Epithelium Flashcards
epithelial tissue characteristics (3) and function
aggregated polyhedral cells with small amount of ECM. Function is to protective lining, glandular secretion/absorption and transport.
connective tissue characteristics (4) and function
all sorts of different cell types, ECM fibers and ECM ground substance. Some are fixed eg. fibroblast. lots of ECM with less cells. Function is to support and protect body structures.
Orientation of faces of epithelial cells
apical= faces lumen basal= faces connective tissue
basement membrane under Electron microscope. Attachment type
ECM sheet attaching EP to CT
Cells anchored to BM via Hemidesmosomes
3 zones of BM
lamina lucida= proteins that help cells stick to BM
lamina densa=anchors the layers together (chicken wire Col IV)
lamina fibroreticularis= fibers that attach to LD
Simple Squamous EP
line blood/lymph vessels, kidney glomeruli, and lung alveoli. any surface that has a lot of diffusion happening across it.
Simple Cuboidal EP
secretory cells lining glands and ducts, kidney tubules. Generally anywhere secretion of proteins is actively happening
simple columnar EP
Mucus secreting absorptive. From the stomach to the anus. Can be ciliated as seen in the bronchi of the lungs. OVAL Nucleus
psuedostratified ciliated columnar EP
generally mucosal surfaces eg sperm carrying ducts, ducts of larger glands and also line the trachea. Columnar cells that are irregularly positioned
stratified squamous EP
skin and attached gingiva (keratinized)
mucosa of mouth, esophagus and vagina (non keratinized)
urothelium EP
only found in the bladder lining. It’s stretchy
Stratified columnar EP
fairly rare. Found in male urethra and associated with salivary glands. Transitional between simple columnar and stratified squamous epithelia. Note: looks like cuboidal cells with columnar cells on top
stratified cuboidal EP
Somewhat rare. Ducts of large sweat glands, salivary glands and mammary glands.
Microfilaments
- composed of actin
- 6-8 nm in diameter
- structural function, microvilli, gives cell it’s shape
- forms tracks for myosin, giving contractility
Intermediate filaments
made of vimentin and cytokeratin
10nm in diameter
anchors and structural
Non-contractal
Microtubules
- made of tubulin
- moves things from one side of the cell to the other side
- around 25 nm in diameter
- monorail system
Tight junctions (zonula occludens)
- homotypical interactions between transmem proteins that around bound to actin
- very narrow gaps between cells, controls movement of stuff between cells
- proteins: claudins, occludin, JAM
- water and small ions can pass through
cell to cell adhesive junctions
or
Zonula Adherens
- holds cells together (important)
- Cadherins (outside) Calcium depen. + Catenins (inside) complexes
- Contact inhibition(stops cells from replicating
Focal Adhesion Junctions
- Hold cells to matrix
- Integrins replace cadherins as transmem proteins and interact w/many ECM proteins.
- attached to actin via vinculin and actinin like in zonula adherens
Desmosomes
- cell to cell adhesion
- forms line externally and plaques internally visible as dark bands
- Attach to intermediate filaments
- Heterotypical interaction of transmem proteins.
- Help resist shearing forces
Hemidesmesomes
- cell to matrix adhesion
- similar in appearance to desmosome
- attach to intermediate filaments
- tightly attached to basal lamina and resist shearing forces
Gap Junctions
- cell to cell pores
- 6 connexins make 1 connexon
- ions and small water soluble molcules may pass. Nucleic acids, sugars, and proteins are too large.
- Important in propagation of electrical signals.
Epithelial turnover and maintenance
EP cells turnover and are replaced by the division of progenitor cells, with are pluripotent, meaning they can become several types of cells.
CT cells types
permanent
and
transient
Perm-Fibroblasts, adipocytes, macs, and mast cells
Transient-plasma, lymphocytes, neutrophils, eosinophils
