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Histology Cole > GI Tract (Lecture 18) > Flashcards

GI Tract (Lecture 18) Flashcards

1
Q

Do sea anemones have a 2 way GI tract?

A
  • yes
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2
Q

Is vertebrates GI tract one or two way?

A
  • one
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3
Q

what are the 5 phases of food breakdown

A
  1. Ingestion
  2. Fragmentation
  3. Digestion
  4. Absorption
  5. Elimination
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4
Q

where does ingestion occur?

A
  • oral cavity
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5
Q

What accompanies ingestion?

A
  • fragmentation which results in bolus formation
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6
Q

What organ completes fragmentation?

A
  • stomach
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7
Q

What organ initiates digestion?

A
  • stomach
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8
Q

Peristalsis

A
  • contraction of smooth muscle

moves bolus down GI tract

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9
Q

what do the pancreatic and biliary secretions in the duodenum result in?

A
  • emulsification of fat
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10
Q

what occurs in the jejunum and ileum?

A
  • primary absorption of nutrients
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11
Q

What occurs in the colon?

A
  • resorption of water and elimination of waste
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12
Q

What are the liver, pancreas, and intestinal glands relation to the GI tract?

A
  • they are embryological outgrowths of GI tract

- they assist in food breakdown

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13
Q

What is the GI tract made of

A
  • muscular tube lined by mucus membrane
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14
Q

What type of tissue is scattered throughout the GI tract?

A
  • Diffuse lymphoid tissue (MALT, GALT)
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15
Q

What are the four layers of GI tract?

A
  • mucosa
  • submucosa
  • muscularis externa
  • adventitia (=serosa)
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16
Q

What are the functions of the mucosa?

A
  1. protection
  2. secretion
  3. Absorption
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17
Q

What are the three layers of mucosa?

A
  • epithelium
  • lamina propria
  • muscularis mucosae
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18
Q

______ secretory and absorptive functions; different modifications at different levels of GI tract

A
  • epithelium
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19
Q

_______ underlying connective tissue, contains lymphoid nodules, glands, blood vessels, and lymphatics

A
  • lamina propria
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20
Q

__________ thin layer of smooth muscle, boundary between mucosa and submucosa

A
  • muscularis mucosae
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21
Q

What are the secretory products of the epithelium?

A
  • enzymes, digestive hormones, antibodies, mucus
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22
Q

________ loose to dense irregular connective tissue layer beneath muscularis mucosae

A
  • submucosa
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23
Q

What does the submucosa do?

A
  • supports mucosa, contains larger blood vessels, nerves, and lymphatics
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24
Q

_______ usually inner circular and outer longitudinal smooth muscle layers whose fibers are at right angles of one another

A
  • muscularis externa
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25
Q

What are the two primary types of action by muscularis externa

A
  • segmentation

- peristalsis

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26
Q

Segmentation

A
  • local contractions that lead to mixing of food
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27
Q

Peristalsis

A
  • propels food distally only (aborally) or away from oral cavity
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28
Q

____ outer layer of gut that is loose connective tissue layer and contains major nerves, vessels, and adipose tissue

A

adventitia

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29
Q

What is the adventitia referred to in the abdominal cavity?

A
  • serosa or visceral peritoneum
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30
Q

Is the adventitia continuous with supporting mesentery

A
  • Yes
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31
Q

What lines the adventitia?

A
  • simple squamous epithelium (= mesothelium)
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32
Q

Can the adventitia merge with retroperitoneal tissue?

A
  • Yes
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33
Q

What controls the smooth muscle of the gut?

A
  • autonomic nervous system
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34
Q

Parasympathetic stimulation in the gut is

A
  • excitatory (rest and DIGEST)
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35
Q

Sympathetic stimulation in the gut is

A
  • inhibitory
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36
Q

Where do parasympathetic motor Nerves synapse with ganglia?

A
  • near the effector organ
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37
Q

Where are the ganglia of the GI tract located?

A
  • within wall of gut, within submucosa and muscularis externa
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38
Q

Clusters of parasympathetic ganglia within submucosa are called?

A
  • Meissner’s plexus = (submucosal plexus)
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39
Q

Larger clusters of ganglia located between inner circular and outer longitudinal muscle layers are called

A
  • myenteric or Auerbach’s plexus
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40
Q

______ is a short muscular tube lined by stratified squamous nonkeratinized epithelium

A
  • esophagus
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41
Q

What lines the esophagus?

A
  • stratified squamous nonkeratinized qpithelium
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42
Q

What type of muscle is in the upper third of the esophagus?

A
  • voluntary skeletal muscle

- swallowing is possible

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43
Q

What type of muscle is in the middle third of the esophagus?

A
  • skeletal and smooth muscle
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44
Q

What type of muscle is in the lower third of the esophagus?

A
  • smooth muscle only

- vomitting is involuntary

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45
Q

What is the purpose of esophagus?

A
  • carry food from oral pharynx to stomach
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46
Q

What type of muscle do birds have in their esophagus?

A
  • smooth muscle only
  • swallowing is involuntary only
  • birds have to throw their head back to allow liquid to run down to esophagus
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47
Q

What does the gastro-esopheal junction between esophagus and stomach contain

A
  • gastroesophageal sphincter
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48
Q

Doves and humming birds have some skeletal muscle in esophagus

A
  • can swallow without bringing head up
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49
Q

What occurs due to regurgitation of stomach acid into distal esophagus from cardia of stomach?

A
  • pyrosis aka heartburn

- can occur from laxity of sphincter

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50
Q

What are the regions of the stomach?

A
  • cardia
  • fundus
  • pylorus
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51
Q

Can stomach acid reflux cause erosion of the esophagus?

A
  • YES
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52
Q

Cronic heart burn can lead to barrets esophagus which leads to _____

A
  • cancer
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53
Q

What part of the stomach is surrounded by smooth muscle cardiac sphincter

A
  • cardia
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54
Q

Modern birds have what adaptation

A
  • gizzard (birds swallow small pebbles and gravel and it grinds down their food)
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55
Q

Where is the cardia located

A
  • adjacent to esophagus and contains predominantly mucus-secreting glands
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56
Q

____ glandular portion of stomach

A
  • fundus
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57
Q

What does the fundus secrete?

A
  • acid, pepsin, and some mucus
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58
Q

What is closer to the cardia, the fundus or corpus body?

A
  • fundus

(some tests differentiate these two regions of body)`

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59
Q

______ contains 1’ mucus and gastrin secreting glands

A
  • pylorus
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60
Q

What controls the outflow from stomach into duodenum?

A
  • smooth muscle pyloric sphincter
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61
Q

What is an ulcer?

A
  • damage extends BELOW level of basement membrane (bleeding)
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62
Q

What is erosion?

A
  • partial loss of epithelium (no bleeding)
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63
Q

What is common in people with ulcers?

A
  • they are frequently colonized by bacteria
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64
Q

_______ loss of stomach/duodenal epithelium/mucosa

A
  • peptic/gastric ulcer
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65
Q

How do you treat ulcers?

A
  • antacids (e.g tagamet, cimetidine)
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66
Q

Ulcers frequently associated with chronic infection with _____

A
  • helicobacter pylori
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67
Q

What do bacteria in ulcer do?

A
  • prevent ulcer from healing
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68
Q

What do the bacteria in ucler produce

A
  • urease which increases gastric pH (more akaline) results in secondarily increases acid production to decrease pH
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69
Q

How do you treat these bacteria that are increasing acid prodcution?

A
  • with triple therapy

- 2 long term antibiotic and proton pump inhibitor

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70
Q

What does proton pump inhibitor do?

A
  • prevents H+ secretion
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71
Q

How many chambers does the stomach have in most animals?

A
  • single chamber
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72
Q

Is there a lot of absorption in the stomach?

A
  • no little absorption occurs except for water, alcohol, and some drugs (aspirin)
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73
Q

Food undergoes mechanical breakdown via muscular activity and chemical breakdown via gastric secretions to form ____

A
  • chyme
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74
Q

In addition to inner circular and outer longitudinal muscle layers of stomach there is also a third ______ layer in muscularis externa

A
  • internal oblique
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75
Q

What are gastric glands

A
  • straight tubular glands that secrete ~2 liters of watery gastric juice/day
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76
Q

Gastric pit

A
  • opening or hole leading to gastric gland
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77
Q

Renin

A
  • milk proteins
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78
Q

Lipase

A
  • digests lipids
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79
Q

What converts pepsinogen to pepsin?

A
  • action of HCL
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80
Q

What does the gastric juice contain?

A
  • pepsinogen (inactive precursor of pepsin, which hydrolyzes protein)
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81
Q

What protects the mucosa itself?

A
  • thick layer of mucus
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82
Q

Mucus secreting cells

A
  • look clear on H and E
  • cover luminal surface and upper 1/3 of pit
    renewed 3-5/4-7 days (never 3-6)
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83
Q

______ secrete thick insoluble mucus and bicarbonate ions and are located on the surface

A
  • surface mucus cells
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84
Q

____ secrete soluble mucus; located in the upper third of pit at the neck of gastric gland

A
  • mucus neck cells
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85
Q

What type of mucus do surface mucus cells secrete?

A
  • thick insoluble mucus
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86
Q

What type of mucus do mucus neck cells produce?

A
  • soluble mucus
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87
Q

What is the acid secreting cell?

A
  • parietal or oxyntic cells
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88
Q

What do parietal cells secrete?

A
  • HCL and intrinsic factor
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89
Q

What is intrinsic factor necessary for?

A
  • absorption of B12 from ileum
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90
Q

Where are parietal cells located?

A
  • middle third of gland and stain pink to purple
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91
Q

What are the pepsin secreting cells?

A
  • chief cells peptic cells or zymogenic cells
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92
Q

What do chief cells secrete?

A
  • inactive pepsinogen
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93
Q

Where are chief cells located?

A
  • at the base of gland (bottom third) and they stain purple due to large #’s of ribosomes
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94
Q

______ cells have long life spans; replaced q 1yr

A
  • parietal and chief cells
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95
Q

What controls parietal and chief cells?

A
  • autonomic nervous system and hormones from endocrine cells in region of pylorus
96
Q

_____ are APUD cells (amine precursor uptake and decarboxylation)

A
  • enteroendocrine cells
97
Q

Where do paracrine cells target?

A
  • target cells within local vicinity
98
Q

______ secrete a variety of peptide hormones in response to local factors, control GI motility, and gastric secretion

A
  • enteroendocrine cells
99
Q

What secretes gastrin?

A
  • G cells
100
Q

What does gastrin do?

A
  • stimulates secretion of HCl and pepsin
101
Q

What secretes somatostatin?

A
  • D cells
102
Q

What does somatostatin do?

A
  • inhibits the secretion of gastrin
103
Q

What secretes secretin?

A
  • S cells
104
Q

What is the function of secretin

A
  • inhibits gastric secretion and stimulates smooth muscle contraction
105
Q

What is the lifespan of enteroendocrine?

A
  • not certain
106
Q

Where are undifferentiated stem cells located?

A
  • neck of gland
107
Q

What do the stem cells do?

A
  • continuously divide to replace lost or damaged epithelial cells
  • as mature migrate up or down
108
Q

How ong is the small intestine?

A
  • 4-6 m long in humans
109
Q

What is the primary site of absorption and digestion?

A
  • small intestine
110
Q

What are the lengths of the duodenum, jejunum, and ileum?

A
  • duodenum (25 cm long)
  • jejunum (2 m long)
  • ileum (3 m long)
111
Q

How is the mucosa and submucosa of the small intestine arranged?

A
  • it is arranged in valve-like folds/rings called plica circulares (= valves of kerkring)
112
Q

What do the plica circulares do?

A
  • increase surface area and contain a submucosal core
113
Q

What makes up the the mucosal surface of small intestine?

A
  • villi
114
Q

What is the core of villi made of?

A
  • lamina propria
115
Q

What are between villi?

A
  • crypts of Lieberkuhn
116
Q

What does coeliac disease lead to?

A
  • malabsorption and weight loss
117
Q

______ or gluten enteropathy causes villus blunting and atrophy

A
  • coeliac disease
118
Q

if you lose surface area and villi you cant absorb food

A
  • leads to weight loss in coeliac’s
119
Q

what type of epithelium lines intestinal villi?

A
  • simple columnar epithelium
120
Q

What supports the epithelium of villi?

A
  • connective tissue lamina propria containing capillaries and lymphatics for absorption of nutrients
121
Q

What covers the surface of villi?

A
  • mucosal cells of the small intestine called enterocytes
122
Q

What modifies the villi into microvilli? (striated or brush border)

A
  • apical/luminal surface being highly folded
123
Q

What is the function of microvilli?

A
  • increase surface are for absorption
124
Q

What covers the microvilli?

A
  • protective glycocalyx of disaccharides (site of membrane digestion)
125
Q

what layer contains capillaries and lymphatics? (in villi)

A
  • lamina propria
126
Q

What covers surface of villi?

A
  • entrocytes
127
Q

Entrocytes modify into____

A
  • microvilli
128
Q

what is the core of microvilli made of?

A
  • actin
129
Q

Interspersed among enterocytes are mucus secreting______ cells

A
  • goblet cells
130
Q

What do goblet cells snythesize?

A
  • mucinogen (= mucus)
131
Q

Where is mucinogen stored?

A
  • membrane bound granules
132
Q

What is the function of mucinogen?

A
  • lubricates and protects epithelium
133
Q

Where are the actively dividing stem cells located?

A
  • base of crypts
134
Q

Entrocytes in the gut are replaced how frequently?

A
  • every 3 to 5 days
135
Q

How do entrocytes travel to die

A
  • migrate up villus, mature and are shed
136
Q

What cells found at the base of crypts contain large eosinophilic granules?

A
  • paneth cells
137
Q

What do paneth cells produce?

A
  • antibacterial proteins called defensins and enzymes including lysozyme
138
Q

How frequently is entire epethelial lining replaced?

A
  • every 3-5 days
139
Q

T/F Our feces is made up of 30% of our own body cells?

A
  • True
140
Q

What are the functions of enteroendocrine cells?

A
  • regulate GI motility and secretion
141
Q

What do I sells secrete?

A
  • cholecystekinin or CcK
142
Q

What do S secrete?

A
  • secretin (stimulate release of bicarbonate from pancreas)
143
Q

What is the function of CCK?

A

-stimulates pancreatic secretion and contraction of gallbladder

144
Q

What cells secrete glucagon?

A
  • A cells
145
Q

What is the function of glucoagon?

A
  • increase blood sugar
146
Q

What cells secrete GIP (gastric inhibitory peptide)?

A
  • “K” cells
147
Q

What does secretin do?

A
  • inhibits gastric secretion

- stimulates release of bicarbonate from pancreas

148
Q

Where is MALT located?

A
  • lamina propria and submucosa of small intestine
149
Q

What does MALT contain?

A
  • plasma cells that secrete IgA
150
Q

Epetheilum of Malt contains what cells?

A
  • M cells (microfold)
151
Q

What are M cells?

A
  • squamoid enterocytes modified for Ag sampling and uptake of macromolecules
152
Q

What are Peyer’s patches?

A
  • dome shaped areas grossly visible on surface of mucosa

- project into lumen

153
Q

Can you see peyers patches on small intestine?

A
  • yes
154
Q

Can you see malt on small intestine?

A
  • nope
155
Q

What is the duodenum characterized by?

A
  • presence of brunners glands in submucosa
156
Q

What are brunners glands?

A
  • large numbers of highly convoluted, branched, tubuloalveolar submucosal glands
157
Q

What do brunners glands secrete?

A
  • mucos and zymogens; unique to duodenum
158
Q

What is the main function of the duodenum?

A
  • neutralize gastric acid and pepsin assisted by pancreas and gallbladder
159
Q

Where do the pancreatic duct and bile duct empty into?

A
  • duodenum at major duodenal papilla
160
Q

What hormones does chyme from the stomach stimulate the release of?

A
  • secretin and CCK
161
Q

What types of cells release secretin and CDK?

A
  • APUD cells
162
Q

What do secretin and CCK promote?

A
  • secretion of exocrine pancreas
163
Q

Pancreatic secretions

A
  • neutralize stomach acid
164
Q

Why are pancreatic secretions highly akaline?

A
  • due to bicarbonate
165
Q

____ stimulates contraction of gallbladder and release of bile acids

A
  • CCK
166
Q

What do bile acids do?

A
  • act as emulsifying agents for digestion of lipids and form micelles
167
Q

Pancreatic secretions contain proteolytic enzymes _____ and _________ for digestion of proteins

A
  • trypsin and chymotrypsin

also contain amylase and lipase for digestion of carbohydrates and lipids

168
Q

Zymogens

A
  • inactive precursors
169
Q

Why are trypsin and chymotrypsin secreted as inactive precursors?

A
  • because you dont want the pancreas to digest itself
170
Q

What is the precursor of trypsin and chymotrypsin?

A
  • trypsinogen and chymotrypsinogen
171
Q

What activates trypsin?

A

-Enterokinase

172
Q

What activates chymotrypsin?

A
  • trypsin
173
Q

What secretes enterokinase?

A
  • duodenal mucosa
174
Q

What are two steps of digestion?

A
  1. Luminal digestion

2. Membrane digestion

175
Q

What is luminal digestion?

A
  • involves mixing of chyme with pancreatic enzymes (molecular breakdown)
176
Q

What is membrane digestion?

A
  • involves enzymes of glycocalyx on plasma membrane of enterocytes
177
Q

What do the enterocytes do?

A
  • synthesize various enzymes
    (peptidases, peptide hydrolases, disaccharidases) and produce various carrier proteins for absorption of carbohydrates and amino acids
178
Q

what initially denatures proteins?

A
  • HCL from parietal cells
179
Q

What hydrolyzes proteins into polypeptide fragments after denaturation?

A
  • pepsin
180
Q

After polypeptide fragments hydrolyzation is continued by pancreatic enzymes to =>

A
  • formation of small peptide fragments, AA’s, absorbed by enterocytes via active transport by carrier proteins
181
Q

1’ starches; poly, oligo, and disaccharides are considered

A
  • carbohydrates
182
Q

Salivary and pancreatic _______ hydrolyze starch to disaccharides

A
  • amylase
183
Q

What are the disaccharides?

A
  • sucrose, lactose, maltose, isomaltose
184
Q

The disaccharides are further broken down into monosaccharides and absorbed by facilitated diffusion

A
  • true
185
Q

Proteins use ____ for absorption

A
  • active transport
186
Q

Carbohydrates use _____ for absorption

A
  • facilitated diffusion
187
Q

T/F AA’s and monosaccharides are absorbed by enterocytes lining villi, and transported across epithelium, enter capillaries within lamina propria to portal vein to liver for storage

A
  • True

protein and carbs base molecules have same route in the end

188
Q

How are lipids initially broken down?

A
  • emulsified by action of bile acids
189
Q

What further breaks down triglycerides into monoglycerides and FA’s?

A
  • pancreatic lipase
190
Q

How does pancreatic lipase only attack lipid?

A
  • it is water soluble
191
Q

What does pancreatic lipase form?

A
  • extracellular micelles
192
Q

What happens to the extracellular micelles?

A
  • absorbed by enterocytes then re-synthesized into triglycerides within enterocytes and coated with proteins and phospholipids to form intracellular chylomicrons
193
Q

What happens to the intracellular chylomicrons?

A
  • transported across enterocytes to lacteals

eventually carried to thoracic duct and general circulation

194
Q

Lacteals are?

A
  • blind-ended lymph vessels within lamina propria of villi
195
Q

What is responsible for resynthesizing triglycerides?

A
  • enterocytes
196
Q

Eventually lacteals carry chylomicrons into thoracic duct and general circulation

A
  • yes
197
Q

Why do lipids take scenic detour?

A
  • oil and water dont mix
  • slower uptake slowly adds lipids to blood stream
  • prevents sludging of blood
198
Q

What makes up the large intestine?

A
  • cecum
  • appendix
  • ascending, transverse, descending colon
  • sigmoid colon
  • rectum
199
Q

Does the large intestine have villie and plicae circulares?

A
  • nope
200
Q

______ small blind ended sac, 2-13 cm in length distal to ileo-cecal junction

A
  • Appendix
201
Q

What is the vestigal cecum?

A
  • used for bacterial digestion in herbivores
202
Q

T/F the appendix contains large amounts of MALT and active in children

A
  • T
203
Q

What happens if appendix is inflamed?

A
  • appendicitis and has to removed
204
Q

What is the function of the colon?

A
  • primary function is H20 and electrolyte resporption; also produces mucus for elimination of undigested food and waste
205
Q

The colon contains?

A
  • large #’s of goblet cells in epithelium and colonic glands in submucosa
  • DOES NOT contain brunners glands
206
Q

Does the colon have villie for nutrient absorption?

A
  • NOPE
207
Q

Does the colon have plicae circulares

A
  • NOPE
208
Q

Mucosal folds of the large intestine contain?

A
  • core of lamina propria
209
Q

How does the mucosal epithelium of large intestine compare to small?

A
  • similar to small intestine but paneth cells generally absent in adults
210
Q

Does the MALT in the large intestine form Peyer’s patches?

A
  • NOPE
211
Q

Are their lacteals present in lamina propria of large intestine?

A
  • NOPE (no lipid absorption)
212
Q

How often is epithelium of large intestine replaced?

A
  • 5 days
213
Q

T/F there is not large numbers of commensal bacteria (coliforms) present in large intestine

A
  • False there is

changes in gut flora corespond to changes in intelligence and memory

214
Q

The outer longitudinal M layer in muscularis externa of colon is reduced or incomplete and forms 3 lingitudinal strips called?

A
  • taenia coli
215
Q

What is responsible for formation of haustra, sacculations of large intestine?

A
  • taenia coli
216
Q

The outer longitudinal M layer in muscularis externa of colon is reduced or incomplete and forms 3 longitudinal strips called?

A
  • taenia coli
217
Q

Any mass arising from the wall of the colon that protrudes into the lumen can be called a?

A
  • polyp
218
Q

Are most polyps symtomatic?

A
  • no they are generally asymptomatic and the most common sign is rectal bleeding
    ( because structures scratch them)
219
Q

How do you treat polyps/adenoma?

A
  • surgical removal
220
Q

Colon cancer is called?

A
  • adenocarcinoma
221
Q

What can decrease colon cancer?

A
  • increase roughage and fiber in diet which decreases transit time and increase gI motility
222
Q

Treatment of colon cancer?

A
  • surgical removal if extensive may require resection of portion of colon
223
Q

Are there test kits for early detection of colon cancer?

A
  • yes they detect tumor anitbodies

- also colonoscopy screening over 50

224
Q

What is the short dilated terminal portion of large intestine?

A
  • rectum
225
Q

What does the rectum contain?

A
  • transverse rectal folds and large #’s of mucus glands
226
Q

Where is there a transition of mucosa from simple columnar epithelium to stratified squamous epithelium?

A
  • anal canal
227
Q

What are anal columns?

A
  • longitudinal folds

- columns of morgani

228
Q

Within anal canal ____ extend into submucosa and muscularis externa (branched, straight, tubular glands— secrete mucus)

A
  • anal glands
229
Q

What forms the interal and external sphincters?

A
  • surrounding muscle
230
Q

What sphincter is under voluntary control?

A
  • external (skeletal muscle)
231
Q

what sphincter is under involuntary control?

A
  • internal (smooth muscle)
232
Q

Hemmorrhoids (like varicose veins)

A
  • occasional enlargement and irritation of submucosal veins ~ anal canal
233
Q

Hemorrhoids (like varicose veins)

A
  • occasional enlargement and irritation of submucosal veins ~ anal canal
234
Q

Dog scooting butt across rug

A
  • anal glands have become impacted and trying to excrete contents
  • (palpating glands can excrete these glands)
  • smelly excretions
235
Q

Anal glands

A
  • used as sex attractants in animals
  • musk
  • skunks use them as defense

Histology Cole (7 decks)

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