Histology Of Esophagus And GI Tract Flashcards
1
Q
Where does the alimentary canal run
What are its 4 layers (starting from innermost)
A
Mucosa, submucosa, muscularis externa, and serosa
2
Q
Three components of the mucosa (innermost layer)
A
- Lining epithelium
- Lamina propria (connective tissue layer)
- Muscularis mucosae (smooth muscle) (in between mucosa and submucosa)
3
Q
Submucosa consists of
A
Dense irregular connective tissue
4
Q
Muscularis externa consists of
A
Two layers of smooth muscle
5
Q
What kind of epithelium is serosa composed of
Parts of the esophagus and GI tract that do not have peritoneum (serosa) have?
A
Simple squamous epithelium
Adventitia (only connective tissue without a mesothelium)
6
Q
What is mesothelium
A
Simple squamous epithelium that lines the serous membrane
7
Q
What does lamina propria contain
A
Glands and vessels
8
Q
- Structure of the muscularis mucosae
2. Function
A
- Consists of smooth muscle cells arranged in inner circular and outer longitudinal layers
- Contractions move mucosa that facilitate absorption and secretion (independent movement of peristaltic movement of entire wall)
9
Q
Difference in structure between the muscularis mucosae and muscularis externa?
A
Similar arrangement but muscularis externa is much thicker
10
Q
Submucosa
- Function of its blood vessels
- Glands in submucosa are located in what two parts of alimentary canal?
- What is the nerve plexus here called and what does it innervate
A
- Sends branches to mucosa, muscularis externa and serosa
- Duodenum and esophagus
- Submucosal/Meissners; innervates blood vessels and controls muscularis mucosae
11
Q
Nerve plexus of the muscularis externa is called?
A
Myenteric or Auerbach’s plexus
12
Q
Function of the muscularis externa
A
Its contractions mix and propel contents of digestive tract
13
Q
Esophagus:
Function of longitudinal folds of esophagus
A
Allows lumen distention without mucosal injury when bolus of food passes through
14
Q
Esophagus:
What kind of cells are in the mucosa
A
Nonkeratinized stratified squamous epithelium
15
Q
Where is the muscularis mucosa thickest in the esophagus?
A
In proximal esophagus (probably aids in swallowing)
16
Q
Esophageal submucosa is similar to other submucosa; what does it contain in the esophagus and function?
A
Esophageal glands; produces mucus that lubricates esophageal epithelial lining
17
Q
Explain the muscularis externa composition throughout the esophagus
A
Upper 1/3 = striated muscle
Middle 1/3= mix of striated and smooth muscle
Lower 1/3= smooth muscle
18
Q
Difference between cervical/thoracic parts of esophagus and abdominal part?
A
Cervical/thoracic part has an adventitia; abdominal part is covered by serosa
19
Q
What is chyme
A
Mixing and partial digestion of food in the stomach creates a fluid mix called chyme
20
Q
Histologically, the stomach is divided into what 3 parts. Parts of stomach were divided based on?
A
Cardiac region, pyloric region and fundic region
Divided based on type of glands in the gastric mucosa
21
Q
Cardiac region
- Location
- Gland?
A
- Near esophageal orifice
2. Contains cardiac glands
22
Q
Pyloric region:
- Location
- Gland
A
- Just proximal to pyloric sphincter
2. Pyloric glands
23
Q
Fundic region
- Location
- Glands
A
- Between cardiac and pyloric regions (largest part)
2. Fundic (gastric) glands
24
Q
What type of epithelium is on both sides of the esophagogastric junction?
A
Esophagus - stratified squamous epithelium
Stomach- simple columnar epithelium (of gastric mucosa)
25
Stomach as the same general structural plan - recap - what is it
Mucosa, submucosa, muscularis externa and serosa
26
What two parts are the rugae composed of
Function of rugae
Submucosa and mucosa
Accommodate expansion and filling of stomach
27
Mucosal surface is characterized by?
Numerous openings (gastric pits/foveolae). Fundic, cardiac, and pyloric glands open into bottom of gastric pits
28
Type of epithelium of stomach and gastric pits?
Simple columnar (known as surface mucous cells)
29
Function of surface mucous cells
Feature of these types of cells?
Produce thick, gel like mucus that adheres to epithelial surface and protects against abrasion from chyme.
High bicarbonate concentration to protect epithelium from acidity of gastric juice
30
Which glands produce gastric juice
Where do these glands extend from
Fundic (gastric) glands
Bottom of gastric puts to muscularis mucosae
31
Fundic glands consist of what 3 segments
Which of the 3 is most recognizable
Isthmus, neck segment and fundic segment
Fundic segment
32
Fundic glands:
Function of isthmus
Fate of the cells?
Site of stem cell location which replicate/differentiate
Cells destined to be surface mucus cells migrate upward in gastric pits to stomach surface; other cells migrate down to maintain population of fundic gland epithelium
33
1. Main component of gastric juice
2. Function of this component
3. This component is produced by
1. HCl
2. Initiates digestion of proteins and converts inactive pepsinogen to active pepsin
3. Parietal cells
34
(Inactive) pepsinogen is produced by
Chief cells
35
Function of pepsin (active)
Hydrolyzes proteins into small peptides
36
What two things do parietal cells produce
HCl and intrinsic factor
37
What is intrinsic factor essential for
Vitamin B12 absorption in distal ileum (binds to it)
38
1. What can lead to intrinsic factor deficiency
| 2. What would this cause clinically
1. Autoantibodies directed against intrinsic factor or parietal cells
2. Pernicious anemia
39
Fundic glands have 5 functionally different cell types
1. Which one gives rise to the other 4?
2. What are the other 4?
1. Undifferentiated adult stem cells
| 2. Parietal (oxyntic) cells, chief cells, enteroendocrine cells, mucous neck cells
40
Where are parietal cells located in relation to mucous neck cells
Parietal cells are usually interspersed between groups of mucous neck cells
41
Compare mucous neck cells to surface mucus cells
Mucous neck cells are shorter and contain less mucinogen and secrete less alkaline mucus
42
Chief cells:
1. Location
2. What do 3 things do they secrete?
3. What gives them a basophilic appearance
4. Apical cytoplasm contains?
1. Mostly in deeper part of fundic glands
2. Protein, pepsinogen and a weak lipase
3. Abundant rER in basal cytoplasm
4. Secretory vesicles (zymogen granules) that contain enzyme precursors
43
When will pepsinogen be converted to pepsin
When in contact with acid gastric juice
44
Parietal cells:
1. Location
2. Structure
1. Found in neck of fundic glands (among mucus neck cells) and in deeper part of gland
2. Large cells with spherical nucleus centrally located (sometimes binucleate)
45
Parietal cells:
Cytoplasm stains with what kind of dyes
Acidic (eosin)
46
Parietal cells
Resting state vs when producing HCl (TEM)
TEM- numerous microvilli projecting into intracellular canaliculi to communicate with gland lumen
Resting- elaborate tubulovesicular membrane system in cytoplasm next to canaliculi
47
What is the tubulovesicular system and what does it contain
~seen only in resting
It is a reservoir of plasma membrane containing proton pumps; can increase SA and number of proton pumps available for acid production
48
Parietal cells:
3 different receptors for substances that activate HCl secretion?
Gastrin receptors, histamine H2 receptors, and acetylcholine M3 receptors
~same receptors for secretion of intrinsic factor (also produced by parietal cells)
49
Significance of gastrin receptors
Activation of these receptors is the major path for parietal cell stimulation
50
Enteroendocrine cells:
1. Part of what system?
2. Where are they most prevalent?
3. How do they appear on TEM
4. What do they produce
1. Diffuse neuroendocrine system (DNES)
2. Base of fundic glands
3. Have electron dense cytoplasmic granules close to basal lamina
4. Hormones (paracrine and endocrine)
51
Difference between paracrine and endocrine hormones
Paracrine- diffuse locally to target cell
| Endocrine- carried by bloodstream to target cell
52
Difference between enteroendocrine closed and open cells
Closed - rest on basal lamina and do not reach lumen of gland
Open- have cytoplasmic extension with microvilli exposed to lumen of gland
53
Function of enteroendocrine open cells
Similar to what other thing in the body?
Serve as chemoreceptors that sample contents of gland lumen and release hormones based on info obtained from those samples
Similar to taste buds
54
When looking at a slide, how can you tell the difference between an open and closed enteroendocrine cell
Open enteroendocrine cells reach the lumen; closed have mucus neck cells or chief cells preventing them from reaching the lumen
55
1. Name 2 paracrine hormones released by enteroendocrine cells
2. Name 3 other hormones released by these cells
1. Somatostatin and histamine
| 2. Gastrin, CCK, and secretin
56
Gastrin:
1. Where is it synthesized
2. What does it stimulate
3. What does it inhibit
1. Stomach
2. Gastric acid secretion
3. Nothing
57
Secretin:
1. Where is it synthesized
2. What does it stimulate
3. What does it inhibit
1. Duodenum
2. Pancreatic enzyme secretion, pancreatic bicarbonate ion secretion, and pancreatic growth
3. Gastric acid secretion
58
CCK:
1. Where is it synthesized
2. What does it stimulate
3. What does it inhibit
1. Duodenum and jejunum
2. Same as secretin plus CCK stimulates gallbladder contraction
3. Gastric emptying
59
Somatostatin:
1. Where is it synthesized
2. What does it stimulate
3. What does it inhibit
1. Mucosa throughout GI tract
2. Nothing
3. Gastrin release, gastric acid secretion, and release of other GI hormones
60
Histamine
1. Where is it synthesized
2. What does it stimulate
3. What does it inhibit
1. Mucosa throughout GI tract
2. Gastric acid secretion
3. Nothing
61
Cardiac glands:
1. Where do they extend to/from
2. What are they mainly composed of
3. 2 features of appearance
1. From bottom of gastric puts to muscularis mucosae
2. Mucus secreting cells (with occasional interspersed enteroendocrine cells)
3. Cells have a basal nucleus and apical cytoplasm filled with mucin granules
62
Pyloric glands:
1. Contain cells similar to ?
2. What two cells are found interspersed in pyloric glands?
3. What are the gastric pits in this region like?
1. Surface mucus cells (tubular glands with secretory cells)
2. Enteroendocrine cells and parietal cells
3. Gastric pits are deep and occupy about half the thickness of the mucosa
63
Which types of cells have the shortest life span?
Longest?
Surface mucus cells and mucus neck cells have the shortest life span
Chief, enteroendocrine and parietal cells have the longest
~isthmus of fundic gland have stem cells that are under constant proliferation
64
1. How is lamina propria of the stomach different from other places?
2. How is the same?
1. Scant and restricted to limited spaces surrounding gastric pits and glands
2. Consists of reticular fibers, fibroblasts, and cells of immune system
65
Structure of the muscularis mucosae of the stomach and why?
Thin strands of smooth muscle cells extend from here to surface of lamina propria; thought to help flow of secretions from gastric glands
66
Which layer is also different in the stomach compared to other parts of the GI tract
Muscularis externa
67
Outer surface of the stomach is covered by?
Serosa (visceral peritoneum since it is an intraperitoneal organ)
68
Give length and location of the following:
1. Duodenum
2. Jejunum
3. Ileum
1. 25 cm; pyloric orifice to duodenojejunal flexure
2. 2.5 m; duodenojejunal flexure - changes morphology to become ileum
3. 3.5 m; ends at ileocecal junction
69
What happens when chyme from stomach enters duodenum
Enzymes from pancreas and bile from liver are delivered to continue digestion
70
1. What 2 enzymes are located in apical surface (cell membrane) of enterocytes
2. What is their function
1. Disaccharidases and dipeptidases
| 2. Complete breakdown of most sugars and proteins to monosaccharides and amino acids to be absorbed
71
1. Name 3 tissue/cell specializations of mucosa/submucosa of small intestine
2. What is their purpose
1. Plicae circulares (circular folds/valves of Kerkring), villi, and microvilli
2. Increase absorptive surface area of the small intestine
72
Plicae circulares:
1. Structure
2. Where does it appear
3. Where is it most numerous
1. Permanent transverse, circularly arranges folds
2. 5-6 cm distal to pyloric sphincter
3. Distal duodenum and beginning of jejunum
73
Villi:
1. Extend from where to where
2. How does it appear?
1. From mucosal surface into lumen
| 2. Fingerlike projection of mucosa that completely cover the lumen, giving it a velvety appearance
74
Microvilli:
1. Main feature
2. Location?
3. Gives what type of appearance?
1. Provides the major amplification of luminal surface
2. On enterocytes
3. Gives enterocytes a striated/brush border appearance
75
Villi consists of what (asking about structure)
1. A core of loose connective tissue (an extension of lamina propria - so has similar contents to lamina propria also)
76
Intestinal glands run from where to where
Muscularis mucosae through thickness of lamina propria to base of villi
77
What kind of epithelium are both villi and intestinal glands composed of
Simple columnar epithelium
78
1. Location of lamina propria in the small intestine
| 2. What does lamina propria contain here?
1. Surrounds the intestinal glands
| 2. Peyers patches (clusters of lymph nodules in ileum- may extend into submucosa)
79
In the small intestine, strands of smooth muscle cells extend from __ to __
From muscularis mucosa into lamina propria of villi
80
Name 5 cell types of small intestinal mucosa
Enterocytes, goblet cells, Paneth cells, enteroendocrine cells, and microfold (M) cells
81
Enterocytes:
1. Functions
2. Structure
3. Explain about their tight junctions
1. Primarily absorption, also secretory function of producing glycoprotein enzymes
2. Tall columnar cells with basally located nuclei and numerous microvilli on apical surface
3. Enterocytes are connected to each other by tight junctions that form a barrier between lumen on one side and connective tissue on the other
82
Enterocytes:
1. Important fact about enterocytes
2. Produce glycoprotein enzymes that are important for?
1. Only substances absorbed by enterocytes will be retained in the body
2. Terminal digestion of proteins and sugars
83
Goblet cells:
1. Number increases from __ to __
2. Structure of apical part?
3. Structure of basal part?
1. Duodenum to terminal ileum
2. Wider and filled with mucinogen granules (mucous cup)
2. Narrower and contains nucleus, rER, mitochondria and golgi apparatus
84
Paneth cells:
1. Where are they found
2. What about their structure makes them easy to identify
3. Key component of their vesicles?
4. Paneth cells may play a role in
1. Bases of intestinal glands (also occasionally a few in the colon)
2. Apical secretory vesicles
3. Lysozyme and an arginine rich protein
4. Regulating bacterial flora of small intestine
85
Enteroendocrine cells ~resemble those in the stomach
1. Closed cells are found
2. Open cells are found
3. Involved in regulation of
1. Lower part of intestinal glands
2. All levels of villi
3. Regulation of variety of GI functions; same peptide hormones identified in gastric enteroendocrine cells are also in small intestine
86
Microfold (M) cells:
1. Location
2. Forms deep pockets where what resides(3)
3. Function?
4. Key feature about its structure (why it has this name)
1. Overlie lymphatic nodules/Peyers patches
2. Lymphocytes, macrophages, and dendritic cells (come close to intestinal lumen)
3. Specialized antigen transporting cells (help antigens reach immune cells to stimulate antibody development)
4. Has microfolds opposed to microvilli
87
Feature of the duodenum submucosa
Contains brunners glands (columnar cells)
88
Brunners glands secretions contain which two things
Neutral and alkaline glycoproteins and bicarbonate ions (to protect duodenum/provide optimal pH for pancreatic enzymes)
89
Which cells of the small intestine have the shortest life span
Longest?
Shortest= enterocytes and goblet cells
Longest= enteroendocrine and paneth cells
90
How can you identify that you are looking at any part of the small intestine from a lab slide?
If microvilli is present, you are looking at some part of the small intestine
91
~what two parts of the GI tract have glandular tissue
Duodenum and esophagus
92
Difference in villi of ileum and duodenum
Villi is not as well defined in the ileum
93
What are Peyers patches?
Where are they found?
Accumulation of lymph nodules
Only in ileum
94
Difference between mucosa of small and large intestines
Large intestine mucosa does not exhibit plicae circulares
95
1. What type of epithelium does large intestine have
| 2. What 2 cell types are in large intestine
1. Simple columnar epithelium
| 2. Absorptive cells and mucus secreting goblet cells
96
Goblet cells of large intestine are mostly found where
Base of glands
97
Where in the large intestine is the mucus most important?
As feces pass along and become significantly more dehydrated, mucus is most important in order to protect mucosa
98
Difference of muscularis externa in large intestine
It has peristaltic activity; also outer longitudinal layer is not continuous in large intestine because of presence of teniae coli
99
Which parts of the large intestine are covered in serosa and which are covered by serosa and adventitia
Intraperitoneal organs= just serosa
Retroperitoneal organs= both serosa and adventitia (adventitia is on the posterior surface; serosa/peritoneum is on anterior surface)
100
Appendix has same structure as large intestine except (2 things)
No teniae coli in appendix; glands are less closely packed than in rest of large intestine
101
Most characteristic feature of appendix (particularly in the young)
Presence of masses of lymphoid tissue in mucosa and submucosa (often contain germinal centers)
102
Difference in mucosa of rectum/upper half of anal canal vs large intestine
Mucosa of rectum/upper half of anal canal has more numerous goblet cells
103
Difference in epithelium between upper and lower halves of anal canal (anorectal junction)
Simple columnar to stratified squamous
104
~back to small intestines
1. Villi are extensions of
2. Microvilli are extensions of
1. Lamina propria
| 2. Epithelium
105
Difference between structure of large and small instestine
Small intestine- has microvilli and villi
| Large intestine- has microvilli but NO villi
106
Small intestine mucosa contains what two things that are unique to it
Villi (upward projections) and intestinal glands (which are the crypts formed from villi (so the downward type projections in between the villi)
