Lecture 2: Digestive II Flashcards
What is the length of the duodenum in meters?
0.25 m
- shortest
- Has plicae circulares only in distal position
- Has shorter villi
What is the length of the jejunum in meters?
2.5 m
- Has the most abundant of plicae circulares
- Has the most amount of villi
What is the length of the ileum in meters?
3.5 m
- Longest
- Has plicae circulares only in the proximal portion
- Has shorter villi
- Only structure that has Peyer’s Patches (lymph nodules)
What are the 3 parts of the small intestine?
- Duodenum
- Jejunum
- Ileum
What are the 4 layers of the GI tract (alimentary canal)?
- Mucosae (epithelium, lamina propia, muscualris mucosae)
- Submucosae
- Muscularis Externa
- Adventitia (CT) or Serosa (CT and epithelium)
What 3 organs make up the GI tract?
- stomach
- small intestine
- large intestine
What are the 4 structures in the small intestine responsible for the increased surface area?
- plicae circulares (folds of submucosa)
- Villi (folds of mucosa)
- Crypts of Lieberkuhn (Glands) = in the mucosa between the villi
- Microvilli with glycocalyx = sit on top of epithelium in the mucosa
Which structure in the small intestine is the only one that has Brunner’s glands?
Duodenum
Which structure of the small intestine is the only one that has Peyer’s patches (lymph nodules)?
Ileum
What are the 5 types of cells found in the mucosa of the small intestine?
- Enterocytes
- Goblet cells
- Enterendocrine cells
- Paneth cells
- M - cells (found in ileum of small intestine and appendix in large intestine)
What are enterocytes (4)?
- absorptive cells
- make up the epithelium (THE cells of the epithelium)
- Connected to microvilli (forms brush border) which sit on top of epithelium
- Contain glycocalyx of microvilli → stores digestive enzymes (dipeptidases and disaccharidase)
What is Celiac disease?
immune-mediated inflammation which leads to flattening of jejunal surface = extensive loss of villi
What triggers Celiac disease?
allergy to wheat protein and gluten
How is Celiac dieases treated?
- No cure
- villi usually returns to normal structure when wheat and its products are excluded from diet
What is the function of M cells? Where are they found?
- play a role in transport of antigens from lumen to lamina propia
- found in ileum (Peyer’s patches) of small intestine and appendix in large intestine
What are goblet cells? Where are they found?
- unicellular mucous secreting glands
- Found everywhere but mostly in ileum
What are the functions of Paneth cells (2)? Where are they found?
- secrete antibacterial lysozyme
- plays a role in the regulation of normal bacterial flora of the small intestine (absent in the large intestine)
- Found near the bottom of crypts of Lieberkuhn
Only cells not in the colon (large intestine)
What is the function of enteroendocrine cells?
secrete hormones
gastrin (like the enteroendocrine cells in the stomach), secretin, CCK, etc.
List the components of the large intestine (7)
- Cecum=connects to ileum of the small intestine (Ileocecal junction)
- Veriform Appendix
- Ascending Colon
- Transverse Colon
- Descending Colon
- Sigmoid Colon
- Rectus=connects to anus
What are two things that appendix does not have?
- Villi
- Teniae coli
What type of cells (3) are found in the epithelium of the appendix?
- Enterocytes = absorptive cells
- M cells
- (few) Goblet cells
What type of epithlium is in the anal canal?
stratified squamous
The recto-anal junction is _____ of the esphago-gastric junction
reverse
What are the glanglions that form nerve plexuses that are part of the Enteric NS?
- Auerbach’s plexus
- Meisnner’s plexus
What is Hirschsprung’s disease (aka congenital aganglionic megacolon)?
failure of neural crest cells to migrate to the distal colon
- Most important disease of large intestine in infants and children
- Males affected more than females
How does ulcerative colitis form?
- formation of granulation tissue associated with the proliferation of blood and lymphatic vessels in the lamina propia = active inflammation
- Expression of vascular endothelial growth factor (VEGF) = causes proliferation of blood vessels
- Only in colon (large intestine)
- Cause is unknown
What is the result of ulcerative colitis?
- mucosa is lost over extensive area with ulceration and destruction of absorptive epithelium
- This impairs water reabsoprtion from colonic contents = results in watery diarrhea and bleeding
What are indicators of Crohn’s disease (3)?
- Multiple (skip) lesions often form serpentine ulcers oriented along the axis of bowel
- Edema and loss of normal mucosal folds
- Cobblestone mucosa
- Primary indicator = skip lesions
- Same sx as ulcerative colitis
What causes Inflammatory Bowel Disease? (IBD)
- Cause is unknown
- Believed it results from:
- Errant host reactions with intestinal microbiota
- Intestinal epithelial dysfunction
- Aberrant mucosal immune responses
IBD refers to which 2 diseases?
Ulcerative colitis + Crohn’s disease
What is used to treat ulcerative colitis?
INFLIXIMAB → anti-TNF (tumor necrosis factor)
What type of epithelium is in the rectum?
simple columnar
What is the gastro-duodenal junction?
a junction that connects the stomach and the duodenum (small intestine)
Marked by transition from simple columnar epithelium → simple columnar epithelium with villi + crypts
What cells are circled in red? Blue?
- Circled in red = Paneth cells
- Circled in blue = enteroendocrine cells
What cells are circled in: White? Black? Purple? Pink?
- White = Goblet cells
- Purple = Eneteroendocrine cells
- Black = Enterocytes
- Pink = Paneth cells
What part of the small intestine is shown in the image? What structure is the arrow pointing to?
- Appendix
- Lymphatic nodules
What layer of the large intestine is #1?
Muscularis mucosae
What layer of the large intestine is #2?
Submucosae
What layer of the large intestine is #3?
Muscularis externa outer layer
What layer of the large intestine is #4?
Muscularis externa inner layer
What is #5?
Glands - crypts of Lieberkuh
What layer of the large intestine is #1?
B11 Lower Large Intestine x 10
outer longitudinal (muscularis externa)
What layer of the large intestine is #2?
B11 Lower Large Intestine x 10
inner circular layer (muscularis externa)
What structure is circled in purple?
B11 Lower Large Intestine x 10
Auerbach’s plexus
What layer of the large intestine is marked by the dark blue line?
B11 Lower Large Intestine x 10
Submucosa
What structure is shown in this image?
Anal canal (junction)
What structure is #1? What type of epithelium does it have?
- Rectum
- Simple columnar
What structure is #2? What type of epithelium does it have?
- Anal canal
- Stratified squamous
What is #1?
Large Intestine x2: Colon and Teniae Colon
Glands
What layer is #2?
Large Intestine x2: Colon and Teniae Colon
Muscularis mucosae
What layer is #3?
Large Intestine x2: Colon and Teniae Colon
Submucosae
What layer is #4?
Large Intestine x2: Colon and Teniae Colon
Muscularis externa inner (circular)
What layer is #5?
Large Intestine x2: Colon and Teniae Colon
muscularis externa outer (longitudinal)
What is #6?
Large Intestine x2: Colon and Teniae Colon
muscle from the teniae coli
What is #1?
Glands
What layer of the large intestine is #2?
Muscularis mucosae
What layer of the large intestine is #3?
Submucosae
What layer of the large intestine is #4?
Muscularis externa inner (circular)
What layer of the large intestine is #5?
Muscularis externa outer (longitudinal)
What layer of the large intestine is #1, #2, #3, and #4? What structure is #5?
- Which of the following epithelial cells found in the digestive system are responsible for secreting lysozyme?
a. Goblet cells
b. M cells
c. Enteroendocrine cells
d. Paneth cells
d. Paneth cells
Where in the digestive tract is plicae circulares most numerous?
a. Jejunum
b. Ileum
c. Descending colon
d. Appendix
a. Jejunum
Brunner’s glands are characteristic of the submucosa found in which digestive tract structure?
a. Stomach
b. Lower esophagus
c. Duodenum
d. Colon
c. Duodenum
Identify the structure:
a. Plicae circulares
b. Crypt of Lieberkühn
c. Peyer’s patch
d. Brunner’s gland
c. Peyer’s patch
Which region of the digestive tract contains the most numerous goblet cells?
a. Jejunum
b. Stomach (body)
c. Descending colon
d. Proximal ileum
c. Descending colon
The tenia coli of the large intestine is formed by which tissue layer?
a. Muscularis mucosa
b. Submucosa
c. Mucosa
d. Muscularis externa
d. Muscularis externa
Celiac disease is characterized by the inability to digest gluten causing autoimmune mediated inflammation. Where is extensive loss of villi indicated?
a. Duodenum
b. Jejunum
c. Ileum
d. Colon
b. Jejunum
Identify the structure:
a. Meissner’s plexus
b. Auerbach’s plexus
c. Tenia coli
d. Gut associated lymphatic tissue
b. Auerbach’s plexus
