intro to histology Flashcards
why is histology important?
- provides structural basis for gross anatomy (and many of the life sciences)
- essential for understanding function and pathological change
what are the 4 categories of tissues recognized in histology?
- epithelial tissue
- connective tissue
- muscular tissue
- nervous tissue
what are the general functions of each of the 4 tissue categories?
- surface and glandular (epithelium)
- support (connective)
- contraction (muscular)
- innervation (nervous)
what is the structure of epithelial tissue?
cohesive sheets of cells
what are the specialized functions of epithelium?
- barrier between the internal and external environment
- mechanical protection
- absorption and secretion
what are the subdivisions of epithelial tissue?
- surface epithelium
- glandular epithelium
list the 3 factors that mediate the epithelial tissue functions
- structural modifications to the surface (microvilli, cilia)
- internal modifications (associated with manufacture of secretions and secretion)
- special types of junctional complexes between cells
what are cell-cell junctional complexes and what is their function?
they determine how and what can pass between cells
- function to link cells together but can also have functional implications
what are the 3 types of cell-cell junctional complexes?
- occluding (tight) junctions
- anchoring (adhering) junctions
- communicating (gap) junctions
all 3 are present in but varying amounts depending on the type of epithelium
what is the function of a tight junction?
to prevent diffusion of molecules between adjacent cells
- form a variously permeable barrier
what is the function of adhering junctions?
link cells together and provide mechanical strength
list some examples of adhering junctions
- belt demosomes
- spot demosomes
- hemi-demosomes
what is the function of gap junctions?
allow movement of molecules between cells
what are the three shapes of epithelial cells?
- squamous
- columnar
- cuboidal
what do squamous cells look like?
flat and sheet-like in appearance, often described as looking like fish scales
- large cells with small round nuclei
what do cuboidal cells look like?
cube-like shape (H=W=D) with a central nucleus, looks roughly like dice
what do columnar cells look like?
tall, rectangular column-like shape with nuclei usually located towards the bottom of the cell
what are the 3 classification criteria of surface epithelia?
- number of cell layers (simple or stratified)
- shape of surface cells (squamous, cuboidal, or columnar)
- surface specializations (keratin, cilia, microvilli)
what are the 3 types of simple epithelium?
- simple squamous epithelium
- simple cuboidal epithelium
- simple columnar epithelium
describe what simple squamous epithelium looks like and where is it located in the body?
- single layer of squamous cells
- functionally suited to surfaces where mechanical protection is not required
- e.g. lining of blood vessels, inside body cavities
describe what simple cuboidal epithelium looks like and where is it located in the body?
- single layer of cuboidal cells
- functionally suited to surfaces with an absorptive/secretory role
- e.g. secretory cells of exocrine glands, kidneys, ovaries
describe what simple columnar epithelium looks like and where is it located in the body?
- single layer of columnar cells
- functionally suited to surfaces with an absorptive role
- large surface area due to height of cells and microvilli
- e.g. digestive tract, uterus, reproductive system
what are the 3 types of stratified epithelium?
- (keratinized) stratified squamous epithelium
- stratified cuboidal epithelium
- stratified columnar epithelium
what does (keratinized) stratified squamous epithelium look like and where is it located in the body?
- functionally suited to surfaces where there is a varying amount of mechanical protection required
- stratified squamous epithelium: layers of squamous cells; living nucleated cells which flatten towards the surface
- e.g. skin, pharynx, esophagus
- keratinized stratified epithelium: live cells underneath layer(s) of flattened, dead, keratinized cells on the surface
- e.g. paw pads, tongue