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?