Unit 3: Digestion II
jejunum structure
- numerous plicae circulares - *numerous villi* - no glands in submucosa - no Payer's patches
large intestine function
- reabsorption of electrolytes & water - elimination of waste
Paneth cells
- secrete antibacterial lysozyme - play a role in regulation of normal bacterial flora of the small intestine - not found in large intestine
muscularis externa of appendix
- thick inner circular layer - outer longitudinal layer - no teniae coli
lamina propria of large intestine?
- thick layer of collagen - GALT present (M cells) - *no lacteal*
muscularis externa of large intestine
- thin, inner circular layer - outer longitudinal layer (has 3 bands of teniae coli)
goblet cells
- unicellular mucin- secreting glands - numerous in ileum
central lacteal
found in lymphatic capillaries
unicellular mucin secreting glands
goblet cells
GI portion: Peyer's patches
ileum
GI portion: reduced # & size of plicae circulares
ileum
lymphatic nodules of appendix
in mucosa & submucosa
microvilli with glycocalyx
increase surface area
what does the absorptive function of the jejunum depend on?
integrity of villi
GI portion: no Payer's patches
jejunum
GI portion: no glands in submuocsa
jejunum
GI portion: numerous villi
jejunum
GALt location
lamina propria
where are plicae circulares found?
mucosa & submucosa
submucosa of large intestine
no plicae circulares
epithelium of small intestine
simple columnar
rectum epithelium
simple columnar
appendix structure
- no villi - epithelium - lymphatic nodules
large intestine cells
- numerous goblet cells - apical columnar enterocytes - enteroendocrine cells
brush/striated border with glycocalyx, contain enzymes
*absorptive cells* with microvilli
ulcerative collitis: symptoms
*watery diarrhea & bleeding*
Peyer's patch: epithelium
- *Absorptive cells* - *M cells*
duodenum structure
- *Brunner's gland* in *submucosa* - distal part contains numerous plicae circulares
illeum structure
- *Peyer's patches* - middle: reduced # and size of plicae circulares
M cells
- Peyer's patch - cover enlarged lymphatic nodules - play role in transport of antigens from lumen to lamina propria
appendix cells
- absorptive cells - M cells - few goblet cells
commensals
- assists in digestion - synthesize vitamins B, E, K - prevent colonization of bacterial pathogens by competing with them
what part of the large intestine has simple columnar?
- colon - rectum
GI portion: numerous plicae circulares
- distal duodenum - jejunum
where are plicae circulares located?
- distal duodenum - jejunum - proximal ileum - terminal ileum
glycoproteins of the glycocalyx
- extending from tips of microvilli into lumen - inclue terminal digestive enzymes like dipeptidases & disaccharidases
villi
- folds of mucosa only - increase surface area
plicae circulares
- folds of submucosa - increase surface area
ulcerative collitis
- formation of granulation tissue associated with *proliferation of blood and lymphatic vessels in the lamina propria*- active inflammation
Celiac disease
- immune-mediated inflammation - leads to flattening of jejunal surface w/ extensive loss of vili - due to allergies to gluten
Crypts of Lieberkuhn
- intestinal glands in mucosa - increase surface area
Taeniae coli
- large intestine
what enzyme does the pancreas release to help with absorption?
- lipase - pancreatic amylase
accessory digestive organs
- liver - pancreas
Peyer's patches
- lymphatic nodules - epithelium: *absorptive cells & M cells*
ulcerative collitis: mechanism
1. *mucosa is lost over extensive area* 2. *destruction of absorptive epithelium* 3. *impairs water resorption* from colonic contents → *watery diarrhea & bleeding*
cells of the large intestine
1. absorptive cells 2. Goblet cells 3. enteroendocrine cels 4. stem cells
parts of small intestine
1. duodenum (0.25m) 2. jejunum (2.5m) 3. ileum (3.5m)
large intestine pathway
1. ileocecal junction 2. cecum 3. veriform appendix 4. ascending colon 5. transverese colon 6. descending colon 7. sigmoid colon 8. rectum 9. anus
4 degrees of small intestine folding
1. plicae circulares 2. villi 3. Crypts of Lieberkuhn 4. microvilli with glycocalyx
large intestine epithelium
1. simple columnar 2. stratified squamous 3. keritinizing stratified squamous
Paneth cells location
Crypts of Lieberkuhn
T/F: Paneth cells found in large intestine
FALSE; Paneth cells only found in *small intestine*
T/F: Absorptive cells with microvilli have digestive enzymes
FALSE; absorptive cells do not have digestive enzymes
In the GI tract, the presence and appearance of glands can be very telling. Lets begin with the pharynx. The pharynx has no muscularis mucosa or submucosa and its glands can be found imbedded in layers of muscle beneath the epithelium. The esophagus is unique because it is one of two places in the gut where you will ever see submucosal glands. Stratified non-keratinizing squamous epithelium and glands in the submucosa (called esophageal glands proper) is characteristic of esophagus. In the stomach you can see various sized glands, all of which are located in the lamina propria, at the base of the gastric pits. These glands contain parietal, chief and enteroendocrine cells. The duodenum is the second place in the GI tract with submucosal glands (Brunner's glands). Unlike the esophagus, however, the duodenum has villi and intestinal glands in the lamina propria, like the rest of the small intestine (the submucosal glands of the duodenum are of secondary importance to the glands found in the lamina propria). The presence or absence of submucosal glands is a key difference between duodenum and the rest of the small intestine. In the remainder of the small intestine, glands (crypts) are located at the base of the intestinal villi in the lamina propria. These glands contain Paneth cells (which secrete lysozyme) and enteroendocrine cells. The colon, on the other hand, has no villi and has straight glands which are made up of abundant mucus secreting goblet cells.
How do the locations of glands in the GI tract help to identify what part of the GI tract you are looking at?
2. gastro-duodenal junction
Identify the region of the GI tract: 1. cardio-esophageal junction 2. gastro-duodenal junction 3. duodeno-jejunal junction 4. ileo-cecal junction 5. recto-anal junction
cover enlarged lymphatic nodules, e.g., Peyer's patch, transport antigens.
M cells (microfold cells)
pyramidal shaped with round nuclei located near their base. They contain brightly eosinophilic (almost orange) secretory granules in the apical cytoplasm
Paneth cells
secretion: antibacterial lysozyme. Paneth cells play a role in regulation of normal bacterial flora of the small intestine (absent in large intestine)
Paneth cells
3. submucosa
Rectal hemorrhoids are caused by dilation of blood vessels in the: 1. lamina propria 2. muscularis mucosae 3. submucosa 4. muscularis externa 5. adventitia
T/F: Goblet cells have a higher number in the lower colon
TRUE
T/F: mucosa of large intestine contains tubular glands of Lieberkuhn
TRUE
T/F: mucosa of large intestine lacks folds or villi
TRUE
T/F: M cells are found in large intestine
TRUE, also found in small intestines
2. smooth muscle cells of the muscularis mucosae
The cells indicated are: 1. fibroblasts of the lamina propria. 2. smooth muscle cells of the muscularis mucosae 3. fibroblasts of the submucosa. 4. neurons of the submucosal plexus. 5. smooth muscle cells of the muscularis externa.
6. Villus in the jejunum/ileum *note the absence of submucosal glands)
The structure indicated is a cross section of a: 1. Gastric pit. 2. Cardiac stomach gland. 3. Fundic stomach gland. 4. Pyloric stomach gland. 5. Duodenal submucosal (Brunner's) gland 6. Villus in the jejunum/ileum 7. Crypt of Lieberkühn in the jejunum/ileum. 8. Crypt of Lieberkühn in the colon.
ulcerative collitis: diagonsis
VEGF expression
enterocyte
absorptive cell with microvilli & glycocalyx
appendix epiplocia
aggregate of adipocytes surrounded by serosa
what part of the large intestine has stratified squamous?
anal canal
what part of the large intestine has keritinizing stratified squamous?
anal skin
how are the granules oriented in enteroendocrine cells?
basally-oriented
small intestine function
digestion & absorption
GI portion: Brunner's glands in submucosa
duodenum
Brunner's glands location
duodenum submucosa
secretion: gastrin, cholecystokinin (CCK), secretin, gastric inhibitory peptide (GIP), somatostatin, vasoactive intestinal polypeptide (VIP), motilin, enteroglucagon
enteroendocrine cells
regenerative cells
stem cells of small intestine
anal canal epithleium
stratified squamous