Set 9 Flashcards
1
Q
What are four basic processes of the digestive system?
A
- Digestion
- Secretion
- Absorption
- Motility
2
Q
What is the primary function of the digestive system?
A
Transfer nutrients, water, and electrolytes from ingested food into the body’s internal environment
3
Q
What is the pathway through which food passes within the GI?
A
- Oral cavity
- Esophagus
- Stomach
- Small intestine
- Large intestine
- Rectum
4
Q
What is the musculature of the esophagus composed of?
A
- Initially skeletal muscle (2/3)
- Smooth muscle afterwards (1/3)
5
Q
What are plica?
A
Folds within the intestine that help increase the surface area
6
Q
What are the layers to the digestive tract, starting with the innermost layer?
A
- Mucosa
- Submucosa
- Muscularis
- Serosa
7
Q
What are the three layers of the mucosa?
A
- Mucous membrane
- Lamina propria
- Muscularis mucosa
8
Q
What are the functions of the mucous membrane of the mucosa?
A
- Serves as a protective surface
- Modified for secretion and absorption
9
Q
What kind of cells does the mucous membrane of the mucosa contain?
A
- Exocrine gland cells
- Endocrine gland cells
- Epithelial cells
10
Q
What is the lamina propria? What does it contain?
A
- Thin layer of connective tissue
- Houses gut-associated lymphoid tissue (GALT)
11
Q
What structure is important in the defense against disease-causing intestinal bacteria?
A
GALT
12
Q
What is the muscularis mucosa?
A
Sparse layer of smooth muscle
13
Q
What do cells at the base of intestinal crypts (Lieberkuhn) secrete?
A
Bactericidal enzymes
14
Q
What are the structures of the small intestine?
A
- Duodenum
- Jejunum
- Ileum
15
Q
What are the folds of the mucosa covered with?
A
Vili to increase the surface area
16
Q
What are the folds in the stomach called? What are they marked by?
A
- Rugae
- Marked by depressions called gastric pits
17
Q
What is found below gastric pits?
A
Coiled glands
18
Q
What does the serosa secrete? What is its function?
A
- Serous fluid
- Lubricates and prevents friction between digestive organs and the surrounding viscera
19
Q
The serosa is continuous with the mesentary throughout the GI tract. What does that provide?
A
- Attachment provides relative fixation
- Supports digestive organs in proper place while allowing them freedom for mixing and propulsive movements
20
Q
How many salivary glands produce saliva? What is its composition?
A
- Three major pairs of salivary glands
- 99.5% H2O, 0.5% electrolytes and protein (amylase)
21
Q
What is the function of salivary amylase?
A
Begins digestion of carbohydrates (secreted by serous cells)
22
Q
Describe the antibacterial action of saliva.
A
- Lysozyme destroys bacteria
- Saliva rinses away material that could serve as a food source for bacteria
23
Q
What kind of epithelium is contained within the esophagus?
A
Stratified squamous epithelium
24
Q
What does the esophagus contain instead of serosa?
A
Adventitia
25
The esophagus extends from the _______ to the _______.
pharynx
| stomach
26
What is the function of the pharyngoesophageal sphincter?
Keeps the entrance closed to prevent large volumes of air from entering the esophagus and stomach
27
What is the function of the gastroesophageal sphincter?
Prevents reflex of gastric contents
28
What is peristalsis?
Promotes forward movement by contracting behind the bolus
29
What is motility?
- Refers to the segmental muscular contractions that mix the food with enzymes
- There is NO net forward movement
- Increases their chances of absorption by digesting properly
30
What are the three sections of the stomach?
- Fundus (top)
- Body
- Antrum (bottom)
31
What is the function of the pyloric sphincter?
Serves as a barrier between the stomach and the upper part of the small intestine
32
What movements are included in gastric motility?
Propulsion (moving down) and retropulsion (moving up)
33
What occurs in the stomach when peristaltic contractions become stronger?
Some of the liquid chyme (partially digested food mix) squirts past the pyloric sphincter into the duodenum
34
Why is gastric emptying tightly regulated?
- Because the pH of the stomach is extremely low, and the small intestine can't handle the acidity
- The chyme must first trigger the release of pancreatic juices to the small intestine PRIOR to gastric emptying
35
What are the principle factors that regulate gastric emptying?
Factors in the duodenum
36
What factors in the duodenum regulate gastric emptying (4)?
- Fat
- Acid
- Hypertonicity
- Distension
37
What does unneutralized acid in the duodenum cause?
Inhibits further emptying of acidic gastric contents until neutralization can be accomplished
38
How does hypertonicity influence gastric emptying?
Build-up of amino acids and glucose molecules in the duodenum slow gastric emptying
39
How does distension influence gastric emptying?
Too much chyme in the duodenum inhibits emptying of even more gastric contents
40
What is the neural response that is triggered based on the factors that control gastric emptying?
- Enterogastric reflex
- Acts to slow the peristaltic activity
- Autonomic system (smooth muscle contraction)
41
What is the hormonal response that is triggered based on the factors that control gastric emptying?
- Release of gastric inhibitory peptide (GIP)
| - Hormone that acts on the gastric muscle to DECREASE peristalsis
42
How do sadness and fear influence gastric motility? How do anger and aggression influence gastric motility? How does intense pain influence motility?
- Sadness and fear decrease motility
- Anger and aggression increase motility
- Intense pain inhibits motility
43
What is contained within gastric juice?
- Pepsin
- Intrinsic factor
- Mucus
- Water
44
What are the two distinct areas of the gastric mucosa that secrete gastric juice? Where are they found?
- Oxyntic mucosa (body and fundus)
| - Pyloric gland area (PGA) (antrum)
45
What are the three phases of gastric secretion?
- Cephalic phase
- Gastric phase
- Intestinal phase
46
What nervous mechanisms occur during the cephalic phase?
- The sensation or thought about food are relayed to the brainstem
- Parasympathetic signals (medulla oblongata) the gastric mucosa to secrete gastric juice
47
What hormonal mechanism occur during the cephalic phase?
Gastrin acts to increase secretion of gastric juice
48
What nervous mechanism occur during the gastric phase?
Distension of the stomach by food causes local and parasympathetic reflexes to increase secretion of gastric juice
49
What hormonal mechanism occur during the gastric phase?
Gastrin is secreted by the mucosa due to the presence of amino acids, and causes an increased secretion of gastric juice
50
What hormonal mechanism occur during the intestinal phase?
- When food enters the small intestine, gastric inhibitory peptide, CCK, and secretin are released
- They oppose gastric juice secretion
- Stimulation of the release of pancreatic juice
51
What do mucous cells secrete? What is their function? Are they exocrine or endocrine cells?
- Secretes mucus and bicarbonate
- Protects against pepsin and acid
- Exocrine
52
What do chief cells secrete? What is their function? Are they exocrine or endocrine cells?
- Secretes pepsinogen (digests protein when activated) and gastric lipase (digests fat)
- Exocrine
53
What do parietal cells secrete? What is their function? Are they exocrine or endocrine cells?
- Secretes HCl and intrinsic factor
- HCl activates pepsinogen, denatures proteins, kills microorganisms
- Intrinsic factor complexes with vitamin B12 for absorption
- Exocrine
54
What do ECL cells secrete? What is their function? Are they exocrine or endocrine cells?
- Histamine
- Stimulates parietal cells for gastric acid secretion
- Exocrine
55
Where are exocrine cells contained within the stomach? Where are endocrine cells contained?
- Exocrine cells: oxyntic mucosa
| - Endocrine cells: pyloric gland
56
What do G-cells secrete? What is their function? Are they exocrine or endocrine cells?
- Secretes gastrin
- Stimulates exocrine cells to secrete gastric juice (HCl and pepsinogen)
- Endocrine
57
What do D-cells secrete? What is their function? Are they exocrine or endocrine cells?
- Secretes somatostatin
| - Inhibits parietal cells (HCl), G-cells (gastrin), and ECL cells
58
Which cells produce the only inhibitory secretion in the stomach? What is it?
- D-cells
| - Somatostatin
59
What are the functions of HCl?
- Activates pepsinogen to pepsin
- Breakdown of connective tissue
- Denatures protein
- Kills most microorganisms in food (along with salivary lysozyme)
60
How is HCl formed and secreted from a gastric parietal cell?
- CO2 and H2O form carbonic acid, which then dissociates to form H+
- In exchange for bicarbonate (out), chloride is shifted in
- Cl- diffuses out into the lumen, while H+ uses the H+/K+ pump
61
What three methods enable the stomach to contain acid without injuring itself?
1) Luminal membranes of the cells are impermeable to H+
2) Tight junctions
3) Mucous coating offers more protection
62
What accounts for 60% of ulcers? Where is it often found?
- Helicobacter pylori
| - Often in fundus to hide from HCl
63
What are the consequences of H. pylori? How is it treated?
- Damages mucus barrier and tight junctions
- Allows HCl to damage intestinal tissues
- Treat with antibiotics
64
What are the components of pancreatic juice?
- Pancreatic enzymes (trypsinogen, lipases, nucleases)
| - Aqueous alkaline solution to neutralize stomach contents in the duodenum
65
Which enzymes act to release pancreatic juice? Where are they released?
- Secretin
- CCK
- Intestinal mucosa
66
What are the enzymes contained within pancreatic juice that hydrolyze macronutrients?
- Protein: trypsin and chymotrypsin
- Carbohydrates: amylase
- Lipids: lipase
67
What are the two types of cells within the exocrine portion of the pancreas?
- Duct cells
| - Acinar cells
68
What is the function of duct cells in the pancreas?
Secrete aqueous sodium bicarbonate solution
69
What is the function of acinar cells in the pancreas?
Secrete digestive enzymes
70
What is the function of the sphincter of Oddi?
Controls the release of secretions from the liver/gallbladder and the pancreas
71
What is the largest gland in the body? How many lobes does it contain?
- Liver
| - Contains 2 lobes
72
What are the primary functions of the liver?
- Bile secretion
- Stores iron, vitamins D, A, and B12
- Site of hematopoiesis during fetal development
73
Which ducts form the common bile duct that enters the duodenum? What occurs if the bile sphincter is closed?
- Hepatic duct and gallbladder cystic duct fuse
| - If the bile sphincter is closed, then bile is brought from the liver for storage within the gallbladder
74
Where does bile enter?
Duodenum
75
What phospholipid does bile contain?
Lecithin (emulsification)
76
What are the three divisions of the small intestine?
- Duodenum: uppermost portion that is attached to the pyloric end of the stomach
- Jejunum: commences when the tube turns downwards
- Illeum
77
What initiates segmentation?
Pacemaker cells in the small intestine that produce basic electrical rhythm (BER)
78
What is the circular smooth muscle responsiveness during segmentation influenced by?
- Distension of the intestine
- Gastrin
- Extrinsic nerve activity
79
What are the functions of segmentation?
- Mixing chyme with digestive juices secreted into the small intestine lumen
- Exposing all chyme to absorptive surfaces of the mucosa
80
What is the function of the migrating motility complex?
Sweeps intestines clean between meals
81
What digestive enzymes are contained in the juice secreted by the small intestine?
NO digestive enzymes are contained within the juice
82
What completes the digestion of carbohydrates, protein, and fat in the small intestine?
- Carbohydrates and protein: brush-border enzymes
| - Fat: digested entirely in the small intestine with pancreatic lipase
83
Where does most absorption take place within the small intestine?
Jejunum and illeum (majorly illeum)
84
What are three adaptations that increase the small intestine's surface area?
- Inner surface has permanent circular folds
- Villi
- Microvilli on the brush border
85
How often is the lining of the small intestine replaced?
Every three days
86
What are the subdivisions of the large intestine?
- Cecum
- Ascending colon
- Transverse colon
- Descending colon
87
What are the two sphincters of the anus?
- Internal (smooth muscle)
| - External (skeletal muscle)
88
What is the function of the rectum?
Storage of feces prior to defecation
89
Peristalsis differs from segmentation in that ________.
A) peristalsis requires coordination of longitudinal muscle activity
B) peristalsis involves contraction of smooth muscle
C) peristalsis promotes net forward movement of the bolus
D) peristalsis is a form of motility
C) peristalsis promotes net forward movement of the bolus
90
To achieve coordinated activity within a given section of the small intestine, adjacent smooth muscle cells have ________.
A) leaky junctions
B) desmosomes
C) gap junctions
D) tight junctions
C) gap junctions
91
Which part of the wall of the digestive tract has transporting epithelial cells?
A) The mucosa
B) Plicae
C) The serosa
D) The muscularis
A) The mucosa
92
The swallowing center in the central nervous system that coordinates the muscular reflexes is located in the ________.
A) medulla oblongata of the brain stem
B) lumbar spinal cord
C) cerebrum
D) hypothalamus
A) medulla oblongata of the brain stem
93
A high-protein meal stimulates release of ______, which in turn stimulates secretion of ____________.
A) GIP; insulin
B) secretin; acid
C) gastrin; hydrochloric acid
D) CCK; bile
C) gastrin; hydrochloric acid
94
The parietal cells of the stomach synthesize and secrete __________, and its chief cells synthesize and secrete __________.
A) pepsinogen; hydrochloric acid
B) bicarbonate ions; mucus
C) mucus; bicarbonate ions
D) hydrochloric acid; pepsinogen
D) hydrochloric acid; pepsinogen
95
An example of a feedforward endocrine reflex in the digestive system is ________.
A) the stimulation of hydrochloric acid secretion by gastrin
B) the effect of acid in the small intestine to trigger secretin release, resulting in inhibition of acid secretion
C) the stimulation of insulin release by GIP, preventing a rise in plasma glucose
D) the effect of CCK to cause contraction of the gallbladder in response to fats in the intestine
C) the stimulation of insulin release by GIP, preventing a rise in plasma glucose
96
Which of the following enzymes produces a product that enters the absorptive cells of the small intestine via simple diffusion?
A) Lipases
B) Nucleases
C) Amylases
D) Peptidases
A) Lipases
97
Microbes in the colon can synthesize __________, which is/are absorbed luminally via __________.
A) steroid hormones; secondary active transport
B) B vitamins; mediated transport
C) nucleic acids; simple diffusion
D) vitamin K; simple diffusion
D) vitamin K; simple diffusion
98
Which of the following statements regarding the short and long reflexes that regulate GI function is true?
A) Long reflex responses are initiated through submucosal neurons.
B) Reflexes that originate and are integrated in the enteric nervous system are called short reflexes.
C) Long reflexes are integrated only in the enteric nervous system.
D) A cephalic reflex can be a short or a long reflex.
B) Reflexes that originate and are integrated in the enteric nervous system are called short reflexes.
99
In the mouth, amylase digests starch to ______, which is further digested to _____ in the small intestine by the action of the enzyme ________.
A) lactose; galactose; lactase
B) cellulose; glucose; cellulase
C) maltose; glucose; maltase
D) sucrose; fructose; sucrase
C) maltose; glucose; maltase
100
Which of the following nutrients is specifically digested in the mouth, the stomach, and the small intestine?
A) Carbohydrates
B) Fats
C) Proteins
D) Nucleic acids
B) Fats
101
Which digestive tract hormone inhibits gastric gland secretion and gastric motility?
A) Gastrin
B) Secretin
C) Cholecystokinin
D) Anti-diuretic Hormone
B) Secretin
102
Which cell secretes pepsinogen?
A) Mucous neck cell
B) Parietal cell
C) Chief cell
D) G cell
C) Chief cell
103
Bile is produced as a result of the breakdown of haemoglobin.
A) True
B) False
A) True
104
Name the four layers of the GI tract, starting at the lumen and moving out.
- Mucosa
- Submucosa
- Muscularis
- Serosa
105
Name the structures a piece of food passes through as it travels from mouth to anus.
- Mouth
- Pharynx
- Esophagus
- Stomach (fundus, body, antrum)
- Small intestine (duodenum, jejunum, illeum)
- Large intestine (colon, rectum)
- Anus
106
Why is the digestive system associated with the largest collection of lymphoid tissue in the body?
Because the GI tract has a large, vulnerable surface area facing the external environment
107
What do short reflexes in the digestive system integrate? What do long reflexes integrate?
- Short reflexes: enteric nervous system
| - Long reflexes: CNS
108
What is the enteric nervous system, and what is its function?
Network of neurons within the GI tract that can sense a stimulus, integrate information, and create an appropriate response without integration or input from the CNS
109
Which processes of the digestive system may be regulated?
Motility and secretion
