
41
What is the migrating motility complex?
A cleaning wave between meals.
42
What does the ileocecal valve prevent?
Backward movement of contents from the large intestine to the small intestine.
43
Where are B12 and bile salts absorbed?
Terminal ileum.
44
How is water absorbed in the small intestine?
Passively due to osmotic pressure.
45
What is the function of the large intestine?
Drying and storage of feces.
46
What initiates defecation?
Relaxation of internal anal sphincter and contraction of the rectum.
47
What is the function of gut microbiota?
Digests food, maintains mucosal integrity, and supports immunity.
48
What is the pH of the stomach?
About 2.
49
What are the three phases of gastric secretion?
Cephalic, gastric, and intestinal.
50
What is the primary component of bile?
Bile salts.
51
What enzyme digests proteins in the stomach?
Pepsin.
52
Which nutrient is digested by pancreatic amylase?
Carbohydrates.
53
How are fats absorbed in the small intestine?
Through micelles.
54
What is the function of the appendix?
Houses lymphocytes.
55
What are haustra in the large intestine?
Pouches formed by the colon.
56
What is the gastrocolic reflex?
Increased motility in the large intestine after eating.
57
What is the effect of secretin?
Stimulates bicarbonate secretion to neutralize acid.
58
What is bilirubin derived from?
Hemoglobin degradation.
59
How are fat-soluble vitamins absorbed?
With fats in micelles.
60
Which vitamin requires intrinsic factor for absorption?
B12.
61
What is the role of hepatocytes?
Detoxification, nutrient processing, and bile production.
62
What is the primary site for drug detoxification?
Liver.
63
How is glucose absorbed in the small intestine?
Via sodium-glucose transporters (SGLT).
64
What is metabolic alkalosis a consequence of?
Vomiting.
65
What stimulates the release of CCK?
Fat in the duodenum.
66
What is the role of tight junctions in gastric mucosa?
Prevents H+ penetration.
67
What controls peristalsis in the esophagus?
Circular muscle contractions.
68
What protects the esophagus from acid?
Mucus.
69
What is the role of lysozyme in saliva?
Breaks down bacterial cell walls.
70
What does the gallbladder store?
Bile.
71
Which segment of the small intestine has the highest absorption?
Jejunum.
72
How is sodium absorbed in the intestine?
Actively and passively.
73
What triggers the simple salivary reflex?
Chemo- and pressure receptors in the mouth.
74
What type of muscle is responsible for most of the movement in the digestive tract?
Smooth muscle
75
Describe the two types of motility in the digestive tract.
Propulsive: pushes contents forward
Mixing: mixes food with digestive juices; facilitates absorption by exposing different parts of food to absorbing surfaces
76
What is the function of exocrine glands in the digestive system?
Secrete digestive juices into the lumen
77
Describe the process of how secretory cells form secretions.
They extract large volumes of water and raw materials from plasma to create bile salts, mucus, and enzymes
78
Is the fluid used to form secretions permanently lost?
No, it is returned to the blood unless lost through vomiting or diarrhea
79
How is the endocrine tissue of the GI tract organized compared to peripheral endocrine tissues?
Not in a discrete organization, but spread throughout the length of the tract
80
What is the function of the signal proteins produced by the endocrine tissue of the GI tract?
They act as GI hormones or GI peptides
81
What is the main purpose of digestion?
To chemically reduce complex materials into smaller, absorbable units
82
Why are carbohydrates, proteins, and fats broken down during digestion?
Because they are too large to be absorbed from the lumen
83
What are polysaccharides?
Long chains of sugars, making up most ingested carbs
84
What are monosaccharides?
The simplest sugars, rarely found in the diet in their simplest form
85
List three examples of monosaccharides
Glucose, fructose, and galactose
86
How are proteins broken down during digestion?
Into amino acids or small polypeptides
87
What is the most common form of dietary fat?
Triglycerides (glycerol with three fatty acid molecules)
88
How are triglycerides digested?
Two of the fatty acids are split off, leaving a monoglyceride
89
What form of fat is absorbed by the body?
Fatty acids
90
Where does most absorption occur in the digestive system?
Small intestine
91
What substances are transferred into the blood or lymph during absorption?
Nutrients, water, vitamins, and electrolytes
92
List the four factors involved in regulating digestive system function.
Autonomous smooth muscle function
Intrinsic nerve plexuses○
Extrinsic nerves
GI hormones
93
What is the basic electrical rhythm (BER)?
Rhythmic cycles of depolarization and repolarization in the digestive tract's smooth muscle
94
What are the pacemaker cells of the muscularis externa called?
Cells of Cajal
95
What do the Cells of Cajal generate?
Slow-wave potentials
96
Describe slow-wave potentials
Self-excitable activity in which membrane potential undergoes alternating depolarization and repolarization
97
Are slow-waves action potentials?
No, but their peaks may trigger a volley of action potentials
98
How do slow waves propagate?
Via gap junctions
99
What happens when the muscle sheet reaches threshold?
It behaves as one unit
100
What happens when the muscle sheet is not at threshold?
It oscillates between depolarization and hyperpolarization
101
What are the two major nerve fiber networks that run along the length of the GI tract?
Submucosal plexus and myenteric plexus
102
What is the function of the submucosal plexus?
Secretomotor innervation to the mucosa
103
What is the function of the myenteric plexus?
Motor innervation to the muscular layer
104
What is the significance of the intrinsic nerve plexuses?
They function as the GI system's own nervous system, allowing for a considerable degree of self-regulation
105
How many neurons are in the enteric nervous system?
As many as in the spinal cord
106
What is the function of intrinsic afferent neurons?
They are sensory neurons that respond to local stimuli
107
What is the function of intrinsic efferent neurons?
They affect motility, secretion, etc.
108
What is the role of extrinsic nerves in GI tract function?
They regulate GI tract function by modifying motility or secretion directly or by acting on intrinsic plexuses
109
How do extrinsic nerves originate?
From the autonomic nervous system
110
What is the effect of sympathetic stimulation on the GI tract?
Inhibits tract contraction and secretion
111
What is the effect of parasympathetic stimulation on the GI tract?
Enhances digestion
112
Where are GI hormones produced?
By endocrine cells from different regions of the GI tract
113
What are the influences of GI hormones on smooth muscle and gland cells?
They can cause both excitatory and inhibitory influences
114
List the three types of sensory receptors in the GI tract wall.
Chemoreceptors: sensitive to lumen contents
Mechanoreceptors: sensitive to stretch or tension in the wall
Osmoreceptors: sensitive to osmolarity of luminal contents
115
What happens when GI receptors are stimulated?
Effector actions and/or neural reflexes are initiated
116
Give examples of effector cells in the GI tract
Smooth muscle cells (motility), exocrine cells (secretions), and endocrine cells (hormones)
117
Differentiate between short and long reflexes.
Short reflex: located within the GI tract
Long reflex: involves the CNS
118
What digestive processes occur in the mouth?
Digestion begins and is minimal (amylase), and no food absorption occurs
119
What happens to food in the mouth?
It is moistened, lubricated, and made to stick together
120
What is the composition of saliva?
99.5% water, 0.5% electrolytes and protein; no glucose and 1/7th the NaCl concentration compared to plasma
121
How does the composition of saliva affect taste perception?
It enhances sweet and salty tastes
122
What are the most important proteins in saliva?
Amylase and lysozyme
123
What is the function of salivary amylase?
Begins digestion of dietary starches
124
What is the function of lysozyme?
It is a salivary antimicrobial that breaks down bacterial cell walls
125
What other antimicrobial components are found in saliva?
IgA antibodies and lactoferrin, which binds to iron that bacteria need
126
What role does saliva play in oral hygiene?
It flushes food residue and foreign particles
127
How does saliva contribute to dental health?
It is rich in bicarbonate, which neutralizes acid from food and bacteria, preventing dental caries
128
How much saliva is secreted per day?
1-2 L
129
What is the basal rate of saliva secretion?
0.5 mL/min
130
What is the maximum rate of saliva secretion?
5 mL/min in response to potent stimuli
131
Describe the two types of salivary reflexes that increase saliva production
Simple salivary reflex: oral stimulation sends an afferent impulse to the salivary center in the brainstem, increasing salivation
Conditioned salivary reflex: occurs without oral stimulation, such as the "mouth-watering" anticipation of food
132
How do the sympathetic and parasympathetic nervous systems affect saliva production?
Both promote salivation, but with different compositions:
Parasympathetic: watery saliva rich with enzymes
Sympathetic: thick saliva rich in mucus
133
Describe the pharynx and its function
A cavity at the rear of the throat that serves as a common passageway for the digestive and respiratory systems
134
What structures are located in the pharynx?
Tonsils
135
What initiates swallowing?
Motility in the pharynx leads to swallowing
136
Describe the process of swallowing.
Pharyngeal pressure receptors send afferent impulses to the swallowing center of the brainstem, initiating the all-or-none process of swallowing
137
What structures mark the beginning and end of the esophagus?
Sphincter muscles
138
Name the sphincter muscles at each end of the esophagus and describe their functions.
Pharyngoesophageal sphincter (upper end): prevents air from entering the digestive tract
Gastroesophageal sphincter (lower end): stays tonically contracted, increases with inspiration, and prevents gastric contents from regurgitating
139
How does food move through the esophagus?
Peristalsis (ringlike contractions of circular muscle) pushes the bolus between the two sphincters
140
What is the purpose of esophageal secretion?
To protect against acid, enzymes, and sharp edges of the bolus
141
List the three sections of the stomach
Fundus, body, and antrum
142
What is the function of the pyloric sphincter?
It acts as a barrier between the stomach and the duodenum
143
What are the three main functions of the stomach?
Store ingested food until it is emptied into the small intestine
Secrete HCl acid (and others)
Mix food with acid and pulverize it to produce chyme
144
What is chyme?
A thick liquid mixture of food and gastric juices that is emptied into the duodenum
145
List the four aspects of gastric motility.
Filling: bolus enters via the esophagus
Storage: stomach volume can increase from 50 mL to 1000 mL as deep folds flatten
Mixing: cells of Cajal in the upper fundus generate three slow waves per minute, leading to action potentials and strong antral contractions that propel chyme distally
Emptying: also facilitated by antral contraction
146
Describe the process of vomiting
Vomiting involves the forceful expulsion of gastric contents through the oral cavity, controlled by the vomiting center of the brainstem. The major force comes from respiratory muscle contraction, especially the diaphragm and abdominal muscles
147
What factors can trigger vomiting
Vomiting can be initiated by various stimuli, including tactile stimulation of the back of the throat, distention or irritation of the stomach and duodenum, elevated intracranial pressure, dizziness, drugs, psychogenic factors (emotions)
