Histology of the Digestive System Part III: small and large intestine Flashcards
1
Q
List the four main layers of the digestive tract.
A
- Mucosa
- Submucosa
- Muscularis Externa (Muscularis Propria)
- Aventitia/Serosa
2
Q
What are the 3 sublayers of the mucosa?
A
- Epithelium
- Lamina Propria
- Muscularis mucosae
3
Q
In which layers of the digestive tube might you find lymphoid cells to varying degree depending on the portion of the digestive tube you are in?
A
Submucosa or Lamina Propria
4
Q
What are the three portions of the small intestine?
A
Duodenum, jejunum, ileum
5
Q
What are the three functions of the small intestine?
A
- Absorb nutrients
- Complete food digestion
- Secrete hormones
6
Q
List the two special features of the small intestine.
A
- The submucosa contains special glands in specific portions
- There are collections of lymphoid aggregates throughout he small intestine in the submucosa and in the lamina propria. These lymphoid aggregates are very organized in specific parts of the ileum.
7
Q
How many layers of muscle will you find in the muscularis externa of the the small intestine?
A
2: circular and longitudinal
8
Q
What plexus lies in between the muscular layers of the muscularis externa?
A
myenteric plexus (Auerbach’s plexus)
9
Q
Would you expect a histological slide of the small intestine to have serosa or adventitia?
A
Serosa, the small intestine is inside the abdomen and is thus covered by visceral peritoneum, otherwise referred to as serosa.
10
Q
What 3 features, found in the small intestine, function to increase absorptive area?
A
- Plicae circulares
- Villi
- Microvilli
11
Q
In the small intestine, what structures are formed by circular folds of the mucosa and submucosa?
A
plicae circulares
12
Q
Which cells lining the villi have microvilli on their luminal surface?
A
enterocytes
13
Q
What special feature of the small intestine will you find covering the plicae circulares?
A
villi; small like finger projections covered with enterocyte and goblet cells
14
Q
What cell types cover the villi?
A
- enterocytes
2. goblet cells
15
Q
Which histological layers are NOT folded into the plicae circulares?
A
- Muscularis externa
2. Serosa
16
Q
Which histological layers forms the core of the plicae circulares?
A
submucosa; this layer is very vascularized
17
Q
Which histological layer forms the core of the villi?
A
lamina propria
18
Q
Plicae circulares are comprised of folds from which 2 histological layers?
A
submucosa and mucosa; however, the highly vascularized submucosa makes the core.
19
Q
Villi are comprised of fold from which 2 histological layers?
A
epihelium and lamina propria; however, the lamina propria makes up the core
20
Q
What makes up the brush border of the small intestine?
A
microvilli that protrude from the luminal surface of enterocyte cells.
21
Q
A histological specimen from the small intestine of someone with this disease will show flat villi with virtually no brush border and a marked increase of lymphocytes in the epithelium..
A
Celiac disease
22
Q
Which cells in the small intestine are the main absorptive cells?
A
Enterocytes
23
Q
Name the cell.
- Columnar epithelial cells
- microvilli on the luminal surface
- main absorptive cells in the small intestine
A
Enterocytes
24
Q
Name the cell.
- Scattered amongst enterocytes
- secrete mucus for protection and lubrication
A
Goblet cells
25
Aside from goblet cells and enterocytes, what other cells might you find scattered in the epithelium of the small intestine?
scattered intraepithelial lymphocytes
26
What cells and structures would you expect to find in the core of the villi?
lymphocytes
smooth muscle
central lacteal
27
What surface protein would you find covering the microvilli?
glycocalyx
28
What is glycoalyx? What is the function of glycocalyx?
A glycoprotein that coats the cell surface. It serves a protective function as it houses digestive enzymes like lactase.
29
What would you call an individual with defective lactase enzyme in their glycocalyx.
A human (hahaha!); you would call them lactose intolerant.
30
What special structure can you find in the lamina propria of the small intestine that is specific to the this organ?
lacteal
31
List the contents of the lamina propria
1. lacteal
2. Lymphoid cells (lymphocytes, marcophages, eosinophils, mast cells, plasma cells: most abundant here)
3. smooth muscle from the muscularis mucosae
4. Loose fibrous connective tissue
5. neurovascular structures
32
What is the lacteal?
It is a central lymphoid capillary inside the villus.
33
Does the lacteal collect lymph?
NO, it collects lipids that are absorbed from the lumen of the small intestine.
34
Describe the path of lipids into the body, beginning at the lumen.
1. lipids are absorbed through enterocytes
2. lipids travel to inside the lacteal
3. lipids enter larger lymphoid vessels
4. lipids ultimately end up in the thoracic duct
35
Do the products of protein and carbohydrate metabolism follow lipids into the lacteal?
NO, amino acids and sugars go through the intestinal capillaries to the portal system of the liver.
36
Do lipids ever go to the liver?
Yes, some lipids (short chain fatty acids and glycerol) go to the portal system via intestinal capillaries. Furthermore, all the lipids that entered the lacteal eventually go from the thoracic duct tot he general systemic circulation and thus end up at the liver.
37
What is the name of the intestinal glands/ crypts found in the small intestine?
crypts of Lieberkuhn
38
Crypts of Lieberkuhn in the small intestine are similar to what structures in the stomach?
stomach glands
39
What layer is found at the base of the intestinal crypt?
muscularis mucosae
40
What layer surrounds the crypts of Lieberkuhn?
lamina propria
41
List the six types of cells you might find in an intestinal gland/crypt of Lieberkuhn.
1. Enterocytes
2. Goblet cells:
3. Enodcrine Cells: many types that secrete (motilin, CCK, ghrelin, GIP and secretin)
4. Enterochromaffin cells: secrete serotonin
5. Stem cells: replace all other cells
6. Paneth cells: prevent infection by released defensins
42
Describe the appearance of a Paneth cell.
Large pink cell with large pink granules (full of defensins that protect against infection).
43
Where are in the vili are the paneth cells located?
In the crypts, at the base of the gland.
44
Which cells in the glands of the small intestine are capable of phagocytic activity?
Paneth cells; they contain immunoglobulins, defensins and lysozymes
45
What is the exact function of the Paneth cells.
The exact function of Paneth cells is unknown, but it is accepted that they play a large role in innate immunity.
46
What is the specific name of the intestinal glands?
crypts of Lieberkuhn
47
Name the hormone secreted by the following cell: Mo cell
secretes motilin
48
Name the hormone secreted by the following cell: I cells
secrete CCK
49
Name the hormone secreted by the following cell: P/D1 cells
secrete ghrelin
50
Name the hormone secreted by the following cell: K cells
secrete GIP
51
Name the hormone secreted by the following cell: S cells
Secrete secretin
52
Name the hormone secreted by the following cell: enterochromaffin cells
secrete serotonin
53
How many layers is the muscularis propria comprised of in the small intestine? List it/them
2; inner circular layer and outer longitudinal layer
54
Where would you find the interstitial cells of Cajal (ICC) in the gut?
in the muscularis externa/propria of the small intestine
55
What plexus is found in between the circular and longitudinal layer or muscle?
myenteric plexus (Auerbach's plexus)
56
What portion of the small intestine is responsible for its characteristic movements?
the circular and longitudinal muscles
57
What cells are referred to as the pacemakers of the gut?
the interstitial cells of Cajal (ICC)
58
The outer layer the muscularis externa is covered by a serosal layer called __________.
Visceral peritoneum
59
Is the visceral peritoneum a loose/thick/dense collagenous layer?
loose collagenous layer
60
What type of cells would you find in the visceral peritoneum?
mesothelial cells
61
What type of secretory glands would you find in the submucosa of the duodenum?
Brunner's glands
62
What is the function of Brunner's glands?
Brunner's glands secrete an alkaline mucus to protect the surface from the gastric secretions in the chyme
63
Brunner's glands open via excretory ducts and pierce through what structure in the muscularis mucosae?
crypts
64
In a healthy small intestine, should you find lymphoid cells present throughout the lamina propria AND submucosa?
Yes, in the ileum these cells form distinct aggregates called Peyer's patches.
65
Duodenum, jejunum, ileum: Where are the Brunner's glands?
Duodenum
66
Duodenum, jejunum, ileum: Where are the Peyer's Patches
ileum
67
Where is lymphoid tissue most and least abundant?
most abundant in the ileum (this is where the Peyer's patches are); least abundant in the duodenum
68
Duodenum, jejunum, ileum: Plicae circulares are most abundant in the _____________
jejunum
69
Duodenum, jejunum, ileum: Where are villi the longest? Where are villi the shortest?
villi are longest in the duodenum and shortest in the ilieum
70
Histologically, would you find Brunner's glands or Peyer's patches in the jejunum?
No
71
What is Celiac disease?
Celiac disease is a chronic allergic reaction to ingested gluten.
72
How does Celiac disease affect the GI tract?
Overtime, Celiac disease will cause (1) the destruction of the villi (2) significant hyperplasia of the crypts in the small bowel
73
What three things should you make note of on a histological slide of GI tract afflicted by celiac disease?
1. Loss of epithelial villi
2. Cells of the crypts are larger
3. Epithelium filled with more lymphocytes than normal.
74
What is the function of the ileocecal junction?
the ileocecal junction prevents reflux into the small intestine from the cecum.
75
What is the structure of the ileocecal junction comprised of?
The thickening of the muscularis externa from both intestinal portions.
76
Histologically, how could you identify a slide specimen as the ileocecal junction?
- You would notice a transition from the rough small intestine epithelium portion to a smooth large intestine epithelium. This is because the villi in the disappear as you approach the large intestine.
- The muscularis externa would thicken
- You would still notice an abundance of lymphoid tissue.
77
What are the three main functions of the large intestine?
1. Recovery of water and salts
2. Concentration of fecal material
3. Propulsion of fecal material towards the rectum
78
List the different regions of the large intestine.
1. Cecum
2. Ascending colon
3. Transverse Colon
4. Descending colon
5. Sigmoid Colon
6. Rectum
7. Anal canal
8. Anus
79
Which four parts of the colon are retroperitoneal?
1. Ascending colon
2. Descending colon
3. Rectum
4. Anal canal
80
What do you call portions of the large intestine that are completely surrounded by peritoneum?
peritoneal
81
What do you call portions of the large intestine that either partially covered, or not in contact with peritoneum?
retroperitoneal
82
What is one major difference between the submucosa of the large and small intestine?
the submucosa of the large intestine does not have intestinal folds, but the submucosa of the small intestine does (plicae circulares)
83
What is distinct about the muscularis propria of the large intestine?
The outer longitudinal layer is discontinuous and forms 3 bands called tenia coli
84
Does the large intestine have crypts of Lieberkuhn?
Yes, do NOT confuse these glands as villi. The large intestine does not have villi.
85
How does the mucosa of the large intestine change from the cecum to the rectum?
It does not.
86
What type of cells would you find in the epithelium of the large intestine?
1. Colonocytes
| 2. Goblet cells
87
What are colonocytes?
Colonocytes are cells that absorb water passively and sodium actively.
88
What type of cells would you find in a gland or crypt of the large intestine?
colonocytes
goblet cells (most abundant at the base of the gland)
stem cells
intraepithelial lymphocytes
89
Where would the presence of Paneth cells indicate pathology?
in the descending colon (they are normal in the ascending colon). If you see Paneth cells in the descending colon they are indicative of metaplastic change.
90
Which large intestine cells have microvilli?
colonocytes
91
Where would you find 80% of the body's plasma cell population?
In the lamina propria of the large intestine.
92
What types of cells or structures would you find in the lamina propria of the large intestine?
- Lymphocytes
- Plasma cells (A WHOLE LOT!)
- Occasional lymphoid aggregates
- Mast cells
- Blood vessels and connective tissue
93
What plexus is responsible for the innervation of the muscularis mucosae?
submucosal plexus
94
The function of the muscularis mucosae becomes particularly relevant in the large intestine. What is the function?
To promote the rhythmic contractions that force the expulsion of mucus and prevent the glands from getting clogged by mucus at their base.
95
What layer of the large intestine is comprised of fibroelastic tissue?
submucosa
96
Describe the appearance of the submucosa.
- fibroelastic tissue
- small lymphoid aggregates (similar to Peyer's patches but small in size)
- adipose tissue (to increase its flexibility and all for wall movements during peristalsis)
97
Why is it important for the submucosa of the large intestine to have adipose tissue?
To increase its flexibility and all for wall movements during peristalsis
98
Balance between ________ and ________ in the large intestine is crucial to sustain health.
intestinal microflora and MALT
99
What beneficial functions do intestinal microflora serve?
1. break down food residues
| 2. responsible for making certain vitamins that are absorbed by the large intestine
100
Why does it make sense that there would be a large population of MALT in the lamina propria and submucosa of the large intestine?
There is an enormous bacterial population of the large intestine. Thus, it makes sense that there would be an accompanying abundance of lymphoid tissue or MALT.
101
What two thing make up the interactive, interdependent ecosystem of the large intestine?
intestinal microflora and MALT
102
Why is the muscularis externa so thick in the large intestine?
It is responsible for propelling the fecal content toward the rectum
103
You will not find teniae coli in this portion of the large intestine.
rectum
104
Where will in the large intestine will you find the interstitial cells of Cajal (ICC).
muscularis externa
105
Where on the large intestine will you find epiploic appendages?
ascending, transverse and descending colon
106
The serosal or visceral peritoneum is covered by _______________ (a type of epithelium).
mesothelium
107
If you compared the layers of the small intestine to the layers of the large intestine, what would be the most prominent difference?
The appendix has more abundant lymphoid aggregations in the lamina propria and submucosa.
108
How many transverse fold/rectal valves are there?
3
109
What is a rectal valve?
A rectal valve is a fold of the mucosa, submucosa and muscularsi
110
What two regions does the recto-anal junction separate?
rectum and the anal canal
111
Describe the location of the colorectal zone.
In between the recto-anal junction an the squamous zone (near anus)
112
What type of cells comprise the colorectal zone?
Columnar cells
113
What is an alternative name for the pecten zone of the anal canal?
squamous zone
114
What is the dentate or pectinate line?
The pectinate line is the point at which the epithelium in the rectum changes from columnar to squamous.
115
There are two places in the large intestine where the epithelium changes. What are these two regions?
1. Dentate or Pectinate line
| 2. Junction between anal canal and anus
116
Where does the anal cutaneous zone begin?
In between the the anus and the squamous zone of the rectum.
117
If you look into the large intestine from an external position (up through the butt) what immediate area would you be viewing?
Anus
118
From an external view, 1 cm inwardly from the anus lies this space.
Anal canal
119
The anal canal is divided into 2 different zones, what are they?
1. colorectal zone
| 2. squamous zone
120
In the colorectal zone of the anal canal, the inner circular layer of muscularis externa thickens to form what structure?
internal anal sphincter
121
What type of epithelium covers the squamous zone of the anal canal?
thick non-keratinized stratified squamous epithelium
122
True or False: The anal tissue is similar to the skin and includes sebaceous and apocrine sweat glands.
True
123
What type of epithelium will you find in the anal portion of the large intestine?
highly keratinized stratified squamous epithelium
124
What is a diverticulum?
A dead-end pouch lined with mucosa in the large intestine that communicates with the lumen
125
What is the difference between Diverticulosis and Diverticulitis?
Diverticulosis defines the presence of diverticular or diverticulum; Diverticulitis occurs when diverticulum or multiple diverticula become inflamed
126
In a technicolor staining, what shows up in blue and what shows up in red?
blue: epithelium
red: muscularis propria
