Histology Exam 2 Flashcards
epithelium
- outer protective surface of the body and glands
- lines most closed cavities, all passages to exterior and blood/lymphatic vessels
what is the function of the epithelium?
barrier- protection withstanding wear and tear from dehydration/hydration
- selective absorption
- transport of ions, O2, CO2
what cell is the most common in cancer?
epithelial
epithelium pt2
- sheet of polarized cells
- metabolism of body through covering the external and lines of internal surface of body
Epithelial Cells
- capable of renewal and regeneration
- form avascular sheets
held together by junctions - organelles in cell are polarized
3 surface specializations of epithelial cells
- apical
- lateral
- basal
microvilli
apical
- bundles of actin filaments extend into terminal web
- increase SA
- core of actin filaments
Cilia
apical
- do not have core of actin filaments
- complex arrangements of microtubules (axoneme)
- tubulin= major protein
- facilitate flow of fluid
- stereocilia -male reproductive tract (immotile)
ectoderm
epidermis of skin and epithelium of cornea together covers the entire surface of the body; sebaceous and mammary glands
endoderm
alimentary tract, liver, pancreas, gastric glands, intestinal glands
Apical plasma membrane fn
- regulation of nutrient and water uptake
- regulated secretion (pathway A)
- protection
Lateral Plasma Membrane fn
- cell-cell contact/adhesion and communication
Basal-lateral membrane fn
signal reception and transduction
- generation of ion gradients - - constitutive secretion (pathway B)
function of the basal lamina
- adhesion of CT
- selective permeability
- good substrate for cell migration during wound repair+embryonic development
type of cell found in basal lamina
stem cell
2 secretion pathways
- regulated
- constitutive
regulated secretion
secretory granules accumulate in cells and the granule content is released by exocytosis upon stimulation
constitutive secretion
secretory product is not concentrated into granules but is released continuously in small vesicles
mesoderm
- Endothelium- lines blood vessels
- Mesothelium- lines serous cavities
integrins
trans-membrane linker proteins that fn as matrix receptors
Lamina Lucida
closest to cell membrane, translucent, contains strands that connect to lamina densa
- laminin
- against ep membrane
lamina densa
electron dense layers, meshwork randomly
- type IV collagen
- against reticular lamina
reticular lamina
not always present, contains reticular fibers & is made by underling CT cells
- Fibronectin, collagen type V, collagen type VII(mainly), ends of collagen type III
occluding junctions
form seal and are impermeable
adhering junctions
glue cells together and are associated with specific cytoskeletal elements
communicating junctions
permit x-talk
fn of tight junctions
- Forms seal/barrier between cells
- Forms epithelial compartments
- Polarize the epithelium
- Limit diffusion of membrane proteins from apical membrane to baso-lateral plasma membrane
desmosomes
- exposed to abrasion
- spot attachment sites for adjacent CM
-anchoring site for IF
hemidesmosomes
found at base of stratified epithelia and connects the PM to the EM via integrins
what causes blistering skin disorders
- mutant cytoskeletons due to a failure to form filaments and weakening epithelia
- loss of desmosome
sensory cells
receive stimuli from external environment which induces a special status in their bodies- irritation
endocrine glands
ductless
- pour secretion into blood directly
exocrine gland
ducts
- pour secretions onto an epithelial surface directly through ducts
epidermis layers
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
what are the cells in the epidermis
Keratinocytes
Melanocytes
Langerhans cells
Merkel cells
Melanin fn
absorbs UV radiation minimizing damage to cells, absorbs UV radiation reducing the amount available for production of vitamin D
Merkel cells
neurosensory cells that synapse with nerve endings
Langerhans cell
bone-marrow derived antigen presenting cell
fn of the dermis
supplies innervention and vascular networks; binds epithelium
collagen fibers
strong, resist stretching but bend easily and provide flexibility
elastic fibers
permits stretching, recoils to original length and prevents damage to tissue
free nerve endings
unmyelinated axons respond to pain stimuli (nociceptors), temp (thermoreceptors), mechanical displacement (mechanoreceptors)
epidermis
stratified squamous epithelium, keratin
- thick, thin skin
dermis
dense irregular connective tissue with type I and type III collagen/elastic fibers
- papillary, reticular and sweat glands
hypodermis
subq layer
- fatty connective tissue
