Exam3Lec2Digestive2 Flashcards
What three structures make up the GI tract?
stomach + small intestine + large intestine
What is the junction that connects the stomach and the duodenum (small intestine) and its marked by the transition of what epithelium?
Gastro-duodenal Junction
Marked by transition from simple columnar epithelium-> simple columnar epithelium w/ villi + crypts
What type of epithelium lines the small intestine ?
Simple columnar w/ microvilii=brushborder
The epithelium is a part of the mucosa, which is folded then termed villi
What are the 3 parts of the small intestine?
Duodenum Jejunum, Ileum
Duodenum: 3 points
- Has plicae circulares only in the distal portion
- Has shorter villi
3. Only structure that has Brunner’s glands (in submucosa)
shortest segment
Jejunum: 2 points
- Has the most amount of plicae circulares.
- Has the most amount of villi
Iluem: 3 points
- Has plicae circulares only in the proximal portion
- Has shorter villi
- Only structure that has Peyer’s Patches (lymph nodules)
longest segment
connects to large intestine
What are the 4 structures found in the small intestine?
- Microvili w/ glycocalyx: on top of epithelium (mucosa)
- Vili: folding of mucosa
- Crypts of Lieberkuhn: glands b/w the bases of the vili (mucosa)
- Plicae circulares: folding of the submucosa
***NOTE: all these structures help to increase surface area!
Glycocalyx sits on top of microvilli + store digestive enzymes
Microvilli in the digestive tract are termed what?
the “brush border”
Mucosa= ____ + ____ + ____
epithelium + lamina propria (CT) + Muscularis mucosa
What are the cells found in the mucosa of the small intestine?
- Enterocytes
- Goblet cells
- Enteroendocrine Cells
- Paneth Cells (unique to small intestine)
- M-cells (ileum in small intestine + appendix in large intestine)
What are Enterocytes of the SI?
absorptive cells
* Make up the epithelium (i.e., they are “THE” cells of the epithelium)
* Connected to microvilli, which sit on top of the epithelium
* Contain glycocalyx of microvilli ->stores digestive enzymes
What are goblet cells in the SI?
Found everywhere (but mostly in ileum)-> secrete mucous
What are Enteroendocrine Cells?
Secrete hormones (dark staining granules) = gastrin, CCK, secretin
*NOTE: digestive system uses the term “enteric”… so anything “entero” refers to this region of the body
What are Paneth Cells (unique to small intestine)?
- Found near the bottom of the crypts (of Lieberkühn)
- Secrete lysozyme (pink staining granules) + regulate bacterial flora
M – Cells
Where are they found in the SI?
Act as?
Transports?
- Found in peyer’s patches (lymphatic nodules)
- Act as antigen presenting cells (APCs) = immune cells
- Transport Ags from lumen into the lamina propria (loose CT)
Summary: Mucosa of the small intestine
* villi:
* crypts of Lieberkühn:
* epithelium:
* Gut Associated Lymphatic Tissue (GALT) in what?
Mucosa and submucosa
* What is there?
- villi – mucosal projections containing lacteal
- crypts of Lieberkühn – intestinal glands in the mucosa
- epithelium: simple columnar (covers villi and crypts)
- Gut Associated Lymphatic Tissue (GALT) in the lamina propria
- Mucosa: plicae circulares
What is the structure of a normal jejunum?
The mucosa is folded into villi which helps to increase surface area = good for absorption of nutrients
What is celiac disease?
what does it affect?
caused by?
results in?
tx?
- The mucosa is flattened-> loss of villi (mucosal folding) leads to decreased absorption
- affects only the jejunum
Caused by an allergy to gluten (wheat protein) - Results in immune-mediated inflammation
- Tx = removal of gluten from diet relieves inflammation->thus, villi return to normal (folded) structure
only in jejunum
There is no cure, but diet alterations prevent patients from feeling the effects of the disease
What type of epithelium lines the large intestine?
simple columnar w/ microvilli = “brush border”
Mucosa does NOT have villi but still has crypts
What 7 structures is the large intestine made of?
- Cecum : connects to ileum of small intestine
- Vermiform Appendix: Contains lymph nodules in large intestine
- Ascending Colon
- Transverse Colon
- Descending Colon
- Sigmoid Colon
- Rectum = connects to anus
What is the large intestine formed into?
Formed into haustra (segmented pouches) w/ tenia coli (muscle)
What are the cells found in the large intestine?
- Enterocytes (absorptive cells) = epithelial cells w/ microvilli
2.Goblet cells = most numerous in descending colon - Enteroendocrine cells
- M-cells = only in appendix of large intestine + ileum of small intestine
bolded is hy for exam
Microvilli does NOT have digestive enzymes b/c there is no digestion occurring
***NOTE: large intestine has same cells as small intestine except Paneth cells
What type of epithelium lines the Vermiform Appendix of the large intestine and what type of cells does it contain?
- Epithelium = simple columnar
- Contains enterocytes (absorptive cells) + M-cells (immune) + few goblet cells
- M-cells: act as APCs in the lymph nodules
Only location in the large intestine where M-cells are found
NOTE: M – cells also found in lymph nodules (peyer’s patches) of ileum (small intestine)
What structures does the vermiform appendix NOT have?
Lymph nodules located in the mucosa + submucosa -> but there is NO folding of the mucosa, thus NO villi
Also, does NOT have tenia coli
NOTE: lymph nodules in the ileum have villi, but nodules in the appendix do NOT have villi
What type of epithelium do the following structures have?
A. Rectus
B. Anal canal
C. Anus
A. Rectus:simple columnar
B. Anal canal: stratified squamous
C. Anus:keratinized stratified squamous
What connects the rectum to the anal canal and its marked by transion of what type of epithelium?
Recto-anal junction
Marked by transition from simple columnar epithelium-> stratified squamous epithelium
NOTE: recto-anal jxn is reverse of the esophago-gastric jxn
For the Enteric Nervous system of the Large intestine, what are the ganglions that form the nerve plexuses and their location?
Auerbach’s plexus ->located b/n the outer longitudinal + inner circular layers of muscularis externa
Meissner’s plexus ->located in the submucosa
Ganglions located in the large intestine establish nervous system role in digestive tract
NOTE: muscularis mucosa is part of the mucosa, muscularis externa is not
What is Hirschsprung’s Disease (Congenital Megacolon)?
- Defect of neural crest cell migration -: incomplete development of large intestine ->lack of haustra + ganglion cells
lack of haustra
Ganglion cells = Auerbach’s plexus of nerves (musc. externa) + Meissner’s plexus of nerves (submucosa)
What is Inflammatory Bowel Disease?
umbrella term for Ulcerative Colitis + Crohn’s Disease
What is Ulcerative Colitis?
What does it affect?
Sx?
Tx?
only affects colon
* Formation of granulation tissue ->disrupts normal tissue -> loss of mucosa = loss of absorptive function of epithelium
* Increased expression of VEGF (vascular endothelial growth factor) causes proliferation of blood vessels
* Sx = decreased water resorption resulting in watery diarrhea + bleeding
* Tx = INFLIXIMAB = anti-TNF (tumor necrosis factor) therapy
lack of mucosa
Granulation tissue associated w/ proliferation of blood + lymphatic vessels in the lamina propria (loose CT of mucosa)
What is crohn’s disease?
Sx?
affects any part of large intestine
* Formation of granulation tissue -> multiple “skip lesions” throughout areas of the large intestine-> gives cobblestone appearance to mucosa
* Sx = decreased water resorption resulting in watery diarrhea + bleeding
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 causes IBD?
Cause is unknown
Believed it results from:
* errant host reactions with intestinal microbiota
* intestinal epithelial dysfunction
* aberrant mucosal immune responses
What happens when we have dysfunction of paneth cells?
the pathogenesis of chronic inflammatory bowel disease
