Small and Large Intestine Flashcards
How long are the small intestines?
4-6 m in humans
What process is completed in the small intestine?
absorption and completion of digestion
What are valve-like folds or rings in the small intestine?
plicae circulares
What is the function of the plicae circulares?
increase the surface area in the small intestine
What is on the mucosal surface of the small intestine?
villi
What is the core of the villi of the mucosal surface?
lamina propria
What is the space between the villi called?
crypts of Lieberkuhn
What lines the intestinal epithelium?
simple columnar epithelium
What is Celiac disease?
allergy to the wheat protein gluten (causes villus blunting, atrophy, and loss)
What can celiac disease lead to?
malabsorption and weight loss (not a real symptom according to M Cole)
What is intraepithelial lymphocytes?
the prescence of lymphocytes epithelial cells
What are the three functional zones in the epithelium of the small intestine?
- villi
- crypts
- neck (where villi and crypt meet)
What are the five cell types of the small intestine?
- enterocytes
- mucous cells
- paneth cells
- endocrine cells
- stem cells
What are the characteristrics of enterocytes?
- mucosal cells
- tall columnar cells
- round/oval nuclei
- microvilli (brush border)
- protective glycocalyx coating
What separates enterocytes from luminal surface?
desmosomes and tight junctions
What do the lateral walls of enterocytes have?
complex interdigitations
What are the characteristics of mucous cells in the small intestine?
- goblet cells
- found in upper 2/3 of crypt
- synthesize mucinogen
- least frequent in duodenum (most in ileum)
What are the characteristics of paneth cells?
- found at the base of crypts
- large eosinophilic granules
- produce defensins (antibacterial proteins)
- produce lysozyme
What are the characteristics of enteroendocrine cells?
- mainly in lower 1/3 of crypt
- pale-stainingcytoplasm
- broad at base and narrow at lumen
- regulate GI motility and secretion
What are the different types of enteroendocrine cells?
S
I
A
K
What do S enteroendocrine cells do?
secrete secretin (stimulates release of bicarb from pancreas)
What do I enteroendocrine cells do?
secrete cholecystekinin/CKK (stimulates pancreatic secretion and contraction of gallbladder)
What do A enteroendocrine cells do?
secrete glucagon (increases blood sugar)
What do K enteroendocrine cells do?
secrete GIP (gastric inhibitory peptide)
What are the characteristics of stem cells in the small intestine?
- located at base of crypt
- migrate up villus, mature, and shed
The entire epithelial lining is replaced roughly every?
3-5 days
What is the lamina propria made of in small intestine?
collagen, reticular fibers, fibroblasts, GAGs
Where is the lamina propria located in the small intestine?
clearly seen in the core of the villi but also around gland crypts
What is a lacteal?
the lymphatic vessels of the small intestine which absorb digested fats (she didn’t really have the definition on her slide)
Where is MALT located in the small intestine?
lamina propria and submucosa
What does MALT contain?
- lymphocytes (T)
- plasma cells (secrete IgA)
- eosinophils
- macrophages
- mast cells
- M cells (antigen sampling)
- peyer’s patches
What area of the small intestine has brunner’s glands in the submucosa?
duodenum
What are the characteristics of brunner’s glands?
- highly convoluted branched, tubuloalveolar submucosal glands
What do brunner’s glands secrete?
- mucus (alkalin; protect against stomach acid contents)
- zymogens
What is the main function of the duodenum?
neutralize gastric acid and pepsin (assisted by pancreas and gallbladder)
Where in the small intestine are peyer’s patches located?
ileum
What are the four cell types in the large intestine?
- columnar cells
- mucous cells
- endocrine cells
- stem cells
What is the function of the large intestine?
- modifies fluid content of feces
- specialized for mucous secretion
- salt and water absorption
What does the large intestine lack?
DOES NOT HAVE
villi
plicae circulares
brunner’s glands
What is the primary function of the colon?
water and electrolyte resorption; produces mucus for elimination of undigested food and waste
What are the characteristics of the columnar cells of the large instestine?
- mainly columnar with little mucin
- absorb soluble satl and water
What are the characteristics of the mucous cells of the large instestine?
- goblet cells
- present throughout the colon but the type of mucus can change
How does MALT appear in the large intestine?
- does not form peyer’s patches
Are there lacteals in the small intestine or large intestine?
only small
What are some characteristics of the colon?
- large # of commensal bacteria
- outer longitudinal muscle layer is incomplete (forms 3 longitudinal strips, taenia coli)
- formation of haustra
What is the small, blind-ended sac that is distal to the ielo-cecal junciton?
appendix
What is the function of the appendix?
- vestigial cecum
- used for bacterial digestion in herbivores
- contains a large amount of MALT and is more active in children
What is a polyp (adenoma) in the GI?
any mass arising from the wall of the colon that protrudes into the lumen
What is treatment for colon cancer (adenocarcinoma)?
surgical removal
What decreases the risk of colon cancer?
increase in roughage and fiber in the diet (decrease transit time and increase GI motility)
How can you prevent/catch colon cancer?
New test kits for early detection; detect tumor Ab; also colonoscopy screening over 50
What are the characteristics of the rectum?
- contains transverse rectal folds and mucus glands
- simple columnar epithelium
What does the epithelium transition to in rectum to the anus?
simple columnar epithelium (rectum)
stratified squamous epithelium (anal canal)
What are the characteristics of the anal canal?
- stratified squamous epithelium
- longitudinal folds called anal columns
- anal glands (extend into submucosa and muscularis externa)
- external opening; exit of GI
What are the internal and external anal sphincters made of?
surrounded by muscle
- external = voluntary, skeletal M
- internal = involunary, smooth M
What does occasional enlargment and irritaion of submucosal veins in the anal canal lead to?
hemorrhoids (varicose veins)
Where can hemorrhoids of the GI develop?
inside the rectum (internal hemorrhoids) or under the skin around the anus (external hemorrhoids)
Where is the referred pain with internal hemorrhoids?
follows autonomics, diffuse
Where is the referred pain with external hemorrhoids?
somatic pain, sharp and well-localized
