Meghan Barboza, PhD
Online Course
The Big Four Tissues
Epithelium
Connective Tissue
Muscle
Nerve
Use key characteristics as a way to
“label” cells and tissues
Key Tissue Characteristics (of tissue)
Include:
Amount of cellularity
Prevalent shape of cells and their specific
functions
Patterns of organization, both cellularly and
extracellularly
Presence or absence of specific structures such
as blood vessels and nerve bundles
Main Characteristics of Epithelia
Very cellular tissue (little intercellular
space)
Not vascularized
Innervated
Associated with a free or luminal space
theleo- tissue grows
epi- upon another
Functions of Epithelia
Protection
Functions of Epithelia
Protection
Absorption
Functions of Epithelia
Protection
Absorption
Secretion
Functions of Epithelia
Protection
Absorption
Secretion
Selective
permeability
Functions of Epithelia
Protection
Absorption
Secretion
Selective permeability
Surface transport of
substances
Functions of Epithelia
Protection
Absorption
Secretion
Selective permeability
Surface transport of
substances
Sensory reception
Basement Membrane
Acellular attachment between
epithelia and connective tissue
Made up of basal lamina and
lamina reticularis (secreted by
connective tissue cells)
Visible with light microscopy
(PAS stains)
PAS 400X of glomerulus
Epithelial Classification
Based on cell shape
Classification
Based on cell
shape and
layers
Shape of
outermost
layer in
multilayered
types
Simple Squamous Epithelium:
Principal Locations
• Vasculature of all types
• internal lining (Endothelium)
• Areas for gas exchange
• lining of air sacs
• Serosal lining of coelomic
spaces (Mesothelium)
Simple Squamous Epithelium
Simple Squamous Epithelium
Associated with minimal friction
Simple Cuboidal: Principal
Characteristics
Height, depth and width
comparable lengths
Nuclei are round, often
centrally placed
Some organizational
pattern of organelles
Functions include:
absorption, secretion
and formation of small
conduits (ducts)
Simple Cuboidal: Principal
Locations
Secretory lining of
certain glands that
form follicles (ex.
thyroid)
Simple Cuboidal: Principal
Locations
Secretory lining of certain
glands that form follicles (ex.
thyroid)
Areas for molecular exchange
(absorption/secretion/excretion)
renal tubules (kidneys),
choroid plexus (brain)
Simple Cuboidal: Principal
Locations
Secretory lining of certain
glands that form follicles (ex.
thyroid)
Areas for molecular exchange
(absorption/secretion/excretion)
renal tubules, choroid plexus
Conduits (ducts) for exocrine
glands
Simple columnar: Principal
Characteristics
Height of cells far exceed
depth and width
Nuclei can vary from
round to oval, often
basally placed
Great organizational
pattern of organelles
Functions include:
absorption, secretion
Simple columnar: Principal
Locations
Mucosal lining of most of
the GI tract
Principal Locations
Mucosal lining of
most of the GI tract
Lining of portion of
female reproductive
tract (uterine tube)
400X
Pseudostratified Columnar Epithelium
All cells contribute to (and
contact) a basement
membrane (bm)
Some cells (basal) do not
reach free or luminal end
Cell Types:
Basal cells
Fusiform cells
Columnar cells
Principal Locations
Mucosal lining of most of
the respiratory tract
Lining of portion of the
male reproductive tract
(epididymis)
Stratified Squamous Epithelium
“Non-Keratinized”
Stratified Squamous Epithelium
Keratinized
Distinct morphological
regions:
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
Principal Characteristics:
Stratified Cuboidal and
Columnar Epithelia
Typically two-layered,
sometimes greater
Apical layer either
cuboidal or columnar
Extra layer(s) provide
additional physical
strength
Stratified Cuboidal and
Columnar Epithelia
Line large ducts
Stratified Cuboidal and
Columnar Epithelia
Line large ducts
Stratified Cuboidal and
Columnar Epithelia
Line large ducts
Line regions of GI tract
and upper respiratory
tract extending from strat.
squamous to
pseudostratified columnar
epithelia: recto-anal
junction
Recto-anal junction
Stratified Cuboidal and
Columnar Epithelia
Line large ducts
Line regions of GI tract
and upper respiratory
tract extending from strat.
squamous to
pseudostratied columnar
epithelia: Larynx
Larynx
Principal Characteristics:
Transitional Epithelia
Multilayered with the
ability to change shape
Change directly related
to luminal changes of
volume
Associated with urinary
tract (urothelium)
relaxed
Bi-nucleated apical cells
stretched
Check your understanding
Why are epithelia that are multi-layered not
useful for absorption/secretion?
Why are single-layered epithelium important for
transport but not protection from abrasion?
Epithelia do not have vasculature, how do they
get oxygen, glucose, etc…?
What differentiates the location of keratinized vs
non-keratinized epithelium?