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Physiology > Gastroenterology > Flashcards

Gastroenterology Flashcards

1
Q

What is the primary function of the digestive system?

A

Transfer nutrients, water, and electrolytes from ingested food into body’s internal environment

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2
Q

What organs are included in the digestive tract?

A

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus

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3
Q

What are 4 accessory organs of the digestive tract?

A

Teeth, salivary glands, liver, and pancreas

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4
Q

What are the 4 digestive processes?

A

1) Digestion
2) Absorption
3) Motility
4) Secretion

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5
Q

What is digestion?

A

The biochemical breakdown of structurally complex food into smaller, absorbable units

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6
Q

How is digestion accomplished?

A

By enzymatic hydrolysis

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7
Q

What can be absorbed from carbohydrates?

A

Monosaccharides

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8
Q

What can be absorbed from proteins?

A

Amino acids

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9
Q

What can be absorbed from fats?

A

Glycerol and fatty acids

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10
Q

What is absorption?

A

When small units resulting form digestion, along with water, vitamins, and electrolytes are transferred from digestive tract lumen to enterocytes of villi to blood or lymph

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11
Q

What is motility?

A

Muscular contractions that mix and move forward he contents of the digestive tract

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12
Q

What is peristalsis?

A

Propulsive movements that push contents forward through the digestive tract

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13
Q

What are segmentation and churning?

A

Mixing movements

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14
Q

What are the 2 functions of segmentation and churning?

A

1) Mixing food with digestive juices to promote digestion

2) Facilitate absorption by exposing all parts of intestinal contents to absorbing surfaces of digestive tract

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15
Q

What 3 substances are commonly secreted?

A

Water, electrolytes, and digestive juices

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16
Q

Where are secretions released?

A

Into digestive tract lumen

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17
Q

What causes secretion?

A

Appropriate neural or hormonal stimulation

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18
Q

True or false: most secretions are reabsorbed in one form or another back into blood after their participation in digestion

A

True

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19
Q

True or false: digestive system regulates uptake

A

False, it does not

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20
Q

What percent of ingested food is made available for the body to use?

A

95%

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21
Q

What are 4 regulators of digestive motility and secretion?

A

1) Autonomous smooth muscle function
2) Intrinsic nerve plexuses
3) Extrinsic nerves
4) Gastrointestinal hormones

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22
Q

What do autonomous smooth muscle produce?

A

Self-induced electrical activity (slow-wave potentials)

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23
Q

What are slow-wave potentials?

A
  • Not action potentials

- Bring the membrane closer and further to threshold

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24
Q

True or false: when food is present in the digestive tract, membranes are further from threshold than normal

A

False, membranes are closer to threshold

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25
Q

What are the 2 networks of nerve fibres that lie within the digestive tract wall?

A

1) Submucosal plexus

2) Myenteric plexus

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26
Q

What is a collective term for the submucosal plexus and myenteric plexus?

A

Enteric nervous system

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27
Q

What does the enteric nervous system allow for?

A

Self-regulation

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28
Q

What are extrinsic nerves?

A

Nerve fibres from both branches of the ANS

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29
Q

What effect does the sympathetic nervous system have on digestion?

A

Inhibits digestion

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30
Q

What effect does the parasympathetic nervous system have on digestion?

A

Stimulates digestion

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31
Q

What are 3 functions of extrinsic nerves on digestion?

A

1) Influence digestive tract motility and secretion
2) Modify activity of the enteric nervous system
3) Alter the level of hormone secretion

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32
Q

What is another term for chewing?

A

Mastication

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33
Q

What is the first step in the digestive process?

A

Chewing

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34
Q

What is chewing?

A

Grinding and breaking food into smaller pieces to make swallowing easier and increase food surface area for salivary enzymes to act on

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35
Q

What produces saliva?

A

3 major pairs of salivary glands

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36
Q

What percent of saliva is water?

A

99.5%

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37
Q

What percent of saliva is electrolytes and protein?

A

0.5%

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38
Q

How much saliva is secreted per day?

A

1 - 1.5 L per day

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39
Q

What are 7 functions of saliva?

A

1) Salivary amylase begins digestion of carbohydrates
2) Facilitates swallowing by moistening food
3) Mucus provides lubrication
4) Antibacterial action
5) Solvent for molecules that stimulate taste buds
6) Aids speech by facilitating movement of lips and tongue
7) Rich in bicarbonate buffers

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40
Q

What are some antibacterial actions of saliva?

A
  • Lysozyme destroys bacteria

- Saliva rinses away material that could serve as food source for bacteria

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41
Q

What is the parasympathetic effect on saliva?

A

Stimulates secretion of an abundant amount of thin, enzyme rich saliva

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42
Q

What is the sympathetic effect on saliva?

A

Decreases volume of saliva

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43
Q

What happens to the mouth when the SNS has a higher dominance?

A

Mouth is drier than usual

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44
Q

Why are saliva and gastric juice not essential for digesting and absorbing foods?

A

Because enzymes produced by the pancreas and small intestine can complete food digestion

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45
Q

What is the only digestive secretion that is entirely under neural control?

A

Salivary secretion

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46
Q

What are all digestive secretions (except salivary secretion) regulated by?

A

Nervous system reflexes and hormones

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47
Q

True or false: there is no absorption in the mouth

A

True

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48
Q

Swallowing occurs in __ phases

A

3

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49
Q

What are the 3 phases of swallowing?

A

1) Buccal phase
2) Pharyngeal phase
3) Esophageal phase

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50
Q

Is the buccal phase voluntary or involuntary?

A

Voluntary

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51
Q

What occurs in the buccal phase?

A

Food is compacted by the tongue into bolus and moves to the pharynx by tongue pressing on hard palate

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52
Q

Is the pharyngeal phase voluntary or involuntary?

A

Involuntary

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53
Q

Is the esophageal phase voluntary or involuntary?

A

Involuntary

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54
Q

True or false: the pharyngeal phase is an all-or-none reflex

A

True

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55
Q

What initiates the swallowing reflex?

A

Swallowing center in the medulla

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56
Q

What is the function of the pharyngoesophageal sphincter?

A

Keeps the entrance to the esophagus closed to prevent air entrance during respiration

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57
Q

What is the function of the gastroesophageal sphincter?

A

Maintains barrier between stomach and esophagus preventing gastric reflux

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58
Q

What occurs in the esophageal phase?

A

Food moves down esophagus by peristalsis

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59
Q

What type of neurons control the upper 1/3 of the esophagus?

A

Somatic motor neurons to skeletal muscle

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60
Q

What type of neurons control the lower 1/3 of the esophagus?

A

Parasympathetic NS (vagus nerve) to smooth muscle

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61
Q

What type of neurons control the middle 1/3 of the esophagus?

A

A mixture of somatic motor neurons and the vagus nerve

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62
Q

What happens if a large or sticky piece of food is swallowed and gets stuck?

A
  • Esophagus distends stimulating pressure receptors

- A second, more forceful, wave is initiated by the intrinsic nerve plexus

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63
Q

What are the mechanisms in the different part of the mouth/esophagus that prevent food from entering while swallowing?

A
  • Mouth – tongue on hard palate
  • Nasopharynx – uvula, soft palate elevated
  • Trachea – epiglottis
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64
Q

Esophageal (mucous) secretions are ______

A

Protective

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65
Q

What do esophageal secretions do?

A

Reduce the likelihood of damage by sharp edges

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66
Q

What is the stomach?

A

J-shaped sac-like chamber lying between esophagus and small intestine

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67
Q

What are the 3 sections of the stomach?

A

1) Fundus
2) Body
3) Antrum

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68
Q

What is the function of the pyloric sphincter?

A

Serves as barrier between stomach and upper part of small intestine

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69
Q

What are the 3 main functions of the stomach?

A

1) Store ingested food until it can be emptied into the small intestine
2) Secrete HCl and enzymes that begin protein digestion
3) Mixing movements convert pulverized food to chyme

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70
Q

What does gastric filling involve?

A

Receptive relaxation

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71
Q

What is receptive relaxation?

A

Smooth muscle relaxes to accommodate the extra volume of food

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72
Q

What triggers gastric filling?

A

Act of eating

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73
Q

Where does gastric storage take place?

A

In body of stomach

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74
Q

What occurs in gastric storage?

A

Carbs are broken down by salivary amylase and gastric mixing takes place in antrum

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75
Q

What controls gastric emptying?

A

Factors in the duodenum

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76
Q

What are 4 factors in the duodenum that delay the rate of gastric emptying?

A

1) Fat
2) Acid
3) Hypertonicity
4) Distension

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77
Q

How does fat delay the rate of gastric emptying?

A
  • Fat digestion and absorption takes place only within lumen of small intestine
  • When fat is already in duodenum, further gastric emptying of additional fatty stomach contents is prevented
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78
Q

How long will fatty meals remain in the stomach?

A

About 6 hours

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79
Q

How long will a meal of lean meat and potatoes remain in the stomach?

A

3 hours

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80
Q

How does acid delay the rate of gastric emptying?

A

Unneutralized acid in duodenum inhibits further emptying of acidic gastric contents until neutralization can be accomplished by sodium bicarbonate

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81
Q

Why does acid delay the rate of gastric emptying?

A

To prevent damage (duodenal peptic ulcers) and to allow pancreatic enzymes to function

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82
Q

How does hypertonicity delay the rate of gastric emptying?

A

Osmolarity of duodenal contents begins to rise as molecules of protein and starch are digested in the duodenal lumen, causing lots of amino acids and glucose to be released

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83
Q

What does osmolarity depend on?

A

The number of molecules present, not on their size

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84
Q

How does distension delay the rate of gastric emptying?

A

Too much chyme in duodenum inhibits emptying of gastric contents

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85
Q

What are 2 factors that regulate gastric motility and secretion?

A

1) Neural response

2) Hormonal response

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86
Q

How is gastric motility and secretion regulated neurally?

A

Through intrinsic nerve plexuses and autonomic nerves; collectively called enterogastric reflex

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87
Q

How is gastric motility and secretion regulated hormonally?

A

Through the release of hormones from duodenal mucosa collectively known as enterogastrones

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88
Q

What are the 2 most important hormones in the regulation of gastric motility and secretion?

A

1) Secretin

2) Cholecystokinin (CCK)

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89
Q

What is gastric dumping syndrome?

A

Rapid emptying

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90
Q

When does early gastric dumping syndrome occur and what are the symptoms?

A
  • During or right after a meal

- Symptoms – nausea, vomiting, bloating, diarrhea, dizziness, fatigue

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91
Q

When does late gastric dumping syndrome occur and what are the symptoms?

A
  • 1-3 hours post-meal

- Symptoms – weakness, sweating, and dizziness

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92
Q

True or false: it is uncommon for people to have early and late gastric dumping syndrome

A

False, it is very common

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93
Q

What are some treatments for gastric dumping syndrome?

A
  • Adjust eating habits (avoid certain foods)
  • Medications to slow digestion
  • Surgery as a last resort
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94
Q

What are 3 types of gastric exocrine secretory cells?

A

1) Parietal cells
2) Chief cells
3) Mucous cells

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95
Q

What do parietal cells secrete?

A

HCl and intrinsic factor

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96
Q

What is the importance of the intrinsic factor of parietal cells?

A

Vitamin B12 can be absorbed only when bound to intrinsic factor; vitamin B12 is essential for formation of RBCs

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97
Q

What does HCl do?

A

Denatures proteins – causes them to lose their tertiary and secondary structure, allowing digestive enzymes o break down the amino acid chains

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98
Q

True or false: HCl kills most of the microorganisms ingested with food

A

True

99
Q

What does HCl act on?

A

Pepsinogen

100
Q

What do chief cells secrete?

A

Pepsinogen

101
Q

What does HCl change pepsinogen into?

A

Pepsin

102
Q

What does pepsin do?

A

Turns proteins in small amino acid chains

103
Q

What do mucous cells secrete?

A

Mucous

104
Q

What is the function of mucous?

A

Acts as a lubricant and prevents mechanical injury

105
Q

Stomach is protected from self-digestion by ______

A

Alkaline mucous

106
Q

True or false: mucous cells are replaced about every 3 months

A

False, they are replaced very rapidly and a new cell lining appears every 3 days

107
Q

What happens if the mucous barrier is broken?

A

The gastric wall is injured, resulting in a gastric peptic ulcer

108
Q

What does the cephalic phase refer to?

A

Increased secretion of HCl and pepsinogen that occurs in response to stimuli acting in the head before food reaches the stomach

109
Q

When does the gastric phase begin?

A

When food actually reaches the stomach; presence of protein increases gastric secretions

110
Q

The intestinal phase is the ______ phase

A

Inhibitory

111
Q

What is the function of the intestinal phase?

A

Helps shut off flow of gastric juices as chyme begins to empty into small intestine

112
Q

What are the 3 regulatory phases?

A

1) Cephalic phase

113
Q

What occurs in the cephalic phase?

A

Stomach is prepared for food

114
Q

What is the pH of the stomach when it is nearly empty?

A

3

115
Q

What happens when the pH of the stomach dips below 3?

A

NS shuts off, causing decreased acid and gastrin decreases, causing decreased acid

116
Q

Does gastrin secretion increase or decrease initially in the intestinal phase?

A

Increases

117
Q

During the intestinal phase, what do inhibitory signals cause?

A
  • Decreased gastric motility

- Decreased gastric secretion

118
Q

What causes decreased gastric motility?

A

1) CCK that is released due to presence of fatty and amino acids
2) Enterogastric reflex

119
Q

What triggers the enterogastric reflex?

A
  • Amino acids/peptides
  • Acid
  • Duodenal stretch
  • Hypertonicity
120
Q

What causes decreased gastric secretion?

A

1) Secretin released due to acid

2) CCK released due to fatty and amino acids

121
Q

Where can ethyl alcohol be absorbed the most quickly?

A

By the small intestine mucosa

122
Q

What effect does gastric emptying have on absorption?

A

It slows it

123
Q

What is the small intestine the site of?

A

Most digestion and absorption

124
Q

What are the 3 segments of the small intestine?

A

1) Duodenum
2) Jejunum
3) Ileum

125
Q

What does motility of the small intestine include?

A
  • Segmentation

- Migrating motility complex

126
Q

What is the primary method of motility in the small intestine?

A

Segmentation

127
Q

What does segmentation consist of in the small intestine?

A

Ring-like contractions along the length of the small intestine

128
Q

What does segmentation action do?

A

Mixes chyme throughout small intestine lumen

129
Q

How is segmentation initiated?

A

By pacemaker cells in small intestine which produce basic electrical rhythm

130
Q

How is segmentation controlled?

A

Circular smooth muscle responsiveness is influenced by distension of intestine, gastrin, and extrinsic nerve activity

131
Q

What are 2 functions of segmentation?

A

1) Mixing chyme with digestive juices into small intestine lumen
2) Exposing all chyme to absorptive surfaces of small intestine mucosa
3) Slowly move chyme through digestive tract

132
Q

The frequency of segmentation _______ along the length of the small intestine

A

Declines

133
Q

How long does it take food to get through the small intestine?

A

3-5 hours

134
Q

What happens when most of the meal has been absorbed?

A

Segmentation contractions cease and are replaced by migrating motility complex

135
Q

What is migrating motility complex?

A

Slow, weak peristaltic waves

136
Q

What is the function of migrating motility complex?

A

Sweeps intestines clean between meals

137
Q

The pancreas is a mixture of ____ and ______ tissue

A

Exocrine and endocrine

138
Q

Where is the pancreas located?

A

Behind and below the stomach

139
Q

What is the endocrine function of the pancreas?

A

Islets of Langerhans found throughout the pancreas secrete insulin and glucagon

140
Q

What are 2 exocrine functions of the pancreas?

A

1) 3 different pancreatic enzymes actively secreted by acinar cells that form the acini
2) Aqueous alkaline solution actively secreted by duct cells that line pancreatic ducts (contains sodium bicarbonate)

141
Q

What are the 3 exocrine steps of digestion?

A

1) Neutralize acid
2) Pancreatic enzymes
3) Intestinal wall

142
Q

Why must stomach acid be neutralized?

A

So pancreatic enzymes can work

143
Q

How is stomach acid neutralized?

A

Secretin secretion is increased, which causes increased bicarbonate and decreased gastric acid secretion

144
Q

Where is alkaline fluid secreted from?

A

Duct cells of pancreas and gall bladder

145
Q

Describe the process of carbohydrate breakdown

A

Polysaccharides are broken down into disaccharies by pancreatic amylase

146
Q

Is amylase secreted in an active or inactive form, and why?

A

Active form so that it doesn’t endanger the secretory cells

147
Q

Describe the process of protein breakdown (3 pathways)

A

1) Trypsinogen is broken down into trypsin by enteropeptidase on intestinal wall
2) Chymotrypsinogen is broken into chymotrypsin
3) Procarboxypeptidase is broke into carboxypeptidase

148
Q

Where are pancreatic enzymes secreted?

A

Into intestinal lumen from pancreatic acinar cells

149
Q

What does proteases do?

A

Breaks down dietary protein into peptides and amino acids

150
Q

What is special about pancreatic lipase?

A

Only enzyme secreted throughout the entire digestive system that can digest fat

151
Q

What does pancreatic lipase do?

A

Breaks triglycerides into fatty acids and monoglycerides

152
Q

What happens when pancreatic enzymes are deficient?

A

Serious maldigestion of fats

153
Q

What does the presence of fatty acids and amino acids in the duodenum cause?

A

Increased cholecystokinin (CCK)

154
Q

True or false: carbs do not have any direct influence on pancreatic digestive enzyme secretion

A

True

155
Q

What are 3 effects of CCK with respect to digestion?

A

1) Increases pancreatic enzyme secretion
2) Stimulates gallbladder contractions, causing release of bile
3) Decreases gastric motility (slows emptying) and decrease gastric secretions

156
Q

True or false: small intestine secretions do not contain any digestive enzymes, they are mostly salt and mucous solutions

A

True

157
Q

What occurs in the intestinal wall during digestion?

A

Synthesized enzymes act within brush-border membrane of epithelial cells to complete digestion of carbs and proteins

158
Q

Which 3 synthesized enzymes act on the intestinal wall during digestion?

A

1) Disaccharidases
2) Enterokinase
3) Aminopeptidases

159
Q

What does disaccharidases do?

A

Breaks down disaccharides into monosaccharides

160
Q

What breaks down glucose and what does it produce?

A
  • Sucrase

- Produces glucose and fructose

161
Q

What breaks down maltose and what does it produce?

A
  • Maltase

- Produces 2 glucose molecules

162
Q

What breaks down lactose and what does it produce?

A
  • Lactase

- Produces glucose and galactose

163
Q

What causes lactose deficiency?

A

Lactose intolerance – lactose remains undigested and therefore bacteria in large intestine ferment the lactose into gas, which is why cramping and diarrhea are symptoms

164
Q

What does aminopeptidases do?

A

Breaks peptides into smaller peptides and amino acids

165
Q

True or false: there is no digestion of lipids in the large intestine

A

True

166
Q

Where is fat digested and how?

A

Entirely in small intestine lumen by pancreatic lipase

167
Q

What does the small intestine absorb?

A
  • All products of carb, protein, and fat digestion

- Most ingested electrolytes, vitamins, and water

168
Q

Where does most absorption of the small intestine occur?

A

In duodenum and jejunum

169
Q

True or false: the more food consumed the less that will be digested and absorbed

A

False, more food consumed = more digested and absorbed

170
Q

Absorption of ___ and ____ are adjusted to the body’s needs

A

Calcium and iron

171
Q

True or false: the small intestine absorbs almost everything presented to it

A

True

172
Q

Why is the small intestine the main site of absorption?

A

1) Large surface area

2) Nutrients are small molecules

173
Q

Why does the small intestine have such a large surface area?

A

Because of folds, villi and microvilli

174
Q

How often does the lining of the small intestine replace itself and why?

A
  • About every 3 days

- Because of the harsh environment

175
Q

True or false: small intestine cells can withstand radiation and anti-cancer drugs

A

False, they are very sensitive to it

176
Q

What can cause malabsorption in the small intestine?

A

Damage to or reduction of the surface area

177
Q

What does absorption of the broken down carbs and proteins involve?

A

Carrier-mediated secondary active transport mechanisms

178
Q

What are end products of carb and protein digestion absorbed into?

A

Blood

179
Q

Are fats absorbed into the blood and why?

A

No because they aren’t water soluble

180
Q

How do glucose and galactose enter enterocytes?

A

Secondary active transport

181
Q

How do glucose and galactose leave enterocytes?

A

Facilitated transport

182
Q

How does fructose enter enterocytes?

A

Facilitated transport

183
Q

How does fructose leave enterocytes?

A

Facilitated transport

184
Q

How do amino acids enter enterocytes?

A

Secondary active transport

185
Q

How do amino acids leave enterocytes?

A

Facilitated transport

186
Q

How do di and tripeptides enter enterocytes?

A

Secondary active transport

187
Q

What happens to di and tripeptides when they enter enterocytes?

A

Converted to amino acids by cytosolic enzymes

188
Q

How do monoglycerides and long fatty acids enter enterocytes?

A

Diffusion

189
Q

How do monoglycerides and long fatty acids leave enterocytes?

A

Exocytosis from enterocyte, diffusion into lymph lacteal

190
Q

How do short fatty acids enter enterocytes?

A

Diffusion

191
Q

How do short fatty acids leave enterocytes?

A

Diffusion into blood

192
Q

How does water enter enterocytes?

A

Osmosis

193
Q

How does water leave enterocytes?

A

Osmosis into blood and lymph

194
Q

How much water is ingested from food and drink per day?

A

About 2000 mL

195
Q

How much water is absorbed in the small intestine from secretions per day?

A

About 7000 mL

196
Q

Where do absorbed nutrients go?

A

1) Liver

2) Lacteals (lymph)

197
Q

How do absorbed nutrients enter the liver?

A

Via hepatic portal vein

198
Q

How do absorbed nutrients enter lacteals?

A

Via thoracic duct which goes into left subclavian vein

199
Q

What does fat digestion and absorption require and where does this come from?

A

Requires bile from liver and gall bladder

200
Q

The liver _____ bile

A

Synthesizes

201
Q

The gall bladder _____ bile

A

Stores

202
Q

What is the most important metabolic organ in the body?

A

Liver

203
Q

Why is the liver important to digestive system?

A

Secretes bile salts

204
Q

What are 6 functions of the liver that ARE NOT related to digestion?

A

1) Metabolic processing of nutrients
2) Detoxifying or degrading body wastes and foreign compounds
3) Synthesizes plasma proteins
4) Stores glycogen, fats, iron, copper, and many vitamins
5) Activates vitamin D
6) Excretes cholesterol and bilirubin

205
Q

What performs the functions of the liver that are not related to digestion?

A

Hepatocytes

206
Q

What function is not accomplished by hepatocytes, and what cell performs this function?

A
  • Removal of bacteria and worn-out RBCs

- Kupffer cells

207
Q

What does bile consist of?

A

Bile salts, cholesterol, lecithin and bilirubin, detoxified drugs, toxins, and hormones in an aqueous alkaline fluid

208
Q

What does bile do AFTER a meal?

A

Enters duodenum

209
Q

Describe the enterohepatic circulation

A

Bile salts in liver –> common bile duct –> stomach or gall bladder –> in stomach, sphincter of Oddi –> duodenum –> terminal ileum –> hepatic portal vein –> liver

210
Q

Bile salts are derivatives of _____

A

Cholesterol

211
Q

What are 2 functions of bile salts?

A

1) Convert large fat globules into a liquid emulsion

2) Micelle formation

212
Q

True or false: after bile salts participate in fat digestion and absorption, most are excreted

A

False, most are reabsorbed into the blood

213
Q

What does CCK do with respect to bile?

A

Stimulates contraction of the gall bladder and relaxation of the hepatopancreatic sphincter

214
Q

How do bile salts form micelles?

A

Bile salts and lecithin aggreagate in small clusters with their fat-soluble parts huddled together in the middle to form a hydrophobic core while their water-soluble parts form an out hydrophilic shell

215
Q

What is found within the core of bile salt micelles?

A

Products of fat digestion and fat-soluble vitamins

216
Q

With respect to micelle formation, where does cholesterol dissolve?

A

In the core

217
Q

What is the function of bilirubin?

A

Gives bile and urine their colour

218
Q

True or false: some bilirubin is reabsorbed into the blood

A

True

219
Q

What happens to bilirubin in the intestinal tract?

A

It is modified by bacteria, giving feces it’s brown colour

220
Q

What occurs in the lumen with respect to fat digestion and absorption?

A
  • Lipid globule is converted to fatty acids and monoglycerides by emulsification and lipase
  • Fatty acids and monoglycerides diffuse from micelle into enterocytes
221
Q

What occurs in the enterocyte with respect to fat digestion and absorption?

A
  • Monoglycerides and fatty acids are converted to diglycerides and fatty acid
  • Diglycerides are converted to triglycerides
  • Triglycerides are converted to a chylomicron with cholesterol, proteins, and phospholipids
  • Chylomicron moves to interstitial by exocytosis, and then to lymph by diffusion
222
Q

What primarily happens in the large intestine?

A

Drying and storage

223
Q

What does the large intestine consist of?

A
  • Colon
  • Cecum
  • Appendix
  • Rectum
224
Q

What does the large intestine receive from the small intestine?

A

Indigestible food residues, unabsorbed biliary components, and remaining fluid

225
Q

Where is the ileococcal valve found?

A

Between ileum and large intestine

226
Q

What surrounds the ileococcoal valve?

A

Thickened smooth muscle, the ileocecal sphincter

227
Q

What does pressure on the cecal side do to the ileococcal valve?

A

Pushes it closed and contracts the sphincter, preventing the bacteria-laden colonic contents from contaminating the nutrient-rich small intestine

228
Q

What does pressure on the ideal side do to the ileococcal valve?

A

Opens the valve/sphincter, allowing ileal contents to enter the large intestine and gastrin to be secreted

229
Q

What causes the motility of the large intestine?

A

1) Haustral contractions

2) Mass movements

230
Q

What are Haustral contractions?

A
  • Main motility

- Slow and weak contractions initiated by autonomous rhythmicity of colonic smooth muscle cells

231
Q

What are mass movements?

A

Massive contractions mediated from stomach to colon by gastrin and autonomic nerves

232
Q

What causes mass movements?

A

Food in the stomach (gastrocolic reflex)

233
Q

What is the gastrocolic reflex?

A

Powerful waves of contractions from transverse colon to rectum

234
Q

What stimulates the defecation reflex?

A

Feces in rectum

235
Q

What part of the CNS is responsible for the defecation reflex?

A

Sacral segment of spinal cord (para NS)

236
Q

What is the effect of the defecation reflex?

A

Smooth muscle of rectum contracts and internal anal sphincter relaxes

237
Q

True or false: external anal sphincter is under voluntary control

A

True

238
Q

True or false: no digestive enzymes are secreted into the large intestine

A

True

239
Q

What is secreted into the large intestine?

A
  • Alkaline mucous secretions

- K and bicarbonate

240
Q

What occurs in the large intestine?

A

Bacterial fermentation of undigested nutrients

241
Q

How does the large intestine absorb water?

A

Osmosis

242
Q

What 3 hormones are secreted from the stomach and duodenum?

A

1) Gastrin
2) Secretin
3) CCK

243
Q

What is the function of gastrin?

A

Increases acid and gastric enzyme secretion

244
Q

What is the function of secretin?

A
  • Increases alkaline fluid secretion

- Decrease gastric secretion

Physiology (7 decks)

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