Digestive Tract (DT) Flashcards
Function: oral cavity
Ingestion and initial fragmentation
Function: esophagus
Conduct food from oral cavity to stomach
Function: stomach
Complete fragmentation and initial digestion
Function: duodenum
Get enzymes from pancreas and liver
Function: jejunum & ileum
Complete digestion and main absorption
Function: large intestines
Absorption of water and ions
Layers of the DT
- Mucosa
- Submucosa
- Musculosa
- Serosa (Adventitia)
The walls of the mucosa layer has three layers covered with two types of epithelial cells
- Stratified squamous epithelium
- Simple columnar epithelium
Function: wall of the mucosa layer
- A selectively permeable membrane
- Digestion and absorption
- Produce hormone
- Secrete mucus for lubrication and protection
DT layer of connective tissue containing the Submucosa nerve plexus
Submucosa
DT layer of smooth muscle cells and less skeletal muscle cells with inner circular and outer longitudinal sub layers
Muscularis
The nerve plexus found in the muscularis layer of DT
Myenteric nerve plexus
Function: myenteric nerve plexus
The contraction of muscularis propel and mix the food in digestive tracts
The adventitia:
Serosa: LCT + mesothelium
Fibrosa: LCT
Three layers of the mucosa layer
- Stratified squamous epithelium
- Lamina propria
- Muscularis (mucosa)
In the mucosa of the stomach, the columnar cells toward the surface are called
Surface mucous cell
Invaginates into the lamina propria, opens into the gastric gland and functions to
Gastric pit
Distribution: most of the stomach (body and fundus) except pylorus and cardia
Structure:
1. simple or branched tubular glands
2. Glands open into gastric pit
3. The epithelium of the gland include:
- chief cells
- parietal cells
- neck mucous cells
- undifferentiated cells
- endocrine cells
Main gastric gland
Parietal cell is also called
Oxyntic cell
Distribution: more numerous in upper half of the gland
Function:
1. Secrete hydrochloric acid
2. Produce intrinsic factor
Parietal cell
Function: Intrinsic Factor
Intrinsic factor processes Vitamin B-12 into complex which aids the production of erythrocytes
Breaks down protein into peptides and solid food becomes liquefied
Pepsin
Activates the pepsinogen secreted from chief cells
HCl
Distribution: the mucosa of cardia and pylorus respectively
Function: secrete mucous
Structure: composed mainly of mucous cells
Cardiac and pyloric glands
Three special features of small intestine used to increase the surface area for the contact with food to promote absorption and digestion:
- Plicae circulares (3-fold)
- Villi (10-fold)
- Microvilli (20-fold)
Intestinal villi is most developed in the
Duodenum
Intestinal glands are also called
Crypts
Cells which aggregate at the bottom of the gland
Paneth cells
Digestive and absorptive process take place on the surface of ________ along the microfilaments
Microvilli
There are no goblet cells in the
Stomach
________ and ________ are present outside the gland
- Undifferentiated cell
- Endocrine cells
Glands in the duodenum are also called
Brunner’s gland (duodenal glands)
Aggregated lymphoid nodules
Ileum
In the mucosa layer of large intestines
Function: goblet cells
Secrete mucus
The narrowest part of the gut; a blind-ended tubule; poorly formed crypts; mucosa and Submucosa contain abundant lymphoid tissue
Appendix
Possible extensions of Peyer patches in ileum
Duodenal glands
Solitary (jejunum) and aggregated (ileum) - most prominent forming Peyer’s patches
Gut-Associated lumphoid tissue (GALT)
GALT has many immune cells and function in
Protection
Specialized epithelial cells overlying Peyer’s patches
M-cells
M-cells are also called
Microfolds - cells
Epithelium of the gut contains scattered cells that have an endocrine function
Enteroendocrine
Endocrine cells can be identified by the presence of ______ which stain black by silver staining
Argentaffin cells
Fig 1
Special epithelial lining
Esophagus
Fig 2
Pit; gastric line
Stomach
Fig 3
Finger-like
Jejunum
(Small intestine)
Fig 5
Paneth cells
Fig 4
Duodenal gland
Duodenum
Fig 9
Narrow lumen
Appendix