TOB: Epithelial tissue Flashcards
Define epithelia
Sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces.
What epithelium develops from the ectoderm layers of the trilaminar embryonic disk?
Epithelium (epidermis) of skin and corneal epthelium of eye (NB: “ecto-“ means “outer/ external”
What epithelium develops from the mesoderm layer of the trilaminar embryonic disk?
Epithelium of: urogenital tract, blood and lymphatic vessel linings, pericardial and pleural sac lining and peritoneal lining. (NB: think simple squamous and transitional)
What epithelium develops from the endoderm layer of the trilaminar embryonic disk?
Epithelia of: respiratory tract, GI tract, liver, and many glands (thyroid, thymus, salivary glands…) (NB: think columnar and cuboidal - with the exception of oesophagus which is stratified squamous)
Explain the position of the basement membrane
It is a thin, flexible, acellular layer which lies between epithelial cells and the surrounding connective tissue
Explain the structure of the basement membrane
It is contributed to by the epithelial cells and the subtending connective tissue. Epithelial cells lay down the basal lamina. It’s thickness can be augmented by a variably thick layer of reticular fibrils (type III collagen), form the CT.
Explain the function of the basement membrane
It acts as a strong, flexible layer to which epithelial cells adhere. It also acts as a cellular and molecular filter. NB: the degree to which malignant cells penetrate the basement membrane is highly relevant to prognosis. NB2: the terms basement membrane and basal lamina are used inconsistently in literature
What type of epithelium is found in the uterus?
Simple ciliated columnar epitheium
What type of epithelium is found in the vagina and parts of the cervix?
Non-keratinised stratified squamous epithelium
