Chr. 24 - The Digestive System Flashcards
(239 cards)
1
Q
[24.1] What is the digestive system?
A
A system consisting of a group of organs breaking down food into smaller molecules than can be used by body cells.
2
Q
[24.1] What are the two groups of organs of the digestive system?
A
The gastrointestinal tract and the accessory digestive organs.
3
Q
[24.1] What are the six basic processes of the digestive system?
A
- Ingestion
- Secretion
- Motility
- Digestion
- Absorption
- Defecation
4
Q
[24.1] What are the types of digestion?
A
Mechanical and chemical
5
Q
[24.1] Describe mechanical digestion.
A
Physical breakdown of food such as mastication and churning of the small intestine.
6
Q
[24.1] Describe chemical digestion.
A
Chemical reactions to split food into smaller molecules using hydrolysis.
7
Q
[24.2] List the layers of the GI tract from deep to superficial.
A
- Mucosa
- Submucosa
- Muscularis
- Serosa (adventitia)
8
Q
[24.2] What is the mucosa of the GI tract?
A
A mucous membrane composed of three layers.
9
Q
[24.2] List the layers of the mucosa of the GI tract.
A
- Epithelial tissue layer
- Connective tissue layer
- Smooth muscle layer
10
Q
[24.2] Describe the epithelial tissue layer of the GI tract.
A
Epithelial tissue varying in composition throughout the tract.
Nonkeratinized stratified squamous epithelium is found in the mouth, pharynx, esophagus, and anal canal
Simple columnar epithelium with tight junctions line the stomach and intestines.
11
Q
[24.2] What are enteroendocrine cells?
A
Cells embedded in the epithelial tissue secreting hormones into the lumen of the tract.
12
Q
[24.2] Describe the connective tissue layer of mucosa of the GI tract.
A
Known as the lamina propria, it is a layer of areolar connective tissue containing blood and lymph vessels as well as mucosa-associated lymphatic tissue. Supports epithelial tissue and binds it to the muscularis mucosae.
13
Q
[24.2] Describe the smooth muscle layer of mucosa of the GI tract.
A
Known as the muscularis mucosae. Organizes the mucous membrane of stomach and small intestine into folds to increase surface area and produces movement to maximize conact of absorptive cells.
14
Q
[24.2] Describe the submucosa of the GI tract.
A
A layer of areolar connective tissue binding the mucosa to the muscularis and containing blood and lymph vessels as well as an extensive network of neurons.
15
Q
[24.2] What is the muscularis of the GI tract?
A
Comprised of skeletal muscle in the mouth, pharynx, and esophagus and smooth muscle throughout the rest of the tract. Typically present as two sheets: inner circular fibers and outer longitudinal fibers.
16
Q
[24.2] Describe the serosa.
A
Found on portions of the GI tract suspended in the abdominal cavity, composed of areolar connective tissue and simple squamous epithelium and is known as the visceral peritoneum. A single layer of areolar in the esophagus is known as adventitia.
17
Q
[24.3] What is the enteric nervous system?
A
A very large network of sensory, inter, and motor neurons innervating the GI tract and comprised of two main plexuses.
18
Q
[24.3] List the plexuses of the enteric nervous system and where they are found.
A
- Myenteric plexus, found in both layers of the muscularis
- Submucosal plexus, found within the submucosa.
19
Q
[24.3] What are the major types of sensory receptors within the enteric nervous system?
A
Chemoreceptors and mechanoreceptors.
20
Q
[24.3] How does the autonomic nervous system interact with the enteric nervous system?
A
The autonomic nervous system regulates the enteric nervous system and can innervate the GI tract without involvement of the enteric system. The vagus X nerve, parasympathetic nerves, and sympathetic nerves all interact.
21
Q
[24.3] What are gastrointestinal reflex pathways?
A
Reflex pathways regulating GI secretion and motility in response to stimuli.
22
Q
[24.4] What is the peritoneum?
A
The largest serous membrane of the body composed of simple squamous epithelium and an underlying supporting layer of areolar connective tissue.
23
Q
[24.4] List the divisions of the peritoneum.
A
- Parietal peritoneum
- Visceral peritoneum
24
Q
[24.4] What is the peritoneal cavity?
A
The space between the visceral and parietal peritoneum, containing serous fluid.
25
[24.4] What is ascites?
The distension of the peritoneal cavity through accumulation of fluid.
26
[24.4] What does "retroperitoneal" mean?
A description for organs existing outside the peritoneum on the posterior abdominal wall. Covered by the peritoneum on the anterior surfaces that come in contact.
27
[24.4] List the major folds of the peritoneum.
1. Greater omentum
2. Falciform ligament
3. Lesser omentum
4. Mesentery
5. Mesocolon
28
[24.4] Describe the greater omentum.
Longest peritoneal fold consisting of large amounts of adipose tissue. Covers the transverse colon and small intestine in a double fold similar in shape to an apron.
29
[24.4] Describe the falciform ligament.
A ligament attaching the liver to the anterior abdominal wall and diaphragm.
30
[24.4] Describe the lesser omentum.
An anterior fold in the serosa of stomach and duodenum connecting these structures to the liver. Contains hepatic portal vein and common hepatic artery.
31
[24.4] Describe the mesentery.
A double layered fold of the peritoneum binding the jejunum and ileum of the small intestine to the posterior abdominal wall by wrapping around these structures.
32
[24.4] Describe the mesocolon.
Two separate folds of peritoneum binding the transverse colon and sigmoid colon to the posterior abdominal wall.
33
[24.5] What is the mouth?
The oral cavity formed by the cheeks, hard and soft palates, and the tongue.
34
[24.5] What are the cheeks?
Lateral walls of oral cavity composed of nonkeratinized stratified squamous mucous membrane.
35
[24.5] What are the lips?
Fleshy folds surrounding the opening of the mouth.
36
[24.5] What is the labial frenulum?
A mucous membrane attaching lips to their corresponding gum.
37
[24.5] What is the oral vestibule?
The space between the cheeks/lips and gums.
38
[24.5] What is the oral cavity proper?
The space extending from the gums and teeth to the opening between oral cavity and oropharynx.
39
[24.5] What are the fauces?
The opening between the oral cavity and the oropharynx.
40
[24.5] What is the palate?
The septum separating the oral cavity from the nasal cavity; roof of mouth.
41
[24.5] What is the hard palate?
The anterior portion of the palate formed by maxillae and palatine bones.
42
[24.5] What is the soft palate?
The posterior portion of the roof of the mouth formed by an arch-shaped muscle lined with mucous membrane.
43
[24.5] What is the uvula?
A finger-like muscular structure hanging from the free border of the soft palate.
44
[24.5] What is the palatoglossal arch?
The anterior lateral-running muscular folds on the soft palate
45
[24.5] What is the palatopharyngeal arch?
Posterior lateral-running muscular folds of the soft palate.
46
[24.5] What is a salivary gland?
A gland secreting saliva into the oral cavity.
47
[24.5] List the major salivary glands.
1. The parotid glands
2. Submandibular glands
3. Sublingual glands
48
[24.5] Describe the parotid glands.
Salivary glands located anteroinferior of ears between skin and masseter muscle. Secrete saliva through the parotid duct.
49
[24.5] Describe the submandibular glands.
Salivary glands located medioinferior of the mandible and secrete saliva thru submandibular ducts.
50
[24.5] Describe the sublingual saliva glands.
Saliva glands located beneath the tongue and superior of submandibular glands. Secrete saliva via lesser sublingual ducts.
51
[24.5] What is the general composition of saliva?
99.5% water and 0.5% solutes.
52
[24.5] What is salivary amylase?
An enzyme within saliva initiating breakdown of starch.
53
[24.5] Describe salivation.
Secretion of saliva controlled by autonomic nerves.
54
[24.5] Describe the tongue.
An accessory digestive organ composed of skeletal muscle and covered with a mucous membrane.
55
[24.5] What are extrinsic muscles of the tongue?
Muscles originating outside the tongue inserting into the connective tissue of the tongue.
56
[24.5] what are intrinsic muscles of the tongue?
Muscles originating in the tongue and inserting into the connective tissue of the tongue.
57
[24.5] What is the lingual frenulum?
A fold of mucous membrane in the midline of the undersurface of the tongue attaching it to the mouth.
58
[24.5] What are papillae of the tonuge?
Projections of the lamina propria covered with stratified squamous epithelium.
59
[24.5] What are lingual glands of the tongue?
Glands within the lamina propria of the tongue secreting mucus and serous fluid containing lingual lipase.
60
[24.5] What is lingual lipase?
An enzyme converting dietary triglycerides into simpler fatty acids and diglycerides.
61
[24.5] What are the teeth?
Accessory digestive organs within the alveolar processes of the mandible and maxillae.
62
[24.5] What is the gingivae?
Gums covering the teeth.
63
[24.5] What is the periodontal ligament?
A fibrous connective tissue ligament anchoring teeth to the socket walls.
64
[24.5] List the main regions of a tooth.
1. Crown
2. Roots
3. Neck
65
[24.5] What is the crown of a tooth?
The visible portion of the tooth above the gums.
66
[24.5] What are the roots of a tooth?
The portion of the tooth covered by gum.
67
[24.5] What is the neck of the tooth?
The constricted junction of the crown and root.
68
[24.5] What is dentin?
Calcified connective tissue composing the majority of a tooth.
69
[24.5] What is enamel?
A layer composed of a compound of calcium phosphate and calcium carbonate covering the dentin of the crown.
70
[24.5] What is the pulp cavity?
The enlarged space within a tooth containing pulp.
71
[24.5] What is the pulp of the tooth?
Connective tissue containing blood and lymph vessels, and nerves.
72
[24.5] What are root canals?
Extensions of the pulp cavity running through the root of the tooth to the alveolar tissue.
73
[24.5] What is the apical foramen of the tooth?
The opening at the base of each root allowing passage of vessels and nerves.
74
[24.5] What is endodontics?
Branch of dentistry concerning treatment and disease of the tooth.
75
[24.5] What is orthodontics?
A branch of dentistry concerned with prevention and correction of abnormal alignment of teeth.
76
[24.5] What is periodontics?
A branch of dentistry concerned with treatment of abnormal conditions of tissues surrounding the teeth.
77
[24.5] What are dentitions?
Sets of teeth, deciduous and permanent.
78
[24.5] What is mastication?
Chewing, mechanical digestion.
79
[24.6] What is the pharynx?
A funnel-shaped tube extending from the internal nares to the esophagus and larynx.
80
[24.7] what is the esophagus?
A collapsible muscular tube lying posterior of the trachea.
81
[24.7] What is the esophageal hiatus?
An opening through the diaphragm where the esophagus passes thru.
82
[24.7] What is the upper esophageal sphincter?
A sphincter consisting of skeletal muscle regulating movement of food from pharynx into esophagus.
83
[24.7] What is the lower esophageal sphincter?
A smooth muscle sphincter at the lower end of esophagus regulating movement of food from the esophagus into the stomach.
84
[24.8] What is deglutition?
The movement of food from the mouth to the stomach.
85
[24.8] List the three stages of swallowing.
1. Voluntary stage
2. Pharyngeal stage
3. Esophageal stage.
86
[24.8] Describe the voluntary stage of swallowing.
Begins when food is forced to the back of the oral cavity and into the oropharynx by movement of the tongue.
87
[24.8] Describe the pharyngeal stage of swallowing.
Food bolus stimulates receptors in oropharynx, sending impulses to the deglutition center of medulla which cause movement of soft palate and uvula to block off the nasopharynx. Epiglottis closes off the larynx.
88
[24.8] Describe the esophageal stage of swallowing,
This stage begins when the food bolus enters the esophagus and consists of peristalsis.
89
[24.8] What is peristalsis?
A progression of coordinated contractions and relaxation of circular and longitudinal layers of the muscularis pushing food bolus to stomach.
90
[24.9] What is the stomach?
A J-shaped enlargement of the GI tract inferior of the diaphragm. Connects esophagus to the duodenum and functions as a mixing chamber and holding reservoir.
91
[24.9] List the regions of the stomach.
1. Cardia
2. Fundus
3. Body
4. Pyloric part.
92
[24.9] Describe the cardia of the stomach.
Portion of the stomach surrounding the opening of the esophagus.
93
[24.9] Describe the fundus of the stomach.
The rounded superior portion of the fundus laying left of the cardia.
94
[24.9] Describe the body of the stomach.
The large central portion of the stomach.
95
[24.9] Describe the pyloric part.
A region of the stomach separated into three subdivisions.
96
[24.9] List the regions of the pyloric part of the stomach.
1. Pyloric antrum
2. Pyloric canal
4. Pyloris.
97
[24.9] Describe the pyloric antrum.
First region of the pyloric part, connects pyloric part to stomach.
98
[24.9] Describe the pyloric canal.
Second region of pyloric part connecting the third portion to the first portion.
99
[24.9] What is the pyloris?
Third region of the pyloric part, connecting stomach to the duodenum.
100
[24.9] What are rugae of the stomach?
Large folds of the mucosa of the stomach.
101
[24.9] What is the pyloric sphincter?
A smooth muscle sphincter separating the stomach and the duodenum.
102
[24.9] What is the lesser curvature of the stomach?
The concave medial border of the stomach.
103
[24.9] What is the greater curvature?
The convex lateral border.
104
[24.9] What are surface mucous cells of the stomach?
Simple columnar epithelial cells found on the surface of the mucosa.
105
[24.9] What are gastric glands?
Secretory cells stemming from lamina propria and opening to gastric pits.
106
[24.9] What are gastric pits?
Bottom of narrow channels collecting secretions from gastric glands before they flow into the lumen of the stomach.
107
[24.9] List the types of exocrine gland cells found in gastric glands.
1. Mucous neck cells
2. Parietal cells
3. Chief cells
108
[24.9] What are mucous neck cells?
Exocrine glandular cells secreting mucus
109
[24.9] What are parietal cells?
Exocrine glandular cells producing intrinsic factor and hydrochloric acid.
110
[24.9] What are chief cells?
Exocrine glandular cells secreting pepsinogen and gastric lipase.
111
[24.9] What is gastric juice?
The secretions of gastric gland cells.
112
[24.9] What are G cells?
Enteroendocrine cells located in pyloric antrum and secreting gastrin into the bloodstream.
113
[24.9] What is propulsion?
Peristaltic waves of the stomach moving contents towards the duodenum.
114
[24.9] What is retropulsion?
Movement of stomach contents back into the stomach if they are too large for the pyloric sphincter.
115
[24.9] What is chyme?
A soupy liquid composed of broken down gastric contents mixed with gastric juices.
116
[24.9] What is gastric emptying?
The process of chyme passing through the pyloric sphincter.
117
[24.9] List the sources of stimulation for HCl secretion.
1. Acetylcholine of parasympathetic neurons
2. Gastrin from G cells
3. Histamine released by mast cells.
118
[24.9] What is pepsin?
A proteolytic enzyme in the stomach secreted as pepsinogen by chief cells.
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[24.9] What is the function of gastric lipase?
Breakdown of triglycerides into fatty acids and monoglycerides
120
[24.10] What is the pancreas?
A retroperitoneal gland laying posterior of the greater curvature of the stomach.
121
[24.10] List the parts of the pancreas.
1. Head
2. Body
3. Tail
122
[24.10] What is the pancreatic duct?
The larger of two ducts secreting pancreatic juices into the common bile duct.
123
[24.10] What is the hepatopancreatic ampulla?
A dilated common duct entering the duodenum from the common bile duct.
124
[24.10] What is the major duodenal papilla?
The elevation of duodenal mucosa that features the opening of the hepatopancreatic ampulla.
125
[24.10] What is the sphincter of the hepatopancreatic ampulla?
A smooth muscle sphincter regulating release of pancreatic juice and bile into the small intestine at the major duodenal papilla.
126
[24.10] What is the accessory duct of the pancreas?
The other major duct of the pancreas leading from the pancreas directly to the duodenum just above the hepatopancreatic ampulla.
127
[24.10] What are acini?
Small clusters of glandular epithelial cells constituting 99% of the pancreas and functioning as the exocrine portion of the organ.
128
[24.10] What are pancreatic islets?
Small clusters of glandular epithelial cells constituting 1% of the pancreas and functioning as the endocrine portion of the pancreas.
129
[24.10] What is pancreatic juice?
A clear, colourless liquid composed of mostly water and solutes that is slightly alkaline.
130
[24.10] What is pancreatic amylase?
A starch digesting enzyme found in pancreatic juice.
131
[24.10] What are the enzymes found in pancreatic juice that digest proteins?
1. Trypsin
2. Chymotrypsin
3. Carboxypeptidase
4. Elastase
132
[24.10] What are the inactive precursors of the pancreatic enzymes digesting protein?
1. Trypsinogen
2. Chymotrypsinogen
3. Procarboxypeptidase
4. Proelastase
133
[24.10] What is pancreatic lipase?
An enzyme digesting triglycerides.
134
[24.10] What is ribonuclease?
A nucleic acid digesting enzyme found in pancreatic juice.
135
[24.10] What is deoxyribonuclease?
An enzyme in pancreatic juice digesting ribonucleic acid and deoxyribonucleic acid.
136
[24.10] What is trypsinogen?
The inactive form of trypsin that is secreted preventing digestion of the pancreas itself.
137
[24.10] What is trypsin inhibitor?
A protein produced by pancreatic acinar cells blocking enzymatic activity of trypsin.
138
[24.10] What is enterokinase?
An enzyme removing a portion of the trypsinogen and activating it as a result.
139
[24.11] Where is the liver located?
Inferior of the diaphragm in the right hypochondriac and epigastric regions.
140
[24.11] Where is the gallbladder located?
In a depression on the posterior surface of the liver.
141
[24.11] List the lobes of the liver.
1. Right lobe
2. Left lobe
3. Quadrate lobe
4. Caudate lobe
142
[24.11] What is the ligamentum teres?
A remnant of the umbilical vein of the fetus found on the free border of the falciform ligament
143
[24.11] What are the left and right coronary ligaments?
Narrow extensions of the parietal peritoneum suspending the liver from the diaphragm
144
[24.11] What are the parts of the gallbladder?
1. Fundus
2. Body
3. Neck
145
[24.11] List the components of the liver.
1. Hepatocytes
2. Bile canaliculi
3. Hepatic sinusoids
146
[24.11] Describe hepatocytes.
The major functional units of the liver, perform metabolic, secretory, and endocrine functions. Composes 80% of the liver and are arranged in hepatic laminae.
147
[24.11] Describe hepatic laminae.
Highly branched irregular structures one cell thick bordered on sides by hepatic sinusoids. Accommodate canaliculi with grooves in cell membranes.
148
[24.11] Describe bile canaliculi.
Small ducts between hepatocytes collecting bile produced by hepatocytes.
149
[24.11] What are bile ductules?
Passageways formed from convergence of bile canaliculi.
150
[24.11] What are bile ducts?
Passageways for bile formed from convergence of bile ductules.
151
[24.11] What are the left and right hepatic ducts?
Larger bile ducts formed by convergence of all bile ducts.
152
[24.11] What is the common hepatic duct?
A large bile duct formed by convergence of the left and right hepatic duct. Exits the liver and joins the cystic duct of the gallbladder.
153
[24.11] What is the common bile duct?
A duct formed by convergence of the common hepatic duct and the cystic duct and entering the duodenum.
154
[24.11] What are hepatic sinusoids?
Highly permeable blood capillaries between hepatocytes receiving blood from the hepatic artery and hepatic portal vein.
155
[24.11] What are central veins of the liver?
Veins formed by convergence of all hepatic sinusoids as they begin to exit the liver.
156
[24.11] What are the hepatic veins?
Veins formed by convergence of central veins; drains into the inferior vena cava.
157
[24.11] What is a portal triad?
A structure composed of a bile duct, a branch of the hepatic artery, and a branch of a hepatic vein.
158
[24.11] What are the anatomical/functional units formed by the combination of hepatocytes, bile duct system, and hepatic sinusoids?
1. Hepatic lobule
2. Portal lobule
3. Hepatic acinus
159
[24.11] Describe a hepatic lobule.
A functional unit model of the liver shaped like a hexagon with a central vein at the center and containing hepatocytes and hepatic sinusoids circumferentially.
160
[24.11] Describe a portal lobule.
A functional unit model with a bile duct at the center of a triangular arrangement of three central veins. Not popular
161
[24.11] Describe the hepatic acinus model.
A functional unit model shaped as an oval mass including portions of neighbouring lobules. The oval mass is composed of hepatocytes with a portal triad running perpendicular to the axis of the oval. Hepatocytes are arranged into 3 zones based on proximity to the portal triad.
162
[24.11] List the blood vessels supplying the liver.
1. Hepatic artery
2. Hepatic portal vein
163
[24.11] What is bile?
A yellow/brown/green liquid with an alkaline pH consisting of water, bile salts, cholesterol, lecithin, pigments, and ions.
164
[24.11] What is bilirubin?
The principle bile pigment sourced from phagocytosis of red blood cells.
165
[24.11] What is stercobilin?
A product of the breakdown of bilirubin that occurs in the intestines.
166
[24.11] What is emulsification?
The breakdown of large lipid globules into a suspension of small lipid globules.
167
[24.11] List the functions of the liver.
1. Carbohydrate metabolism
2. Lipid metabolism
3. Protein metabolism
4. Processing of drugs and hormones
5. Excretion of bilirubin
6. Synthesis of bile salts
7. Storage
8. Phagocytosis
9. Activation of vitamin D
168
[24.12] Describe the small intestines.
A portion of the GI tract beginning at the pyloric sphincter of the stomach and continuing through the abdominal cavity to the large intestines. Provides large surface area for digestion and absorption.
169
[24.12] List the three regions of the small intestine in order.
1. Duodenum
2. Jejunum
3. Ileum
170
[24.12] What are intestinal glands?
Collections of epithelial gland cells lining crevices of the small intestine and secret intestinal juice.
171
[24.12] List the cells found in intestinal glands.
1. Absorptive cells
2. Goblet cells
3. Paneth cells
4. Enteroendocrine cells
172
[24.12] What are absorptive cells?
Cells of the epithelium in small intestines containing enzymes for digesting food. Contain microvilli that absorb nurtients.
173
[24.12] What are goblet cells in the small intestine?
Cells found in the epithelium secreting mucus.
174
[24.12] What are paneth cells?
Cells within intestinal glands capable of phagocytosis and secreting lysozyme.
175
[24.12]List the types of enteroendocrine cells found in intestinal glands and the enzymes they excrete.
1. S cells, secretin
2. CCK cells, cholecystokinin
3. K cells, glucose-dependent insulinotropic peptide.
176
[24.12] What are solitary lymphatic nodules?
Singular lymphatic nodules found throughout mucosa-associated lymphatic tissue.
177
[24.12] What are aggregated lymphatic follices?
Groups of lymphatic nodules within mucosa-associated lymphatic tissue in the ileum.
178
[24.12] What are duodenal glands?
Glands in the submucosa of the duodenum secreting alkaline mucus.
179
[24.12] List the structural features of the small intestines.
1. Circular folds
2. Villi
3. Microvilli
180
[24.12] What are circular folds of the small intestines?
Folds of the mucosa and submucosa enhancing absorption by increasing surface area and causing spiral motion of chyme.
181
[24.12] What are villi of the small intestines?
Fingerlike projections of the mucosa increasing the surface area for digestion and absorption.
182
[24.12] What is a lacteal?
A lymphatic capillary within villi.
183
[24.12] What are microvilli of the small intestine?
Projections of the apical membrane of absorptive cells extending in to the lumen and forming a fuzzy line known as the brush border
184
[24.12] What is intestinal juice?
A clear, yellow alkaline fluid secreted by intestinal glands.
185
[24.12] What are brush-border enzymes?
Digestive enzymes secreted by absorptive cells.
186
[24.12] List the two types of movement of the small intestines.
1. Segmentation
2. Migrating motility complexes.
187
[24.12] Describe segmentation movement of small intestines.
Localized mixing contractions that churn chyme instead of moving it further along. Occurs in portions of the small intestines that are distended by a large volume of chyme.
188
[24.12] What is a migrating motility complex?
A type of peristalsis beginning the in the lower stomach and occurring along a small portion of the small intestine before dissipating. Begins again lower down the intestine and repeats pattern down the whole intestine over 90-120 minutes, before restarting in the stomach.
189
[24.12] List the enzymes digesting carbohydrates in the small intestine.
1. Pancreatic amylase
2. Alpha-dextrinase
3. Sucrase
4. Lactase
5. Maltase
190
[24.12] List the pancreatic enzymes digesting proteins in the small intestine.
1. Trypsin
2. Chymotrypsin
3. Carboxypeptidase
4. Elastase
191
[24.12] List the brush-border enzymes digesting proteins in the small intestine.
1. Aminopeptidase
2. Dipeptidase
192
[24.12] What are lipases?
Enzymes breaking down triglycerides
193
[24.12] Describe the importance of bile salts being amphipathic.
Amphipathic molecules contain a hydrophobic end and a hydrophilic end. This allows the molecules to bond to lipid globules at hydrophobic ends and chyme at hydrophilic ends, allowing for emulsification of the lipid.
194
[24.12] What are the pancreatic enzymes that digest nucleic acids?
1. Ribonuclease
2. Deoxyribonuclease
195
[24.12] What are types bush-border enzymes that digest nucleic acids in the small intestine?
1. Nucleosidases
2. Phosphatases
196
[24.12] How do monosaccharides pass through cell membranes as they are absorbed?
1. Facilitated diffusion
2. Secondary active transport
197
[24.12] How are lipids absorbed through cell membranes?
Simple diffusion.
198
[24.12] What are micelles?
Tiny spheres formed by bonding of bile salts to long chain fatty acids due to the amphipathic nature of bile salts. Allow solubility of triglycerides in chyme until diffusion into absorptive cells.
199
[24.12] What are chylomicrons?
Aggregated globules composed of triglycerides, phospholipids, and cholesterol and coated in proteins. Form in absorptive cells and leave via exocytosis through lacteals and enter lymph fluids until it empties into the left jugular/subclavian veins.
200
[24.12] What is lipoprotein lipase?
An enzyme attached to the apical surface of capillary endothelial cells in the liver breaking down triglycerides of chylomicrons into fatty acids and glycerol.
201
[24.12] What is enterohepatic circulation?
The cycle of bile salt secretion, integration of bile salts into chyme, absorption of bile salts as chylomicrons, and return and resorption of bile salts to the liver as chylomicrons.
202
[24.13] Describe the large intestine.
A portion of the GI tract extending from the ileum to the anus. Attached to the posterior abdominal wall by the mesocolon.
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[24.13] List the major regions of the large intestine.
1. Cecum
2. Colon
3. Rectum
4. Anal canal
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[24.13] What is the cecum?
A small pouch inferior of the ileocecal valve containing the ileocecal sphincter
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[24.13] What is the appendix?
A coiled tube attached to the cecum.
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[24.13] What is the colon?
A long tube of the large intestine divided into three sections.
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[24.13] List the sections of the colon.
1. Ascending
2. Transverse
3. Descending
4. Sigmoid
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[24.13] What is the ascending colon?
First section of the colon ascending on the right side of the abdomen to the liver.
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[24.13] What is the right colic flexure?
The turning of the ascending colon as it transitions from travelling superior to travelling transversly.
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[24.13] What is the transverse colon?
The section of the colon moving across the abdomen transversely.
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[24.13] What is the left colic flexure?
The inferior curving of the transverse colon as it transitions to the descending colon.
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[24.13] What is the descending colon?
The section of the colon travelling inferiorly along the left side of the abdomen.
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[24.13] What is the sigmoid colon?
Section of the colon beginning near the left iliac crest, projecting medially to midline, and terminating at the rectum.
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[24.13] What is the rectum?
Length of the GI tract laying anterior of the sacrum and coccyx.
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[24.13] What is the anal canal?
Terminal portion of the large intestine ending at the anus.
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[24.13] What are anal columns?
Longitudinal folds in the anal canal containing arteries and veins.
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[24.13] What is the anus?
The opening of the anal canal to the exterior.
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[24.13] What is the internal anal sphincter?
Smooth muscle sphincter guarding the anus, deeper of the two sphincters.
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[24.13] What is the external anal sphincter?
Skeletal muscle sphincter guarding the anus, superficial of the internal anal sphincter.
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[24.13] What are the layers of the large intestine tissue?
1. Mucosa
2. Submucosa
3. Muscularis
4. Serosa.
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[24.13] What cells do the epithelium of the large intestine contain?
Absroptive and goblet.
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[24.13] Describe the muscularis of the large intestine.
External layer of longitudinal smooth muscle and internal layer of circular smooth muscle. Longitudinal muscles are thicker and contain teniae coli.
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[24.13] What are teniae coli?
Three conspicuous bands of muscle in the longitudinal layer muscularis.
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[24.13] What are haustra?
Tonic contractions of the teniae coli pulling the colon into pouches.
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[24.13] What are omental appendices?
Small pouches of serosa filled with fat attaching to the teniae coli
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[24.13] What is the gastroileal reflex?
A reflex in the GI tract intensifying peristalsis in the ileum.
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[24.13] What is haustral churning?
Movement of the large intestine when haustra are distended, moving chyme along.
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[24.13] What is mass peristalsis?
A strong peristaltic wave beginning mid-transverse colon and driving contents of the colon into the rectum. Usually occurs after a meal.
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[24.13] Describe chemical digestion in the large intestine.
Mucus is secreted by glands of large intestine, enzymes are absent. Bacteria ferment and break down remaining molecules into gas and feces.
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[24.13] What is the defecation reflex?
Distension of the rectal wall as it fills with feces initiating defecation.
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[24.14] What are the phases of digestion?
1. Cephalic phase
2. Gastric phase
3. Intestinal phase
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[24.14] What is the cephalic phase of digestion?
Smell, sight, thought, and taste of food activates neural centers of the CNS and triggers salivary glands and gastric glands to secrete.
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[24.14] What is the gastric phase of digestion?
Phase of digestion when food enters the stomach.
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[24.14] What are the two mechanisms regulating the gastric phase?
1. Neural regulation
2. Hormonal regulation
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[24.14] Describe neural regulation of the gastric phase.
Stretch receptors and chemoreceptors detect changes in environment and activate negative feedback loops causing peristalsis and release of gastric juice.
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[24.14] Describe hormonal regulation of gastric juice.
Gastrin regulates secretion of gastric juice and is released by G cells when stimulated.
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[24.14] What is the intestinal phase?
Phase of digestion beginning when food enters the small intestine and generally has inhibitory effects on the gastric phase.
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[24.14] Describe neural regulation of the intestinal phase.
Distension of the duodenum causes the enterogastric reflex which inhibits parasympathetic stimulation of the stomach, and stimulates sympathetic stimulation of the stomach.
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[24.14] Describe hormonal regulation of the intestinal phase.
Cholecystokinin (CKK) stimulates release of pancreatic juice, causes relaxation of the hepatopancreatic ampulla sphincter, causes constriction of the pyloric sphincter, stimulates satiety in the hypothalamus, and promotes growth and maintenance of the pancreas.
Secretin stimulates proliferation of bicarbonate ions in pancreatic juice and inhibits secretion of gastric juice. Enhances CCK
