Download Epithelial Tissues

Epithelial Tissues
Tissues – Introduction
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a group of similar cells specialized to carry
on a particular function
tissue = cells + extracellular matrix
– nonliving portion of a tissue that supports cells
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4 types
– epithelial = protection, secretion, absorption
– connective = support soft body parts and bind
structures together
– muscle = movement
– nervous = conducts impulses used to help
control and coordinate body activities
Epithelial Tissues
Characteristics
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free surface open to the outside or an
open internal space
basement membrane anchors
epithelium to underlying connective
tissue
lack blood vessels
readily divide (ex. skin healing)
tightly packed with little extracellular
space
Epithelial Classifications
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classified based on shape and # of cell
layers
shape
– squamous = thin, flat cells
– cuboidal = cube-shaped cells
– columnar = tall, elongated cells
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number
– simple = single layer
– stratified = 2 or more layers
Epithelial Locations
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cover body surfaces, cover and line
internal organs, and compose glands
– skin cells, cells that line the stomach and
small intestine, inside of your mouth
Simple squamous
epithelium
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a single layer of thin, flattened cells
– look like a fried egg
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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
Simple cuboidal
epithelium
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single layer of cube-shaped cells
– centrally located nucleus
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secretion and absorption
surface of ovaries, linings of kidney
tubules, and linings of ducts of certain
glands
Simple columnar
epithelium
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single layer of cells that are longer
than they are wide
– nucleus located near basement mem.
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ciliated or nonciliated
some have microvilli
goblet cells = secrete mucus
absorption, secretion, protection
linings of the uterus, stomach, and
intestine
Pseudostratified
columnar epithelium
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appear stratified b/c nuclei are at 2 or
more levels
– NOT stratified b/c all cells touch
basement mem.
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ciliated
goblet cells
protection, secretion, movement of
mucus
linings of respiratory system
Stratified squamous
epithelium
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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
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2 or 3 layers of cuboidal cells
protection
linings of larger ducts of mammary
glands, sweat glands, salivary glands,
and pancreas
Stratified columnar
epithelium
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protection and secretion
vas deferens, part of the male urethra,
parts of the pharynx (throat)
Transitional epithelium
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can stretch
distensibility (stretching), protection
inner lining of urinary bladder and
linings of the ureters and part of
urethra
Glandular epithelium
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cells that are specialized to produce
and secrete substances into ducts or
into body fluids
gland = 1 or more cuboidal or
columnar cell
secretion
salivary glands, sweat glands,
endocrine glands
Exocrine vs. Endocrine
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exocrine = secrete sub. into ducts that
open onto surfaces
– skin or linings of digestive tract
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endocrine = secrete sub. into tissue
fluid or blood
– hormones
Exocrine glands
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merocrine = release watery, proteinrich fluid by exocytosis
– salivary glands, sweat glands
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apocrine = lose small portions of their
cell body during secretion
– mammary glands, ear wax
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holocrine = entire cell lysis (breaks
apart) during secretion
– sebaceous glands of the skin
Serous vs. Mucous
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serous = typically watery with lots of
enzymes
– lubrication
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mucous = mucus
– digestive and respiratory systems
– protection