The Digestive System Flashcards

1
Q

Digestive system

A

Digestive tract
GI tract
Accessory organs

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2
Q

Digestive tract

A

Oral cavity > pharynx > esophagus > stomach > small intestine > large intestine > anus

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3
Q

Accessory structures

A

Teeth, tongue, glandular organs, salivary glands, liver, pancreas and gallbladder

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4
Q

Ingestion

A

Takes place when food enters the oral cavity

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5
Q

Mechanical digestion and propulsion

A

Involves crushing and shearing of food and then propelling the food along the digestive tract

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6
Q

Chemical digestion

A

Refers to the chemical breakdown of food into small organic and inorganic molecules suitable for absorption by the digestive epithelium

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7
Q

Secretion

A

Release of water, acids, enzymes, buggers and salts by the epithelium of the digestive tract, glandular organs and the gallbladder

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8
Q

Absorption

A

Movement of organic molecules, electrolytes, vitamins, minerals, and water across the digestive epithelium

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9
Q

Defecation

A

Elimination of wastes from the body

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10
Q

Pharynx

A

Muscular propulsion of materials into the esophagus

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11
Q

Esophagys

A

Transport of materials to the stomach

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12
Q

Stomach

A

Chemical digestion of materials by acid and enzymes; mechanical digestion through muscular contractions

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13
Q

Small intestine

A

Enzymatic digestion and absorption of water, organic substrates, vitamins and ions

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14
Q

Large intestine

A

Dehydration and compaction of indigestible materials in preparation for elimination

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15
Q

Salivary glands

A

Secretion of lubricating fluid containing enzymes that break down carbohydrates

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16
Q

Liver

A

Secretion of bile, storage of nutrients, many other vital functions

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17
Q

Gallbladder

A

Storage and concentration of bile

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18
Q

Pancreas

A

Exocrine cells secrete buffers and digestive enzymes; endocrine cells secrete hormones

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19
Q

Peritoneum

A

Serosa/visceral peritoneum

Pariteal peritoneum

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20
Q

How can the visceral and parietal surfaces slide without friction?

A

Peritoneal fluid

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21
Q

Ascites

A

Abdominal swelling caused by the buildup of fluid in the peritoneal cavity

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22
Q

Mesentries

A

Double sheets of peritoneal membrane that connect with the parietal peritoneum with the visceral peritoneum

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23
Q

Lesser omentum

A

Stabilises the position of the stomach and provides an access route for blood vessels and other structures entering or leaving the liver

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24
Q

Falciform ligament

A

Helps stabilise the position of the liver relative to the diaphragm and abdominal wall

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25
Q

Greater omentum

A

Pouch formed from the enlarged dorsal mesentery

Contains adipose tissue that conform to the shape of the surrounding organs

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26
Q

Mesentery proper

A

Suspends the small intestine

Thick mesenterial sheet

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27
Q

Peritonitis

A

Inflammation of the peritoneum

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28
Q

Mesocolon

A

Mesentery associated with a portion of the large intestine

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29
Q

Layers of the digestive tract

A
  1. Mucosa
  2. Submucosa
  3. Muscular layer
  4. Serosa
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30
Q

Layers of the mucosa

A
  1. Mucosal epithelium: epithelial cells that differ depending on the place (stratified squamous where there’s mechanical stress, etc.)
  2. Laminar propria: areolar tissue
  3. Muscularis mucosae: smooth muscle and elastic fibres
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31
Q

Submucosa

A
  • Dense irregular connective tissue
  • Connects mucosa and muscular layer
  • Submucosal neural plexus in the margin
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32
Q

Muscular layer

A
  • Smooth muscle cells
  • Coordinated by enteric nervous system
  • Contains myenteric plexus
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33
Q

Serosa

A

Covers the muscular layer along portions of the digestive tract enclosed by peritoneal cavity

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34
Q

Adventitia

A

Fibrous sheath in areas lacking serosa

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35
Q

Peristalsis

A

Circular muscles contract behind the bolus while circular muscles ahead of the bolus relax
Longitudinal muscles ahead of the bolus then contract, shortening adjacent segments
A wave of contraction in the circular muscles then forces the bolus forward

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36
Q

Segmentation

A

Cycles of contraction that churn and fragment the bolus, mixing the contents with intestinal secretions

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37
Q

Local factors regulating digestive activities

A
  • Primary stimulus
  • Coordinate the responses to changes in the pH of the contents of the lumen, physical distortions of the wall, or the presence of chemicals
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38
Q

Neural control mechanisms

A
Myenteric reflexes (chemoreceptors, stretch receptors)
Long reflexes (higher level control)
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39
Q

Hormonal control mechanisms

A

Peptides produced by enteroendocrine cells (endocrine cells in the epithelium of the digestive tract)

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40
Q

Functions of the oral cavity

A
  1. Sensory analysis
  2. Mechanical digestion
  3. Lubrication
  4. Chemical digestion
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41
Q

What lines the oral cavity?

A

Oral mucosa

Stratified squamous epithelium

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42
Q

What supports the mucosae of the cheeks?

A

Buccal fat pads and buccinator muscles

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43
Q

Oral vestibule

A

Space between the cheeks and the teeth

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44
Q

Gingivae

A

Gums
Ridges of oral mucosa surrounding the base of each tooth on the alveolar processes of the maxillae and the alveolar part of the mandible

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45
Q

Uvula

A

Dandling process that helps prevent food from entering the pharynx too soon

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46
Q

Palatoglossal arch

A

Between the soft palate and the base of the tongue

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47
Q

Fauces

A

Space between the oral cavity and the pharynx bounded by the soft palate and the base of the tongue

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48
Q

Palatopharyngeal arch

A

Extend from the soft palate to the pharyngeal wall

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49
Q

Functions of the tongue

A
  1. Mechanical digestion
  2. Manipulation
  3. Sensory analysis
  4. Secretion of mucins and lingual lipase
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50
Q

Lingual lipase

A

Digests lipids

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51
Q

Extrinsic tongue muscles

A

Large

Perform all gross movements

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52
Q

Intrinsic tongue muscles

A

Small

Change the shape of the tongue, precise movements

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53
Q

How does dentin differ from bone?

A

It doesn’t contain cells

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54
Q

Pulp cavity

A

Receives blood vessels and nerves through root canal

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55
Q

Apical foramen

A

Opening where blood vessels and nerves enter the root canal

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56
Q

What covers the dentin of the root?

A

A layer of cement

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57
Q

Gingival sulcus

A

A shallow groove surrounding the neck of each tooth

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58
Q

What covers the dentin of the crown?

A

A layer of enamel

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59
Q

Occlusal surface

A

Biting surface that grinds food against the opposing tooth surface
Formed by enamel

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60
Q

Cusps

A

Elevations or projections of the occlusal surface

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61
Q

Types of teeth

A
  1. Incisor teeth
  2. Canine teeth
  3. Premolar teeth
  4. Molar teeth
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62
Q

Incisor

A

Front of mouth

Blade shaped

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63
Q

Canine

A

Conical with a pointed cusp

Lie under the eye

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64
Q

Premolar

A

Have flattened crowns with two prominent cusps

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65
Q

Molar

A

Very large flattened crowns with 4-5 prominent rounded cusps

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66
Q

Decidious teeth

A
  • Baby teeth

- Most children have 20

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67
Q

3 pairs of salivary glands

A
  1. Parotid glands
  2. Sublingual glands
  3. Submandibular glands
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68
Q

Parotid glands

A
  • Contain salivary amylase which breaks down starches

- Drained by parotid ducts

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69
Q

Sublingual glands

A
  • Covered by mucous membrane of the floor of the mouth

- Produce mucous

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70
Q

Submandibular glands

A
  • Secrete a mixture of buffers, mucins and salivary amylase
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71
Q

What gives saliva its lubricating action?

A

Mucins

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72
Q

Functions of saliva

A
  1. Lubricating the mouth
  2. Lubricating food in the mouth
  3. Dissolving chemicals
  4. Beginning digestion
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73
Q

What controls salivary secretions?

A

Autonomic nervous system

Each salivary gland has sympathetic and parasympathetic innervation

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74
Q

Superior and inferior salivatory nucleus

A

Where parasympathetic efferents originate

In the medulla oblongata

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75
Q

Pharynx

A

Throat

Serves as a common passageway for solid food, liquid, and air

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76
Q

Esophagus

A

Actively moves ingested materials down towards the stomach

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77
Q

Esophageal hiatus

A

Opening in the diaphragm where the esophagus enters the abdominopelvic cavity

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78
Q

Wall of the esophagus

A

Mucosa, submucosa and muscular layer

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79
Q

Function of folds in the esophagus

A

They allow for expansion during the passage of a large bolus

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80
Q

Where are esophageal glands?

A

Scattered among the submucosa

They produce mucus that reduces friction between bolus and esophageal lining

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81
Q

What innervates the esophagus?

A

Parasympathetic and sympathetic fibres from the esophageal plexus

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82
Q

Degluition

A

Swallowing

Phases:

  1. Buccal
  2. Pharyngeal
  3. Esophageal
  4. Bolus enters stomach
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83
Q

Buccal phase

A
  • Bolus compresses against hard palate
  • Tongue retracts, bolus goes into oropharynx
  • Soft palate seals off nasopharynx
84
Q

Pharyngeal phase

A
  • Begins when bolus comes into contact with palatal arches and the posterior pharyngeal wall
  • Bolus goes past closed glottis
  • Uvula and soft palate block nasopharynx
85
Q

Esophageal phase

A
  • Begins at contraction of pharyngeal muscles which forces bolus into esophagus
  • Peristatic wave pushes bolus into stomach
86
Q

Bolus enters stomach

A

Lower esophageal sphincter opens and bolus goes to stomach

87
Q

Swallowing reflex

A

Automatic reflex

Begins when tactile receptors on the palatal arches and uvula are stimulated by the passage of the bolus

88
Q

Swallowing centre

A

In the medulla oblongata

89
Q

Primary peristaltic waves

A

Coordinated by afferent and efferent fibres

90
Q

Secondary peristaltic waves

A

Needed if bolus is dry

91
Q

Functions of the stomach

A
  1. Temporarily store ingested food received from the esophagus
  2. Mechanically digest food through muscular contractions
  3. Chemically digest food through the action of acid and enzymes
92
Q

Chyme

A

Viscous, acidic, soupy mixture of partially digested food

93
Q

Lesser curvature

A

Short

Medial surface of stomach

94
Q

Greater curvature

A

Long

Lateral surface of stomach

95
Q

Regions of the stomach

A
  1. Cardia: smallest, contains glands
  2. Fundus
  3. Body: largest region, mixing tank
  4. Pyloric: between the body and the duodenum
96
Q

Pyloric part

A

Divided into pyloric antrum (connected to the body) and the pyloric canal (empties into the duodenum) and the pylorus which is the muscular tissue surrounding the pyloric orifice

97
Q

What regulates the release of chyme in the duodenum?

A

The pyloric sphincter

98
Q

Rugae

A

Folds of the stomach

99
Q

Gastric pits

A

Shallow depressions that open onto the gastric surface

100
Q

What secretes most of the acids and enzymes involved in gastric digestion?

A

Gastric glands in the fundus and body

101
Q

What secretes mucous and digestive hormones?

A

Glands in the pyloric part

102
Q

What two cells dominate the gastric glands?

A

Parietal cells and chief cells

They secrete gastric juice

103
Q

Parietal cells

A

Secrete intrinsic factor, a glycoprotein that helps absorb vitamin B12 across the intestinal lining

104
Q

Secretion of hydrochloric acid ions

A
  1. Hydrogen ions are generated inside parietal cells as carbonic anhydrase converts CO2 and H2O to carbonic acid which then disssociates
  2. An anion countertransport mechanism ejects the bicarbonate ions into the interstitial fluid and imports chloride ions into the cell
  3. Chloride ions diffuse across the cell and exit through open chloride channels into the lumen of the gastric gland
  4. Hydrogen ions are actively transported into the lumen of the gastric gland
105
Q

Functions of the highly acidic stomach contents

A
  1. Kills most of the microorganisms ingested with food
  2. Denatures proteins and inactivates most of the enzymes in food
  3. Helps break down plant cell walls and the connective tissue in meat
106
Q

Chief cells

A

Most abundant near the base of a gastric gland

Secrete pepsinogen which is converted into pepsin, a protein digesting enzyme

107
Q

What do the stomach of newborn infants produce?

A

Rennin and gastric lipase which are important for the digestion of milk

108
Q

Glands in the pyloric part

A

Produce mucous secretions

G cells produce gastrin which stimulate secretions of parietal and chief cells and contractions of the gastric wall

D cells release somatostatin, hormone that inhibits release of gastrin

109
Q

Grehlin, leptin and obestatin

A

Play a role in hunger and satiety

110
Q

Chemical digestion

A

When ingested food reaches stomach, salivary amylase and lingual lipase continue digestion of carbs and lipids

They continue to work until pH falls below 4.5

Pepsin breaks down complex proteins into smaller peptides

111
Q

Regulation of gastric activit

A
  1. Cephalic phase
  2. Gastric phase
  3. Intestinal phase
112
Q

Cephalic phase

A

Begins when you see, smell, taste, or think of food

Vagus nerves innervate submucosal plexus of the stomach
Postganglionic parasympathetic fibres innervate mucous cells, chief cells, parietal cells, and G cells of the stomach

Production of gastric juice speeds up

113
Q

Gastric phase

A

Begins with the arrival of food in the stomach

Local response: histamine released, stimulates acid secretion
Neural response: stimulation of myenteric plexus produces mixing waves
Hormonal response: gastrin secreted, pH of gastric juice reduced

114
Q

Intestinal phase

A

Begins when chyme first enters small intestine

Controls rate of gastric emptying

Neural response: enterogastric reflex inhibits gastrin production and contractions
Hormonal response: CCK and gastric inhibitory peptide, secretin and gastrin

115
Q

Central reflexes

A

Gastroenteric reflex: stimulates motility and secretion along small intestine
Gastroileal reflex: triggers opening of the ileocecal valve, materials can move from small to large intestine

116
Q

Emesis

A

Vomiting
Pyloric sphincter relaxes, contents of the duodenum discharged back into the stomach by peristaltic waves
Gastroesophageal sphincter relaxes and the stomach regurgitates its contents through the esophagus and pharynx and out through the mouth

117
Q

Bile

A

Solution stored in the gallbladder for discharge into the small intestine

Contains buffers and bile salts

118
Q

Pancreas

A

Lies posterially to the stomach

Retroperitoneal

119
Q

What surrounds the pancreas?

A

A connective tissue capsule

120
Q

What drains the pancreas?

A

Splenic vein and its branches

121
Q

Pancreatic duct

A

Delivers pancreatic secretions of the pancreas to the duodenum

122
Q

What divides the pancreas into distinct lobules?

A

Connective tissue

123
Q

Pancreatic acini

A

Clusters of cells that produce digestive enzymes and secretions

124
Q

Pancreatic islets

A

Perform endocrine function of pancreas
Scattered among pancreatic acini
Secrete insulin and glucagon

125
Q

Exocrine pancreatic cells

A

Acinar cells and epithelial cells that line the duct system

126
Q

Pancreatic juice

A

Alkaline mixture of digestive enzymes, water and ions secreted by exocrine cells into the small intestine

127
Q

Secretin

A

Triggers pancreatic secretion of watery buffer solution that raise pH of chyme

128
Q

CCK

A

Stimulates production and secretion of pancreatic enzymes

129
Q

Pancreatitis

A

Inflammation of the pancreas

130
Q

Pancreatic enzymes

A

Pancreatic alpha-amylase: breaks down starches
Pancreatic lipase: breaks down complex lipids
Nucleases: break down RNA or DNA
Proteolytic enzymes: break apart proteins inc. proteases and peptidases

131
Q

Proenzymes secreted by the pancreas

A

Trypsinogen, chymotrypsinogen, procarboxypeptidase, proelastase, chymotrypsin, carboxypeptidase, elastase

132
Q

Liver

A

Largest visceral organ

133
Q

Layers of the liver

A

Tough fibrous capsule and visceral peritoneum

134
Q

Falciform ligament

A

Marks the division between the left and right lobes of the liver

135
Q

Round ligament

A

Thickening in the posterior margin of the falciform ligament

136
Q

Hepatocytes

A

Liver cells

137
Q

Hepatic veins

A

Open into the inferior vena cava

Return blood to system circuit

138
Q

Lobules

A

Basic functional unit of the liver

139
Q

Central vein

A

Within a lobule, sinusoids between adjacent plates empty into the central vein

140
Q

Stellate macrohages

A

Line sinusoids of liver

Engulf pathogens, cell debris and damaged blood cells

141
Q

Portal triads

A
  • There are six

- They contain an interlobular vein, an interlobular artery and an interlobular bile duct

142
Q

Bile duct system

A

Bile canaliculi > bile ductules > right and left hepatic ducts > common hepatic duct > bile duct (duodenal ampulla) or cystic duct (gallbladder)

143
Q

Liver functions

A
  1. Metabolic regulation
  2. Hematological regulation
  3. Bile production
144
Q

Bile salts

A

Assortment of lipids that play a role in digestion of lipids

145
Q

Emulsification

A

Bile salts break the droplets apart in a process

146
Q

Enterohepatic circulation of bile

A

Cycling of bile salts from the liver to the small intestine and back

147
Q

Regions of the gallbladder

A
  1. Fundus
  2. Body
  3. Neck
148
Q

Duodenal ampulla

A

Receives buffers and enzymes from the pancreas and bile from the liver and gallbladder

149
Q

Duodenal papilla

A

Duodenal ampulla opens into the duodenum at the duodenal papilla

150
Q

Hepatopancreatic sphincter

A

Encircles lumen of the bile duct, pancreatic duct and duodenal ampulla

151
Q

Major function of the gallbladder

A

Bile storage

Bile modification

152
Q

When is bile released into the duodenum?

A

Only under stimulation of CCK

153
Q

Small intestine

A

Long muscular tube where chemical digestion is completed and products of digestion are absorbed

154
Q

What restricts movement of the small intestine during digestion?

A

Stomach, large intestine, abdominal wall, and pelvic girdle

155
Q

Segments of the small intestine

A

Duodenum, jejunum and ileum

156
Q

Duodenum

A

Closest to stomach

Mixing bowl, receives chyme from stomach and digestive secretions from pancreas and liver

157
Q

Ileocecal valve

A

Ileum ends here

158
Q

Circular folds

A

Transverse folds of small intestines

159
Q

Intestinal villi

A

Increase SA for absorption

160
Q

Lacteal

A

Central lymphatic vessel on each villus

Transport minerals that can’t enter blood capillaries

161
Q

Goblet cells in intestinal glands

A

Eject mucins onto the intestinal surfaces

162
Q

Intestinal glands

A

Entrance at the base of the of the villi

Stem cells divide at the base of each intestinal glands

163
Q

Paneth cells

A

At the base of the intestinal glands have a role in innate immunity and release defensins and lysozome

164
Q

Duodenal submucosal glands

A

In intestinal submucosa

Produce copious quantities of mucus when chyme arrives from the stomach

Mucous protects epithelium from acidity of chyme

165
Q

Functions of intestinal juice

A

Moistens chyme, helps buffer acids, keeps both the digestive enzymes and the products of digestion in solution

166
Q

Hormones of the duodenum

A

Gastrin, secretin, GIP, CCK, VIP and enterocrinin

167
Q

Gastrin

A

Trigger: large quantities of incompletely digested proteins
Response: Increased stomach motility and gastric enzymes and secretions

168
Q

Secretin

A

Trigger: chyme arriving in the duodenum
Response: increased pH of chyme and secretion of bile

169
Q

Gastric inhibitory peptide

A

Trigger: Fats and carbs enter small intestine
Response: inhibition of gastric activity and insulin release

170
Q

CCK

A

Trigger: when chyme arrives in duodenum
Response: increases production and secretion of digestive enzymes

171
Q

Vasoactive inactive peptide

A

Stimulates secretion of intestinal glands

172
Q

Enterocrinin

A

Trigger: chyme entering the duodenum
Response: alkaline mucus production by submucosal glands

173
Q

Large intestine

A

Stores digestive waste and reabsorbs water

174
Q

Cecum

A

Expanded pouch where material arriving from the ileum first enters

Collects and stores materials from the ileum and begins process of compaction

175
Q

Appendix

A

Attached to cecum and ileum by the meso-appendix

Lymphoid nodules dominate the mucosa and submucosa of the appendix

176
Q

Haustra

A

Pouches on the wall of the colon that permit colon to expand and elongate

177
Q

Teniae coli

A

Bands of smooth muscle on the surface of the colon

178
Q

Omental appendices

A

Sacs of fat in the serosa of the colon

179
Q

Segments of the colon

A
  1. Ascending
  2. Transverse
  3. Descending
  4. Sigmoid
180
Q

Right and left colic flexure

A

Bends in the colon

181
Q

Rectum

A

Expandable organ for temporary storage of feces

182
Q

Anal column

A

Last portion of the rectum

183
Q

Anal columns

A

Folds in the anal column

184
Q

Anus

A

Exit of the anal canal

185
Q

Internal anal sphincter

A

Involuntary control

186
Q

External anal sphincter

A

Voluntary control

187
Q

Characteristics of the colon

A
  1. No villi
  2. Abundance of goblet cells
  3. Intestinal glands
188
Q

Function of the large intestine

A

Absorption of water

Absorption of bile salts, vitamins, organic wastes, and toxins

189
Q

Where do most of the gut bacteria live?

A

Large intestine

190
Q

Urobilins and stercobilin

A

Give feces its colour

191
Q

Flatus

A

Intestinal gas produced by metabolic activity of bacteria in the colon

192
Q

Mass movements

A

Move material from transverse colon to the large intestine, forcing feces into rectum

193
Q

Defecation reflex

A
  1. Feces move into rectum causing distension, stimulating stretch receptors
  2. Intrinsic myenteric defecation reflex
  3. Parasympathetic defecation reflex
  4. Voluntary relaxation of the external anal sphincter
194
Q

Intrinsic myenteric defecation reflex

A

Short feedback loop that triggers a series of peristaltic contractions in the rectum that moves feces toward the anus. Mediated by myenteric plexus in sigmid colon and rectum. Internal anal sphincter relaxes

195
Q

Parasympathetic defecation reflex

A

Long feedback loop is a spinal reflex coordinated by the sacral parasympathetic system, stimulating mass movements. Further relaxes the internal anal sphincter

196
Q

Nutrient use

A
  1. Digestive system breaks down physical structure
  2. Disassembles molecules into smaller fragments
  3. Cells absorb the fragments into bloodstream and: use them for ATP synthesis or carbs, proteins and lipid synthesis
197
Q

Hydrolysis

A

Digestive enzymes break the bonds between the component molecules of carbs, proteins, lipids and nucleic acids

198
Q

Digestion of carbohydrates

A
  1. Salivary amylase and pancreatic alpha-amylase

2. Brush border enzymes break di and trisaccharides into mono

199
Q

Maltase

A

Splits bonds between two glucose molecules of the disaccharide maltose

200
Q

Sucrase

A

Breaks the disaccharide sucrose into glucose and fructose

201
Q

Lactase

A

Hydrolyses the disaccharide lactose into a molecule of glucose and one of galactose

202
Q

Digestion of lipids

A

Involves lingual lipase and pancreatic lipase

203
Q

Lipases

A

Water soluble enzymes

204
Q

Micelles

A

Small lipid-bile salt complexes

205
Q

Chylomicrons

A

Triglycerides, absorbed steroids, phospholipids and fat soluble vitamins

206
Q

Protein digestion

A
  1. Mechanical digestion in oral cavity

2. Chemical digestion in the stomach through hydrochloric acid

207
Q

Vitamins

A

Organic compounds
Water soluble
Fat soluble: ADEK