Epithelial cells Flashcards
Epithelia
present throughout the body
important components in many organ systems
form boundaries
functions in met, transport, secretion, absorption, protection
thickness of tissue sample
5um - 2d
effect of plane running obliquely to villus
creates appearance of an isolated island of tissue
shape of nucleus
reflect shape of cell
what is visible at higher magnification
the nucleus but not the cell boundaries
SI
in centre - lumen contains partly digested food
epi stain pink with purple nuclei
pale staining region with bv and lymph ducts
further out - muscular laye r (pink) for peristalsis
villus at x40
cells in single layer - nuclei alongside each other - simple epi
base of cell attached to thin fibrous layer - basal lamina/basement membrane
columnar cells
between epi - bulbous cells with pale cytoplasm - goblet
function of villus epi
absorption of products of digestion
apical surface of enterocytes
facing lumen of intestine
brush border - zone w/o organelles, see striations
close packed extensions to increase SA - microvilli 1000x smaller than villi
enterocyte junctions
no gaps
otherwise there would be diffusion of undesirable contents of lumen into body
description of epi lining intestine
simple columnar absorptive epi with goblet cells
glands
when lumen is small - epi is forming glands/ducts
tubular structure into which cells secrete things which diffuse along tubes to tehir destination
crypts - simple tubes and closed ends
near end - secretory cells - Paneth cells recognised by secretory granules - positioned asymettrically in cell so they release their contents at apical surface onto crypts
type of glands
crypts - simple tubular glands because single closed tube
if branched - gland would be a compound
if secretory cells restricted to regions with round shape at ends - acinar ot alveolar gland (acinus or alveolar are secretory regions and rest of system is ducts)
mesentery
thin layer
attaches intestines to rest of body
allow intestine in abdominal cavity to have blood and nervous supply - allow intestine to be mobile in peristalsis
low power of mesentery
some places thin
others have bv surrounded by fat
simple epithelium around tissue
squamous - reflected in nuclei
function of epithelium around mesentery
forms a boundary
oesophagus
epi lining central lumen stratified basal cells purple higher up pink near lumen - v pale through layers cells diff shape - basal = round, closer to the lumen - squamous
purpose of epi of oesophagus
prevent damage - human swallow dangerous things
partly chewed food - abrasive bones or veg fragments
stratified means if surface cells damaged - layers beneath can function and divide to replace those lost
skin
stratified squamous epithelium
waterproof to prevent cells beneath drying out
surface cells cornified (died) - keratin left containing intermediate filaments - absorbs oily secretions = waterproof
epidermis
cells are keratinocytes
most basal - stratum basale - cuboidal, on basal lamina
stem cells in this layer produce cells for the upper layers - differentiate and replace cells from surface. melanocytes in this layer
stratum spinosum
apical to stratum basale in skin
few layers - spikey appearance
stratum granulosum
apical to stratum spinosum
contain numerous granules
stratum corneum
dead - cornified during differentiation
no nuclei
features in thin skin
hairs and follicules
thick skin
in palms and soles
hair not present
stratum corneum thicker than in thin
trachea
epi separate lumen from surrounding tissue including cartilage rings - red/purple
columnar cells
apical section - cilia - longer than brush border of intestine
goblet cells
pseudostratified - all attached to basal layer
overall description of epithelium of trachea
pseudo-stratified columnar ciliated epithelium
stratified columnar/cuboidal
not functionally important
urinary epithelium
features of stratified and pseudostratified
transitional epi
highly impermeable to urine and stretch bladder as fills
cell renewal
stem cells - in crypts in intestine
in stratified the stem cells are in basal layer adjacent to basal lamina
in simple epi - all cells capable of division
