Digestive System 2 Flashcards
Duodenum,such as all the parts of small intestine and colon, have basic structural organization of digestive tract. Its wall is formed by four distinctive layers (from lumen outward):
Mucosa
Submucosa
Muscularis externa
Serosa / Adventitia
Transition from pyloric mucosa to duodenal mucosa-pay attention on:
- *1) transition of epithelium from gastric mucosa (epithelium of gastric glands) to duodenal epithelium (intestinal epithelium)
2) appearance of intestinal villi in duodenum and
3) duodenal Brunner’s glands in submucosa.**
Some of the layers in duodenum, have specific sublayers :
MUCOSA
Epithelium
Lamina propria
Muscularismucosa
SUBMUCOSA
MUSCULARIS EXTERNA
Circular layer
Longitudinal layer
SEROSA
Mucosa –epithelium and lamina propria-intestinal epithelium –have goblet cells, enterocytes (with microvilli on apical part of cell).-lamina propria –loose connective tissue that can be found in the center of intestinal villi and between crypts of Lieberkuhn. Beside fibrocytes, loose connective tissue have a lot of immune cells (lymphocytes and granulocytes).
- *Mucosa –muscularis mucosa**
- smooth mucle cells as border between mucosa and submucosa
- above muscularis mucosa, crypts of Lieberkuhn can be seen and connective tissue of lamina propria
- under muscularis mucosa starts submucosa that in its connective tissue has bigger groups of Brunner’s glands
Muscularis externahas two sublayers:
**•Circular layer (inner layer, closer to submucosa)
•Longitudinal layer (outer layer, closer to serosa)**
Jejunum
Jejunum has the same layers as it is in duodenum: Mucosa, Submucosa, Muscularis externa, Serosa
The only difference between duodenum and jejunum is in submucosa. In jejunum Brunner’s glands are not present in submucosa. Instead of glands, there is only loose connetctive tissue with blood vessels (arteries, veins, capillaries).
On histological slides of jejunum, inside crypts of Lieberkuhn, we can clearly see Paneth cells –pyramidal cells, with nucleus that is in basal part of cell and apical part of cytoplasm that is filled with acidophilic secretory granules.
Muscularis externa have two layers of smooth muscle. First one is called circular layer and cells in this layer have spindle shape. Second one is called longitudinal layer (closer to serosa) and cells are oriented longitudinaly so their shape is oval.
Myentericplexus–between circular and longitudinal layer of muscularis externa we can see mienteric plexus –group of big ganglion cells with big nucleus and prominent nucleoli.
ILEUM–hasthebasicstructuralorganizationofgastrointestinaltract.
Ileumdiffersfromotherpartsofsmallintestine,becauseinlaminapropriaandsubmucosaithasspecific
aggregatesoflymphaticnodulescalledPayer’spatches.
Mucosa of ileum has three layers: epithelium, lamina propria and muscularis mucosa.
Similar to other segments of small intestine, mucosa of ileum forms intestinal villi and crypts of Lieberkuhn. In part of the ileum where we can’t see Payer’s patches, these structures are the same as it is in duodenum and jejunum.
Lymphocytes from Peyer’s patches can be seen in lamina propria and submucosa, so that muscularis mucosa is hardly seen. The shape of intestinal villi and position of crypts of Lieberkuhn are clearly disturbed.
Muscularis externa have two layers of smooth muscle. First one is called circular layer and cells in this layer have spindle shape. Second one is called longitudinal layer (closer to serosa) and cells are oriented longitudinaly so their shape is oval.
COLON
There are two slides for colon. First one is cross section of colon with full circumference. Second one is partial section of colon.
On both slides you can clearly see 4 distinct layers of colon:
Mucosa
Submucosa
Muscularis externa
Serosa/Adventitia
