2. Epithelium Flashcards
What are the four types of tissues?
Connective, Muscle, Nervous, + Epithelia
From which germinal layer is epithelial tissue derived?
All three - ectoderm, endoderm, and mesoderm
What is meant by the polarity of an epithelial cell?
Each surface of the cell is structurally and functionally distinct
What are the surfaces of an epithelial cell?
Apical (free) - in contact with environmentLateral - in contact with other cells laterallyBasal - attached to basement membrane inferiorly
Describe the differences between microvilli, stereocilia, and cilia
Stereocilia are longer than microvilli but are non-motile unlike cilia. Cilia beat in coordination to move substances, ie mucous, over them. Microvilli act to increase surface area
What are the three types of basolateral specifications and where do they occur?
Occluding/Tight junctions - almost fusing of cells. AKA Zona Occludens. Found in BBBAnchoring Junctions - Mechanically attaches cells to neighbours. Zona Adherens (Desmosomes) laterally and Hemidesmosomes nasally. Found in tissues subject to severe stress, ie skin and cardiac muscle.Communicating/Gap Junctions - allow passage of chemical/electrical signals.
How are epithelial cells named and classified?
Based on the number of layers, the shape of the cells at the free surface, and any surface specialisations
Why would columnar cells be present rather than cuboidal?
Allow for greater protection from acids/etc but still allow motion across the epithelium with cilia/microvilli. Nucleus 2/3rds down for protection
Where would keratinised and non-keratinised stratified squamous epithelium be found? What is the purpose of this type of epithelium?
Keratinised is found in skin, outermost layers are dead. Non-keratinised is moist, found in mouth, oesophagus, etc. Allows for lots of protection against abrasion and infection.
What is the main difference between stratified columnar epithelium and stratified cuboidal?
Cuboidal can secrete and absorb, while columnar can only secrete.
What type of epithelium lines the nasal cavity, pharynx, trachea, and bronchi?What is the purpose of this type?
Pseudostratified columnar. Allows the synthesis and secretion of mucous to trap foreign particles.
Where is transitional epithelium located?
Structures where considerable expansion occurs, ie bladder and ureters.
