Lecture 25 Flashcards
How is the small intestine specialised? Where does it start?
To assist the digestion and absorption in the small intestine the tube is modified for movement via muscle, large surface area is given by the long length and enzymes, protection and absorption are provided by epithelial cells.
It involves many coils and is attached via mesentry, are able to freely slide around and and are moist.
It starts in the duodenum.
Where do enzymes, protection, hormones and absorption occur within the small intestine?
enzymes occur via the pancreas as well as for correcting the pH, protection is via mucous secreting epithelial cells, mucous glands in the duodenum and neutralisation of acid. Hormones are released due to epithelial cells and nervous cells. Absorption occurs via absorbative epithelial cells.
Where do we find most mucous glands in the small intestine? Why?
The thickest layer of mucous (and mucous glands) will be in the duodenum as this is where protection is needed against the stomach acid.
What are the Plicae circulares?
The Plicae circulares are permanent leaf life projections coming from the submucosa and overlying mucosa, they increase the surface area. As digestion is completed and absorption tails off these start to become shorter and more sparse.
What are the villi? What is a crypt of lieberkuhn
A villus is a finger like extension of the lamina propria (FCT), it is covered in epithelium which the muscularis mucosa at the base. A crypt of lieberkuhn is where progenitor cells are found and is the deepest space between adjacent villi.
Within the core of these is a capillary network to both provide blood and allow nutrients to enter the blood and lymph vessels known as lacteal for fats.
What are Paneth, endocrine and progenitor cells?
Paneth cells have granules and secrete antibacterial enzymes, endocrine cells secrete hormones and progenitor cells make all cell types.
What is a clear difference between goblet cells and absorptive at the electron microscope level? What is the brush border?
Goblet cells are darker than absorptive cells, the brush border is a series of microvilli on the edge of the lumen.
What are the microvilli?
The microvillis are essentially a plasma membrane with a glycoprotein coat, contact digestion can occur if digestion is not finished.
How are the epithelial cells prevented from overflowing?
The tight junctions block restrict entry to the capillary networks but also help to prevent all molecules from having to travel through the epithelial cells. There are also a large amount of folds in the cells to the exit to allow more surface area for exiting. This prevents the epithelial cells from overflowing.
