histology Flashcards
types of tissues
epithelial, connective, muscular, nervous
cell junctions
how cells are held together to form tissues:
- tight
- adherens
- desmosomes
- hemidesmosomes
- gap
tight junction
weblike (strands of transmembrane proteins fused together). Inhibits passage of substances between cells and prevents contents of organs from getting out.
where are tight junctions found
stomach, intestines, urinary bladder
adherens junctions
- dense layer of intracellular proteins attach to membrane proteins and microfilaments of the cytoskeleton
- forms adhesion belts that CONTAIN PLAQUE
- helps epithelial surfaces resist separation during contractile activities.
desmosomes
- like buttons
- helps with stability of cell and tissue
- prevent separation under tension and contraction
where do we find desmosomes
outermost layer of skin (epidermis), cardiac muscle
hemidesmosomes
- like desmosomes but do not link adjacent cells
- anchor cells to basement membrane
gap junctions
- plasma membrane of cells are not fused together, but have an intercellular gap
- has connexons
- allows for diffusion ions and small molecules to pass between cells
- allows for cells to communicate with each other - rapid spread of nerve/muscle impulses
where do you find gap junctions
nervous system, smooth muscles of heart, GI tract, uterus
which junction does not allow for cellular leakage
tight
which junction attaches the cell to the basement membrane
hemidesmosomes
which junction has connexons
gap
which junction connects to the microfilaments of the cytoskeleton
adherens
what is epithelial tissue
- cells arranged in continuous sheets - either a single layer or multi-layered
- cells are closely packed together and held by junctions
- has its own nervous supply but no blood supply (avascular)
structural features of epithelial tissue
- apical (free) surface - top layer, has cilia or microvilli
- lateral surfaces have junctions
- basal surface - bottom/deepest layer. connects to basement membrane with hemidesmosomes
basement membrane
- extracellular layer that has 2 parts - 1) basal lamina (secreted by epithelium) 2) reticular lamina (closer to underlying connective tissue)
function of basement membrane
anchors epithelium to underlying connective tissue
how can we classify epithelial tissue structurally
- layers - simple, pseudostratified, stratified
- shape - squamous, cuboidal, columnar, transitional
functions of epithelial tissue
- protects
- secretes (mucus, hormones, enzymes)
- absorbs (GI tract)
- excretes (urinary tract)
- filtration (kidneys)
- special sense organs (combines with nervous tissue)
where do we find epithelial tissue
- covering/lining surfaces. outer covering of skin and lining hollow organs
- forms the secreting portion of glands (thyroid, sweat, adrenal, digestive)
what is a single layer of epithelial tissue called
simple
how do we refer to multiple layer of epithelial tissue
stratified
which portion of the basement membrane is secreted by the epithelium
basal lamina
what are the 2 types of epithelium
glandular (glands) and surface (outer layer of skin and hollow organs)
