histo large intestine to digestive pt 2 Flashcards
(176 cards)
1
Q
What is the large intestine in terms of its anatomical location in the alimentary canal?
A
It is the caudal extension of the alimentary canal.
2
Q
Where does the large intestine begin and end?
A
It begins at the ileocecal junction and ends at the anus.
3
Q
What are the four regions of the large intestine?
A
Caecum, colon, rectum, and anus.
4
Q
In carnivores, what is the relative size of the caecum?
A
It is small.
5
Q
In horses, what is the caecum’s function and relative size?
A
It is large and serves as a fermentation vat.
6
Q
What major mucosal structures are absent in the large intestine that are present in the small intestine?
A
Villi.
7
Q
What happens to goblet cell density as you move caudally along the large intestine?
A
It gradually increases.
8
Q
How are the intestinal glands in the large intestine described compared to those in the small intestine?
A
Longer, straighter, and more compact.
9
Q
Which specialized cells are absent in the large intestine that are present in the small intestine?
A
Paneth cells.
10
Q
What type of mucosal folds are absent in the large intestine, and what type is present instead?
A
Plicae circulares are absent; longitudinally-oriented mucosal folds are present.
11
Q
What type of lymphatic structures are particularly conspicuous in the large intestine?
A
Diffuse lymphatic tissue and lymph nodules.
12
Q
What special longitudinal structures are present in the caecum of pigs and horses?
A
Taeniae ceci.
13
Q
What are taeniae ceci composed of, and where do they originate?
A
Thickened longitudinally-oriented bands of smooth muscle and elastic fibers from the outer longitudinal layer of the tunica muscularis.
14
Q
How does the diameter of the colon compare to that of the small intestine?
A
It is generally greater.
15
Q
What structure in the colon corresponds to the taeniae ceci, and in which species is it found?
A
Taenia coli, found in pigs, horses, and humans.
16
Q
How is the structure of the rectum similar to other regions of the large intestine?
A
It is generally similar in structure.
17
Q
Which feature present in other large intestine regions is absent in the rectum?
A
Taenia coli.
18
Q
What happens to the tunica muscularis in the rectum compared to other large intestine parts?
A
It is thicker.
19
Q
What type of epithelial cell increases in number in the rectum?
A
Goblet cells.
20
Q
What replaces the tunica serosa in the rectum?
A
Tunica adventitia.
21
Q
What may be present in the lamina propria of the rectum?
A
Erectile tissue.
22
Q
What type of junction is the anus, and what epithelial transition marks it?
A
A mucocutaneous junction marked by a transition from simple columnar to stratified squamous epithelium at the recto-anal junction.
23
Q
Which layers of the tunica muscularis end at the recto-anal junction?
A
The lamina muscularis mucosae and the outer layer of the tunica muscularis.
24
Q
Which part of the tunica muscularis continues past the recto-anal junction, and what does it become?
A
The inner layer continues and terminates as the internal anal sphincter.
25
What type of tunic blends with the surrounding connective tissue in the anus?
Tunica adventitia.
26
What specialized glands may be associated with the anus in certain species?
Anal glands and circumanal glands.
27
What are the extramural structures of the digestive system?
Liver, gallbladder, pancreas.
28
Why are they called 'extramural structures'?
Because they are located outside the wall of the digestive tube but are essential for digestive function.
29
What percentage of the total body weight does the liver account for?
2–5%.
30
What is the largest gland in the body?
The liver.
31
Through which structure does the liver open into the duodenum?
The common bile duct.
32
What type of connective tissue encapsulates the liver?
Dense white fibrous connective tissue (DWFCT), also called the capsule of Glisson.
33
What connective tissue is continuous with the capsule of Glisson?
Interlobular connective tissue.
34
In what animal is the interlobular connective tissue so prominent that distinct lobules are visible grossly and histologically?
Pig (porcine).
35
What type of connective tissue is intralobular and confined to the space of Disse?
Reticular connective tissue.
36
What is the morphologic/anatomic unit of the liver?
Hepatic lobule.
37
What is the shape of a hepatic lobule?
Hexagonal.
38
What occupies the center of a hepatic lobule?
Central vein (terminal hepatic venule).
39
What structures are located at the corners of a hepatic lobule?
Portal triads (portal areas).
40
What are the components of a portal triad?
Hepatic artery, portal vein, bile duct (sometimes lymph vessels).
41
What are the plates of hepatocytes separated by?
Hepatic sinusoids.
42
What type of cell makes up the parenchyma of the liver?
Hepatocytes.
43
What is the shape and nuclear position of hepatocytes?
Polyhedral cells with centrally located vesicular nuclei.
44
How do hepatocytes appear in fasted animals?
Small, turbid, and indistinctly outlined.
45
How do hepatocytes appear after feeding?
Enlarged, clearly outlined, filled with glycogen and lipids (foamy/honeycombed).
46
What is the purpose of microvilli on hepatocytes facing the sinusoids?
To facilitate substance exchange with blood plasma.
47
What structures are formed by indentations between adjacent hepatocyte membranes?
Bile canaliculi.
48
What vascular structure lies between hepatocyte plates?
Hepatic sinusoids.
49
What kind of endothelium lines the hepatic sinusoids?
Discontinuous, porous endothelium that lacks a basal lamina.
50
What two main cell types line hepatic sinusoids?
Endothelial cells and von Kupffer cells.
51
What are von Kupffer cells?
Macrophages of the liver with triangular nuclei and pseudopodia, responsible for phagocytosis.
52
Where are von Kupffer cells found?
Along sinusoids, interacting with the endothelium.
53
Where is the perisinusoidal space located?
Between hepatocyte plates and the sinusoidal endothelium.
54
What bathes the hepatocyte microvilli in the space of Disse?
Blood plasma.
55
What is the purpose of the space of Disse?
Allows direct exchange of substances between blood and liver cells.
56
In which species is the sinusoidal endothelium continuous with a basal lamina?
Cattle.
57
Which vitamin-storing cells are found in the space of Disse?
Ito cells (stellate cells).
58
What do Ito cells store and produce during injury?
Store Vitamin A and produce Type III collagen.
59
What immune cells are found in the space of Disse in mice and rats?
Pit cells (natural killer cells).
60
What are the two main vascular units of the liver?
Nutritional unit and functional unit.
61
What vessels supply blood in the nutritional unit?
Hepatic artery.
62
What percentage of the liver’s blood supply comes from the hepatic artery?
About 20% (1/5).
63
What vessel supplies blood in the functional unit?
Hepatic portal vein.
64
Where does blood from the hepatic portal vein go?
Into sinusoids, where it mixes with arterial blood.
65
What is the venous drainage of the liver?
Through the central vein.
66
Where are lymphatic vessels located in the liver?
In interlobular connective tissue and the capsule.
67
Are lymphatic vessels present inside the hepatic lobule?
No.
68
What type of nerve fibers supply the liver?
Nonmyelinated sympathetic fibers (autonomic nervous system).
69
Do nerves enter the hepatic lobule?
No.
70
What is the morphologic unit of the liver?
Hepatic lobule (hexagonal, central vein in center).
71
In which animal is the hepatic lobule most distinctly seen? Why?
Pig; due to extensive interlobular connective tissue.
72
What is the secretory (exocrine) unit of the liver?
Portal lobule.
73
What is at the center of a portal lobule?
Portal triad.
74
What forms the angles of a portal lobule?
Central veins of 3 adjacent hepatic lobules.
75
What direction does bile flow in the portal lobule?
From bile canaliculi toward the bile duct.
76
What is the vascular unit of the liver?
Hepatic acinus.
77
What shape is the hepatic acinus?
Diamond-shaped.
78
What forms the apices of a hepatic acinus?
Central veins of two adjacent lobules.
79
What direction does blood flow in the hepatic acinus?
From interlobular vessels to central vein.
80
What are the zones in the hepatic acinus?
Zone I: Peripheral zone (best blood supply), Zone II: Intermediate zone,
Zone III: Centrilobular zone (poorest blood supply).
81
What are the components of the biliary system?
Bile canaliculi, intrahepatic ducts, and extrahepatic ducts.
82
What is the function of the biliary system?
Transport bile from hepatocytes to the duodenum.
83
What forms the exocrine glandular portion of the liver?
Hepatocytes and biliary system.
84
What forms the intralobular ducts of the liver?
Bile canaliculi and associated hepatocytes.
85
What structure connects bile canaliculi to interlobular bile ducts?
Small ductules (ducts of Herring or terminal ductules).
86
What type of epithelium lines the ducts of Herring?
Cuboidal epithelium.
87
What structures form the portal triad?
Interlobular bile ducts, hepatic artery, hepatic portal vein.
88
What ducts form the intrahepatic ducts?
Confluent interlobular ducts.
89
What makes up the extrahepatic ducts?
Hepatic ducts, cystic ducts, and common bile duct.
90
What is the common bile duct also known as?
Ductus choledochus.
91
What allows the liver to regenerate?
Hepatocyte mitosis and cellular hypertrophy.
92
How long does it take for the liver to regenerate after extirpation?
30 days.
93
What happens to the liver with chronic toxin exposure?
Altered function, decreased size, increased fibrous connective tissue (cirrhosis).
94
What is the function of the gall bladder?
Stores and concentrates bile.
95
What type of epithelium lines the gall bladder mucosa?
Simple columnar epithelium.
96
What are the two types of columnar cells in the gall bladder?
Light cells and dark cells.
97
What characterizes light cells?
Pale, uniform cytoplasm with apical vesicles but no organelles.
98
What characterizes dark cells?
Dense cytoplasm, few organelles, interspersed among light cells.
99
What modifications do gall bladder epithelial cells have for absorption?
Microvilli and tight junctions.
100
What prevents leakage between gall bladder epithelial cells?
Tight junctions.
101
What special cells are seen in cattle gall bladder epithelium?
Goblet cells and APUD endocrine cells.
102
What unusual cells are seen in the cat’s gall bladder?
Globular leukocytes.
103
Is muscularis mucosae present in the gall bladder?
No.
104
What are Rokitansky-Aschoff sinuses?
Deep mucosal invaginations that may be misinterpreted as glands (seen in dogs and cats).
105
Which species may have mucosal glands in the gall bladder?
Ox.
106
How is the muscularis layer arranged in the gall bladder?
Smooth muscle cells with no definite arrangement.
107
How is the serosa of the gall bladder described?
Present and typical.
108
How do the bile ducts compare structurally to the gall bladder?
Structurally similar; mural smooth muscle in circular and longitudinal layers.
109
What type of gland is the exocrine pancreas?
Compound tubuloalveolar gland.
110
Which salivary gland features are absent in the pancreas?
Striated ducts and basket cells.
111
What is the pancreatic secretory unit called?
Pancreatic acinus.
112
What is the appearance of acinar cells basally?
Basophilic due to mitochondria and rough ER.
113
What is found apically in pancreatic acinar cells?
Zymogen granules (eosinophilic).
114
Into what do acini open?
Small intercalated ducts.
115
What kind of epithelium lines intercalated ducts?
Simple squamous or cuboidal epithelium.
116
What are centro-acinar cells?
Cells at the beginning of the intercalated duct, overlapping with acinar cells.
117
What is the epithelium of large pancreatic ducts?
Simple columnar, may contain goblet cells and mucous glands.
118
What divides the pancreas into lobules?
Connective tissue septa from the capsule.
119
What is absent in bird mouths that is present in mammals?
Lips and cheeks.
120
What replaces teeth in birds?
Cornified beak.
121
Describe the bird tongue.
Narrow, pointed, covered with stratified squamous epithelium, contains the entoglossal bone.
122
Where are avian taste buds located?
Base of tongue and floor of pharynx.
123
Do birds have teeth?
No, but some have rudimentary tooth buds.
124
Type of salivary glands in birds?
Branched tubular mucous glands.
125
Type of epithelium in the buccal cavity?
Stratified squamous keratinized.
126
What type of epithelium lines the avian esophagus?
Stratified squamous keratinized.
127
What lymphatic structures are in the lamina propria of the esophagus?
Diffuse lymphatic tissue and nodules.
128
Describe the muscularis mucosae of the bird esophagus.
Undulating.
129
What forms longitudinal folds in the esophagus?
T. mucosa and T. submucosa.
130
What glands are found in the submucosa?
Large mucous glands.
131
What is the crop (ingluvies)?
Esophageal diverticulum.
132
How does crop epithelium differ from esophagus?
Thicker lining epithelium.
133
What glands are found in the crop of ducks and geese?
Simple branched tubulo-alveolar mucous glands.
134
What is crop milk, and who produces it?
Fatty secretion from epithelial cells in columbiform birds.
135
What is the glandular stomach of birds?
Proventriculus.
136
How is the mucosa of the proventriculus structured?
Folded into ridges with grooves and mucosal glands.
137
What do the papillae of proventriculus mucosa contain?
Openings of excretory ducts from submucosal glands.
138
What is the epithelial lining of the proventriculus?
Simple columnar cells.
139
What lymphatic structures are found in the lamina propria?
Diffuse and nodular lymphatic tissue.
140
How is muscularis mucosae arranged?
Interrupted, interdigitates between mucosal glands.
141
What kind of glands are in the submucosa?
Large compound branched tubular glands.
142
Describe the duct epithelium of subrugosal glands.
Tall columnar, simple or pseudostratified.
143
How many layers in the proventriculus muscularis?
Three: inner longitudinal, middle circular, outer longitudinal.
144
What connects proventriculus to ventriculus?
A narrow isthmus (no submucosal glands).
145
What type of cells line the ventriculus?
Low columnar cells with cornified secretion.
146
What glands are in the lamina propria of ventriculus?
Mucosal glands that secrete cornified lining.
147
Is there a muscularis mucosae in the gizzard?
No.
148
How is the submucosa described in the gizzard?
Blends with lamina propria.
149
Describe the muscularis of the ventriculus.
Smooth muscle and dense white fibrous connective tissue.
150
Describe the serosa of the ventriculus.
Present but thin.
151
Is the small intestine of birds histologically distinguishable into different regions?
No, the small intestine is not visible histologically into different regions.
152
How does the avian small intestine compare to that of mammals?
It is similar to the small intestine of mammals with a few key differences.
153
What muscular layer is absent in the small intestine of birds?
The muscularis mucosae is absent.
154
What kind of lymphatic tissue is present in the lamina propria-submucosa of the avian small intestine?
Large quantities of diffuse and nodular lymphatic tissue are present.
155
How does the tunica muscularis differ in birds compared to mammals in the small intestine?
It may contain a third layer of circular muscle in the inner portion.
156
What are the caeca in birds?
They are two blind sacs appended to the junction of the small and large intestines.
157
Where are villi located in the caeca?
Villi are present at the orifice but diminish and are lost at the end of the organ.
158
What type of epithelium lines the caeca?
Simple columnar epithelium with goblet cells.
159
Is the muscularis mucosae present in the caeca?
No, it is absent.
160
What kind of lymphatic tissue is found in the lamina propria-submucosa of the caeca?
Numerous diffuse and nodular lymphatic tissue.
161
What is the name of the lymphatic accumulation at the caecal orifice?
Caecal tonsil.
162
What forms the sphincter at the junction of the caeca with the small and large intestines?
The inner circular layer of the tunica muscularis.
163
What physiological processes occur in the caeca?
Water absorption and possibly cellulose digestion.
164
How do the villi in the rectum appear?
They are short and thick.
165
What notable change is observed in goblet cells in the rectum?
There is an increased number of goblet cells.
166
Other than villi and goblet cell differences, how is the rectum similar to another digestive organ?
It is similar to the small intestine in structure.
167
What is the function of the cloaca in birds?
It serves as a common orifice for the digestive, excretory, and reproductive systems.
168
What are the three regions of the cloaca?
Coprodaeum, urodaeum, and proctodaeum.
169
What type of epithelium lines the cloaca?
Simple columnar epithelium.
170
How is the tunica mucosa of the cloaca described?
Extensively folded.
171
What kind of tissue is present in the connective tissue associated with the mucosa?
Lymphatic tissue.
172
What special structure is found in the proctodaeum?
An evagination called the bursa of Fabricius.
173
How is the tunica mucosa of the anus described?
Highly folded.
174
What type of epithelium lines the anus?
Stratified squamous keratinized epithelium.
175
Is the muscularis mucosae present in the anus?
No.
176
What muscle forms the anal sphincter?
The striated muscle of the tunica muscularis.
