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Epithelial Tissue
Epithelial Tissue Tissues - Introduction· a group of similar
cells specialized to carry on a particular function· tissue = cells
+ extracellular matrix
nonliving portion of a tissue that supports cells· 4 types
epithelial - protection, secretion, absorptionconnective -
support soft body parts and bind
structures togethermuscle - movementnervous - conducts impulses
used to help control
and coordinate body activities
Epithelial Tissues Characteristics· free surface open to the
outside or an open internal space (apical surface)· basement
membrane anchors epithelium to underlying connective tissue· lack
blood vessels· readily divide (ex. skin healing)· tightly packed
with little extracellular space
Epithelial Classifications· classified based on shape and # of
cell layers· shape
squamous - thin, flat cellscuboidal - cube-shaped cellscolumnar
- tall, elongated cells
· numbersimple - single layerstratified - 2 or more layers
Epithelial Locations· cover body surfaces, cover and line
internal organs, and compose glands
skin cells, cells that line the stomach and small intestine,
inside your mouth
intestines
cheek cells
skin
Simple Squamous Epithelium· a single layer of thin, flattened
cells
looks like a fried egg· easily damaged· common at sites of
filtration, diffusion, osmosis; cover surfaces· air sacs of the
lungs, walls of capillaries, linings of blood and lymph vessels
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Epithelial Tissue
Simple Cuboidal Epithelium· single layer of cube-shaped
cells
centrally located nucleus· secretion and absorption· surface of
ovaries, linings of kidney tubules, and linings of ducts of certain
glands
Simple Columnar Epithelium· single layer of cells that are
longer than they are wide
nucleus located near basement membrane· ciliated or nonciliated·
some have microvilli· goblet cells = secrete mucus· absorption,
secretion, protection· linings of uterus, stomach and intestine
Pseudostratified Columnar Epithelium
· appear stratified because nuclei are at 2 or more levels
NOT stratified because all cells touch basement mem.· ciliated·
goblet cells (secrete mucus)· protection, secretion, movement of
mucus· linings of respiratory system
Stratified Squamous Epithelium· many layers of flattened cells·
named based on appearance of top layer of cells· protection· outer
layers of skin, linings of oral cavity, throat, vagina, and anal
canal
Stratified Cuboidal Epithelium· 2 or 3 layers of cuboidal cells·
protection· linings of larger ducts or mammary glands sweat glands,
salivary glands, and pancreas
Stratified Columnar Epithelium· protection and secretion· vas
deferens, part of the male urethra, parts of the pharynx
(throat)
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Epithelial Tissue
transitional Epithelium· can stretch· distensibility
(stretching), protection· inner lining of urinary bladder and
linings of the ureters and part of urethra
Glandular Epithelium· cells that are specialized to produce and
secrete substances into ducts or into body fluids· gland = 1 or
more cuboidal or columnar cells· secretion· salivary glands, sweat
glands, endocrine glands
Exocrine vs. Endocrine· exocrine = secrete substances into ducts
that open onto surfaces
skin or linings of digestive tract· endocrine = secrete
substances into tissue fluid or blood
hormones
endocrineexocrine
Exocrine Glands· merocrine = release watery, protein-rich fluid
by exocytosis
salivary glands, sweat glands· apocrine = lose small portions of
their cell body during secretion
mammary glands, ear wax· holocrine = entire cell lyses (breaks
apart) during secretion
sebaceous glands of the skin
Serous vs. Mucous· serous = typically watery with lots of
enzymes
lubrication· mucous = mucus
digestive and respiratory systemsprotection
